Development of bicycle pedal part II

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faManufacturing Mini Project of
Development of Bicycle Pedal
Part II

Casting processes
Here we are going to develop the bicycle pedal that is used in normal bicycle. We are trying to
improve the quality and also the usability of the bicycle pedal. Also, there are several improvements
that will help to reduce the weight of the total product also increase the grip between the foot and the
pedal.
In casting processes use only metallic components, either ferrous metals or nonferrous metals. So
that we can avoid other types of parts in nonmetallic components. for the discussion of suitability of
the casting processes.
There are several components that are in metals, and we can see that these parts can be
manufactured using casting processes. These components are except standard nuts and bolts,
• Middle part of the bicycle pedal
• Metallic cup of the bicycle
• Metal strips
• Axel of the bicycle
• Arm of cog wheel
• Cog wheel
Here in this list of parts some of them can be manufactured in forging and forming processes,
because these materials that are going to use have ability to make the part not in casting processes.
Other thing is the castability of the materials are low in case of properties that we have selected.
When we are selected the metallic cup and two metal strips, these parts can be manufactured
using sheet metal forming processes. These parts have higher surface area relative to the thickness
and volume of the material. So that we can see their design can be easily done using sheet metal
forming processes. Metallic cup is made with deep drawing and metal strips can be used using die
and punch and also have to use bending machines. Applicability and suitable materials, also the
properties of the materials are described in sheet metal forming process.
In cog wheel and manufacturing process, that materials have to be manufactured using forging
methods because the castability of the selected material is lower. The material can be easily made
with the forging processes and described in another section. And also, the material type of the cog
wheel is aluminum type and manufacturers are making these kinds of products in forging processes.
Basically, these processes are categorized under press working. The tooth tolerances and
dimensional accuracy should be higher. So that the expensiveness of the part fabrication method is
higher. The acceptability of the forging process is mentioned under the part manufacturing
description.
The arm of the bicycle is also manufactured in forging process. That arm is a bulk material part
and has no standard shape. We can see that this part can be manufactured using casting processes
also because the part designing can be easier in that. But in the forging processes, the part can be

manufactured easily. The applicability of the manufacturing process is also described in that part
manufacturing process.
These are the parts that we suppose to manufacture using casting processes.
Some parts can be manufactured using press work because that parts will have lower thickness
compared to the other parts. As an example, bicycle cog wheel can be produced using press
working, forging. So that we can get net shape of the product and with the help of further machining,
can get the desired shape. That process has also advantages and disadvantages also. In the
manufacturing process of the cog wheel arm it can be manufactured using drop forging. We have to
compare and contrast these two processes also. If there are different types of processes for the same
part we have to select best or most suitable manufacturing processes.
Before move in to the casting process component, we have to consider about the material type,
classification. their properties, how the properties will change after the manufacture, and suitability
of each casting processes.
All of these components are types of steels. We have identified the material type of each
component previously. So that we can directly access to the material type and compare the
suitability of them.
In the selecting material for the selected part, there are some properties of them. As we can see
some of the components should have higher strength than another one. Some of the parts should
have close tolerances, because the measurements of some parts are very important. Another thing is
that some of the materials should be ductile and other should be brittle. Some other properties are
toughness, hardness etc.
Middle part of the pedal
The middle part of the pedal plays important role because total load that applied on the pedal is
basically applied in into this component. So that we have to select high strength material for this
component. The outer surface, basically the finishing of the component is necessary. And there are
few threads also a cylindrical hole through axis of the component. That thread must be produced
using machining. And also, the cylindrical hole that use to pass the axel through it, should have
precise diameter. With considering these properties, that component should have higher
machinability.
This component is based on complex shapes. As we can see that there is no standard shape in that
part. We can observe that basically this part contains 7 cylindrical shapes, main middle cylindrical
part and six small cylindrical fins that support the outer rubber part of the material. To reduce stress
concentration and other manufacturing defects, sharp edges are avoided and fillets are used. Part
should be ductile, because that should absorb much energy before failure occurs, and also, we have
to get notification before final cracks.

The surface of the material gets rubbing always because of the contact of the foot or shoe. So that
there is a chance to occur corrosion in the surface of the material. Another reason for corrosion is the
body is more expose to the outer environment of the surface and therefore there will be a chance to
react with the other chemicals and impurities.
The part should have higher strength to weight ratio. We have to select a suitable material type
that is light in weight and higher strength with corrosion resistance capability.
By considering these results we can say that basically these materials should be a type of steel. But it
should avoid corrosions. so that we have to select stain steel material for the making of the pedal
body.
So, we are trying to verify the type of material among the various types of stainless steel
materials. With the use of large variation of composition, there can be countless stainless steels
made. We are trying to select suitable stainless steel among these materials by considering the
required material properties. Table 3 contains some stainless-steel metals and their properties.
Amount these stainless steels, there are some commonly used stainless steels types and their use.
Table 4 contains variation of the stainless steel with the material specifications.
• Stainless Steel 304 (1.4308)
Most common stainless steel and this is applied in various applications. That consists of
minimum 18% chromium and 8% nickel. This metal has no magnetic properties. Used in
food industry applications
• Stainless Steel 304L (1.4309)
This metal has additional indication ‘L’ that means that is consists of low carbon steel. So
that this has higher weldability and machinability. Used in food industry applications.
• Stainless Steel 316 (1.4408)
This type is more expensive steel type. This alloy contains at least 16% chromium, 10%
nickel and 2% molybdenum. With the addition of molybdenum this material has higher
resistance to corrosion under salty environment also in acids. So that most of the applications
used in chemical industry is used these steels. Used in automotive applications.
• Stainless Steel 316L (1.4409)
This has same characteristics as previous one, but has low carbon percentage than that. So
that weldability and machinability is improved. Mostly used in food industry applications.
The characteristics of the material is shown in the Appendix A. with the help of these data values we
can compare and contrast the mechanical, thermal properties and using the melting and cooling rates
can select most suitable material for the application that we are looking for. Here are the
comparative characteristics of the mentioned stainless castable materials.

Type of material Hardness – Rockwell type B Yield tensile
strength (MPa)
Elastic modulus
(GPa)
304 70 215 193
304L 82 210 193-200
316 79 290 193
316L 80 205 193
Table 1: Mechanical Properties comparison of the material
We can see that when we compare the hardness values that comes from same hardness value
testing method, 304L steel has higher hardness, so that we have to get higher tooling cost in
machining purposes. But in the 316 steel has lower hardness value among these 4. That means we
can machine these materials much easier than another one. All four materials have almost same
elastic modulus. Other that tensile strength, 316 steels has higher tensile strength. In the application,
the part is subjected to higher tensile strength during the operation, we discussed the reasons before.
So that we can say this material has higher acceptability from other 4 materials.
Type of material Specific heat capacity
(J/g℃)
Thermal
conductivity
(W/mK)
Melting point
(℃)
304 0.500 16.2 (0-100℃)
21.5 (500℃)
1400 – 1455
304L 0.500 14.0 – 16.3 1400 – 1450
316 0.500 16.3 1370 – 1400
316L 0.500 14.0 – 15.9 1375 - 1400
Table 2: Thermal Properties comparison of the material
Here we can see that all four material has same specific heat capacity. But there is a variation of
thermal conductivity. So that cooling rates of the materials have different values. That is directly
affected in casting processes, because the molten material has to be solidified in the mold cavity.
Also, there won’t be any misruns in the mold. If the material has higher solicitation rate, that will be
some kind of trouble, and have to analyse and design the proper molten material flowing runners
also. If the thermal conductivity gets higher values, material can transfer thermal energy easily. If the
material thermal conductivity is higher, the melting temperature will have reduced. According to the
data given the 316 steel has lower melting point and also same solidification temperature as other
materials. In 304 and 304L has higher melting points. In casting point of view, material should have
lower melting temperature in order to reduce the energy need to melt the material. So, in accordance
with the thermal properties, 316 steel has lower melting temperature, and higher thermal conductivity
with compared to the other types of steels. So, 316 steels can be recommended for the application.

Properties of the 316 steels
1. Corrosion resistance – has higher corrosion resistance even in salty conditions
2. Heat resistance – has good oxidation resistance, better in higher temperatures. Oxidation
resistance varies with the temperature, intermittent service to 870℃ and continuous service
to 925℃.
3. Heat treatment – basically heat treated with annealing process
4. Welding – has excellent weldability
5. Machining – has good machining characteristics and tend to work harden if machined too
quickly. So low speeds and constant feed rates are recommended.
So, by considering most of the cases, we can get that stainless steel 316 has characteristics that are
relevant to the middle part of the bicycle pedal. That stainless steel has higher machinability, ability
to casting, and can be manufactured by various casting processes.
Types of casting processes and their applicability
Since we are considered about the casting processes, there are various types of casting processes and
applications. These variations are categorized because of the part characteristics as well as the
economic benefits.
Here are some casting processes and the applicable materials can be cast. Also, properties of the
casted material are also given.
• Green sand molding – that casting process uses mold made of compressed or compacted
moist sand. And there is a pattern that would be manufactured using wood or metal. The sand
mixture packed around that pattern. There are two or more halves of mold that use in the
casting. After that these molds are positioned in the manner of complete the mold.
• No- baking molding – there use chemical binders that mixed with the sand and applied
around the pattern. The mold become rigid with the help of catalysts.
• Resin shell molding – basically, silica sand is placed onto a heated pattern that will make the
mold halves. There are ejector pins enable the mold to be released from the pattern. Entire
casting cycle will end within couple of seconds and that will totally depend on the shell
thickness of the casting. The two halves of the mold should have glued and clamped together
before the pouring of the material. Here pattern cost is higher and that will most suitable in
higher production rate manufacturing processes.
• Permanent mold – here mold cavity is machined into metal die blocks. That mold can be
used in repetitively. Basic mold manufacturing materials are cast iron or steels. There are
large range of materials that can be used under permanent mold casting. There are two sub
categories of permeant mold casting.

o Gravity permanent mold – flow of molten material into the mold is happened due to
gravitational forces. That process more accurate than shell molding.
o Low pressure permanent mold – here use minimal amount of pressure to fill the
mold.
• Die casting – that process is basically done for large volume applications of zinc, aluminum
and magnesium alloys. Here molten metal is injected under high pressure in to the mold
cavity in order to fill the mold cavity. Basically, the rate of production of material parts are
depend on the complexity of the shape of material, sectional thickness of the casting, and
also properties of the casting materials.
• Investment casting (Lost wax casting) – here use 3-dimensional pattern that can be used to
produce whole part in destructible mold. Here first these patterns that made with wax is
arranged in tree pattern and then immersed into a fluidized bed of refectory particles.
Repeated same process until desired thickness is gained. Then wax pattern get meted out and
can get the final mold. Using that process, there can be manufacture various types of parts in
various types materials. but mostly that process is used in higher production rating processes
only, because of the higher investment and tooling cost of the making mold.
• Expandable pattern casting (Lost foam) – that method is economical method of producing
complex geometers that has close tolerances. Here use expandable polystyrene pattern and
unbounded sand.
• Centrifugal casting – here use permanent tooling that is rotated horizontally or vertically
when the molten material poured into the mold. This process typically used in manufacturing
pipes or mainly in other cylindrical components.
• V-process – that is also dry sand casting method that uses a vacuum to hold a membrane on
the surface of the pattern. Here can get higher dimensional control than others.
There are materials also shapes that can be manufactured using each type casting processes. In
permanent mold method, materials that typically used are aluminum and copper base materials. so
that we can remove that process in feasibility searching. Also in manufacturing using die cast irons,
mostly use aluminum, zinc, magnesium, and copper base. In the centrifugal casting process, mostly
used to produce cylindrical shape products such as tubes. So that we can avoid further consideration
of these manufacturing processes. In vacuum casting process, basically need pattern that in plate,
plated pattern. We can avoid that method as well.
Other than that, most of the casting metals are used in part manufacturing process, can be used in
another manufacturing processes. For further selection of best casting processes, we have to consider
about the advantages and disadvantages, limitations and properties of the parts just after casting.

Casting process Advantages Limitations and disadvantages
Green sand
molding
• Most ferrous and nonferrous
materials can be used
• Low pattern material cost
• No limitation of size, shape,
weight of the part
• Can use higher and low quantities
of material
• Low design complexity
• Low dimensional accuracy
No-Bake
molding
• Can use for large as well as small
quantities
• Mold strength is high
• Better as cast surfaces
• Less skills and labor requirement
• Better dimensional control
• Pattern require additional
maintenance
• Sand temperature is critical
Resin Shell
molding
• Applicable for large and medium
size parts
materials can be used.
• Higher production rate
• Good dimensional accuracy
• Pattern cost and pattern
wear is higher
• Energy cost is higher
• Material cost is higher than
previous types
Investment
casting
• Excellent accuracy and flexibility
of design
• Useful for materials that are
difficult to machine
• Can get fine finish
• No flash or parting line tolerance
• Limitation on size of casting
• Higher casting cost
Table 3: Casting processes and their advantages and disadvantages

When we discuss about the tolerance of the material that we are going to manufacture must have
0.1mm because that is the main component in the pedal. Also, there should be such accuracy
because few other parts are going to set to that part. There are few threads and also the middle
cylinder that should contains axel through it. So that we have to select a process that cans get such
dimensional accuracy. After that we have to consider about the surface finish of the material. Here
the surface should have surface finish not as like as perfectly. But the outer appearance should be
good. Then we have to consider about the economic benefits of the production. Because these
products are going to manufacture to get the economic benefits. So that we have to consider the
initial investment cost and how we can manufacture number of products from that casting.
Sometimes even if the initial cost is higher, finally that will more economical than the low
investment casting product, because with the increment of the manufacturing number of parts, the
cost is getting low.
We can see that with the increment of the number of casting, relative cost per component is
decreasing.
Here are some other characteristics of the casting methods deeper in detail.
Chart 1: Process economics

Casting
process
Average
tooling
cost
Relative
cost for
high
quality
Relative
cost for low
quality
Surface finish
RMS value
Ease of
casting
complex
design
Ease of
changing
design
Green sand Low Low Low 420 - 900 Fair to good Best
No bake/
airset
Low Low Low 420 - 900 Fair to good Best
Shell
model
Medium Medium Medium 200 - 350 Good Fair
Investment
casting
Medium High Medium 60-120 Best Fair
Lost foam Low High Low Per type of
foam used
Good Good
Table 4: Characteristics of difference casting processes
Here we can see that tooling cost, investment in increasing with the decrease of surface roughness.
But the design complexity is getting lower in the low tooling cost casting process. If we are
supposed to manufacture high end product, definitely we have to get the higher tooling cost in order
to design and make good pattern.
The production rate of this component is going in high production rate are in small or medium
production rate because in the manufacturing aspects, these parts are not going to manufacture in
hundreds of thousands in each manufacturing time. We can use any casting method for that because
of this. But if we can use green sand cast iron, the total cost per unit part is minimum and if we are
going to use investment casting, surface roughness is reduced, so that the surface finish is good.
Other thing is pattern and mold making complicity. In the investment casting is much higher. So that
we have to select middle type castings in order to manufacture the product.
In the design of pattern and core, in no baking molding, the pattern has to be in additional
maintenance procedure because of the wear. And in resin shell model material cost is much higher.
In no bake molding process, the pattern has to be undergo maintenance procedures because of the
wearing effects. The advantage is that the dimensional controlling is easier in this process. So, with
considering all the aspects, we come to know that no bake molding is much same as sand casting,
additionally there are few advantages.
So, we can conclude that if the manufacture has intended to make parts in higher number of count,
they have to consider the investment casting procedures, that will be easy as well as economical in
manufacturing above 10000 parts. But when the manufacture decided to manufacture these products
in medium or small scale, he can use sand casting as the easiest as well as most economical type of
casting.

In finally, we consider to use the process of investment casting of the product in detail.
Tolerances and parting line effect of the sand casting process and investment casting process is the
next part.
Casting process Tolerances Size range
Green sand 0-3’ – 0.03’’ per in.
+0.005’’ per inch for each
additional inch.
Across parting line add 0.020’’
to small castings and 0.090’’
for large casting
All size per foundry
capabilities
Investment +/-0.005’’ per inch up to 3’’
and add 0.002 per in. over 3’’
0.1 to 100 lbs.
Table 5: caparison between sand casting and investment casting
When we consider about the green sand casting, if we select the initial tolerance is 0.03’’ per inch,
that means 0.762mm. for additional inch add 0.005’’, 0.127mm. the pedal body is about 5 inches and
the tolerance we can get minimum is 2mm tolerance. That means has to machining and surface
finishing of the part is a must.
In investment casting, when the pedal is 5 inches, the minimum tolerance that we can get is 0.019
inched, 0.4826 mm that is smaller and using surface finishing procedure, we can get the desired
properties of the surface finish as well as tolerances.
So that we can conclude investment casting can get higher finish than sand casting. In investment
casting there is no parting line. So that tolerance is not affected in the final part. But in the sand
casting tolerance is also affected.
The melting range that use in the casting process is about 2500-2550 ℃, the data is taken out from
the stainless-steel manufacturing company.
Here we consider about the mold designing part. That is a crucial because the total manufacturing
procedure is depend on this process. if there is small error or mistake in any parameter in mod
designing it would be huge waste of money and also waste of materials. So that have to be
considered about the parameters that we have to change and consider.
There are few factors that we have to consider about the pattern making procedures because there
are some allowances in order to make proper product without defects.
1. Tolerance – there should be consideration of the tolerance in pattern making also mold
making procedures. If the tolerance value is higher in casting, that is decided by the engineer
would be good in order to finishing the part. But the material wastage is higher in higher
tolerances. So that there should be designed the correct tolerances in each manufacturing
processes.

2. Shrinkage allowances – when the material is getting cold, material particles getting closer
together. That will cause for some material defects also. There should be proper analysis of
shrinkage. Shrinkage is changed from one material to the other.
3. Heat transferring phenomena of component casting – cooling characteristics of the products
are varying with the time and also the properties of the part is changed
4. Stress concentration – that should avoid in the mould making because that will be cause for
internal as well as external cracks.
Here we are going to get the mold parameters and how it would be affected to the final product
• Minimum draft required – 0-1 degree
• Minimum sectional thickness – stainless steel – 0.125’’ = 0.3175mm
• Pattern oversize factor for each direction – 1.05-1.10
• Finishes allowances – 0.5% to 1.0%
• Shrinkage allowance - contraction
o 2.0%
o 20mm per meter
In the mold design in investment casting the draft angle required is much lower because the
pattern removing is not as like the sand casting.
In investment casting there are few phases that have to pass through. These stages are describing
as follows.
1. Injecting wax model – fluid wax is injected into a mould. After wax is hardened, remove the
wax model and wax tree, that is the casting mould is made
2. Ceramic coating – wax molding is given a fire-resistance ceramic molding. After that wax
molds are molten and ceramic casting mold is formed
3. The casting process – the heated mold tree is removed from the kiln and then poured molten
material into the mold.
4. Finishing – give heat treatment and surface finish of the part. Also done inspection and final
product is ready to installation.
5. Inspection – check the defects, properties and dimensional tolerances of the material
Each of part has own sub steps and have to consider about each process. Very carefully. All the
processes are interrelated, not totally independent. In casting process, if there is a mistake in the
designing of the wax mold, total casting processes get ruined. Also in the processes of
manufacturing, if there is an error caused by the change of parameter in the process, the
characteristics of the parts are changed as well. So that we cannot get the desired shape or desired
characteristics in our final product. Appendix A has illustration of typical investment casting
procedure. The common procedure of the investment casting is describing as follows.
Phase 1 – injecting wax model

• Mold engineering and production
Here the mold is designed, that is going to manufacture the wax mold. That is a negative
piece of the final casting. These molds are usually made with aluminum or steel. Here there
must be a precise inspection as well as control in parameters of the material. The surface
finish and tolerances must be take into account otherwise the mold is getting failure.
• Wax mold injection and construct the mold
That mold is filled with wax and let the wax cool. After that model is ejected using ejector
pins and then these wax models are assembled as a tree, called wax tree. That assembling
part is done, heating the attachment of the point until it becomes fluid and then stick to the
branch. That castings created the casting mold. That total wax tree consists of sprue and
runner system that properly developed and then use it to manufacture components.
Phase 2 – Ceramic coating
• Take the wax model and rinse once, to remove the surface contaminants. Another useful
aspect is this rinse procedure is helpful for proper adhesion of the wax into the wax tree.
Then fire resistance ceramic coating is created in the wax tree by plunging the wax tree
multiple times. There should certain thickness of the ceramic coating in order to create
proper molding and casting. After applying ceramic coating, the ceramic layer in the casting
mold must be dried in chamber called drying chamber in atmospheric conditions.
• After that these wax models have to be removed. That is why this process is called as lost
wax coating method. That process is done in an autoclave. Basically, in industries use steam
to melt down the wax models. After that wax model is disappeared and the shape of wax
model is transferred to the ceramic coating. The molten was can be reused in the next wax
molding method.
• Sintering process, that cause to increase the strength of the ceramic mold. The ceramic mold
is fired in a furnace, called ‘sintered’ at a high temperature. That is about 1000℃. Also, this
process helps to remove the extra contaminated wax in the ceramic mold. The additional
wax is melted or burned under this temperature.
Phase 3 – The casting process
• The alloy steel that we are going to use in our product is melted and poured into the mold.
• First the molten material is melted in smelting furnace, temperature is about 1600℃. Some
materials temperature is about 2500℃ also. And the same time, ceramic mould is heated in a
kiln. That temperature is about 1000℃, lower than the melting temperature of the molten
material. After that heated mould is removed from the kiln and poured the molten material
into the mold. The runners help to flow the molten material to the mold cavities. This takes
some times to start solidification of the material because the mold also heated at elevated
temperatures. After the tree has been filled with the material, that cool off on a cooling lane

under controlled conditions. the solidification process must be happened under controlled
conditions, because this is crucial.
Phase 4 – finishing
• The ceramic skin is removed by breaking the shell. After that the casted pieces are get vibrated
and separated from the ceramic particles, these ceramic pieces will be able to reuse, but that
will depend on the type of material is used.
• Then the extra ceramic particles have been removed from the casting product, with the use of
steel or water blasting. After that sanding process is used to improve the neatness of the
product. All the products must be visually inspected before going to next step.
• Then necessary machining process is done. In in pedal body there is a cylindrical hole as well
as internal threads. That’s not going to made with the casting. So that machining part is
essential. Here have to use lathing, milling.
• After that heat treatment process must be done to improve the strength, tensile strength and
elasticity. Describe the type of heat treatment
In the pattern making procedure for the pedal body is little bit different. Here the part has inner
hole. So that pattern making is somewhat complicated. Because the process of the making wax
mold is gets longer than usual products. We have to get two types of wax, in order to make the wax
mold.
Fist have to make a wax mold that can be used to make inner hole in the part. To that there should
be properly designed mold. The mold is set and fill with the wax. That wax has special
characteristic is solubility. Then after the wax is cooled and solidified, the pattern is taken out
from the mold.
Then that soluble wax core is placed inside the casting mold. That is the second mold that we are
going to use in the process of making pattern. Then casing wax, that is not soluble as previous wax
type, is injected into the mold and give some times to solidify it.
After solidifying the material, the pattern is taken out from the mold. After that part with two
waxed is placed inside the water tank. Here the purpose is let the soluble wax core dissolve in the
water leaving. So that after dissolving the casing wax pattern is left. Then the wax pattern is taken
out from the water tank and let it dry.
That is the final pattern use in the making of the product.

Axel of the bicycle pedal
In the bicycle axel is small component with complex geometry shapes. And also, it is the one of
most important part among the products. So that we have to make the material that the properties
are satisfied according to the given data. In previous testing data we came to know that axel is made
with stainless steel that is harder than the metal that is going to use in the pedal body.
Also, the pedal axel has to be made with the higher accuracy, that means limit accuracy is higher
than the pedal body part. Surface finish must be in higher values. Because of that we have to be
select most prominent procedure to get such higher accuracy and tolerances.
With considering the mechanical properties of the axel. It should have higher strength, higher
toughness and higher hardness. The bicycle balls are rubbing with the axel in each rotation. So that
wear of the axel is in higher value. To avoid that the hardness must be increased.
In the consideration of strength of the material, that should be higher also, because the axel should
have to bear high tensile and compressive loads in axial directions. To withstand that characteristics,
the yield modulus must be higher in value. And also, the elastic modulus has to be lower in order to
increase the resistance to deformation. But the ductility will be increased. So that considering all
facts according to the given table above with the mechanical properties values, can select 316L
material or 316 materials. Both of the material has higher yield strength and elastic modulus.
According to the thermal properties of the stainless-steel materials thermal conductivity should be
lower in values. Because of the rubbing with the other parts, the thermal energy that dissipated is
higher in values. So that if the part getting high thermal energy in fewer times, the distortion of the
material will occur. Also, the melting point should be higher than the pedal body part. So that when
we consider about the thermal properties 316L material can be selected as a suitable stainless-steel
material for the bicycle axel.
Bicycle axel manufacturing procedure is also a casting process. the part making rate is medium or
large-scale manufacturing. The designs of the axel and also the pedal body is changed with the time.
If there is novelty in design, the mold design also has to be replaced. But the same design of parts is
going to use in same model of the bicycles as well as most of the time, the axel design will be used
for couple of years. So that the casting process of the same part is higher and we can even move to
expensive casting techniques.
The surface finish of the material has to be higher, because after finishing must be lower. So that we
have to select manufacturing procedure in higher level of finishing. also, it has to be higher tolerance
accuracy. Because the miss alignment of the axis of the axel cannot be recovered after
manufacturing the part, and also it will cause for the failure of the component.
Such tolerance levels can be get through the investment casting. The tolerance of the axel is
0.01mm. such a high precision casting can be done under investment casting. In sand casting the

surface finish is low as well as when the production rate is increased there is no visible advantage of
the economic as well. But the tooling cost is lower and the design changes can be done easily.
In shell model as well as no bake molding methods have disadvantage of higher tolerances, and part
should be machined in order to get the higher dimensional accuracy. Repetitively, we are saying the
dimensional accuracy is important. So that the casting process can be selected as investment casing
because of the less machining is required and lower tolerance values can be achieved.
These are the pattern making parameters for the axel of the material.
• Minimum draft required – 0-1 degree
• Minimum sectional thickness – stainless steel – 0.125’’ = 0.3175mm
• Pattern oversize factor for each direction – 1.05-1.10
• Finishes allowances – 0.5% to 1.0%
• Shrinkage allowance - contraction
o 2.0%
o 20mm per meter
Also, there is a shrinkage in the wax as well. When we consider about the shrinkages of the wax,
there are many research articles, and most used wax patterns and core use following shrinkage
values as well. From wax composition to composition, the molding characteristics are changed.
• Linear shrinkage profiles – 0.398%
• Pattern sprue shrinkage – 0.646%
• Machine wax shrinkage – 0.738%
When we start with the final product there is a 2% shrinkage allowance, 0.7% finishing allowance
and 0.05% paten oversizing allowance. All these parameters we taken from manufacturing
companies and research papers.
So that in the mold should have additional 2.75% total allowance.
For the make of internal core, shrinkage allowance is 0.398% for wax and 0.05% oversizing
allowance. So totally 0.898% allowance is added to the core mold.
In pattern wax molding 0.398% shrinkage allowance, 0.05% pattern oversizing allowance and 0.5%
finishing allowance is added. So that finally 0.987% is added to the mold.
We know that the properties if the material in room temperature. During the casting process material
is melted and cooled into room temperature. So that there will be material property changes.
When the increment of the temperature of the material the strength is decreased of the material and
also stress on the material is decreased. The short-elevated temperature and creep data are given as
follows. Tabular data for strength and creep data are same as the 316L steel. And also, most of the
material property changes are same except the numerical values of both 316 and 316L.

Temperature ℃ 600 700 800 900 1000
Strength MPa 460 320 190 120 70
Table 6: Strength with short time elevated temperature
Temperature ℃ 550 600 650 700 800
Stress MPa 160 120 90 60 20
Table 7: Creep data
The heat treatment is used is annealing. The heat from 1010℃ to 1120℃ and cool rapidly in air or
water will give the best corrosion resistance and, final annealing temperature is above 1070℃
should for better performance.
Also for stress relieving heat from 200-400℃ and air is used. With the help of some journal articles,
we come to know that, the strength of the sigma austenite interface is an important factor that would
helpful to determine the long-term creep rupture behavior.
Also, the tension variation of the materials under uniaxial was examined at 25℃ and small elevated
temperature, is given below. At low temperatures thematical is gone infer martensitic
transformation. But strain induced transformation of austenite is responsible for the significance
change in mechanical properties. These mechanical properties are flow stress, work hardening rates,
fracture toughness and low cycle fatigue characteristics etc. In tensile deformation behavior,
Here we can see that in room temperature flow curve becomes almost linear. But the elevated
temperature flow curve is slightly different that work hardening rate is increasing. So, the true stress
is increased with the increment of the true plastic strain when temperature is increasing.
In fatigue endurance tests, we can see that the reduction in the life at 600℃ by about a factor of five
for the cold-worked material. At higher temperatures, life of the component gets reduced.

Chart 3: true stress against true plastic strain plots for AISI 316 stainless
steel at low temperature
Chart 3: Work hardening rate plotted as a function of plastic strain
and test temperatures

Forging process
Bicycle Cog Wheel
Bicycle cog wheel is one of the utmost important parts of a bicycle. It is the main mechanism that is
used to transmit power given by the rider to the rear wheel with the help of a chain. For this the cog
wheel plays a vital role. Under this section the manufacturing process of the cog wheel is described.
Here the main process we selected to manufacture the cog wheel is the forging process. There are many
other processes like machining and using computer numerically controlled machines. In other words,
we can use latest CNC technique to manufacture the cog wheel too. Under this section we consider why
use forging other than such advanced automated systems.
Here what we do is cold die forging. Cold die forging is the process of forging that is formed to the
required shape and size by machined impressions in specially prepared dies. We can control those dies
three dimensionally. By this method it is possible to manipulate the ring shape and tooth profile more
effectively and more precisely. By this process a harder and tougher tooth surface is created and the
durability of the tooth face also is increased. By this method we can concern about the individual tooth
profile and their alternating tooth angles too.
Cold forming process is much harder to do than hot forging process. The force required is higher
in cold forging process. And also, the cold forging process reduces the ductility of the material. And
also, only a certain amount of change can be obtained by this method. But there are several advantages
in cold forging. Amidst them, the increase of the hardness due to strain hardening can be given. And
also, the direction of the grains can be controlled and can obtain desired directional strength properties.
Apart from that the cost that is required to heating is not necessary in this process. So, a lot energy is
saved and the final product’s cost is very cheap than machining.

When we consider about this process as we know forging is the process by which metal is shaped
applying heavy compressive forces. The height of the forging machine is about two stories and a mass
of one thousand tons is used to forge this. It is clear that this process is not a simple task or easy thing
to be done. Similar to wood metal too has grains. When we consider about forging it refines the grain
structure and the refined grain structure has improved physical properties.
When forging is done, as shown in the figure the original coarse grain structure is subjected to
high compressive loads and also heat rises. Due to that plastic deformation takes place. Due to plastic
deformation the grains become elongated. Then recrystallization occurs and finally growth of new fine
grains take place.
So, it is clear that by this method we can transform the material to be consist more sound properties and
it is not possible to be done by machining. If we do machining we cannot change the grain orientation
of the material. It is clear that the newly formed structure has qualities like higher strength and higher
toughness. When we compare this method with the casting process, as we know castings have no fine
grain orientations. Castings have neither grain flow nor directional strength and also it isn’t possible to
control some metallurgical defects too. Apart from that dendritic structures, Alloy segregation’s and
many other imperfections are refined in forging.
Here the material we use for this is the 7075 T6 Aluminum and the blanks of these are the starting part.
Then the required circular section is cut off and it is placed in the forging machine. The cut-off parts
are as follows.
Then the metal round which is placed in the forging machine is subjected to forging. Here the
main idea is that providing a very high stress in a fraction of time. No re forging is done in order to
maintain the quality of the product. With the hit done by one shot we get the shape of the gears as
follows.

Then the unwanted parts that should be sheared off are removed using shearing tools. By that
we can get the gear profile clean and since we can evoke our attention towards each tooth a more
trustworthy product can be released.
When we consider about the material that is used to manufacture the cog wheel, the material we
have used is the aluminum 7075-T6. The composition of this material is as follows.
Component Wt.% Component Wt.%
Al 87.1-91.4 Mn Max 0.3
Cr 0.18-0.28 Si Max 0.4
Cu 1.2-2 Ti Max 0.2
Fe Max 0.5 Zn 5.1-6.1
Mg 2.1-2.9 Other Max 0.15

Main reason to use this material is that this has very high strength and this suits to highly stressed
structures. And also, this material has improved stress-corrosion cracking resistance. The basic
mechanical properties of this material are as follows. It is clear that this material is more hard and
applicable to corrosive environments very easily.
Density 2.81g/cc
Hardness, Rockwell A 53.5
Ultimate Tensile Stress 572 MPa
Modulus of Elasticity 71.7 GPa
Fatigue Strength 159 Mpa
Shear Strength 331 MPa
Shear Modulus 26.9 GPa
Melting Point 477-6350
C
Other than forging we can use the following methods too.
➢ Casting
➢ Machining
If we compare this with casting process, there are several advantages in forging over casting
when we do this process. Amidst them,
•Strength- When consider about castings we cannot obtain the strengthening effect of hot
and cold working. Forging surpasses casting in predictable strength properties-producing superior
strength which is assured.
• Refinement of defects - A casting don’t have both grain flow and directional strength.
Apart from that metallurgical problems too occur. Pre-working forge stock produces a grain flow
oriented in directions requiring maximum strength. Dendritic structures, alloy segregation's and like
imperfections are refined in forging.
•Reliability - Casting defects occur in a variety of forms. Because hot working refines
grain pattern and imparts high strength, ductility and resistance properties, forged products are more
reliable.
•Less Cost – When compare with the cost that is spent to forging is much smaller than
that of casting. When do casting the cost becomes higher since it is a must to follow tighter processes
add more costs. And also in casting perfect inspection is required.
•Better response in heat treatment- Castings require close control of melting and cooling
processes because alloy segregation may occur. This results in non-uniform heat treatment response

that can affect straightness of finished parts. Forgings respond more predictably to heat treatment
and offer better dimensional stability.
When consider the forging process with the machining, we can see several advantages of
forging over machining too.
•Broader size ranges- Sizes and shapes of products made from steel bar and plate are
limited to the dimensions in which these materials are supplied. Often, forging may be the only
metalworking process available with certain grades in desired sizes. Forgings can be economically
produced in a wide range of sizes from parts whose largest dimension is less than 1 in. to parts
weighing more than 450,000 lbs.
•Oriented Grains- Machined plate may be more susceptible to fatigue and stress corrosion
because machining cuts material grain pattern. In most cases, forging yields a grain structure oriented
to the part shape, resulting in optimum strength, ductility and resistance to impact and fatigue.
•Economical- Flame cutting plate is a wasteful process one of several fabricating steps
that consumes more material than needed to make such parts as rings or sprockets. Even more is lost
in subsequent machining.
•Less scrap- Forgings, especially near-net shapes, make better use of material and
generate little scrap. In high-volume production runs, forgings have the decisive cost advantage.
• Less secondary operations- As supplied, some grades of plate require additional operations
such as turning, grinding and polishing to remove surface irregularities and achieve desired finish,
dimensional accuracy, machine-ability and strength. Often, forgings can be put into service without
expensive secondary operations.Some properties of the final production with the use of Aluminum
7075 T6 is as follows. Commonly the material properties when machined are the same for the billets.
Property Machined Forged
Ultimate Tensile Strength (Ftu) 77 74
Yield Tensile Strength (Fty) 66 63
Yield Compressive Strength (Fcy) 64 66
Ultimate Shear Strength (Fsu) 46 43
Ultimate Bearing Strength (Fbu) 100 104
Density (lb/in3
) 0.101 0.101
Modulus of Elasticity×103
10.3 10.0
According to the table given above it is clear that there is not that much difference between the two
materials. But the most important thing is that in forging after making the die of the cog wheel the cost
required to produce ne part is very less than in machining.
But the thing is that when machining manufacturer can change the design easily and he can upgrade
the design easily. But in forging it is not effective to upgrade the same die and due to that it is required

to design the die again. But as a whole we can conclude that forging is better when thinking about the
manufacturing the cog wheel.
Pedal Arm
When we consider about the bicycle, the pedal arm must be strong enough to endure high compressible
forces since the arm of the pedal should endure them and should transmit the supplied power to the cog
wheel efficiently. So that arm has to be strong enough. And the machinability has to be there because
there has a thread in one side where the bicycle axel is going to fit. So that there must be enough ability
to machine the material. Also, the shape of the arm is not a standard shape. We can get an idea of the
machinability and other material properties through comparisons and contrasts.
Since the material is identified as medium carbon steel, there are some relevant properties that
directly involve the properties of the material.
When consider about medium carbon steel has characteristics between low carbon steel and
high carbon steel. It contains about 0.25% - 0.60% carbon content. Here are some characteristics of the
high carbon steels and low carbon steels.
Properties High carbon steel Low carbon steel
Carbon percentage by
weight
0.30% - 1.70 % 0.05% - 0.15%
Strength Higher strength Low strength compared to the
high carbon steel
Brittleness Higher brittleness Higher ductility
Weldability Difficult to weld Easy to weld into difference
shapes
Heat treatment Can undergo heat treatment Difficult in heat treatment
Applications Rail steels, wire rope, Wire, thin plates
Table 8: Properties of high carbon and low carbon steels
Here we can see that low carbon steel cannot be used in manufacturing process of the wheel
arm, because it must have higher strength and some ductile applications. Another thing is low carbon
steels used in some processes that use high corrosion resistance that not require hardened surface. But
in the application of the wheel arm there must be harder surface.
The values of the characteristics are given in table 3.

When we are looking for a steel that has characteristics
in between of these two, medium carbon steel has
properties and characteristics what we are looking for.
Here the material can contain chromium, nickel and
molybdenum to get the higher strength. Strength is a
most usable characteristic of the material. Another thing
is there are some grades. Among them AISI 1045 is used
in commonly. That material hardness can be increased
by heating about 820-850 ℃. In machinability
comparison chart, we can see that it has much higher
machinability that can be used for the cog wheel. Key
properties and values of the material AISI 1045 are
tabulated below and detailed values are in Appendix A
Mechanical property Values Thermal property Value
Hardness
Rockwell B
88 Specific heat capacity
(J/g℃)
0.486
Yield strength
(MPa)
515 Thermal conductivity
(W/mK)
51.9
Elastic modulus
(GPa)
206
Table 9: Properties of AISI 1045 steel
Here AISI 1045 medium carbon steel is mainly used for forging processes. But cast ability is
also available under limitations of it. Here under casting, we can discuss about the process further.
When we go towards the manufacturing process we can come to a conclusion that forging is much
better than casting. When we consider about types of forging there are mainly four types of forging
processes.
1. Impression Die Forging
2. Cold Forging
3. Open Die Forging
Table 2: Machinability comparison chart

4. Seamless Rolled Ring Forging
Impression Die Forging
Impression die forging presses metal between two dies that contain a precut profile of the
desired part. Parts from a few ounces to 60,000 lbs. can be made using this process.
Commonly referred to as closed-die forging, impression-die forging of steel, aluminum,
titanium and other alloys can produce an almost limitless variety of 3-D shapes that range in weight
from mere ounces up to more than 25 tons. Impression-die forgings are routinely produced on hydraulic
presses, mechanical presses and hammers, with capacities up to 50,000 tons, 20,000 tons and 50,000
lbs. respectively.
As the name implies, two or more dies containing impressions of the part shape are brought
together as forging stock undergoes plastic deformation. Because metal flow is restricted by the die
contours, this process can yield more complex shapes and closer tolerances than open-die forging
processes.
Most engineering metals and alloys can be forged via conventional impression-die processes,
among them: carbon and alloy steels, tool steels, and stainless, aluminum and copper alloys, and certain
titanium alloys.
Cold Forging
Most forging is done as hot work, at temperatures up to 2300 0
F, however, a variation of
impression die forging is cold forging. Cold forging encompasses many processes such as bending, cold
drawing, cold heading, coining, extrusions. The temperature of metals being cold forged may range
from room temperature to several hundred degrees.
Cold forging encompasses many processes bending, cold drawing, cold heading, coining,
extrusion, punching, thread rolling and more to yield a diverse range of part shapes. These include
various shaft-like components, cup-shaped geometry's, hollow parts with stems and shafts, all kinds of
upset and bent configurations, as well as combinations.
Open Die Forging
Open die forging is performed between flat dies with no precut profiles in the dies. Movement
of the work piece is the key to this method. Larger parts over 200,000 lbs. and 80 feet in length can be
hammered or pressed into shape this way.
Open-die forging can produce forgings from a few pounds up to more than 150 tons. Called
open-die because the metal is not confined laterally by impression dies during forging, this process
progressively works the starting stock into the desired shape, most commonly between flat-faced dies.
In practice, open-die forging comprises many process variations, permitting an extremely broad range

of shapes and sizes to be produced. In fact, when design criteria dictate optimum structural integrity for
a huge metal component, the sheer size capability of open-die forging makes it the clear process choice
over non-forging alternatives. At the high end of the size range, open-die forgings are limited only by
the size of the starting stock, namely, the largest ingot that can be cast.
Not unlike successive forging operations in a sequence of dies, multiple open-die forging
operations can be combined to produce the required shape. At the same time, these forging methods
can be tailored to attain the proper amount of total deformation and optimum grain-flow structure,
thereby maximizing property enhancement and ultimate performance for a particular application.
Seamless Rolled Ring Forging
Seamless rolled ring forging is typically performed by punching a hole in a thick, round piece
of metal (creating a donut shape), and then rolling and squeezing (or in some cases, pounding) the donut
into a thin ring. Ring diameters can be anywhere from a few inches to 30 feet.
Rings forged by the seamless ring rolling process can weigh < 1 lb up to 350,000 lbs., while
O.D.’s range from just a few inches up to 30-ft. in diameter. Performance-wise, there is no equal for
forged, circular-cross-section rings used in energy generation, mining, aerospace, off-highway
equipment and other critical applications.
Seamless ring configurations can be flat (like a washer), or feature higher vertical walls (approximating
a hollow cylindrical section). Heights of rolled rings range from less than an inch up to more than 9 ft.
Depending on the equipment utilized, wall-thickness/height ratios of rings typically range from 1:16
up to 16:1, although greater proportions have been achieved with special processing. In fact, seamless
tubes up to 48-in. diameter and over 20-ft long are extruded on 20 to 30,000-ton forging presses.
For this process we use impression die forging since it suits mostly to forge a part like this. At
the very outset we must get a bulk rod like part as our base material. Then the part should be subjected
to heat until it reaches red hot temperature. Then the forging is done. This is a hot forging process since
we supply heat to the process. The die which is mounted in the machine impacts with the red hot
medium carbon steel bar and the required basic shape is acquired.
When we consider about this process it is clear that we don’t need to provide very high compressive
loads since the steel rod is red hot. By using this process, we can reduce the time required in machining
and after making the die at the initial state the cost required is very low. When forging we should add
heat to the system until it reaches to a temperature range which has the upper limit at 220000
F to 17000
F. Forging processes align the grain of the metal through the use of massive pressure. Apart from that
the forged cranks are tougher and the durability of them are very high.
Since we are using hot forging the ductility of the component is increased. And also, we can obtain
homogenized grain structures too. But due to hot forging we have to face problems like less precise

tolerances and also reactions between metal and the surrounding atmosphere and some other
disadvantages too.
After the forging is done annealing is done since we have to machine he crank arm at the final stage.
Next the thing that is done is hardening the annealed crank arm. Full annealing of C1045 is carried out
from 1450-16000
F which is followed by furnace cooling at 500
c per hour to 12000
F by soaking and air
cooling. Then the crank arm is machined in order to obtain required shape exactly. Here what we do
under machining is not a complex process and we only use machining to obtain the exact dimensions
and finishing. And also, we can cut the thread of the inner hole of the crank arm in-order to fix the pedal
to crank arm.
Under machining some amount of unwanted material is also removed in-order to obtain a final product
that doesn’t weigh a lot. After that the hardening is carried out. This is carried out from and austenitizing
temperature of 1475-15500
F. The cooling media that is used is oil or water quenching. And also, this is
followed by the tempering process in order to reduce stresses in the case without affecting the hardness
of the crank arm.
There are several other processes that can be used apart from forging. The following are the most
common among them.
• Casting Process
• Machining process
When consider about the casting process, there are several advantages and also disadvantages
of casting too. When we compare this process with the selected hot forging process we have to add
more heat to the material since we need to melt the material. For casting processes, we have to make
a mould which contains a hollow cavity that has the required shape. Due to the shape of the bicycle
crank arm it is possible to make a mould which can use again and again by ejecting. But in most cases
the mould has to be broken in order to get the cast out. So, it is not cost effective and time effective to
make the mould again and again.
Since casting is a solidification process, most of the defects occur during the solidification.
Amidst them gas porosity and solidification shrinkage occur badly. In solidification it occurs in two
steps. First the nucleation occurs and then the growth of crystal occurs.
When consider about the grain macrostructure, in ingots and most castings there are three
distinct regions. They are the chill zone, columnar zone and the equiaxed zone. At the wall the chill

zone occurs and the nucleation phase of solidification takes place there. When more heat is removed
from the cast grains grow towards the center of the cast and those are thin long columns which are
perpendicular to the casting surface. They are undesirable since they consist of anisotropic properties.
Next the equiaxed zone (center area) contains spherical grains which are desirable due to isotropic
properties of them.
So, it is clear that the grain structure won’t remain the same all-over the casting. Due to that
the stress concentrations may occur and the part that is made becomes very brittle. And due to the
absence of aligned grain pattern, the toughness and strength of the cast is a little lower than forging.
And the final cast consist of a coarse surface and contains risers. So careful machining is required to
get the required final product. When consider about the castings there are several defects that we
should concern too. Amidst them the main types of defects are the gas porosity, shrinkage defects,
mould material defects, pouring metal defects and metallurgical defects can be given.
And also, the energy required to melt the material is very high comparing to the forging and
occurring of defects is also very high. So, it is better to use forging Apart from casting to produce the
pedal arm.
When we evoke our attention towards the machining process which can be used apart from
forging, it is one of the latest techniques. Here if we machine this bicycle pedal arm we have to use
CNC machines which can be operated by programmes that were developed using computers. There
are several advantages and disadvantages in here too. Other than machining using CNC we can use
hand operated machines too. But the main problems which occur there are that if we machine with
using the operators’ ability and talent the manufacturing process would cost a lot well practised
labouring and skilled operators. Apart from that the parts won’t be in exact sizes since deviations may
occur.
But if we consider about CNC machining then such problems won’t happen. The main
disadvantage which would occur there is that the cost of the machines is very high. And apart from
that it is a must that to use computer programmes in CNC as mentioned before. But these programmes
need operators with perfect knowledge about the software.
Apart from that the workpiece that is used for machining consists the row material and due to
that the improvement of grain structure which occur in the forging won’t occur hear. So, the hardness
of the part and strength of it will be less in the machined part. And the final cost of the production will
be higher in machined parts compared to the forged parts.
So, it is better to use hot forging to produce the bicycle pedal arm other-than machining or
casting.

Polymer process
What is a polymer?
Polymer is compound consisting of long chain molecules each molecule made up of 1000-
10000 repeating units connected together. Most polymers are based on carbon and are therefore
considered organic compounds. The common characteristics of polymers are
Advantages
• Low density
• Low coefficient of friction
• Good corrosion resistance
• Good mound ability
• Excellent surface finish can be obtained
• Can be produced with close dimensional tolerance
• Can be produced transparent or in different colors.
Limitations
• Economical
• Poor tensile strength
• Low mechanical properties
• Poor temperature resistance
Certain categories of polymers

Types of polymers that we discuss through this report are
1. Plastics
2. Rubber
Metal Plastic / Rubber using Shaping or forming process Possibility and
suitability
There are two components which we hope to manufacture by using metal plastic/ rubber using
shaping and forming processes. They are,
1. Gripper of bicycle pedal
2. Cover of cog wheel
In the following part we hope to discuss, why we select the polymer component and metal
plastic/ rubber using shaping and forming processes to manufacture above two components
separately. For that, we considered the characteristics and functionalities of each component and
how we can achieve them by using metal plastic/ rubber using shaping and forming processes.
Also, we discuss the reasons for improving and changing each parts from firstly designed and
original product of the project.
A. Gripper of bicycle pedal
In the first part of the project we used metal cover for design this part. But here we use rubber
grip instead of metal cover. Through this change we hope to achieve some benefits they are,
1) Light weight – Using rubber makes the weight lighter than using metal
2) High friction coefficient – Rubber has higher friction coefficient so it can make higher
resistance against slipping. If we use a metallic component it the surface is wet with

water or any other liquid there is more chance to slip. But rubber can give higher
friction force while it having a wet surface.
3) More comfort to foot – When we use rubber it is no need of smoothen the surface to
get more comfort to foot when ridding the bicycle. If we use a metal as mater
4) High ability to shock absorb – Rubber has a high ability to shock absorb more than
metal and plastic as it more elastic properties than metal and plastics
5) Fatigue resistance
Following are the properties which are expected further
• High resistance to wear
• Capability to rough use
• High strength
• Holes can be made easily
There can be found few types of rubber which can use to manufacture this product.
Rubber type
NBR
HNBR
EPDM
CR
ACM
AEM
SBR
AU/AE
FVMQ
NR
Strength G VG G G A G A G A VG
Compression
resistance
VG VG VG G P G G A G VG
Water swell
resistance
G G VG A P G VG P VG VG
Abrasion
resistance
G G G G G G VG VG P VG
Temperature
range
212-(-22)0F
300-(-22)0F
300-(-60)0F
250-(-40)0F
300-(-60)0F
300-(-40)0F
212-(-50)0F
175-(-60)0F
400-(-75)0F
220-(-60)0F

Advantages of Polyurethane
1. Wide range of Hardness – The hardness values of the polyurethane depend on the
polymer’s molecular structure and can be manufactures from 20 SHORE A to SHORE
D.
2. High load Bearing Capacity – Polyurethane can bear high load capacity in both tension
and compression. Also, polyurethane change its shape when it undergoes a heavy load
and return again to its original shape when the load is removed from the component.
3. Tear Resistance – Has high tear resistance along with high tensile properties.
4. Resistance to Water, Oil and Grease – polyurethane has a high ability to remain stable
or with minimum swelling in water, oil and grease.
5. Wide Resiliency Range – Has a wide range of rebound range. Resilience range of 10-
40% use to low rebound components as for shock-absorbing elastomer applications and
40-65% use to high rebound components as for high frequency vibration.
Polyurethane Type L42 L100 L167 L315
Hardness, Durometer Value
(ASTM d676-59T)
80A 90A 95A 75D*
Specific Gravity 1.07 1.10 1.13 1.21
Tensile Strength, MPa (psi)
(ASTM D412-61T)
20.7 (3,000) 31.0 (4,500) 34.5 (5,000) 62.0(9,000)
Elongation At Break, %
(ASTM D412-61T)
800 450 400 270
100% Modulus, MPa (psi)
(ASTM D412-61T)
2.8 (400) 7.6(1,100) 12.4(1,800) 32.0(4,650)
Compression Set, %
Method B (ASTM D395)
Method A (ASTM D395)**
45
-
27
9
40
10
-
10
Resilience, %
Rebound (Bashore) - 45 40 45
Abrasion Index, NBS, %
(ASTM D1630, Nat'l Bureau
of Standards Abrader)
110 175 400 435
Tear Strength Split, kN/m
(pli)
(ASTM D470)
12.2(70) 13.1 (75) 26.2 (150) 192.2 (110)

6. Capable for rough use and tropical environment – Polyurethane is stable in appreciable
temperature range, rough environment condition and many types of chemicals will not
cause material degradation.
7. Economical – Usually polyurethane used to manufacture a high volume, reiterate and
producing one product at one time (one iteration) of process products.
8. Available in various colors
Following are the Advantages of Polyurethane when compared to other material types
(Rubber, metal and Plastics)
With Rubber With Metal With Metal
High abrasion resistance
High cut & tear resistance
Superior load bearing
Thick section molding
Having color range
Oil resistance
Ozone resistance
Radiation resistance
Broader hardness range
Castable nature
Low pressure tooling
Lightweight
Noise reduction
Abrasion resistance
Less expensive fabrication
Corrosion resistance
Resilience
Impact resistance
Flexibility
Easily moldable
Non-conductive
Non-sparking
High impact resistance
Elastic memory
Abrasion resistance
Noise reduction
Variable coefficient of friction
Resilience
Thick section molding
Lower cost tooling
Low temperature resistance
Cold flow resistance
Radiation resistance
Following are the processes which can use to manufacture rubber
1) Extrusion
2) Injection molding
3) Compression molding
4) Transfer molding

1. Extrusion of rubber
The extrusion process begins with the unvulcanized rubber compound being fed into the extruder.
Next, the flutes of the revolving screw will begin to carry the rubber forward into the die, with an
increase in pressure and temperature occurring as the material gets closer to the die itself. Once it
reaches the die, the built up pressure forces the material through the openings, where it will
consequently swell in various degrees based on the material compound and hardness. Because of
this tendency towards swelling, many extruded parts require plus or minus tolerances on their cross
sections. During the vulcanization, the extruded rubber will well or shrink in both its cross section
and its length depending on the type of rubber compound used. After vulcanization, a length
of rubber extrusion will tend to be reduced in dimension more in the center of the length than in
the ends.
Extruded rubber products will differ from molded rubber products based on the process where
extruded parts are forced through a die of the required cross section under pressure of an extruder.
Often extruded products are unvulcanized prior to being extruded, leaving the rubber in a soft and
pliable state post extrusion. If this is indeed the case, the finished extruded products will normally
need to be vulcanized before they are rendered usable.

Extrusion Dies for Extruded Rubber
The extrusion die is a precise and specific tool made by cutting an opening shaped in the form of
the finished rubber cross section desired through a blank of steel. Once in place, the rubber material will
be forced through this die via the pressure that builds up from the revolving screw of the extruder. Many
rubber compounds will tend to swell when passing through the extrusion die, causing them to
experience an increase in dimensions. Thus, each die is made according to each particular part and
material to ensure that all tolerances are met for the finished extruded rubber part.
RMA Standards for Cross Sectional Tolerance Table — Rubber Extrusions
The closer tolerance classes outlined below should not be specified unless required to do so
by the final application and they should be restricted to the critical dimensions. The closer
tolerances demanded, the tighter the control must be exercised when the material is being extruded
and hence the higher the cost incurred.

Dimensions in millimeters
RMA Class 1 - High Precision 2 - Precision 3 - Commercial
Drawing Designations E1 E2 E3
Above Up to
0 1.5 ±0.15 ±0.25 ±0.40
1.5 2.5 0.20 0.35 0.50
2.5 4.0 0.25 0.40 0.70
4.0 6.3 0.35 0.50 0.80
6.3 10.0 0.40 0.70 1.00
10.0 16.0 0.50 0.80 1.30
16.0 25.0 0.70 1.00 1.60
25.0 40.0 0.80 1.30 2.00
40.0 63.0 1.00 1.60 2.50
63.0 100.0 1.30 2.00 3.20

Dimensions in inches
RMA Class 1 - High Precision 2 - Precision 3 - Commercial
Drawing Designations E1 E2 E3
Above Up to
0.00 0.06 ±0.006 ±0.010 ±0.015
0.06 0.10 0.008 0.014 0.020
0.10 0.16 0.010 0.016 0.027
0.16 0.25 0.014 0.020 0.031
0.25 0.39 0.016 0.027 0.039
0.39 0.63 0.020 0.031 0.051
0.63 0.98 0.027 0.039 0.063
0.98 1.57 0.031 0.051 0.079
1.57 2.48 0.039 0.063 0.098
2.48 3.94 0.051 0.079 0.126
Rubber injection molding
The rubber injection molding process starts with an uncured rubber ribbon stock that is fed into a rotating
screw of the injection unit. A controlled amount of material is pulled into the injection unit. Here the
material is plasticized to a target elevated temperature. The rubber material is then injected into the mold
cavity through a runner and gate system where it is held in the mold under high pressure and elevated
temperature to activate the cure system in the rubber compound (rubber is vulcanized). The cycle time
is established to reach an optimal level of cure. At the end of the cycle, the parts are removed or ejected
from the cavities and the next cycle begins.

In this process fist the raw material is completely converted into liquid form and in the manufacturing
process re solidification is done so the material properties are changed. The new material properties are
depend on cooling rate and design of the mold
Rubber Injection Molding Steps
1) Make ready the materials in injection unite to inject in to cavity.
2) Materials injected through runner system to the cavity.
3) Parts are cured in mold utile cure process is completed.
4) Finished rubber parts are removed from the mold .
Advantages of injection molding
• Handing of blank is completely eliminated.
• The mold is filled in a closed position so formation of flash is avoided
• Complex cavities and flow channels can be filled easily
• The curing time is very short
• Process can be fully automated
Disadvantages of injection molding
• The molds and machines are more expensive
• The process need greater technical knowledge.
• There are strong requirements for the rubber compound to have low viscosity and to be
homogeneous
• Gates and injection runners contain vulcanized rubber which must be discarded
• Limited parts cannot be produced.
Compression molding
The rubber compression molding process begins with a piece of uncured rubber which has been
performed to a controlled weight and shape. This preform is placed directly into the rubber mold cavity
prior to mold closure. As the mold is closed, the material is compressed between the plates causing the
compound to flow to fills the cavity. The material is held in the mold under high pressure and elevated
temperature to activate the cure system in the rubber compound (rubber is vulcanized). The cycle time
is established to reach an optimal level of cure. At the end of the cycle, the parts are removed or ejected
from the cavities and the next cycle begins.
During this process the material is subjected to high pressure and considerable temperature so the
material properties may change from the raw material. Due to increase of the temperature the strength

of the inner molecular bonds of the material is weaken and due to compression force they are arranged
in to new compacted formation which is more stronger and harder than before.
Advantages of compression molding
• The mold is simple and only requires relatively simple press and molds. It is an appropriate
method for short runs
• Allows manufacturing of composite products which contain non rubber reinforcing material
• Suitable for products with larger surface or larger spreading
• Can be used for rubber compound with high viscosity and poor flow properties
Disadvantages of compression molding
• the preparation of blanks and the insertion of blanks into the mold are time consuming
• complicated cavities are difficult to fill out completely
• Formation of flash is relatively high.
• Production rate is relatively low
Transfer molding
Transfer molding is a natural propagation in the development when attempting to limit the
disadvantages of compression molding. The blank is loads into a loading chamber and is then distributed
into several cavities. The rubber is squeezes out of the loading chamber by means of the closing
mechanism of the press itself, or with separate pistons into each respective cavity. Since the rubber is
forced to flow through channels and gates, preheating takes place in the rubber into each cavity will be
obtained and the formation of flash will be reduced to a minimum.
This process is relatively similar to compression molding process so the changes happen to the material
properties can be assumed similar to compression molding process.

Advantages of transfer molding
• Propagation of blanks and their handling is made considerably easier
• The preheating of the rubber reduces the curing time
• Since rubber is preheated it flows easier and fills the mold cavities more efficiently.
• The mold is closed when rubber is injected into the cavities which means that less flash is formed
and smaller dimensional variations of the product are obtained.
Disadvantages of transfer molding
• The mold are more complicated and more expensive
• Parts with textile inserts cannot be produced
• The method requires material that are relatively simple to process.
Selecting a better manufacturing process
Using above four processes the rubber grip which required for bicycle paddle can be manufactured but
Each of them have benefits and drawbacks.
To select a better manufacturing process for the manufacture rubber grip following features are mainly
considered.
• Cost
• Strength of the component
• Complexity of the manufacturing process
• We don’t need very high dimensional accuracy for this rubber grip

Let’s compare above processes one by one
Extrusion process
• The products which manufacture from this process have smooth surfaces but the rubber grip
which we want to manufacture is want some surface roughness to achieve friction forces.
• The hardness and the strength of the component which manufacture from this product is low than
products manufacture from compression molding and transfer molding.
• Low cost is a advantage of this process
Injection molding
• The main drawback of this process is high cost. We can’t waste more money for this rubber grip
as it is not a major component of our product.
• The product is not harder and stronger which like compression molding and transfer molding
• The process is somewhat complex.
• We need another process to achieve surface roughness which want to achieve friction forces.
• Molds and machines are more expensive and this process cannot continue for less number of
products.
Compression molding
• When consider our requirements and above processes this is the best product to manufacture our
rubber grip
• This process is simple and low cost it is a very good benefit
• We can achieve the shape and surface features from a simple mould
• As we use this process we can achieve high hardness and strength
Transfer molding
• This is a more advanced process like compression molding. As this process is more advanced
than compression molding this may take high cost than compression molding.
B. Cover of Cogwheel
There are many varieties of plastics can be seen. Through them we have to select one to
manufacture our component. In the process of manufacturing this component we have considered
some characteristic which would have the material of this component. They are,
▪ Light weight
▪ Resistance to water and sun light
▪ Medium strength

▪ Low cost
▪ Good appearance
When we consider above features we can select polystyrene as the material to manufacture this
product. Following are some features of polystyrene
▪ Light weight
▪ Hard
▪ Stiff
▪ Transparent
▪ Brittle
▪ Good water resistance
Types of Plastic Forming and Shaping Processes
1. Extrusion
In plastic extrusion method mostly used to manufacture a various type of components which
has a simple shapes with uniform cross section such as pipes, rods, tubing, cables and etc. the
extrusion method is similar to injection molding method. The raw materials such as pallets,
granules or powder placed into the hopper. The raw material flow through the feed throat of the
down part of the hopper into the due to the extruder’s barrel due to the gravity-fed. The barrel is
contain with a screw which has a three sections and it blends and convey to down the barrel by
melting raw material. The raw materials are melted in barrel by subjecting them to high
temperature. Feed section, Melt or transition section, Pumping section are the three section of a
screw part. The molten plastic forced in to the die through the screen pack and feed pipe. After
forcing the melted material into the die cavity, the material is then cooled by forcing through the
cooling chamber. The formed product exit through the die with having uniform cross section.

There are some specialty plastic extrusion processes such as blown film extrusion, Coextrusion,
Tubing extrusion and etc.
• Advantages of extrusion process
The extruded process is continuous
Has high production volumes
Low cost per pound
Efficient melting
Can be find many types of raw materials
Has a good mixing or compounding are some of the advantages
• Limitations of extrusion process
Has a limited complexity of parts
Can make uniform cross sectional parts
2. Injection Molding
Injection molding method is the widely used manufacturing process for making plastic
products. Various types of plastic products which vary in their sizes, complexity and application
greatly are produce using injection molding method. This method is same as the casting process
which used to form the metal components. The raw material which is in a form of powder or
granular is placed in to the hopper. By rotating the screw in the barrel forced the raw material
through a heaters. After the all materials has melted, the screw push the melted material into the
mould by acting as a ram in the barrel. The melted plastic material keep little time for cools and
solidifies.
• Advantages of Injection Molding process
o Wide variety of plastics can be manufactured
o Design flexibility
o Low operating cost
o Relatively low labor cost
o Good and smooth surface finish
o Uniform melting
• Limitations of Injection Molding process
o Highly investment and running cost
o High pressure involved
o Problems in designing molds
o Product quality depend on the contamination of raw material

3. Structural Foam Molding
The large structural plastic parts which can be used to replace wood, metals, fiber glass and
concrete are produced in structural foam molding process. It is also known as the low pressure
molding process. This process is same as the conventional molding process but here, the mixed
the melted material with an inert gas such as nitrogen in the barrel of the molding machine. This
plastic/ gas mixture is then injected into a mold using low pressure which is lower than the pressure
used in injection molding process. Therefore, the mold is not completely filled with mixture
material during the injection process. Due to the consistence of nitrogen gas in the melted material,
the gas/ polymer mixture expand and pack out the mold cavity. This process make a plastic
structure density reduce and rigid.
Advantages of Structural Foam Molding process
• Has high strength and stiffness
• Low warpage due to low stresses
• Impact resistance is high
• Low cost for molds
• Lower cost for materials
Limitations of Structural Foam Molding process
• Air trapped in mould causing the burning
• Bubbles are showing in the finished part due to the moisture
• Shrinkage occurs due to not enough plastic for moulding
• In the product surface, there are some marks due to unbalanced flow of mould in the
gates and runners
4. Blow Molding
In blow molding process, the air pressure around 25 – 50 psi is used to distend soft plastic into
the mold cavity. This process is very important to make thin walled, hollow plastic products such
as plastic bottles, containers and etc. The extrusion, injection and stretch blow molding are the
three main processes under blow molding processes.
Extrusion blow molding process – In this process, extruder barrel with screw part used to
make hollow, circular (usually) pipe with having a uniform cross section. To make molten plastic
material flow under gravity, the molten polymer is led through a right angle. Then, the circular

pipe (also called Parison) can be achieve vertically. The hollow mould is closed when the parison
has reached a sufficient length for the blowing process. The parison is cut at the top by using a
cutter or knife. The mold move to the second position and blow air into the parison to inflate it to
the shape of the mould. The inflated material is then cooled by keeping opened mold sideway.
Injection blow molding process – Injection blow moulding is used for the Production of
hollow objects in large quantities. The main applications are bottles, jars and other containers.
The Injection blow moulding process produces bottles of superior visual and dimensional quality
compared to extrusion blow moulding. The process is ideal for both narrow and wide-mouthed
containers and produces them fully finished with no flash. This process is used to following
materials
▪ Polyethylene
▪ Polypropylene
▪ Polyethylene
▪ Polyvinylchloride
▪ Polyethylene
Advantages of Blow Molding process
• Low cooling cost
• Fast production rate
• Ability to make complex shapes
• Can be recycling
Limitations of Blow Molding process
• Only for hollow parts
• Defects may be seen
• Thick parts cannot be manufactured
5. Compression Molding
This is a high volume, high pressure plastic molding method which use a preheated polymer
and opened, heated mold cavity. The preheated molding compound which having a higher volume
than the mold cavity volume is placed in a heated mold cavity. Mold is closed by its top half of
the mold cavity and pressure is then applied to force the material to fulfill mold cavity. Overflow

grooves use to remove the excess materials from mould. Heat and pressure are maintain until the
polymer has cured.
Advantages of Compression Molding process
• Low cost
• Uniform density
• Improve
• Impact strength
• Dimensional accuracy
• Short cycle time
• High volume production
Limitations of Compression Molding process
• Curing time large
• Uneven parting line present
• Scrap cannot ne reprocess
• High initial capital investment
6. Thermoforming
A plastic sheet which has greater length and width than the finished part is clamped to the
window type clamp frame and move it into an oven. The plastic sheet then heated to the forming
temperature for make it pliable and soften. After soften the plastic sheet, it can be formed into any shape
easily. Soften plastic sheet then placed into the mold (female and male type of molds) and produce final
shape of the product by interconnecting two mold parts. Vacuum forming, Pressure forming, Mechanical
forming are three types of thermoforming processes which vary according to their forming section type.
Advantages of Thermoforming process
• Flexible design
• Rapid prototype development
• High production rate
• Low set up cost
• Less thermal stress
Limitations of Thermoforming process
• Not eligible for thermosets
• All parts need to be trimmed

• Parts may non uniform thickness
7. Rotational Molding
Rotational molding is a thermoplastic process which used to manufacture a components which
are having a hollow parts. This process also called as rotomolding or rotocast. The raw material
(powder resin) is filled into the hollow mold cavity and the mold is then heated after closing the
mold cavity. The mold cavity rotate slowly on two axis. The mold undergoes to a cooling section
and cooled by using air or water usually after powder resin becomes fully melted.
Advantages of Rotational Molding process
• Give good surface finish
• Low pressure
• Thicker corers and stress free parts
• Very large parts possible
• Low mould and equipment cost
• Easy color and resin changes
• Easy mold changes
Limitations of Rotational Molding process
• Simple shapes only
• Poor dimensional tolerance control
• Generally thicker overall walls
• Slow molding cycles
• Low part mechanical properties

Since the Plastic cover of the cog wheel hasn’t any hollow shape and continuous cross section
it can be manufactured by using only following four processes. They are,
1. Injection molding
2. Compression molding
3. Thermoforming molding
4. Structural Foam molding
Following are the comparison of the above mentioned four processes to choose a suitable
forming process for this component.
Molding process Description
Injection
• Low operating cost
• Fast production Rate
• Good and smooth surface finish
• Highly Automated process
• Can make complex shapes

According to the above features most suitable processes are compression molding and injection
molding process. The structural foam molding process was eliminated because, plastic cover of
the cog wheel is not a large part and this process usually use to make higher volume parts.
According to above features injection molding is the better process to make this product. As it
takes low cost and we can make this one in fast rate. And we can achieve better surface finish
Compression
• Low cost
• Has uniform density
• Impact strength is high
• Cycle time is short
• High volume production
Thermoforming
• Low machine cost
• Low mold cost
• Fast mold cycle
• Strong and flexibility
Structural Foam
• Low cost tooling
• Large parts can be produce
• High flexibility
• High strength to weight ratio

Sheet metal process
Pedal cup
Here we are going to discuss about the making of pedal cup in the pedal axle. This cup is made by
using sheet metal. Therefore, sheet metal processes which is associated with the sheet metal
forming have to be discussed.
Here different types of sheet metal forming processes can be identified. They can be listed as,
• Shearing
• Bending
• Roll forming
• Deep drawing
• Spinning
• Stamping and etc.

Among of them, we have to remove some processes and have to select most suitable process for
doing this manufacturing progress. There is a cup shape of this item. further it has a threaded
portion inside this cup. So we have to focus our attention above mentioned two side of the pedal
cup.
Making a cup shape
Mainly, arranging a sheet metal part for the machining process with suitable dimensions have to
be discussed. Therefore, we have to prepare a die and blanking punch to separate circular shape
from the sheet. It will be the main step of making pedal cup. Place the sheet metal piece on the die
and then punch it from using the blanking punch. As we know, here shearing forming process has
been used. This method can be used for remove a blank of suitable dimensions for further
processing. This sheet metal part is subjected to shear stresses.
While there are many different types of shears, the basic process is the same. the application of
extreme pressure by a moving blade (shear or punch) pushing the workpiece against a fixed blade
(die or anvil). With advances in technology, high-volume shearing has extended beyond its cam-
driven roots and benefits from CNC advances.
Since shearing cuts without forming chips or burning or melting the material, the process works
well with most softer metals. However, it is less ideal with harder metals. For example, shearing
tungsten is simply a bad idea; because tungsten is extremely hard and often brittle, it can cause
delamination or fracturing of the tungsten part, as well as significant wear on the tool itself.
Perhaps the biggest advantage of shearing is that it produces minimal or no kerf, with virtually no
loss of material. However, shearing also has some notable disadvantages. It cannot be considered
burr free cutting since the force of the shearing action often creates burrs and end deformation. As a
result, it may not be the best choice for applications where a clean end finish is required. For larger
diameters with large clearance (i.e., separation between the blades), there may be heavy burring if
the parts twist or are not securely clamped in place during shearing.
After that we have to focus the area of deep drawing process and the spinning. Using both these
method, sheet metal can be form into cup shape. Deep drawing is one of the most popular metal
forming methods available to manufacturers. it involves the use of metal dies to form blank sheets
of metal into a desired shape. Specifically, if the depth of the item created is equal to or greater than
its radius, then the metal forming process can be called deep drawing. It is very Important method
which every engineer should know when they are in mechanical field.

Further we can identify how that process is done for the blank sheet metal. As well as shear
forming, die and puncher are used. According to the dimensions of pedal cup, die and puncher
should be made. Then put the blank sheet on the die and punch it using the puncher.
It is important to know about the benefits of the deep drawing. Deep drawing is especially
beneficial when producing high volumes, since unit cost decreases considerably as unit count
increases: once the tooling and dies have been created, the process can continue with very little
downtime or upkeep. Tool construction costs are lower in comparison to similar manufacturing
processes, such as progressive die stamping, even in smaller volumes; in these situations, deep
drawing may also prove the most cost-effective manufacturing solution.
When considering the functionality of the end product, deep drawing poses still more advantages.
Specifically, the technique is ideal for products that require significant strength and minimal weight.
The process is also recommended for product geometries that are unachievable through other
manufacturing techniques.
Deep drawing is perhaps most useful for creating cylindrical objects: a circular metal blank can
easily be drawn down into a 3D circular object with a single draw ratio, minimizing both production
time and cost. Production of aluminum cans is one example of a popular use of this method.
Squares, rectangles and more complex geometries may create slight complications, but are still
easily and efficiently created through the deep drawing process. Typically, as complexity of the
geometry increases, the number of draw ratios and production costs will increase.
one main disadvantage to the deep drawing process is that it isn’t valued as effective in small
quantities. The cost of press setup is remarkably high and requires significant experience and
expertise, rendering deep drawing more expensive for short runs. Generally, for deep drawn
production to be cost effective, the minimum order quantity should be in the hundreds. So to take
financial profit we have to manufacture this item in large scale.

There is another method to create a cup shape from a sheet metal. It is called spinning. Spinning
can be done using the lathe machine. Spinning can be known as spin forming or spinning or metal
turning most commonly, is a metalworking process by which a disc or tube of metal is rotated at
high speed and formed into an axially symmetric part. Spinning can be performed by hand or by a
CNC lathe. But we have to compare these two method of manufacturing cup what suitability is to
do.
When compare these two methods, it can be seen some suitability of using deep drawing process
to make pedal cup. They are, number of wrinkles, time per work piece, work on small workpiece
and financial profit. Let’s see one by one.
• At the spinning process, Roller force is acting in three directions tangentially, axially and
radial. But at the deep drawing process punch force is acting in downwards. It causes
wrinkles on the body of cup. But comparatively wrinkle defects is less at the deep drawing
process.
• Required time for the spinning process is higher than deep drawing per workpiece.
• For smaller components tooling and machining cost would be very high at the spinning rather
than deep drawing. So financial profit of the pedal cup making is higher at the deep drawing
process.
When considering the above compares, we can conclude that deep drawing process is more
suitable for making of pedal cup.
After the making of cup, inside threads should be created. That process is the final main process
of that. We have to do using metal forming too. In this part, we have to make die with threaded part
according to the pedal axle thread. Then the cup part is caught by arm and die goes into the cup.
Where die is stationary and arm come downward. When the threaded die and portion of the cup
which should be threaded, coincide with each other. Then the arm will rotate around die and it

causes some forging process to form a thread inside a cup. After the process we can see thread
inside the cup as well as outside of it.
We cannot be forming thread using lathe tool dynamometer. Because this is sheet metal and it
cannot grab using jaw-chuck of the lathe. It will undergo deformation and it cause scratch and holes
due to the sharp edge tools. So we can conclude that above mentioned method is the most suitable
method to form a thread of the pedal cup.
Rubber holder
This part is also made by using sheet metals. We can see that it has mostly v shape and
manufacturing process which is known as bending has been used to produce it. Additionally, there
are few holes on the surface of the body which are used to put the nut and tighten rubber grip to the
pedal body.
As mentioned above, we can use die and blanking punch to remove rubber holder part as well as
holes on the surface. For that progressive die can be used here. Because there are multiple
operations which should be done on sheet metal part. As mentioned in the pedal cup making
process, we make 3 –blanks and then remove the required shape part from the metal sheet. It will be
the first step of making of rubber holder. Dies, blanking punch and piercing punch should be used.
the Piercing punch is used to create holes. That process is called Perforating. And blanking punch is
used to remove required metal part from the sheet.
After that. We have to move the way of bending process. First of all, we have to know what
bending is. Bending is a manufacturing process that produces a V-shape, U-shape, or channel shape
along a straight axis in ductile materials, most commonly sheet metal. Bending processes differ in
the methods they use to plastically deform the sheet or plate. Work piece material, size and
thickness are important factors when deciding on a type of metal bending process. Also important is
the size of the bend, bend radius, angle of bend, curvature of bend and location of bend in the work
piece. Sheet metal process design should select the most effective type of bending process based on
the nature of the desired bend and the work material. Many bends can be effectively formed by a
variety of different processes and available machinery will often determine the bending method.
Here we are discussed about only three types of bending. Such that,
1. V bending
2. Edge bending with wiping die
3. Rotary bending
Now we can understand them at large,

V bending
One of the most common types of sheet metal manufacturing processes is V bending. The V
shaped punch forces the work into the V shaped die and hence bends it. This type of process can
bend both very acute and very obtuse angles, also anything in between, including 90 degrees.
Edge bending with wiping die
Edge bending is another very common sheet metal process and is performed with a wiping die. Edge
bending gives a good mechanical advantage when forming a bend. However, angles greater than 90
degrees will require more complex equipment, capable of some horizontal force delivery. Also,
wiping die employed in edge bending must have a pressure pad. The action of the pressure pad may
be controlled separately than that of the punch. Basically the pressure pad holds a section of the
work in place on the die, the area for the bend is located on the edge of the die and the rest of the
work is held over space like a cantilever beam. The punch then applies force to the cantilever beam
section, causing the work to bend over the edge of the die.

Rotary bending
Rotary bending forms the work by a similar mechanism as edge bending. However, rotary bending
uses a different design than the wiping die. A cylinder, with the desired angle cut out, serves as the
punch. The cylinder can rotate about one axis and is securely constrained in all other degrees of
motion by its attachment to the saddle. The sheet metal is placed cantilevered over the edge of the
lower die, similar to the setup in edge bending. Unlike in edge bending, with rotary bending, there is
no pressure pad. Force is transmitted to the punch causing it to close with the work. The groove on
the cylinder is dimensioned to create the correctly angled bend. The groove can be less than or
greater than 90 degrees allowing for a range of acute and obtuse bends. The cylinders V groove has
two surfaces. One surface contacts the work transmitting pressure and holding the sheet metal in
place on the lower die. As force is transmitted through the cylinder it rotates, causing the other
surface to bend the work over the edge of the die, while the first surface continues to hold the work
in place. Rotary bending provides a good mechanical advantage.
Then we have to select better bending process for the making of rubber holder. The rotary
bending process provides benefits over a standard edge bending operation, in that it eliminates the
need for a pressure pad and it is capable of bending over 90 degrees without any horizontally acting
equipment. Rotary bending is relatively new and is gaining popularity in manufacturing industry.
Therefore, we can also use rotary bending method for the edge bending of the rubber holder.

Assembling Process
When we consider about the bicycle pedal that we have designed assembling plays a vital role
since it is the thing that connects each part with other parts and make the pedal a system that can be used
to transmit power between the rider and the wheel. First let’s think the method of assembling the pedal
arm with the bicycle cog wheel. There we can use several processes. Amidst them, we can connect them
using
• Forging and using a key way
• Welding
• Using several screws and fix with them
If we don’t directly cast the whole part together; in other words, if we do not make the crank arm
and the chain ring as a one part we have to use one of the above method. There are several reasons why
we don’t make the whole part to be one. If we make the whole part to be one then the maintenance cost
and the material wastage when the part is damaged is very high. But if we make the two parts separate
we can overcome those problems.
So as the first method and the most appropriate method for our design we must use forging. Thing
is that since when riding the bicycle forge alone won’t be able to beat the thrust loads and especially the
torque provided by the rider. So, it is a must to use one or more key ways in order to increase the ability
to withstand the torque. Forging is required since it would stop the crank arm getting ejected from the
key. Due to the easiness and the less machining required it seems to be the best and most suitable method
to fix them together.
When we think about welding the crank arm with the cog wheel we can clearly understand that
the weld won’t bear the torque occurring while pedaling and also the material that we have chosen are
also different in two parts. So, welding two types of material may occur problems.
If we try to fix them using several screws then it is clear that we cannot do it with the design that
we have. We have to go for a more complex design when designing the arm of the cog wheel. The
material that requires will be higher and also cost for one pedal arm will also rise. As engineers we
always must try to use material effectively and when looking from the side of a cycler he would prefer
a bicycle which weighs a little. And also, there is a danger of screws driving out from the nuts and that
will cause accidents too.
So as a whole we can use a key way and forging to fix the pedal arm with the crank wheel.
To fix the pedal axel with the pedal arm we can use several methods too.

• By using a threaded edged pedal axel
• By welding
• By forging
If we concern about the first method in order to our point of view it is the best method to fix two
parts together.
In the pedal arm there is a thread which suits to this thread. We can fix the axel and remove
when necessary using this method and also in repairs it is very important to replace the smallest part
possible both in user’s side and environment side. This method provides room to replace this part only
when required.
If we use welding to fix these two parts with one another then the above-mentioned advantage
won’t be acquired. And also since the pedal arm is made of C1045 and the pedal axil is made of 316L
we cannot do weld due to the difference between the two materials. And due to the fatigue occur the
weld will easily break down and also due to the bending moment occur due to the application of force
by the rider.
Forging is also a good method to fix these two parts with each other. But the main problem in
forging is that if we forge it to pedal arm then they won’t be able to dismantle unless they are broken. If
one part wears off or break then the user will have to change the whole thing. So, such designs won’t be
good since these parts are highly stressed and face to fatigue. They won’t have a very high life and due
to that for the consecutive use of the production it is a must to let change and repair each part. So, the
best method to fix these two parts with each other is using a threaded axel.
When fixing the pedal with the pedal axil we have to place the balls in the right places and then we must
fix the pedal to axil tightly. The thing that we should think mainly I that we have to let freedom to the
pedal to rotate around the pedal axel. So, we cannot use welding or forging. If we use one of those
methods then the pedal won’t rotate. So, we can use two methods. We can use a fake nut and another
nut to do this purpose or we can forge the far corner after mounting the pedal on to the pedal axel.

The same problem which occurred occurs here too. If we forge after mounting the pedal on the pedal
axel when a replacement is required then the whole thing should be replaced. This is not practical and
also is not a sound manufacturing quality. So, we have to use other method.
As we can see the best method which allows the pedal to rotate on its axel and which allows
replacement is using a fake nut and another nut. Here what we do is fasten the fake nut not to be very
tight allowing the space between the nut and the pedal to rotate. Then we use another nut and fix that nut
tightly to the fake nut not allowing it to move. By this method we can replace or remove the pedal when
required and we can adjust the pedal as the user needs.
When we pave our attention towards the rubber part of the pedal it is fixed to the metal body of
the pedal with three screws. For that we can use riveting too. But it is more easier to maintain and replace
the rubber part when required if we use screws apart from rivets.
There are two more parts that should be assembled to complete the whole production. They are
the end cup for the axel and the plastic plate in the cog wheel. The purpose of the end cup is to prevent
water to enter in to the pedal and decay the balls and also to hold the lubricants inside the pedal body for
a smoother riding. For that we used a small thread in the cup to fix on to the pedal axel. We used this
method since it is necessary to eject this art when required to approach to the two nuts. If we used welding
we won’t be able to fulfill that target.
The other part is the plastic casing. To mount the plastic casing on the cog wheel we can use 5
screws and since that part is made out of plastic we cannot use other methods like welding or forging.
References

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pp. 131-140, 2006.
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APPENDIX A – Material properties data table
Table A.1: Different types of stainless steels
Table A.2: Steel Classification according to EN 10027-2. Design system for steel.

Table A.4: Properties of the 304 Stainless steel
Table A.3: Properties of AISI 1045

Table A.5: Properties of the 304L Stainless steel
Table A.6: Properties of the 316 Stainless steel

Table A.7: Properties of the 316L Stainless steel
Figure A.1: Process of investment casting

In designing the punching and blanking punch, here are the calculation
Volume of the pedal cup = 700.76 mm3
.
Selected sheet metal material thickness = 0.081 inch = 0.20574 cm
Area of the sheet material that use to produce pedal cup = 340.60 mm2
.
Radius of the blanking metal sheet = 10.40 mm
Die clearance = 0.012 inch = 0.03048 mm
So that punch radius = 10.39 mm
Die radius = 10.39 + 0.030 mm = 10.42 mm
Draft angle of the die = 0.5⁰
All these values have taken from industrial catalogs and from some research papers.

Figure A.2: Wax core model making mold
Figure 4: Final model that use to
make ceramic mold

Development of bicycle pedal part II

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