Final Project Report- Shreyas Gupta, IIT Guwahati

Final Project Report
Submitted by : Shreyas Gupta
Submitted to : Mr. N Jayaganthan (Group Manager, Machining)
Company : Royal Enﬁeld Motors
Academic Institute : Indian Institute of Technology, Guwahati
Date of Submission : 9 July 2015
Identification of Crankcases by
Model Sensing
Implementation of automatic program selection for
machining operation
Problem Details:
1. Introduction:  
Crankcases are machined in ‘Makino PS 65’ machines in sets of two. There are 4
different dies which are used to make a single type of component. This arises a need to
select different work offsets for each type of die. As two components are machined
together there are 16 different combinations of work offsets possible that might be used
for machining. To reduce the number of required offsets, workers sort and segregate
different components on the basis of their die number. This leaves them with 4 possible
combinations of work offsets. Now manually they select the program and work offset for
machining operation.
!1

2. Problem Description: 
Due to manual segregation and manual offset selection, there is a risk of machining
components with wrong offsets. Also there is an added need to segregate the components
in the ﬁrst place. Wrong machining of components causes rejection of the component as
well as reduces tool life and induces a risk of tool breakage.
!2
Makino PS 65 CNC Machine

Literature Review:
(Casting techniques : Evolution with time and their Limitations)
 
History
Casting processes were first used in the 3500 BC, nearly 5500 years ago. Since then, they have
improved significantly and many new type of casting processes have been introduced.
Casting process is one of the oldest metal forming processes known to humans. It essentially consists
of pouring molten metal into a refractory mold cavity and allowing it to solidify. The solidified object
is taken out from the mold either by breaking or taking the mold apart.
1500 years after it’s first introduction, amidst the Bronze Age in 2000 BC many refinements of the
casting process took place. One significant advancement being the use of cores for making hollow
sockets in the cast objects was invented. These cores were made form baked sand. Also lost wax
process, a type of investment casting process was extensively used for making intricate shapes and
ornaments.
Chinese further improved the casting process around 1500 BC, to make the perfect mold to the last
detail so hardly any finishing work was required on the casting made from the molds.
Fluidity
Fluidity of molten metal helps in producing sound casting with fewer defects. It is very important to
analyse the fluidity of the casting metal to produce sound casting with fewer defects like ‘misruns’.
Gating is important as the gating system performs the function to introduce clean metal into mold
cavity in a manner as free of turbulence as possible. To produce sound casting gate must also be
designed to completely fill the mold cavity to promote feeding for establishing proper temperature
gradients.
To fill the complicated castings sections completely, flow rates must be high but not so high as to cause
turbulence.
Types of casting techniques and their limitations
1. Sand Casting
Sand casting is the earliest type of casting technique that was invented by humans. In this method
molds are made from sand. Sand casting can be used to make very big and heavy castings like diesel
!3

engine blocks. Sand casts are cheap to produce and have to be produced for each new casting as they
are destroyed each time. It is extensively used to make large machine components which are not
possible to be casted by other techniques. Sand casting process is however limited to castings of thick
walled and high volume objects. It does not produce a good surface finish. Also, as each sand mold is
made individually, maintaining high consistency becomes a challenge. Due to this limitation there is a
need to provide high tolerances for shrinkage, machining, etc. Hence it is not suitable for making
smaller mass scale components or components with thin walls. Sand casting although cheap, requires
a large floor area and time for carrying out the process. Hence it is not suitable for casting of
crankcases.
2. Permanent Mold Casting
Also known as gravity die casting, permanent mold casting makes use of a mold or metallic die which
is permanent. Molten metal is poured into the mold under gravity only and no external pressure is
applied to force the liquid metal into the mold cavity. The metallic mold can be reused many times
before it is discarded or rebuilt. These molds are made of dense, fine grained, heat resistant cast iron,
steel, bronze, anodised aluminium, graphite or other suitable refractoriness. The mold is made in two
halves in order to facilitate the removal of casting from the mold.
Advantages:
1. No blow holes exist in casting of this kind.
2. This process is economical for mass production
3. Close dimensional tolerance or job accuracy is possible to achieve on the cast product.
4. Good surface finish and surface details are obtained.
5. Casting defects observed in sand castings are eliminated.
6. Fast rate of production can be attained.
7. The process requires less labor.
Gravity casting is one of the suitable methods that can be used to cast crankcases.
3. Pressure Die Casting
Unlike permanent mold or gravity die casting, molten metal is forced into metallic mold or die under
pressure in pressure die casting. The pressure is generally created by compressed air or hydraulically
means. Also this pressure is maintained till the casting solidifies.
Die casting is widely used for mass production and is most suitable for non-ferrous metals and alloys
of low fusion temperature. The casting process is economic and rapid. The surface achieved in casting
!4

is so smooth that it does not require any finishing operation. The material is dense and homogeneous
and has no possibility of sand inclusions or other cast impurities. Uniform thickness on castings can
also be maintained.
There are two general types of molten metal ejection mechanisms adopted in die casting setups which
are:
(i) Hot chamber type:
The process requires high temperature to be maintained in the casting chamber. Due to high
temperature relatively less pressure is required to force the liquid metal into the die.
The sprues, risers, runners, gates and vents are machined into the parting surface for one or both
mold halves. The runner channels are inclined, to minimize turbulence of the incoming metal. Water
passages in the mold or cooling fins made on outside the mold surface are blown by air otherwise
water mist will create chilling effect. A chill is commonly used to promote directional solidification.
(ii) Cold chamber type:
Cold chamber die casting process differs from hot chamber die casting in following respects.
1. Melting unit is generally not an integral part of the cold chamber die casting machine. Molten
metal is brought and poured into die casting machine with help of ladles.
2. Molten metal poured into the cold chamber casting machine is generally at lower temperature as
compared to that poured in hot chamber die casting machine.
3. For this reasoning, a cold chamber die casting process has to be made use of pressure much
higher than those applied in hot chamber process.
4. Lower temperature of molten metal accompanied with higher injection pressure with produce
castings of dense structure sustained dimensional accuracy and free from blow-holes.
5. Die components experience less thermal stresses due to lower temperature of molten metal.
However, the dies are often required to be made stronger in order to bear higher pressures.
Advantages of Die Casting
1. Quick process
2. Used in mass production
3. Improved surface finish
4. thin sections can be easily casted
5. Good tolerances
6. Less floor space required
7. Economic process
!5

8. High life of die
9. Consistent dimensions of castings
Disadvantages
1. Only thin castings can be produced
2. High skill labor is required
3. Unless special precautions are adopted for evaluation of air from die-cavity some air is always
entrapped in castings causing porosity.
4. It is not suitable for low production.
Selecting the best and most suitable method
We have established with above explanations that Pressure die casting and Permanent die casting are
two suitable techniques for crankcases.
They have several advantages over sand casting. They are:
1. Die casting requires less ﬂoor space in comparison to sand casting.
2. It helps in providing precision dimensional control with a subsequent reduction in machining cost.
3. It provides greater improved surface ﬁnish.
4. Thin section of complex shape can be produced in die casting.
5. More true shape can be produced with close tolerance in die casting.
6. Castings produced by die casting are usually less defective.
7. It is very quick process.
8. Its rate of production is high as much as 800 casting / hour.
Clearly sand casting is not suitable for casting crankcases for the engines due to all the limitations
associated with it.
This leaves us to choose between Permanent mold casting and Pressure die casting.
!6

Comparison between these two processes:
Conclusion
Considering the points of floorspace, surface finish and production rate it is more suitable to use
Pressure die casting as the process for casting of crankcases.
Also, specifically Cold_Chamber PDC is more suitable considering the size of castings to be produced
and the production rate required to meet the demands.
Even though PDC is a very precise process and 2 different crankcases produced from 2 different dies
will have minor differences in offsets leading to the fact that the dies are not 100% identical. Also, due
to this reasons different off-sets for machining are required.
Permanent Mold Casting Pressure Die Casting
Dies are less costly Dies are costlier
Relatively more floor area required Relatively less floor area required
Surface finish is good Surface finish is very fine
Less skill required Higher skill required
Production rate is lower Production rate is significantly higher
Suitable for small and medium sized castings Suitable for small sized castings
S. No. Casting
Process
Uses/Applications Limitation
1 Sand Casting Big machine components,
fixtures, engine blocks
Slow, Surface finish not good, not suitable
for thin walled castings
2 Lost Wax
Process
Ornaments, complex shapes, Slow process, costly in mass production,
not suitable for thin walled castings
3 Permanent
Mold Casting
Carburetor bodies, oil pumps,
connecting rods, pistons
Surface finish is not upto requirement,
Production rate is low
4 Centrifugal
Casting
Wheels, cylindrical components,
boilers
Only symmetrical components can be
casted
6 Shell Mold
Casting
Bushing, valve bodies, rocker
arms, bearing caps, gears
Slow process, not suitable for thin walled
castings, expensive
7 Continuous
Casting
Blooms, billets, slabs, sheets,
copper bars
Shapes of only uniform cross-section can
be produced
8 Pressure Die
Casting
Crankcases, connecting rods
and automotive parts, gears,
High volume production
High initial cost of investment, unsuitable
for low production volume
!7

Solution to the Problem:
The problem can be solved with automatic detection of die number and auto selection of the work
offsets. The idea is to make extrusions or projections at 2 different positions of the crankcases. Further
use these 2 projections to identify the die number using 2 sensors.
!8
ISA2 Series Air Catch Sensors

By developing a binary logic for each sensors, 2 sensors can successfully identify 4 different kinds of
dies. This works on the principle of a digital signals as (00, 01, 10, 11).
Essentially this means with 4 sensors both components of 2 ﬁxtures can be individually identiﬁed,
eliminating the need for segregation of components.
Once the program receives the macro-variables from the sensor’s I/O, it calls different work offsets
from pre-loaded 16 offsets. Once the program receives the offsets, its starts machining the components
without error and reducing the risk of machining wrong components.
Furthermore in the event of a blockage of a sensor, the program can automatically trigger an alarm as
each blockage will give an independent signal as there is a single pressure hole for the sensor.
Sample program to explain macro-variables and auto program selection.
Value Stores to #900: X39.0 to X39.4 Input status
Parameter:
14425: Component selector Exist
0: NOT Exist
1: EXIST
Default Value: 0
14425 1 Program Selection exists
14426: COMPONENT SELECTION ENABLE
0: NOT IGNORE
#900 X39.3 X39.2 X39.1 X39.0
0 0 0 0 0
1 0 0 0 1
2 0 0 1 0
3 0 0 1 1
4 0 1 0 0
5 0 1 0 1
6 0 1 1 0
7 0 1 1 1
8 1 0 0 0
9 1 0 0 1
10 1 0 1 0
11 1 0 1 1
12 1 1 0 0
13 1 1 0 1
14 1 1 1 0
15 1 1 1 1
!9

1: IGNORE
Default Value: 0
14426 1 for through Component selector
14025: ROYAL ENFIELD AIRSEAT INPUT UPDATE TO
#900n0:ENABLEn1: DISABLE 0: Enable (update to #900)
1: Disable (Not update to #900)
Default Value: 0
14425 0 for Air seat through Component selector
14026: Component Selection PROGRAM Number Conﬁrm with Button
0: NOT IGNORE
1: IGNORE
Default Value: 0
O0150
G28G91Z0
G28G91Z0Y0
G53
#500=#900
GOTO [#500+10]
G04X4.
N10 [DIE 1]
G04X0.1
M30
N11 [DIE 2]
G04X0.1
M30
N12 [DIE 3]
G04X0.1
M30
N13 [DIE 4]
G04X0.1
M30
N14 [DIE 5]
G04X0.1
M30
N15 [DIE 6]
G04X0.1
M30
N16 [DIE 7]
G04X0.1
M30
N17 [DIE 8]
G04X0.1
M30
N18 [DIE 9]
G04X0.1
M30
N19 [DIE 10]
!10

G04X0.1
M30
N20 [DIE 11]
G04X0.1
M30
N21 [DIE 12]
G04X0.1
M30
N22 [DIE 13]
G04X0.1
M30
N23 [DIE 14]
G04X0.1
M30
N24 [DIE 15]
G04X0.1
M30
N25 [DIE 16]
G04X0.1
M30
%
Conclusion
With all these modifications to the machining operations, there are many improvements over manual
machining can be achieved, they are:
1. Reduce the number of rejections to the lowest possible.
2. Reduce the risk of tool breakage and increase tool life.
3. Eliminate the segregation and sorting process of crankcases.
4. Reduce manpower requirement.
5. Improve production speed and efficiency.
6. Have multiple combinations to machine crankcases depending on die number.
7. Reduce human intervention in program selection and identification, hence reducing overall risk of
wrong program selection.
!11

Final Project Report- Shreyas Gupta, IIT Guwahati

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