Developing an experimental set up for measurement of cutting temperature in Turning Operation

Developing an Experimental Set
Up for Measurement of Cutting
Temperature in Turning
Operation
Presented By:
1. AMIT KUMAR
2. ANKIT RAIPURIA
3. ARPIT KUMAR GAHLOT
4. HIMANSHU KUMAR SINGH

Motivation
 In machining process, the importance of knowledge of the tool temperature in cutting
tools is well recognized as temperature has a critical influence on tool life and work
piece surface integrity.
 High temperature generated leads to many problems like built-up-edge formation,
reducing the shear strength, dimensional inaccuracy of the work piece, surface damage
by oxidation, rapid corrosion and burning, rapid tool wear which reduce tool life.
Problem Definition
Developing an experimental set up for measurement of cutting temperature in
turning operation
Goal Statement
To accurately predict the temperature in turning operation.

Performance Specifications
 Common thermocouple parameters are:
 Coating Material
 Operating Range
 Thickness of coating
 Sensor Parameters:
 Rise time
 Setting time
 Heating at tool tip during cutting operation using single-point cutting tool depends upon the
following factors:
 Feed Rate
 Depth of cut
 Cutting Velocity
 Friction
 Sources of error:
 Chatter at tool tip
 Cutting fluids
 Chip formation

Literature review
The main techniques used to evaluate the temperature during machining (tool–chip
thermocouple, embedded thermocouple, and thermal radiation method) are shown in figure.
Thermocouples have always been a popular transducer used in temperature
measurement. Thermocouples are very rugged and inexpensive and can operate over a wide
temperature range.
Standard thermocouples embedded in the cutting tool or workpiece material can be used to
measure the temperature at a single point or at different locations to establish the
temperature distribution in the tool.

Thermocouple
• A Thermocouple is a sensor used to measure temperature. Thermocouples consist of two
wire legs made from different metals. The wires legs are welded together at one end,
creating a junction. This junction is where the temperature is measured. When the
junction experiences a change in temperature, a voltage is created. The voltage can
then be interpreted using thermocouple reference table to calculate the temperature.
• There are many types of thermocouples, each with its own unique characteristics in terms of
temperature range, durability, vibration resistance, chemical resistance, and application
compatibility. Type J, K, T, & E are “Base Metal” thermocouples, the most common types of
thermocouples. Type R, S, and B thermocouples are “Noble Metal” thermocouples, which are
used in high temperature applications
We will use type K thermocouple due to following
reasons
• High temperature measuring range
• Type K thermocouple are inexpensive
• Type K thermocouple are accurate
• Type K thermocouple are reliable

Specification of type K thermocouple
Temperature Range:
• Thermocouple grade wire, –454 to 2,300F (–270 to 1260C)
• Extension wire, 32 to 392F (0 to 200C)
• Melting Point, 2550°F (1400°C)
Accuracy (whichever is greater):
• Standard: +/- 2.2C or +/- .75%
• Special Limits of Error: +/- 1.1C or 0.4%
• Chromel {90% nickel and 10% chromium}
• Alumel {95% nickel, 2% manganese, 2% aluminium and 1% silicon}
Composition of type K thermocouple

Schematic and Construction
Sequence of coating-substrate
thermocouple fabrication, (a)
part of coating was removed
and two pieces of wire were
adhered (different wires are
used) (b) to fix the coating-
substrate thermocouple on tool
holder
Mica is used for insulation.
Much research has been
done on proper coating to be
used for thermocouples.
However, proper prediction of
temperatures is an incumbent
challenge.

Experimental Setup
 Schematic representation of the coating-substrate thermocouple
The cutting experiment is performed
with a turning lathe. A general overview
of the experimental setup is shown in
alongside. Tool and work piece are
insulated from the machine tool. The
coating-substrate thermocouple is
mounted on the tool holder. The
electric signals can be translated from
the sensor to computer through the
amplifier and A/D convertor. This
experiment is an oblique cutting test.

Developing an experimental set up for measurement of cutting temperature in Turning Operation

Thermocouple
 Ease of experimental
setup
 Capable of notifying
temperature at various
points without changing
setup
 Can be used for
processes like grinding,
drilling, milling, etc.
 Temperature of surface
cannot be measured
directly.It is a
destructive technique
 Cannot be used for
processes like grinding,
drilling, milling, etc.
 For making observation
at different point, setup
is required to be
rearranged after
stopping the machining
Tool-Work Transverse Embedded

Use of thermocouples
1. Tool-work thermocouple has always been a
populartooltobeusedintemperaturemeasurements
duringmetalcutting
2. Thermocouplesareconductive,ruggedandinexpensiveandcanoperate
over a wide temperature range.
3. In machiningapplications,athermoelectricemfisgeneratedbetween
thetoolandtheworkpiece.Withthesemethod,the
entiretoolisusedasapartofthethermocoupleandthe
workpieceastheotherpart.
4. Thecuttingzoneformsthehotjunctionwhileacoldpartofthetoolandthework
pieceformsthecoldjunction.Thistechniqueiseasyto
applybutonlymeasuresthemeantemperatureoverthe
entirecontactareaoftoolandworkpiece.

Factors in temperature measurement
 For HSS tools, during machining of steel
based alloys, O’ Sullivan and Cottrell
found that an increase in cutting speed
resulted in a decrease in cutting forces
and machined surface temperatures.
This reduction in temperature was
attributed to the higher metal removable
rate which carried more heat being carried
away by the chip
 Kurimoto cut low alloy engineering steel using
cemented carbide tool over a range of speeds. The
results showed that the chip-tool interface
temperature increased with increasing cutting
speed during machining. Cutting fluids reduced
the mean chip-tool interface temperatures in relation
to the dry cutting
The friction on the
flank face has a big influence on the heat
generated
Cutting often employs various lubricants
such as wet and dry type, emulsifiers and
SAE-oils.

Graph of temperature variation during
cutting and cooling for HSS cutting tool

Graph of temperature variation during cutting
and cooling for carbide cutting tool

Prototype components
Cutting tool material - heat treated Iron
tool signature –
10, 20, 7, 6 ,8 ,15 ,1/32
Thermocouple used - type k
Binding agent - mica strip coating
MAXIMUM TEMPERATURE RANGE
Thermocouple Grade
– 328 to 2282°F
– 200 to 1250°C

Datasheet of type K thermocouple

Tool-Thermocouple Interface
 Insertion of thermocople hot junction: Since this must be as close as possible to the insert
tool, generally a small hole is made in th holder through which wire penetrates. In case of
single attachment tools, an external insert is necessary.
 Insulation of thermocouple junction from other metallic contact: This is usually done by
providing insulation with mica or ceramic. Certain industrial glues have sufficient strength to
be used for directly attaching the junction. For example, the glue DB5015, has thermal
resistane within temperatures from -40 °C to 1220 °C. The DB5015 glue is a composite of
silver powder and abio-aluminate. The shear strength of the glue is 7.42 MPa.
 Cold-junction contact with workpiece: A popular method in literature is using mercury baths
with a wheel attached to the spindle for maintaining electrical contact during motion of
workpiece.
 Instead, we propose to use Hall-Effect sensors during machining. Hall Effect sensors are
routinely used as very accurate sensors for proximity sensing. They generate small
currents/emf when some object with corresponding mating magnet comes very close. We
propose using a metal junction and a magnetised T-slot. As the workpiece will move ahead,
the cold junction will remain at nearly constant potential. A small battery powered external
There are three main challenges to thermocouple setting:

Analysis and Limitations
 Data Aquisition and Plotting
 FEM is the most popular method for modelling heat affected zones.
 A sampling rate of 5-10 per second is minimum requiremnet for precise readings
 Thermocouples do not work properly with alloys and materials with low
conductivities.
 Calibration of tool-work piece pair is difficult.
 Limited transient response time

Concluding Remarks
The tool-work thermocouple measurement technique is an economic and fairly accurate technique
of temperature measurement. However, this technique is not universal and has its limitations.
An IR pyrometer can be used in conjugation with the above apparatus to obtain better results.
Thermocouples are prone to stress , strain and corrosion, particularly as they age.
These thermocouples used generally suffer from a standard error of Standard: ± 2.2C% or ±.75%
The chromel element is subject to what is known as "green rot." When this happens, the chromium
becomes oxidized and turns green and corroded. This occurs in reduced oxygen environments from
815° to 1,040°C. Such depleted-oxygen environments are called reducing, and K-type
thermocouples should never be used in either reducing or cyclically oxidizing and reducing
atmospheres e.g presence of carbon and graphite in coolant. In such cases, tool-work type of setup
is not accurate. Embedded sensors are preferred in such circumstances.

Developing an experimental set up for measurement of cutting temperature in Turning Operation

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Developing an experimental set up for measurement of cutting temperature in Turning Operation