STUDY OF THE BEHAVIOR OF VARIOUS MILD STEEL GRADES DURING THE MACHINING PROCESS USING A CNC TURNING MACHINE
Introduction
Mild steel grades, such as EN8 and
EN24, are widely used in industries like automotive, aerospace, and
construction due to their excellent machinability, weldability, and
affordability. To meet the increasing demand for high-precision and
high-quality mild steel components, it is essential to understand their
machining behaviour. This project aims to investigate the machining behaviour
of EN8 and EN24 mild steel grades during the turning process using a CNC
turning machine, evaluating the effects of cutting speed, feed rate, and depth
of cut on cutting forces, surface roughness, and tool wear.
How CNC Machines Works
CNC (Computer Numerical Control)
machines are automated machining tools controlled by a
computer that executes pre-programmed sequences of machine control commands.
They are used in manufacturing to produce precise and complex parts with high
accuracy and efficiency.
1) Design & Programming –
A CAD (Computer-Aided Design) model
is designed and translated into a CAM (Computer-Aided
Manufacturing) file.
2) G-Code Generation – The CAM software
compiles into G-code,
a programming language that directs the motion of the
machine.
3) Machine Execution – The CNC machine
interprets the G-code and moves in accordance with the programmed instructions
to produce the desired shape or part.
Types of CNC Machines
CNC (Computer Numerical
Control) machines are computer-programmed, automated machining devices. Following are
the primary categories of CNC machines
A. CNC Milling Machine – Employing rotating cutting tools
to remove materials.
B. CNC Lathe – Spins the workpiece while
cutting tools form it.
C. CNC Router – Suitable for cutting plastic,
wood, and soft metals.
D. CNC Plasma Cutter – Employing
a high-temperature plasma
torch to cut through metals.
E. CNC Laser Cutter – Utilizes a laser beam to cut accurately.
F. CNC Electrical Discharge Machine – Employs electrical sparks to form materials.
Materials Used
EN8 Steel: EN8 is a medium-carbon steel containing about 0.40% carbon. It is
extensively used in cases where
there is moderate tensile strength and excellent machinability.
EN24 Steel: EN24 is a steel alloy with high carbon, containing approximately
0.40% to 0.50% of carbon. It contains alloying elements of chromium,
molybdenum, and nickel, which impart superior mechanical properties to EN8,
including greater tensile strength, hardness, and resistance to fatigue.
Cutting Tool
The cutting tool employed in this project
is a 0.8 mm nose radius tungsten
carbide insert with a clearance angle of 7°. The cutting tool
is held on a tool holder and fixed on the CNC turning machine.
CNC Turning Machine Setup
CNC turning is done on a Computer
Numerical Control (CNC)
lathe machine. The lathe can control cutting parameters like spindle speed,
feed rate, and toolpath direction.
1.
Tool Material: Carbide inserts
are utilized because
they have high wear resistance and can accommodate
the high temperatures that are developed during machining.
2. Cutting Fluids: A coolant (typically an oil-based emulsion) is employed to minimize friction and heat generation during cutting.
Experimental Procedure
1. Choosing the machining parameters, including cutting speed,
feed rate, and depth of cut.
2.
Workpiece preparation by machining it to the required length
and diameter.
3.
Mounting the cutting tool on the tool holder
and fixing it to the CNC turning
machine.
4.
Securing the workpiece on the CNC turning machine
by a chuck or collet.
5.
Plugging the sensors and measuring devices
into the CNC turning machine
and workpiece.
6.
Mounting the temperature sensor
on the workpiece and cutting
tool.
7.
Conducting the experiment with the chosen
machining parameters.
8. Measuring the response variables, including cutting forces, surface roughness, and wear on tools.
Result
The
findings of the research show that the machining characteristics of EN8 and EN24 mild steel
grades are greatly influenced by the machining parameters. The best machining parameters for EN8 mild steel grade were determined to be a cutting speed of 150m/min, feed rate of 0.2 mm/rev,
and depth of cut
of 1.5 mm. Similarly, the best machining parameters for EN24 mild steel grade
were established as a cutting speed of 120 m/min, feed rate of 0.15 mm/rev, and
depth of cut of 1.2 mm.
Conclusion
Finally, in this study, the
machining behavior of EN8 and EN24 mild steel grades has been examined during
turning using a CNC turning machine. The findings have demonstrated that the
machining characteristics of the steel grades are influenced to a large
extent by the machining parameters. The optimum machining parameters for the different
steel grades have been determined, and the findings can be utilized for optimizing the machining process
for increased productivity and quality of the product. The research has added knowledge
on the machining characteristics of the mild steel grades and has presented
useful information for industry practitioners.
Author Bios:
1. S. Mohankumar, - AP/Mech,
2. S. Sanjai, – IV Mech
3. S. Srirooban, – IV Mech
4. B. Vihash, – IV Mech
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