BENG (HONS) MECHANICAL/ELECTRONICS & ELECTRICAL ENGINEERING IN COLLABORATION WITH THE UNIVERSITY OF SUNDERLAND MANUFACTURING PROCESS EAT227 Workshop Topic: MACHINING PROCESSES
Submitted by: Ho Kim Xiang UOS ID: SCSJ-0018699 Date:
EVALUATION: INTRODUCTION & OBJECTIVES THEORY PROCEDURES RESULTS DISCUSSION CONCLUSION REPORT PRESENTATION OVERALL MARK
10 marks 15 marks 15 marks 15 marks 15 marks 15 marks 15 marks 100 Marks
Name and signature (of evaluator): …………………………………………….
MACHINING Operations - Turning and drilling Introduction & Objective 1
To machine a closed die for powder metallurgy part. To produce a high accuracy workpiece. To complete the workpiece in the most simplest and effective way.
Material
Mild Steel cylindrical rod 25 mm diameter & 100 mm long. Mild Steel cylindrical rod 25 mm diameter & 53 mm long.
Tools Required Steel Rule, Marking knife, Vernier callipers, Chuck Key, Cutting tool, Drilling tool, Lathe machine.
Operations Required 1. Job setting
2. Facing
3. Plane turning
4. Marking
5. Stepping
6. Edge cutting
7. Resetting
8. Finishing
9. Drilling
10. Inspection
Theory 1. Orthogonal cutting
The cutting edge is straight. It is set in a position that is perpendicular to the direction of primary motion. This allows us to deal with stresses and strains that act in a plane.
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Cutting forces :
Total cutting force F is conveniently resolved into horizontal component FC and
vertical component FD. Cutting force FC is in the direction of primary motion. The cutting force formed about 70~80 % of the total force F and is used to calculate the power P required to perform the machining operation, P = Fc x V .
Thrust force FD is in direction of feed motion in orthogonal cutting. The thrust force is used to calculate the power of feed
The cutting horsepower =
Fc x V Hp c = 33000
motion.
2. Oblique cuttiing The cutting edge is set at an angle (the tool cutting edge inclination λs). This is the case of three-dimensional stress and strain conditions.
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Cutting Force :
Extra one force component appears along the third
axis. Thrust force FD is further resolved into two more
components, Feed force Ff is the direction of feed motion. Back force Fp is the other perpendicular to it and to the cutting force FC , which is in the direction
of the cutting tool axis. Fc > Ff > Fp (100% > 40-50% > 25%) 2 2 2 Cutting force = √ Fc + Ff + Fp
Cutting force per unit area = k c
Power of machine =
Rotational speed = N =
4
PC
= V πDo
Feed rate = Fr = N x f
=
Fc x V c 60
Fc Ac
L fr
Time of machining = T m =
Material Removal Rate = MRR = vfd
3. Cutting Temperature Nearly total energy consumed in machining converted into heat. High temperature will reduce tool’s life and cause dimension error in the machined surface. Heat generated is shared by the chip, cutting tool, and the blank. 10-20 % of the total heat goes into the tool and some heat is absorbed in the blank.
Primary heat source – Major part of energy is
converted into heat. Secondary heat source – Further heat is generated at the chip due
to shear. Heat loss – Friction between the chip and tool on the tool flank.
3 Modes of Tools Failure
Fracture failure – Brittle fracture will occur, when the cutting force is exceeded the tool point.
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Temperature failure - This failure occurs when the cutting temperature is too high for the tool material, causing the material at the tool point to soften, which leads to plastic deformation and loss of the sharp edge.
Gradual failure - Gradual wearing of the cutting edge causes loss of tool shape, reduction in cutting efficiency, accelerated wear, and final tool failure in a manner similar to a temperature failure.
Taylor Tool Life Equation n Vx T =C
V = Cutting speed, T = Tool life, n & C = constant and their values are depend on feed, depth of cut, work materials, tool material, and tool life criterion used.
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4. Drilling Is a metal removal process where part of metal is removed using a twisting motion with large force exerted against the workpiece; which causes shearing and extrusion of material chip out of the created hole.
Principle of drilling
The rotating edge of the drill exerts a large force on the workpiece and the hole is generated. The removal of metal in a drilling operation is by shearing and extrusion. When the drill bit is being rotated, a force is applied to it by a weight.
Formula Vc x 12 ℼXD
RPM =
Cutting speed = Vc =
(Rev/min) RPM x ℼ x D 12
( m/min ) 7
Feed rate = Vf = IPR x RPM
Cross-section area of hole AT = ℼ x r
Material Removal Rate = Q = Vf x AT
Torque = Mc =
( m/min ) 2 ( m )
2
3 ( m /min)
Hp x 5252 RPM
(ft/lbs)
Experiment Procedure 1. Measured the given Mild Steel round rod’s length and diameter with the help of steel ruler and Vernier callipers. 2. Set the long Mild Steel rod in the Lathe machine and tighten it with chuck key. 3. The Lathe machine is turning in a high speed with the long Mild Steel rod and the cutting tool removed a thin layer of metal from the rod surface slowly. 4. Drill a 10 mm diameter hole and 50 mm long at both centre point of the long Mild Steel rod. 5. Set the short Mild Steel rod at the Lathe machine and tighten it with chuck key. 6. The Lathe machine is turning in a high speed with the short Mild Steel rod and the cutting tool removed a thin layer of metal from the rod surface slowly. 7. Use the cutting tool to remove 3mm long from the short Mild Steel rod, to get desired length which is 50 mm. 8. In order to remove 15 mm outer diameter at the first 20 mm long part, we are required to use the cutting tool to cut its surface in a direction of feed motion and increase its depth of cut gradually. 9. Repeat the previous step 4-5 times on the short Mild Steel rod.
Results
For 25mm x 50 mm Mild steel rod part, can be considered successful in the cutting section. 8
Failed in having a 0.5 mm rivet. For 25mm x 100 mm Mild steel rod part, completed cutting section as well. Failed in drilling section.
(a) 25mm x 50 mm Mild steel rod
(b) 25mm x 100 mm Mild steel rod
Discussion Lack of experience, knowledge and practical skill always is the biggest obstacle to us. This is also one of the reason why the drill bit will be broken and
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