Experiment 1
Aim: To study of Orthogonal & Oblique Cutting on a Lathe.
Apparatus: Lathe Machine
Theory:
It is appears from the diagram in the following figure that while turning ductile material by a sharp tool, the continuous chip would flow over the tool’s rake surface and in the direction apparently perpendicular to the principal cutting edge, i.e., along orthogonal plane which is normal to the cutting plane containing the principal cutting edge. But practically, the chip may not flow along the orthogonal plane for several factors like presence of inclination angle, λ, etc.
The role of inclination angle, λ on the direction of chip flow is schematically shown in figure which visualizes that,
• when λ=0, the chip flows along orthogonal plane, i.e, ρc = 0
• when λ≠0, the chip flow is deviated from πo and ρc = λ where ρc is chip flow deviation (from πo) angle
Orthogonal cutting: when chip flows along orthogonal plane, πo, i.e., ρc = 0
Oblique cutting : when chip flow deviates from orthogonal plane, i.e. ρc≠0
But practically ρc may be zero even if λ= 0 and ρc may not be exactly equal to λ even if λ≠0. Because there are some other (than λ) factors also which may cause chip flow deviation.
Result: Hence the study of Orthogonal & Oblique Cutting on a Lathe is completed.
Experiment 2
Aim: To calculate the machining time for cylindrical turning on a Lathe and compare with the actual machining time.
Apparatus: Lathe Machine
Theory:
The major aim and objectives in machining industries generally are;
• reduction of total manufacturing time, T
• increase in MRR, i.e., productivity
• reduction in machining cost without sacrificing product quality
• increase in profit or profit rate, i.e., profitability.
Hence, it becomes extremely necessary to determine the actual machining time, TC required to produce a job mainly for,
• assessment of productivity
• evaluation of machining cost
• measurement of labour cost component
• assessment of relative performance or capability of any machine tool, cutting tool, cutting fluid or any special or new techniques in terms of saving in machining time.
The machining time, TC required for a particular operation can be determined
ο roughly by calculation i.e., estimation
ο precisely, if required, by measurement.
Measurement definitely gives more accurate result and in detail but is tedious and expensive. Whereas, estimation by simple calculations, though may not be that accurate, is simple, quick and inexpensive.
Hence, determination of machining time, specially by simple calculations using suitable equations is essentially done regularly for various purposes.
Procedure:
The factors that govern machining time will be understood from a simple case of machining. A steel rod has to be reduced in diameter from D1 to D2 over a length L by straight turning in a centre lathe as indicated in Fig.
Calculations:
| Sl No | L | A | O | LC | VC | D | N | SO | D1 | D2 | T | np | Tc |
| | | | | | | | | | | | | | |
| | | | | | | | | | | | | | |
| | | | | | | | | | | | | | |
Where,
L= length of the work piece in mm;
A= approach run in mm;
O= over run in mm;
Lc=actual length of cut in mm;
Vc= cutting velocity in mm/min;
D= diameter of the job before cut in mm;
N=spindle speed in rpm;
So= tool feed in mm/rev;
D1= initial diameter before passes in mm;
D2=final diameter after passes in mm;
t=depth of cut in one pass in mm;
np=no of passes;
Tc=machining time in min;
Result: The machining time of the turning operation is done and compared.
Experiment 3
Aim: To study the Too Life while Milling a component on the Milling Machine.
Apparatus: Milling Machine
Theory:
Tool life: Time of cutting during two successive milling or indexing of the tool. Tool life is the length of cutting time that a tool can be used or a certain flank wear value has occurred (0.02”).
v Tn = C
v = cutting speed
n = cutting exponent
C = cutting constant
T = tool life
n and C depend on speed, work material, tool material, etc.
Cutting Speed can be obtained by the formula as shown:
N= (v*1000) / (π*d)
Where :
N=spindle speed in rpm;
v=cutting speed in m/min;
d=diameter of cutter in mm;
Procedure:
1. Determine the cutting speed by using given d and N values.
2. Apply Taylor
Calculations:
| Sl No | n | C | d | N | V | T |
| | | | | | | |
| | | | | | | |
Result: Thus the tool life of milling cutter is found out.
Experiment 4
Aim: To study Tool wear of a cutting tool while Drilling on a Drilling Machine.
Apparatus: Drilling Machine
Theory:
Tool wears are classified as shown below
Result: Study of the tool wear of cutting tool on drilling machine is completed.
Experiment 5
Aim: To study the Speed, Feed, Tool, Preparatory (Geometric) and miscellaneous functions for NC part programming
Apparatus: NC Machine
Theory:
Part program: A computer program to specify
- Which tool should be loaded on the machine spindle;
- What are the cutting conditions (speed, feed, coolant ON/OFF etc)
- The start point and end point of a motion segment
- how to move the tool with respect to the machine.
Standard Part programming language: RS 274-D (Gerber, GN-code)
Controlling a CNC machine: RS 274
Procedure:
Part Programming Example
Tool size = 0.25 inch,
Feed rate = 6 inch per minute,
Cutting speed = 300 rpm,
Tool start position: 2.0, 2.0
Programming in inches
Motion of tool:
p0 à p1 à p2 à p3 à p4 à p5 à p1 à p0
1. Set up the programming parameters
2. Set up the machining conditions
3. Move tool from p0 to p1 in straight line
5. Cut profile from p2 to p3
6. Cut along circle from p3 to p4
7. Cut from p4 to p5
8. Cut from p5 to p1
9. Return to home position, stop program
10. Complete RS-274 program
N010 G70 G90 G94 G97 M04
N020 G17 G75 F6.0 S300 T1001 M08
N030 G01 X3.875 Y3.698
N040 G01 X3.875 Y9.125
N050 G01 X5.634 Y9.125
N060 G03 X7.366 Y9.125 I0.866 J-0.125
N070 G01 X9.302
N080 G01 X3.875 Y3.698
N090 G01 X2.0 Y2.0 M30
Result: Hence the study of NC part programming is completed.
Experiment 6
Aim: To study the part programming on a NC Lathe: Step Turning, Taper Turning, Drilling
Apparatus: NC Lathe Machine
Procedure:
Example for step turning.
Example for taper turning.
Experiment 8
Aim: To study the part programming on a NC Milling Machine for a Rectangular Slot.
Apparatus: NC Milling Machine
Procedure:
