DSCE Bangalore – 78 MANUAL Department of Mechanical Engineering CIM & AUTOMATION LAB: 10MEL78 CONTENTS Page No. 1. Introduction to CNC Turning, programs on turning 2 2. Introduction to CNC Milling, programs on Milling 32 3. CapsTurn and CapsMill 46 4. Simulation of Hydraulic and pneumatic circuits using LMS Image Lab (AMESim) Software. 48 5. Exercise Problems 50 6. Definitions of FMS and ASRS 52 1
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DSCEBangalore – 78
MANUALDepartment of Mechanical
EngineeringCIM & AUTOMATION LAB: 10MEL78
CONTENTSPage No.
1. Introduction to CNC Turning, programs on turning 2
2. Introduction to CNC Milling, programs on Milling 32
3. CapsTurn and CapsMill 46
4. Simulation of Hydraulic and pneumatic circuits using LMS Image
Lab (AMESim) Software. 48
5. Exercise Problems 50
6. Definitions of FMS and ASRS 52
1
DSCEBangalore – 78
MANUALDepartment of Mechanical
EngineeringCIM & AUTOMATION LAB: 10MEL78
1. INTRODUCTION TO CNC TURNING, PROGRAMS ON TURNING
NC TECHNOLOGY
1.1 Numerical Control (NC):
It is the acronym for ‘Numerical Control’. Numerical Control refers to the use of coded
numerical information in the automatic control of equipment. NC can be defined as a kind of
programmable automation in which the process is controlled by numbers, letters & symbols. The
numbers letters & symbols are arranged as a ‘program of instructions’ for a particular job. Such a
program is called a part program.
NC can be applied to various operations in engineering, like drafting, machining, assembly,
inspection, etc. The main area of NC application is metal machining operations.
1.2 Basic Components of an NC System:
An NC system consists of three basic components.
1. Program of instructions
2. Machine control unit
3. Machine tool
Above Figure shows the block diagram of an NC machine. The program of instructions sends
commands to the Machine Control Unit, which in turn controls the machine tool.
1.3 NC Coordinate systems:
The relative movement of the machine tool spindle & worktable is due to the individual slides
being operated by instructions from the part program.
Normally, three slides are required in a NC machine tool.
Longitudinal
Vertical
Transverse
2
PROGRAM OF INSTRUCTIONS
MACHINE CONTROL UNIT MACHINE TOOL
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MANUALDepartment of Mechanical
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The position and direction of movement of each slide is given by the right hand coordinate
system. Here we have three axes X, Y & Z mutually perpendicular to each other.
Position of axes: Usually the Z axis is located (positioned) along the machine tool spindle. The
X axis is positioned parallel to the machine worktable and perpendicular to the Z axis. The Y
axis is perpendicular to both Z & X axis.
Direction of axes: If the movement of the slide is such that the tool moves away from the work
piece, the direction of that slide axis is positive (+ ve). Similarly, if the movement of the slide is
such that the tool moves nearer to or into the work piece, the direction of that slide axis is
negative ( - ve).
Zero points & Reference points:
The accurate position of the machine tool slides with the machine tool is established by the ‘Zero
Point’. The Zero Points may be (a) Machine Zero Point & (b) Work Zero Point.
Machine Zero Point is specified by the manufacturer of the machine. This is the zero point for
the coordinate systems and other reference points in the machine.
Workpiece Zero Point determines the workpiece coordinate system in relation to the machine
zero point. This point is chosen by the programmer, and input into the CNC system when setting
up the machine. The position of this point can be freely chosen by the programmer within the
workpiece envelope of the machine. Its position is chosen such that the dimensions in the
workpiece drawing can be conveniently converted into coordinate values and also to effectively
take care about the clamping/chucking, setting up, etc.
Reference Point or Home Position serves for calibrating and controlling the measuring systems
of the slides and tool traverses. The position of the reference point is accurately predetermined in
every traverse axis by the trip dogs and the limit switches. Therefore the reference point
coordinates always have the same precisely known numerical values in relation to the machine
zero point. After initiating the control system, the reference point must always be approached
from all axes to calibrate the traverse measuring system.
Dimension System: Dimensional information in the work piece drawing can be stated in 2
In Absolute dimensioning, the coordinate data are taken with respect to a fixed reference point on
the workpiece drawing (usually the workpiece zero).
3
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MANUALDepartment of Mechanical
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In Incremental Dimensioning, the coordinate data are taken with respect to the previous
coordinate value. i.e., every coordinate programmed will be the origin for the next coordinate to
be programmed.
1.4 NC & CNC: During the early period of NC technology, most of the control activities in the
controller were performed by electronic hardware devices like diode valves. The electronics
consisted of many mechanical devices which frequently posed problems of non-contact. The
machine tools and processes then controlled by such controllers were called as NC Machines.
With the improvement of technology and with the evolution of ‘integrated circuits’ mechanical
problems with electronic devices were solved. Also with the very fast development of
computers, almost all the control activities, performed by the hardware of the controller unit,
could then be tackled by software (programs). The machine tools and processes presently being
controlled by powerful computers is termed as CNC Machines. CNC is the acronym for
‘Computer Numerical Control’.
1.5 CNC Part Program:
It consists of a set of properly arranged sequence of instructions which when executed
initiates the controller to send various signals to different machine tool drives in accordance with
the program sequence so as to perform the desired work/job.
The CNC program (also called as the CNC part program) is made up of number of ‘lines of
instructions’. Each ‘line of instruction’ is called a Block. Each Block in turn consists of a few
‘alpha-numeric words’ called as ‘CNC Words’
Figure here shows a sample part program depicting the ‘Blocks’ and ‘CNC Words’.
Also, it may be noted that each CNC word starts
with a Word Address (upper-case alphabet) followed
by a numeric data.
Such a CNC program format is called ‘Word
Address Format’.
CNC Words: The different types of CNC words
used in CNC programming are as follows.
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MANUALDepartment of Mechanical
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a) Sequence Number (N-word): It is used to identify a block.
b) Preparatory function word (G-code): This command prepares the machine controller to
follow a given instruction. E.g. G00 stands for Rapid Movement (point-to-point position)
c) Coordinate Data(X, Y & Z words): These words specify the coordinate position of the
cutting tool. E.g. X15, Y-40, Z-2
Coordinate Data may also contain the I, J & K words which specify the coordinate values
of the arc. I, J & K values are also called as the ‘interpolation parameters’.
d) Arc Radius (R-word): Instead of programming the interpolation parameters (arc-center-
coordinates) I, J & K, the arc radius can be programmed using the R-word.
e) Feed Rate (F-word): These words specify the feed rate of the tool in a machining
operation. It is usually expressed in mm/min. E.g. F30
f) Cutting Speed (S-word): These words specify the cutting speed of the tool/spindle
rotation in RPM. E.g. S1200
g) Tool Selection (T-word): This command is used to access a required tool from a tool
turret or an automatic tool changer. This command is usually used in CNC machines with
Automatic Tool Changing facility. E.g. T10 may specify that a 10 mm drill must be
selected from position number 10 of a tool magazine (holder).
h) Miscellaneous Functions (M-code): These are used to specify certain miscellaneous or
auxiliary functions (coolant on, coolant off, spindle on CW/CCW, spindle stop, etc)
available on the given machine.
NC LATHE
5
Z +Z –
Length
Dia
Face
(0,0)
X
Z
Chuck
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1.6 Dimensional Notations used in CNC lathe are:
1. Absolute Dimensioning – X & Z are used.
2. Incremental Dimensioning – U & W are used.
PointABSOLUTE INCREMENTAL
X Z U W
P1 20 0 20 0
P2 20 -25 0 -25
P3 25 -25 5 0
P4 25 -55 0 -30
P5 30 -55 5 0
P6 30 -80 0 -25
Note: Incremental program is easy to program but tedious to change values in between. Error
committed in any block is carried over to the consecutive blocks. Whereas, absolute
programming is a bit inconvenient as all coordinates are measured from a fixed point. Error
committed in any block will affect only that block. Consecutive blocks are not affected.
6
P1P2
P3P4
P5P6
30
25
20
25 30 25
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MANUALDepartment of Mechanical
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1.7 Zero points & Reference points on a CNC lathe:
Above figure shows the location and the relationship between Zero Points & Reference Point on
a CNC lathe.
1.8 Commonly used G-codes on the XLTURN machine:
G00 Positioning(Rapid Feed)
G01 Linear Interpolation(Cutting Feed)
G02 Circular Interpolation CW
G03 Circular Interpolation CCW
G04 Dwell
G17 XY Plane
G18 ZX Plane
G19 YZ Plane
G20 Inch Mode Input
G21 Metric Mode Input
G28 Return To Reference Point(Homing)
G70 Finishing Cycle
G71 Profile Turning Cycle
G72 Profile Facing Cycle
G74 Drilling Cycle
G75 Grooving Cycle
G76 Threading cycle
G90 Turning Cycle
G92 Treading Cycle
G94 Facing Cycle
(0,0)
X
Z
Max Z
Max
X
WM
R
M: Machine Zero Point W : Workpiece(Program) Zero Point
R: Reference point OR Home Position
7
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G98 Feed per Minute
G99 Feed per Revolution
1.9 Commonly used M-codes on the XLTURN machine:
M00 Program Stop
M01 Optional Stop
M02 Program Reset
M03 Spindle Forward
M04 Spindle Reverse
M05 Spindle Stop
M06 Auto Tool Change
M08 Coolant ON
M09 Coolant OFF
M13 Spindle Forward and Coolant ON
M14 Spindle Reverse and Coolant ON
M98 Sub Program Call
M99 Sub Program Exit
M30 Program Reset and Rewind
G00 Rapid traverse
When the tool being positioned at a point preparatory to a cutting motion, to save time it is
moved along a straight line at Rapid traverse, at a fixed traverse rate which is pre-programmed
into the machine's control system. Typical rapid traverse rates are 10 to 25 m /min., but can be as
high as 80 m/min.
Format
N_ G00 X_ Z_
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G01 Linear interpolation (feed traverse)
The tool moves along a straight line in one or two axis simultaneously at a programmed linear
speed, the feed rate.
Format
N__ G01 X__ Z__ F__
G02/03 Circular interpolation
Format
N__ G02/03 X__ Z__ I__ K__ F__ using the arc center
OR
N__ G02/03 X__ Z__ R__ F__ using the arc radius
G02 moves along a CW arc
G03 moves along a CCW arc
Arc center
The arc center is specified by addresses I and K. I and K are the X and Z co-ordinates of the arc
center with reference to the arc start point.
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I =(X coord. of center - X coord. of start point)/2
K = Z coord. of center - Z coord. of start point
I and K must be written with their signs.
Arc radius
The radius is
Specified with address R.
G02 X__ Z__ R__ F__
N__ G03 X__ Z__ R__ F__
If the radius is used, only arcs of less than 180 deg. can be programmed in a block. An arc with
included angle greater than 180 deg. must be specified in two blocks.
1.10 Canned cycles
A canned cycle simplifies a program by using a few blocks containing G-codes functions to
specify the machining operations usually specified in several blocks
I. Turning Cycle - G71
Format
G71 U (d) R (e)
G71 P(n) Q(n) U(u) W(w) F(f)
N (n) _ _ _ _
_ _ _ _ _ _ _
_ _ _ _ _ _ _
N (n) _ _ _ _
d = Depth of cut
10
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e = Retract amount
n = Number of the first block of the shape
n = Number of the last block of the shape
u = Finishing allowance in X
w =Finishing allowance in Z
f = Feed rate
II. Step Facing Cycle (G94 Cycle):
It is a ‘Box type’ cutting cycle.
SYNTAX:
G94 X… (U….) Z….. (W…..) F…..
Where,
X is the diameter to which the movement is being made OR U is the incremental distance from
the current tool position to the required final diameter.
Z is the Z axis coordinate to which the movement is being made OR W is the incremental
distance from the current tool position to the required Z axis position.
F is the feed rate.
TP-1. Write a program to perform the step facing of the component as shown in the figure:
O1001
([BILLET X30 Z70)
G21 G98
G28 U0 W0
M06 T0101
M03 S1200
G00 X31 Z0
G94 X10 Z-0.5 F30
Z-1
Z-1.5
Z-2
Z-2.5
X20 Z-3
Z-3.5
11
F R
R
F
Tool Entry point
30
20
10
2.5 2.5
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Z-4
Z-4.5
Z-5
G28 U0 W0
M05
M30
12
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MANUALDepartment of Mechanical
EngineeringCIM & AUTOMATION LAB: 10MEL78
III. Step Turning Operation using the Box Turning Cycle (G90):
The Step Turning Operation can be performed by using the “Box Turning Cycle – G90 Cycle” as
below.
SYNTAX:
G90 X…..Z……F…….
Where,
X is the diameter to which movement is being made
Z is the Z axis coordinate to which the movement is being made
F is the feed rate being used
TP-2 Using the G90 Cycle; write a part program to step turn a work piece as shown below:
O1003
G21 G98
G28 U0 W0
M06 T0101
M03 S1200
G00 X30 Z1
G90 X30 Z-55 F30
X29
X28
X27
X26
X25
G00 X25 Z1
G90 X25 Z-25 F30
X24
X23
X22
X21
X20
G28 U0 W0
13
Tool Entry point
30
25
20
30 25
F
R
R
F
Tool Entry
Point
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M05
M30
14
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IV. Taper Turning Cycle (G90 Cycle):
The above taper turning operation can be performed by the standard “G90 Taper Turning
Cycle”. Its syntax is:
G90 X….Z….R…..F…..
Where,
X is the diameter to which the movement is being made.
Z is the Z axis coordinate to which the movement is being made.
R is the difference in incremental of the cut start radius value and the cut finish radius value.
TP-3 Write a part program to perform the taper turning operation using the “G90 Taper Turning
Cycle (R –ve)” for the work part shown in figure.
O1004
G21 G98
G28 U0 W0
M06 T0101
M03 S1200
G00 X30 Z1
G90 X30 Z-10 R0 F50 [(30-30)/2 = 0]
X30 R-0.5 [(29-30)/2 = -0.5]
X30 R-1 [(28-30)/2 = -1]
X30 R-1.5 [(27-30)/2 = -1.5]
X30 R-2 [(26-30)/2 = -2]
X30 R-2.5 [(25-30)/2 = -2.5]
G28 U0 W0
M05
M30
15
Tool Entry point
30
25
10
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MANUALDepartment of Mechanical
EngineeringCIM & AUTOMATION LAB: 10MEL78
TP-4. Write a part program to perform the taper turning operation using the “G90 Taper Turning
Cycle (R +ve)” for the work part shown in figure.
O1005
G21 G98
G28 U0 W0
M06 T0101
M03 S1200
G00 X30 Z1
G90 X30 Z-10 R0 F50 [(30-30)/2 = 0]
X29 R0.5 [(30-29)/2 = 0.5]
X28 R1 [(30-28)/2 = 1]
X27 R1.5 [(30-27)/2 = 1.5]
X26 R2 [(30-26)/2 = 2]
X25 R2.5 [(30-25)/2 = 2.5]
G28 U0 W0
M05
M30
V. Multiple Turning Cycle (G71 Cycle):
The Multiple Turning Cycle is used when the major direction of cut is along the Z axis. This
cycle causes the profile to be roughed out by turning. Two G71 blocks are needed to specify all
the values.
Syntax: G71 U……R……
G71 P…..Q……U…..W…..F……
VI. Finishing Cycle (G70 Cycle):
16
Tool Entry point
30
25
10
X29X28X27X26
X25
Tool Entry Point
Tool Entry Point
U is the depth of cut.R is the relief or retract amount
P is the block number of the start of the final profile
Q is the block number of the end of the final profile.
U is the finishing allowance for the X axisW is the finishing allowance for the Z axis
F is the feed rate
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MANUALDepartment of Mechanical
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On completion of any roughing operation, the material left as finishing allowance is removed
using the ‘Finishing Cycle’. The same tool path used in the roughing operation is used in the
G70 cycle. The G70 Cycle causes a range of specified blocks to be executed, then control passes
on to the block after the G70 Cycle.
Syntax: G70 P….Q….F…..
Where, P is the block number of the start of the final profile
Q is the block number of the end of the final profile.
TP-5 Write a part program for Multiple Turning operation for the component shown in the
figure.
O1006
G21 G98
G28 U0 W0
M06 T0101
M03 S1200
G00 X30 Z1
G71 U0.5 R1
G71 P1 Q10 U0.5 W0.5 F50
N1 G01 X7
N2 X9 Z-2
N3 Z-15
N4 G02 X14 Z-22 R8
N5 G01 X17 Z-27
N6 Z-32
N7 G03 X22 Z-39 R8
N8 G01 X24
N9 X28 Z-44
N10 X30
G70 P1 Q10 F50
POINT X Z
P1 7 0
P2 9 -2
P3 9 -15
P4 14 -22
P5 17 -27
P6 17 -32
P7 22 -39
P8 24 -39
P9 28 -44
P10 30 -4417
Tool Entry point
30 28
22
17
14
9
R 8
R 8
13 275575
24
P1P2P3
P4
P5P6
P7P8
P9
P10
7
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MANUALDepartment of Mechanical
EngineeringCIM & AUTOMATION LAB: 10MEL78
G28 U0 W0
M05
M30
18
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TP-6 Write a part program for Multiple Turning operation for the component shown in the
figure. Use a finishing tool for the finishing cycle.
O1007
[BILLET X30 Z70
G21 G98
G28 U0 W0
M06 T0101 (Select roughing tool)
M03 S1200
G00 X30 Z1 (Select Entry Point)
G71 U0.5 R1
G71 P10 Q20 U0.5 W0.5 F50
N10 G01 X8
X10 Z-2
Z-15
G03 X20 Z-25 R10
N20 G01 X30 Z-35
G28 U0 W0
M06 T0303
M03 S1450
G00 X30 Z1
G70 P10 Q20 F40
G28 U0 W0
M05
M30
Note: Whenever a tool change is to be made, current tool must be sent to ‘Home Position’ by
using the G28 command, so as to ensure that turret indexing will not interfere with workpiece or
machine tool parts (work table).
19
Select Finishing Tool
30
20
10 8
R 10
10 13 210
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MANUALDepartment of Mechanical
EngineeringCIM & AUTOMATION LAB: 10MEL78
TP-7 Write a part program for Multiple Turning operation for the component shown in the
figure. Note that it is the same component as shown above except that there is an extra taper
before the circular interpolation.
It should be noted that the G71 cycle works only for continuously increasing (for external
operation) or decreasing (for internal operations) dimensions only. Hence the shaded portion in
the figure must be removed separately (by using the G90 R +ve cycle) after using the G71 cycle.
O1008
G21 G98
G28 U0 W0
M06 T0101
M03 S1200
G00 X30 Z1
G71 U0.5 R1
G71 P10 Q20 U0.5 W0.5 F50
N10 G01 X8
X10 Z-2
Z-15
G03 X20 Z-25 R10
N20 G01 X30 Z-35
G00 X10 Z-2
G90 X10 Z-15 R0 F30
X9 R0.5
X8 R1
X7 R1.5
X6 R2
X5 R2.5
G28 U0 W0
M05
M30
20
Tool Entry point
G90 Cycle to machine the taper.
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1.12 Subprogram:
A CNC program is divided into a main program & a subprogram. Normally the CNC operates
according to the main program but when a command calling a subprogram is encountered in the
main program, control is passed to the subprogram. When a command indicating a return to the
main program is encountered in the subprogram, control is returned to the main program. The
first block of the main program & sub program must contain a program number starting with
letter ‘O’.
Use of subprogram: When a program contains certain fixed sequences or frequently repeated
patterns, these sequences or patterns can be entered into the memory as a subprogram to simplify
programming. If a subprogram can call another subprogram, it is regarded as a one loop sub
program call.
Syntax: M98 P0000000
M99
21
Subprogram No.
No. of repetitions
Subprogram call
Command used in main program
Command used in Subprogram
O0001
……..
……..
M980012222
……..
……..
……..
M30
Main ProgramO2222
……..
……..
M980013333
……..
……..
……..
M99
O3333
……..
……..
……..
……..
……..
……..
M99
Subprogram Subprogram
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Note: If the Number of repetition is omitted, the called subprogram is executed only once.
22
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TP-8. Write a part program to machine the component shown in the figure making use of a sub
program.
O1009
[BILLET X22 Z70
G21 G98
G28 U0 W0
M06 T0101
M03 S1200
G00 X22 Z1
G90 X22 Z-40 F50
X21
X20
G00 X20 Z0
M98 P0032000
G00 X20 Z-30
G90 X20 Z-40 F50
X19
X18
X17
X16
X15
G28 U0 W0
M05
M30
Note: (1) While writing the subprogram, incremental dimensioning is normally used.
Dimensions which remain constant in every pass can be programmed as absolute dimensions.
(2) Main program and sub-programs are written in separate files
Subprogram Nesting: When one subprogram calls for another subprogram, subprogram nesting
is said to be done.
23
22
15
20
10 5 5 5 5 5 5
Tool Entry point
O2000G90 X20 W-5 R0 F30
X20 R-0.5X20 R-1X20 R-1.5X20 R-2X20 R-2.5
G00 X20 W-5G90 X20 W-5 R0 F30
X19 R0.5X18 R1X17 R1.5X16 R2X15 R2.5
G00 X20 W-5M99
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TP-9 Write a part program for the component shown in figure making use of the ‘Subprogram
Nesting’.
O1010
[BILLET X22 Z70
G21 G98
G28 U0 W0
M06 T0101
M03 S1200
G00 X22 Z1
G90 X22 Z-60 F50
X21
X20
G00 X20 Z0
M98 P0012020
M98 P0012020
M98 P0012020
G28 U0 W0
M05
M30
O2020
G90 X20 W-5 R0 F30
X20 R-0.5
X20 R-1
X20 R-1.5
X20 R-2
X20 R-2.5
G00 X20 W-10
G90 X20 W-5 R0 F30
X19 R0.5
X18 R1
24
22
15
20
5 5 5 5 5 5 55 5 5 55
Tool Entry point
O2030
G90 X20 W-5 F50
X19
X18
X17
X16
X15
G00 X20 W-5
M99
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X17 R1.5
X16 R2
X15 R2.5
G00 X20 W-5
M98 P0012030
M99
VII. External Grooving (G81 Cycle):
Syntax: G81 X….Z…..F…..
Where,
X is the diameter up to which the grooving must be done.
Z is the Z-axis coordinate where the grooving must be done.
F is the feed rate.
TP-10 Write a part program for performing the external grooving operation for the component
shown in figure.
O1011
[BILLET X22 Z70
G21 G98
G28 U0 W0
M06 T0101
M03 S1200
G00 X22 Z1
G71 U0.5 R1
G71 P10 Q20 U0.5 W0.5 F40
N10 G01 X10
X12 Z-2
X12 Z-20
G02 X18 Z-27
G01 X18 Z-37
N20 X22 Z-45
25
Tool Entry point
3 mm
Note: The required grooves are 4 mm wide whereas the width of the tool tip is only 3mm. Hence, the sequence of G81 cycles are used twice, during the second set, tool is made to move by 1 mm so that the final groove width will be 4 mm.