This document provides an introduction and overview of CNC turning. It describes what CNC turning is, the basic components of a CNC turning machine, important checklists and safety procedures, basic CNC principles including coordinate systems and programming codes, and includes examples of CNC part programs for turning operations and thread cutting cycles.

1. CNC Turning- An Introduction
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February 24, 2023
Department Of Mechanical Engineering
Indian Institute of Technology Patna
By: Himanshu Pathak

2. What is CNC Turning
• In Conventional machine, operator controls the feed
rate, spindle speed and other input parameters
manually.
• In Numerically controlled machine, all input
parameters feeded in some specific format in NC
directory and according to these input, M/C itself
decide and control the all Machining parameters.
• CNC Turn can perform facing, turning, boring, grooving,
threading, parting, roughing, chamfering and all most
every operation on cylindrical work piece.
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3. Component of CNC Turn
• Head Stock and Tail Stock
• Coolant Tank and Pump
• Chip tray
• Automatic Central Lubrication System
• AC Panel Cooler
• Tooling Package (Turret)
• Encoder
• Servomotor
• Control Panel with Display
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4. Check List
• Power Supply is as specified (3phase,415V AC,
12kVA)
• Level of the coolant and lubricant
• Emergency Stop is in Off position
• Tools are rigidly clamped in the Turret
• Tailstock always be placed in the end position
• Work piece should be rigidly mounted in the
Chuck.
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5. Basic CNC Principles
• All computer controlled machines are able to accurately and
repeatedly control motion in various directions. Each of these
directions of motion is called an axis. Depending on the
machine type there are commonly two to five axes.
• Additionally, a CNC axis may be either a linear axis in which
movement is in a straight line, or a rotary axis with motion
following a circular path. All CNC machining begins with a
part program, which is a sequential instructions or coded
commands that direct the specific machine functions.
• The part program may be manually generated or, more
commonly, generated by computer aided part programming
systems.
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6. CNC Coordinate System
• Machine Coordinate System
This point only represents a reference point defined
by the Machine manufacturer.
-Machine Zero Point
-Reference Point
• Work piece Coordinate System
The Coordinate system described in geometry of a
work piece in the part program.
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7. Coordinates System
Absolute Coordinate System Incremental Coordinate System
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8. General terms In Part Programme
• N – Block Number
• G – Preparatory function
• X – Slide motion in x axis direction
• U - Incremental Slide motion in x axis direction
• Z - Slide motion in z axis direction
• W - Incremental Slide motion in z axis direction
• F – Feed Rate
• M – Specific Function
• S – Spindle Speed
• T- Tool Specification
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9. G Code Overview
• G00 Positioning
• G01 linear Interpolation
• G02 Circular Interpolation CW
• G03 Circular Interpolation CCW
• G70 Input in Inches
• G71 Input in Milimeters
• G90 Absolute Commands
• G91 Incremental Commands
• G94 Feed per Minute
• G95 Feed per Revolution
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10. Important M (Functional) codes
• M00 Program stop
• M01 Optional program stop
• M02 Program end
• M03 Spindle on clockwise
• M04 Spindle on counterclockwise
• M05 Spindle stop
• M06 Tool change
• M08 Coolant on
• M09 Coolant off
• M10 Clamps on
• M11 Clamps off
• M13 Spindle CW and Coolant On
• M14 Spindle CCW and Coolant On
• M30 Program stop, reset to start
• M17 Sub-Program Exit
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11. G90 G71 G94
G00 X0 Z0 D0
T1 D1
M3 S1200
G00 X32 Z10
G01 Z2 F100
CYCLE 95 (“NPP”,MID,FALZ,FALX,FAL,FF1,FF2,FF3,VARI,DT,DAM,VRT)
G00 X0 Z0 D0
M05
M30
SUBROUTINE:
G01 X18 Z0 F120
G01 X20 Z-5
G01 Z-17
G03 X24 Z-21 CR=4
G01 Z-31
G01 X32 Z-39
M17
Part Programm Overview
Φ18
G90 G71 G94
G00 X0 Z0 D0
T1 D1
M3 S1200
G00 X32 Z10
G01 Z2 F100
CYCLE 95 (“NPP”,MID,FALZ,FALX,FAL,FF1,FF2,FF3,VARI,DT,DAM,VRT)
G00 X0 Z0 D0
M05
M30
SUBROUTINE:
G01 X18 Z0 F120
G01 X20 Z-5
G01 Z-17
G03 X24 Z-21 CR=4
G01 Z-31
G01 X32 Z-39
M17
G90 G71 G94
G00 X0 Z0 D0
T1 D1
M3 S1200
G00 X32 Z10
G01 Z2 F100
CYCLE 95 (“NPP”,MID,FALZ,FALX,FAL,FF1,FF2,FF3,VARI,DT,DAM,VRT)
G00 X0 Z0 D0
M05
M30
SUBROUTINE:
G01 X18 Z0 F120
G01 X20 Z-5
G01 Z-17
G03 X24 Z-21 CR=4
G01 Z-31
G01 X32 Z-39
M17
Φ32
Φ24
Φ20
R4
5
12
4
10
8
70
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12. CYCLE Description:
CYCLE 95: Turning Operation
NPP: SUBROUTINE NAME
MID: FEED IN DEPTH PER PASS 0.1
FALZ: FINISHING ALLOWANCE IN Z 0.05
FALX: FINISHING ALLOWANCE IN X 0.05
FAL: OVERALL FINISHING ALLOWANCE
FF1: FEED RATE FOR ROUGHNING 180
FF2: FEED RATE FOR PLUNGING 80
FF3: FEED RATE FOR FINISHING 100
VARI: MACHINING TYPE 9 (FIXED)
DT: DWELL (NOT NEEDED)
DAM: PATH FOR CHIP BREAKING (NOT NEEDED)
VRT: RETRACT 2
Part Programm Contd…
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13. G90 G71 G94
G00 X0 Z0 D0
T1D1
M3 S1000
G00 X33 Z10
G01 Z5 F80
G01 X32.5 F80
CYCLE 97
(PIT,MPIT,SPL,FPL,DM1,DM2,APP,ROP,TDEP,FAL,IANG,NSP,NRC,NID,V
ARI,NUMT)
G00 X0 Z0 D0
M05
M30
Part Programm Contd…
70 14
M32×1
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14. CYCLE Description:
CYCLE 97: Thread Cutting
PIT: THREAD PITCH VALUE 1
MPIT: THREAD PITCH SIZE (NOT NEEDED)
SPL: THREAD STARTING POINT IN LONGITUDINAL AXIS 2
FPL: THREAD END POINT IN LONGITUDINAL AXIS -14
DM1: THREAD DIAMETER AT STARTING POINT 32
DM2: THREAD DIAMETER AT END POINT 32
APP: RUN IN PATH 3
ROP: RUN OUT PATH 0
TDEP: THREAD DEPTH 0.613
FAL: FINISHING ALLOWANCE 0.01
IANG: INFEED ANGLE 30
NSP: STARTING POINT OFFSET
NRC: NUMBER OF ROUGHNINH CUT 18
NID: NUMBER OF IDLE PASS 4
VARI: MACHINING TYPE 1
NUMT: NUMBER OF THREAD STARTS 1
Part Programm Contd…
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