CNC lathe machines use stepper motors to control movement along the X and Z axes. The spindle, controlled by a DC motor, rotates the workpiece. An 8-tool turret, driven by an AC stepper motor, indexes the cutting and drilling tools. Tool offsetting sets the tool positions in the software by touching off tools to the workpiece surface and diameter. Defining tool offsets allows the machine to accurately position each tool during machining operations defined in CNC programs.

1. Introduction of CNC lathe machine
and
its operation
(Module 2)
Presented by: Mr. Dinesh Kumar
(AP/UCER)
Department of Mechanical Engineering

2. Session 4
Working of CNC Lathe Machine &
Simulation of CNC program

3. CNC LATHE
2 Axis :
For X- axis- Towards
operator positive (+)
Away to operator
negative (-)
For z-axis- Towards tail
positive (+)
Towards head stock
negative (-)
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Note: For the axis movement Stepper motor used

4. SPINDLE
Spindle is a device incorporated 3 jaw chuck in
which work piece mounted and takes rotation.
• The speed of spindle in program denoted by
‘S’
• To rotate spindle DC motor used.
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5. TURRET
• 8 tool station turret used-
• 4 cutting tool
• 4 drilling tool
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6. TOOL INDEXING
• Tool indexing- home position tool is called tool
no. 1 or reference tool.
• Counting the tool w.r.t. first tool in clock wise.
• To drive turret, A.C. stepper motor used.
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7. HOW TO START
• Main switch ‘ON’
• Key switch ‘ON’ (Main ON- indication should Glow)
• Start CPU- window xp will open. Double click
on short cut to “ Cut Viewer “ icon. Software
window will open.
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9. SETTING OF STOCK
Go To Mode Select simulation mode Run
Rebuilt wrong (no stock found. Do you want
to the stock to be defined. Yes Define the
stock as the cylinder. Continuous
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10. Wrong – No tool found. Do you want the tool be defined.
Yes
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12. HOW EXECUTE THE PROGRAM ON MACHINE
• Go To Mode Machine mode Utilities
JOG window will open
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Goto Run Rebuilt

13. WHAT IS TOOL OFFSETTING & HOW IT IS USED ?
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14. FOLLOW THE STEPS FOR TOOL
OFFSETTING
• First Select the JOG mode to move the X, Z axis.
• Select the proper pulse rate & move the tool near to the
job.
• Reduce the pulses & just touch the tool to face of the job.
• Here you have to define the Z position as zero, so select
the
• Tool Position window & here select the Z Position
• window & enter value 0. Now the Z position is Zero.
• Now move the tool just away from the job & then
towards
• X+ direction.

15. •Then Move the tool to touch the diameter of the job.
• Here we have to give the diameter value for X axis, so select
the Tool Position window & here select the X Position
window & enter value of the diameter of the job. (For ex.
22)
• After doing this procedure take the tool away from the job
from jog mode until it comes to the initial setting (For ex. i.e.
X=22, Z=0).
•Then go to TOOL OFFSET window and check that in the
Tool No. Window there is Tool no. 1 present & then click the
SET THE CURRENT POSITION AS REF. Option here you
have found X=22 & Z=0 and then Click X-offset and Z –
Offset .
•This is your first Tool offsetting

17. •Index the tool by which you will start the job. Normally it is tool no. 1 (HOME TOOL)
• Now from the Tool Offset window select the second no. tool.

18. • Now as you select the Tool no. 2 the turret will go to the Tool Change
Position as you specified and it will change the tool .and again come back to
the Intermediate position as you specified.
• Now move the tool no 2 (which is generally your Drill Tool) manually and
touch the tip of the tool to the Z face and set is as Z Offset.
• Now again move the tool in X+ dir. and touch the diameter of the drill to the
job diameter and note down the reading for “X” from the Coordinate Window.
(For ex. The “X” value should be –10.5)
• Now bring the tool back without moving the:”X” direction up to Z =0 position
i.e. safe position for the drill tool. And minus the drill dia. from the noted “X”
value and move the tool to X- dir. up to that value. (For ex. Your drill dia. is
8mm & your “X” value is –10.5 so the final value is –10.5 – 8 = –18.5 )
And set this value as “X” offset.(cross check:- for seeing the correct offset just
check that the drill tip comes in front of the job diameter face)
• Now select the third tool from the tool offset window. As previously selected.

20. •It will do the same procedure as previously done .and by
changing the tool it will come to the intermediate position.
• Now again move the tool to the job position and touch
the tip of the tool to the Z face and set the “Z “ offset.
• Again move the tool to the “X+” position and touch to
the job diameter. and
set the “X “ offset.
• Similarly do the same procedure for the other tools

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