1. Numerical Control Programming

2. 6.1 NC PART PROGRAMMING
Introduction
Coordinate Systems
NC Words

3. 6.1.1 Coordinate System Z // rotating spindle Z AXIS
workpiece-rotating machine:
Z is parallel to the spindle
tool-rotating machine:
Z is parallel to the tool axis Z Z Z

4. 6.1.1 Coordinate System X // table X AXIS workpiece-rotating machine:
X is the direction of tool movement
horizontal milling machine :
X axis is parallel to the table
vertical machine :
+X axis points to the right
when the programmer
is facing the machine. X Z X Z Z X

5. 6.1.5 NC Words N, G, X, Y Z, A, B, C, I, J, K, F, S, T, R, M
N: specify the sequence number
G: preparatory word
to prepare for control functions (the motion of each axis, coordinate system, coordinate plane, cutter radius compensation, tool length offset……)
M: miscellaneous word
to control miscellaneous functions (spindle on/off, start/stop the machine, turn on/off the coolant, change the tool, and rewind the program tape)

6. NC Words
Traverse， Circular, dwell, acceleration, deceleration, metric format,

7. 6.1.5 NC Words M CODES M00 Program stop M06 Tool change M01
Optional stop
M07
Flood coolant on
M02
End of program
M08
Mist coolant on
M03
Spindle CW
M09
Coolant off
M04
Spindle CCW
M30
End of tape

8. 6.1.5 NC Words Modal codes and non modal codes/ modal functions
Modal functions stay active until some other command changes it. Modal commands are arranged in sets called “modal groups”, and only one member of a modal group may be in forces at any given time.
non-modal functions
Non-modal functions have effect only on the lines on which they occur.

9. NC Words
modal groups
traverse

10. 6.1.5 NC Words M CODES modal groups M00 Program stop M06 Tool change
Optional stop
M07
Flood coolant on
M02
End of program
M08
Mist coolant on
M03
Spindle CW
M09
Coolant off
M04
Spindle CCW
M30
End of tape

11. 6.1.5 NC Words N, G, X, Y , Z, A, B, C, I, J, K, F, S, T, R, M
F: feed rate of the tool motion
S: cutting-speed
T: tool number

12. 6.1.5 NC Words N, G, X, Y , Z, A, B, C, I, J, K, F, S, T, R, M
X, Y, Z, A, B, C: provide the coordinate positions of the tool. X, Y, and Z define the three translational (Cartesian) axes of a machine. A, B and C are used for the three rotational axes about the X, Y, and Z axes.
I, J, K: specify the center for circular motion

13. 6.1.5 NC Words N, G, X, Y, Z, A, B, C, I, J, K, F, S, T, R, M
R: specify the clearance height in canned-cycle
N0010 G81 X1.000 Y2.000 Z0.000 R1.300
Operations in drill cycle G81 :
1. Rapid to location (1,2,2).
2. Rapid down to the R plane:(1,2,1.3)
3. Feed to the Z point, the bottom of the hole:(1,2,0)
4. Operation at the bottom of the hole .
5. Rapid or feed to either the R plane or the initial height.

14. NC Words

15. G codes Unit selection: Coordinates selection:
G70 (inch), G71(metric)
Coordinates selection:
G90(absolute), G91(incremental)
Working plane selection:
G17(X-Y), G18(Z-X), G19(Y-Z)

16. Set up working coordinate
25.2 23 Z X
G92 X25.2 Z23.0
Machine zero
is unchangeable and usually is set up with the machine
Working coordinate
(is decided by the offset from the machine zero)
G92
Be defined in program
MDI: Multi-Document Interface
Machine zero
G55
G54
G56
G57
G58
G59

17. G90: absolute coordinates
Rapid traverse: G00
G00:
to make the machine move at maximum speed.
It is used for positioning motion.
G90 G00 X20.0 Y10.0
G90: absolute coordinates
Start
End
(20,10)
(10,10)
(0,0)

18. Linear interpolation: G01
linear interpolation at feed speed.
G91 G0l X200.0 Y100.0 F200.0
G91: incremental coordinates Y
100.0 X
Start
End
200.0

19. Circular interpolation: G02, G03
For circular interpolation, the tool destination and the circle center are programmed in one block
G02 is clockwise interpolation, G03 is counterclockwise interpolation
End point
Circle center, radius

20. Circular interpolation: G02, G03
Specify Center with I, J, K
I, J, K are the incremental distance from the start of the arc;
Viewing the start of arc as the origin, I, J, K have positive or negative signs.
Center Y
Start
End X i j

21. Circular interpolation: G02, G03
N0010 G92 X Y40.0 Z0；
N0020 G90 G03 X Y R60.0 F300；
N0030 G02 X Y R50.0；
G92:
To define working coordinate
G90: absolute coordinates
R60
R50
100 60 40 O Y X

22. Circular interpolation: G02, G03
Annotation for Circular Interpolation
I0.0, J0.0, and K0.0 can be omitted.
If X,Y,Z are all omitted in the program, that means start and end of arc are same points.
N0020 G02 I20.0 (a full circle)
If I, J, K, and R all appears in circular interpolation instruction, R is valid and I, J, and K are invalid

23. Return to Machine Zero: G28
The machine passes by the specified point, and then move to the machine zero.
G91 G28 X_, Y_, Z_
X,Y,Z are the coordinate of specified point that is saved in memory of machine.
Usually this instruction is used in the beginning and end of program.
G91: incremental coordinates A
Machine Zero
Specified point

24. Return to the Specified point : G29
The machine passes from the machine zero by the point that is specified in G28, and then move to the new specified point.
G29 X_, Y_, Z_
X, Y, Z are the coordinate of new specified point
G28,G29 are usually used to change tool
Specified point in G28 A
Machine Zero
New specified point in G29

25. M code miscellaneous word miscellaneous functions:
turn the spindle on/off
start/stop the machine
turn on/off the coolant
change the tool
rewind the program (tape)

26. M code modal groups M00 Program stop M06 Tool change M01 Optional stop
Flood coolant on
M02
End of program
M08
Mist coolant on
M03
Spindle CW
M09
Coolant off
M04
Spindle CCW
M30
End of tape
modal groups

27. M code: M00, M01
M00 and M01 both stop the machine in the middle of a program.
M01 is effective only when the optional stop button on the control panel is depressed. The program can be resumed through the control panel.

28. M code: M03, M04, M05 M03 turns on the spindle clockwise.
M04 turns the spindle on counterclockwise.
(The spindle rpm must be specified in the same line or in a previous line. )
M05 turns off the spindle.

29. M code: M07, M08, M09 M07 and M08 turn on different modes of coolant.
M07: flood coolant on
M08: mist coolant on
M09 turns off the coolant.

30. M code: M06 M06 signals the tool-change operation.
On a machine equipped with an automatic tool changer, it stops the spindle, retracts the spindle to the tool-change position, and then changes the tool to the one specified in the T-code.

31. M code: M02, M30 M02 marks the end of the program.
M30 marks the end of the tape. It stops the spindle and rewinds the program (tape)

32. Example
A 2.0-in 2.0-in. square is to be milled using a 1/2-in. end milling cutter (end mill). Write an NC part program to make the square.

33. Example Part program Explanation N0010 G41 S1000 F5 M03
N0020 G00 X6.000 Y6.000
N0030 G01 Z-1.000
N0040 G01 Y8.000
N0050 G01 X8.000 M96
N0060 G01 Y6.000 M96
N0070 G01 X6.000 M96
N0080 G01 Z1.000
N0090 G40 M30
Begin compensation（left）, set feed and speed, spindle on （CW）
Move to lower left corner
Plunge down the tool
Cut to upper left corner
Cut to upper right corner with external curve
Cut to lower right corner with external curve
Cut to lower left corner with external curve
Lift the tool
End the composition, stop the machine

34. G codes with animations

35. Manual 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  p1  p2  p3  p4  p5  p1  p0

36. 1. Set up the programming parameters
Programming in inches
Use absolute coordinates
Feed in ipm
N010 G70 G90 G94 G97 M04
Spindle speed in rpm
Spindle CCW

37. 2. Set up the machining conditions
Machine moves in XY-plane
Use full-circle interpolation
Feed rate
Spindle speed
N020 G17 G75 F6.0 S300 T1001 M08
Tool no.
Flood coolant ON

38. 3. Move tool from p0 to p1 in straight line
Linear interpolation
target coordinates
N030 G01 X3.875 Y3.698

39. 4. Cut profile from p1 to p2 N040 G01 X3.875 Y9.125 or N040 G01 Y9.125
Linear interpolation
target coordinates
N040 G01 X3.875 Y9.125 or
N040 G01 Y9.125
X-coordinate does not change  no need to program it

40. 5. Cut profile from p2 to p3 N050 G01 X5.634 Y9.125
Linear interpolation
target coordinates
N050 G01 X5.634 Y9.125

41. 6. Cut along circle from p3 to p4
circular interpolation, CCW motion
target coordinates
N060 G03 X7.366 Y9.125 I6.5 J9.0
coordinates of center of circle
N060 G03 X7.366 Y9.125 I0.866 J-0.125

42. 7. Cut from p4 to p5 N070 G01 X9.302 Linear interpolation
target coordinates (Y is unchanged)
N070 G01 X9.302

43. 8. Cut from p5 to p1 N080 G01 X3.875 Y3.698 Linear interpolation
target coordinates (see step 3)
N080 G01 X3.875 Y3.698

44. 9. Return to home position, stop program
Linear interpolation
target coordinates (see step 3)
N090 G01 X2.0 Y2.0 M30
end of data
N100 M00
program stop

45. 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

46. Automatic Part Programming
Software programs can automatic generation of CNC data
Define Tool
CNC data
Make 3D model
Simulate
cutting

47. Automatic part programming and DNC
Very complex part shapes  very large NC program
NC controller memory may not handle HUGE part program
computer feeds few blocks of
NC program to controller
When almost all blocks executed,
controller requests more blocks

48. Assignment (Learn this software)
CNC Simulator
Download from

49. Direct Numerical Control (DNC):
A system in which a central computer downloads the NC programs block by block to many NC machine tools simultaneously is called Direct Numerical Control (DNC) system.
2004

50. DNC
Direct numerical control (DNC) – control of multiple machine tools by a single (mainframe) computer through direct connection and in real time
1960s technology
Two way communication
Distributed numerical control (DNC) – network consisting of central computer connected to machine tool MCUs, which are CNC
Present technology

51. Direct Numerical Control (DNC):
This system used to work with the early NC machine tools which can not read more than a block of information at a time. The central computer feed the program information one block at a time. When the machine execute the information, the next block of information would be fed.
2004

52. Distributed Numerical Control (DNC):
Distributed NC is known by the same acronym as Direct Numerical Control (DNC). After the introduction of CNC, the machine tools have had the capability of storing large amount of information. Therefore, there have been no need to have drip feed information system, like, Direct Numerical Control. Instead, Distributed Numerical Control is introduced. In such a system, a host computer communicate with many CNC machine tools via networks and download or upload programs.
2004

53. Distributed Numerical Control (DNC):
With Distributed Numerical Control systems, it is possible to monitor the activities in individual CNC machine tools on host computer.
Therefore, better shop floor control can be achieved.
2004

54. TYPES of CNC CONTROL SYSTEMS
Open-loop control
Closed-loop control
2004

55. OPEN-LOOP CONTROL SYSTEM
In open-loop control system step motors are used
Step motors are driven by electric pulses
Every pulse rotates the motor spindle through a certain amount
By counting the pulses, the amount of motion can be controlled
No feedback signal for error correction
Lower positioning accuracy
2004

56. CLOSED-LOOP CONTROL SYSTEMS
In closed-loop control systems DC or AC motors are used
Position transducers are used to generate position feedback signals for error correction
Better accuracy can be achieved
More expensive
Suitable for large size machine tools
2004