1. CNC Programming “Milling”
12 April 2017
CNC Programming “Milling”
Module Objectives: 1) To use Topmill 2) To create NC programs for different milling operations
IAT - DXB 2008

2. Milling Machine

3. G-Codes
G00, G01, G02, G03, G04, G54, G90, G91, G94 and G95 Are the same as explained in module 4.
New important G codes:
Function
Description
G17,G18, and G19
Working plane selection
G40
Cutter radius compensation OFF.
G41
Cutter radius compensation ON Left.
G42
Cutter radius compensation ON Right.
G70
Input system inch
G71
Input system metric

4. G-Codes
The following G-Codes and their relative slides will be used as a reference when solving some practical tasks in this module.
Function
Description
G111
Polar coordinate interpolation
G147
Approach with a straight line.
G148
Leave in a straight line.
G247
Approach with a quarter a circle.
G248
Leave with a quarter a circle.

5. G17, G18, and G19 Used to select the working plane G17 XY Plane
G18 ZX Plane
G19 YZ Plane
The tool axis is vertical to the working plane

6. What Is The Correct G-code To Select The Top Surface Of The Workpiece As a Working Plane ?

7. G41, G42 and G40
With G41 / G42 the tool traverse at equal distances to the programmed contour along its path. This distance is the dimension of the radius of the cutter.
If the cutter is left to the contour this is programmed by G41 (This called cutter radius compensation left).

8. G41, G42 and G40
If the cutter is right to the contour this is programmed by G42.
(This called cutter radius compensation right)
To cancel the radius compensation use G40

9. G70 / G71
G70: The controller of the CNC milling machine reads the input values in imperial system (Inch)
G71: The controller of the CNC milling machine reads the input values in metric system (mm)

10. G111
If we want to use polar coordinate system to move the tool, we need first to locate the pole (zero point of the polar coordinate system) measured from original workpiece zero point, this is done by G111.
Then write the required movement in polar system by specifying the Angle (AP) and the radius (RP).
Example:
G111 X30 Y40 Z0
G01 RP=40 AP=60 F300

11. G147, G148, G247 and G248 Soft approach and leaving commands.
The function of soft approach and leaving serves to approach the starting point of a contour tangentially irrespective of the position of the initial point.
The function is mainly used in connection with the tool radius correction; however, it is not obligatory.

12. G147, G148, G247 and G248 G147 Approach with straight line
G148 Leave in straight line.
G247 Approach with a quarter a circle
G248 Leave in a quarter a circle

13. Cycles Cycle Description Cycle 81
Drilling; to make a hole in one phase.
Cycle 83
Deep Drilling; to make a deep hole, which requires introducing the tool with several phases. (Chip-breaking and chip removal).
Pocket
To engrave a circular or a rectangular area on a surface.
Holes
To repeat a drilling operation following circular or linear contours.

14. Cycle 81 – Drilling Cycle
To make a hole in one phase

15. Cycle 81

16. Cycle 81 To make a hole in one phase Example: Make a hole at
point X20 Y20
to a depth = 10mm

17. Cycle 81 Solution: Cycle Parameters: G54 S1500 M3 F120
G00 X20 Y20 Z2
Cycle 81 (2,0,1,-10,0)
G0 Z40
M30
Cycle Parameters:
Return plane absolute 2
Reference plane absolute 0
Safety distance 1
Final drilling depth -10
Depth incremental 0

18. Cycle 83 Deep Drilling Cycle

19. Cycle 83

20. Cycle 83
Cycle 83 (2,2,,-86,,,35,4,1,1,1,1)

21. Holes 1
To make a row of holes

22. Holes 1

23. Holes 1 - Example

24. Holes 2
To make a circle of holes

25. Holes 2

26. Holes 2 - Example

27. Pocket – (Pocket1/Pocket2)

28. Pocket 1

29. Pocket 1 - Example

30. Pocket 2

31. Pocket 2 - Example

32. Example of CNC Programming
12 April 2017
Example of CNC Programming
What Must Be Done To Drill A Hole On A CNC Vertical Milling Machine?
Given That:
Absolute Positioning Mode,
Cutting Tool No. 1, Spindle Speed 1000 RPM, Clockwise Direction Of Rotation At Feed Rate 200 mm/min .
Hole Position X10, Y12, And Depth Of Hole 10 mm.
An example of creating a CNC program using a simple hole drilled on a computer numerical controlled (CNC) vertical milling machine.
IAT - DXB 2008

33. Solution NC-Program %Mill_1 N005 G54 N010 G90 N015 G97 S1000 M03
N020 T1 D1 M6
N025 …………………
N030 …………………

34. N025 G00 X10 Y12 Z10 Rapid To Hole Position (Above The Hole) Tool Home
12 April 2017
N025 G00 X10 Y12 Z10
Rapid To Hole Position (Above The Hole)
Tool Home
Top View
Front View
In this case, we are using a simple analogy to stress how a programmer must be able to visualize a CNC program’s execution. We first look at how a machinist would machine a hole in a work piece held in a vise on a milling machine. Then we’ll show how the same operation will be performed with a CNC program.
The machinist standing in front of the milling machine has everything they need right in front of them. They wouldn’t forget something as simple as turning the spindle on before trying to drill the hole. On the other hand, a CNC programmer must typically work with nothing more than a blueprint, a pencil, a calculator, and a blank piece of paper. They must be able to visualize every motion and function of the program’s execution in their minds.
IAT - DXB 2008

35. Z Axis Feed To Drill The Hole
12 April 2017
N030 G01 Z-10 F200
Z Axis Feed To Drill The Hole
Top View
Front View
IAT - DXB 2008

36. Rapid Movement In Z Axis Out Of Hole
12 April 2017
N035 G00 Z6
Rapid Movement In Z Axis Out Of Hole
Top View
Front View
IAT - DXB 2008

37. The NC-Program %Mill_1 N005 G54 N010 G90 N015 G97 S1000 M03
N020 T1 D1 M6
N025 G00 X10 Y12 Z10
N030 G01 Z-10 F200
N035 G00 Z6
N040 M05
N045 G00 X100 Y100 Z100
N050 M30