CNC Programming “Milling”

Module Objectives:

1) To use Topmill2) To create NC programs for different milling operations

Milling Machine

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

G00, G01, G02, G03, G04, G54, G90, G91, G94 and G95 Are the same as explained in module 4.

New important G codes:

G-Codes

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.

The following G-Codes and their relative slides will be used as a reference when solving some practical tasks in this module.

G17, G18, and G19Used to select the working

plane G17 XY Plane G18 ZX Plane G19 YZ Plane

The tool axis is vertical to the working plane

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

G17

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).

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

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)

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 Z0G01 RP=40 AP=60 F300

G147, G148, G247 and G248Soft 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.

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

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.

Cycle 81 – Drilling CycleTo make a hole in one phase

Cycle 81

Cycle 81 To make a hole in one phase

Example:Make a hole atpoint X20 Y20 to a depth = 10mm

Cycle 81

Solution:

G54 S1500 M3 F120 G00 X20 Y20 Z2Cycle 81 (2,0,1,-10,0)G0 Z40M30

Cycle Parameters:

Return plane absolute 2

Reference plane absolute 0

Safety distance 1 Final drilling depth -10 Depth incremental 0

Cycle 83 Deep Drilling Cycle

Cycle 83

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

Holes 1

To make a row of holes

Holes 1

Holes 1 - Example

Holes 2To make a circle of holes

Holes 2

Holes 2 - Example

Pocket – (Pocket1/Pocket2)

Pocket 1

Pocket 1 - Example

Pocket 2

Pocket 2 - Example

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.

SolutionNC-Program

%Mill_1

N005 G54 N010 G90N015 G97 S1000 M03N020 T1 D1 M6N025 …………………

N030 …………………

Rapid To Hole Position (Above The Hole)

N025 G00 X10 Y12 Z10

Tool HomeTop View

Front View

Z Axis Feed To Drill The Hole

N030 G01 Z-10 F200

Top View

Front View

Rapid Movement In Z Axis Out Of Hole

N035 G00 Z6

Top View

Front View

The NC-Program

%Mill_1 N005 G54 N010 G90N015 G97 S1000 M03N020 T1 D1 M6

N030 G01 Z-10 F200N035 G00 Z6

N025 G00 X10 Y12 Z10

N045 G00 X100 Y100 Z100N040 M05

N050 M30