4 G Codes Part 2

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1995

UMY

UniversitasMuhammadiyah

Yogyakarta

www.umy.ac.id

CNC/CAM#4 G Codes Part 2

Tutik Sriani, S.T., M.Eng, PhD

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NC Milling: Cutter Radius Offset

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NC Milling: Cutter Radius Offset

• Manual programming calculation of coordinates center

of mill-cutter calculate by hand

• Manual offset only valid for one cutter (ex: Ø.75 tool)

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CNC Milling: Cutter Radius Offset

• Cutter radius offset: a feature of the control system that allowsprogramming a contour without knowing the exact diameter (radius)of the cutter.

• Considerations:

Unknown size of the cutter radius

Adjusting for thecutter wear , deflection, etc

Roughing and finishing operations

Maintaining machining tolerances, etc

• Based on three items:

a. Points of the drawing contourb. Specified direction of the cutter motion

c. Radius of the cutter stored in the control system

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Direction of cutter motion:

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G41: Offset (compensation) of the cutter radius to the LEFT of the contouring direction

G42: Offset (compensation) of the cutter radius to the RIGHT of the contouring direction

G40: Cutter radius offset mode CANCEL

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Radius of the cutter

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Four major keys to a successful use of the cutter radius offset feature:

1. To know how to start the offset

2. To know how to change the offset

3. To know how to end the offset

4. To know what towatch between the start and end

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Start-up Methods : Always select the start position of the

cutter away from the contour, in the clear area

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Seq Code Explanation

N01 G90 G20 Absolute, imperial (inches)

N02 G17 G40 XY plane, cutter radius

compensation cancel,

N03 G54 G00X-0.625 Y-0.625 Z1.0 S920 M03 Work coordinate offset, startposition, spindle 920 rpm CW

N04 G01 Z-0.55 F25.0 M08 Tool infeed, P1

N05 G41X0 D01 F15.0 Start offset use cutter D01

N06 Y1.125 P2

N07 X2.25 Y1.8561 P3

N08 Y0.625 P4

N09 G02X1.625 Y0 CR0.625 P5

N10 G01X-0.625 P1

N11 G00 G40 Y-0.625 Z5

M30

Safe position, cutter radius

compensation cancel, stop

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CNC Turning: Tool Address

• Ex: T0204 will cause the turret to index to the tool station

#2(first two digits) which will become the working station

(active tool). At the same time, the associated tool wearoffset number (the second pair of digits) will become

effective as well.

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G00 T0214: Tool station 02, wear offset 14



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• Tolerances: only ondiameter , only on shoulders, both on diameter and shoulders

• Sample of tolerances only on diameter using three cutter

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The tolerances in all three examples are for

training purposes only and will be much smaller in

reality.

All chamfer tolerances are 0.010, and non-

specified tolerances are 0.005.

Material is a 1.5 inch aluminum bar and three

tools are used:

1. T01: for the face and rough contour

2. T03: for the finishing of the contour to size

3. T05: 0.125 wide part-off tool

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(T01 – Face and Rough Turn )

N01 G90 G20T0100 Absolute, inches, tool #1, no wear

N02 G96 S500 M03 Constant surface speed, spindle CW

N03 G00 G41 X0.85 Z0

T0101 M08

Rapid move, cutter compensation left,

XZ-tool change position, tool #1 offset

01, coolant ON

N04 G01 X-0.07 F0.005 Facing with feedrate 0.005 in/rev

N05 Z0.1 Tool retract in +Z

N06 G00 G42 X0.775 Rapid move, cutter compensation

right, X position (radius)

N07 G71P8 Q15 U0.04

F0.01

Rough cutting cycle, P8: start block of

rough contour cycle, Q14: end block of

rough contour cycle, U: 0.04 allowance

on diameter for rough cut, feedrate

N08 G00 X0.365 Rapid move to X0.365

N09 G01 X0.3125 Z-0.03F0.003

Cut to XZ-position with feedrate 0.003inch/rev

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(T01 – Face and Rough Turn )

N10 Z-0.4 Cut 1st block to –Z 0.4 inch

N11 X0.5 C-0.03 Cut chamfer length 0.03 in @ Ø 1.0 inch

N12 Z-0.75 Cut to –Z 0.75 inch

N13 X0.6875 C-0.03 Cut chamfer length 0.03 in @ Ø 1.375 inch

N14 Z-1.255 Cut to –Z 1.255 inch (plus parting-off area)

N15 U0.2 0.2 allowance on diameter for rough cut

N16 G00 G40 X5.0

Z5.0 T0100

Rapid move to XZ position, cutter

compensation cancel, tool #1 no wear

N17 M01 Stop a running program temporarily

(T03 – Finish Turn)

N18 G50 S3500

T0300

Reset scaling (if any), spindle 3500 rpm,

tool #3 with no wear

N19 G96 S750 M03 Constant surface speed, spindle ON-CW

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(T03 – Finish Turn)

N20 G00 G42 X0.85

Z0.1 T0313 M08

Rapid move to XZ position, cutter

radius compensation right, tool #3

wear offset 13, coolant ON

N21 X0.365 Move to X position

N22 G01 X0.3125 Z-0.03F0.002

Cut 1st block to XZ position, feedrate0.002 in/rev

N23 Z-0.4 Cut to –Z 0.4

N24 X0.5 C-0.03 Cut chamfer length 0.03 inch

N25 Z-0.75 Cut to –Z 0.75 in

N26 X0.6875 C-0.03 Cut chamfer length 0.03 inch

N27 Z-1.255 Cut to –Z 1.255

N28 G00 G40 X5 Z5 Rapid move to XZ

N29 M01 Stop a running program temporarily

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(T05 – 0.125 wide part off)

N30 T0500 S2000 M03 Tool #5 no wear, spindle CW

N31 G00 X0.85 Z-1.255

T0505 M08

Rapid move to XZ position, tool #5

wear offset 05, coolant ON

N32 G01 X0.6 F0.002 Cut to X 0.6 inch

N33 G00 X0.9 Rapid move to X position

N34 Z-1.1825 Rapid move to Z position

N35 G01 X0.5675 Z-

1.25 F0.001

Cut to XZ position

N36 X-0.02 F0.0015 Cut offN37 G00 X5 Tool retract in X direction

N38 Z5 T0500 M09 Tool retract in Z, tool #5 no wear,

coolant OFF

N39 M30 Program stop

4 G Codes Part 2

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