CNC Milling | G68 and G69 Codes | Coordinate Rotation

In this article, we describe how to use G68 and G69 codes for coordinate rotation in CNC milling machines with all details and examples.

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Introduction

A programmed shape can be rotated. By using this function it becomes possible, for example, to modify a program using a rotation command when a workpiece has been placed with some angle rotated from the programmed position on the machine. Further, when there is a pattern comprising some identical shapes in the positions rotated from a shape, the time required for programming and the length of the program can be reduced by preparing a subprogram of the shape and calling it after rotation.

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G68 and G69 Codes Format

G17, G18 or G19 ; Select the plane in which contains the figure to be rotated.
G68 α_β_ R_ ; Start rotation of a coordinate system.
……..
G69 ; Coordinate system rotation cancel command

Parameters

α_β_ : Absolute programming for two of the X_, Y_, and Z_ axes that correspond to the current plane selected by a command (G17, G18, or G19). The command specifies the coordinates of the center of rotation for the values specified subsequent to G68.
R_ : Angular displacement with a positive value indicates counter clockwise rotation.

G68 Code Examples

G68 CNC Program Example – 1

CNC Coordinate Rotation – G68 Code Example Program


G00 Z3
G00 X22 Y13
G01 Z–3
G01 X47.27 Y29.59
G03 X29.59 Y47.27 R12.52
G01 X13 Y22
G01 X22 Y13
G00 Z5

G00 Z3
G68 X0 Y0 R135
G00 X22 Y13
G01 Z–3
G01 X47.27 Y29.59
G03 X29.59 Y47.27 R12.52
G01 X13 Y22
G01 X22 Y13
G00 Z5

G00 Z3
G68 X0 Y0 R225
G00 X22 Y13
G01 Z–3
G01 X47.27 Y29.59
G03 X29.59 Y47.27 R12.52
G01 X13 Y22
G01 X22 Y13
G00 Z5

G00 Z3
G68 X0 Y0 R315 (or R–45)
G00 X22 Y13
G01 Z–3
G01 X47.27 Y29.59
G03 X29.59 Y47.27 R12.52
G01 X13 Y22
G01 X22 Y13
G00 Z5

G68 CNC Program Example – 2

CNC Coordinate Rotation – G68 Code Example Program – 2

N390 G54 G90
N395 T1 M6
N400 G99 F300 M3 S1000
N405 G43 G0 Z20 H1
N410 G00 Z5
N390 G00 G90
N395 G00 X68Y0
N400 G01 Z–5
N465 G03 I–20
N470 G00 Z5
N475 G68 X0 Y0 R72
N480 G00 X68 Y0
N485 G01 Z–5
N480 G03 I–20
N485 G0Z5
N490 G68 X0 Y0 R144
N490 G00 X68 Y0
N495 G01 Z–5
N500 G03 I–20
N505 G0 Z5
N475 G68 X0 Y0 R216
N480 G00 X68 Y0
N485 G01 Z–5
N480 G03 I–20
N470 G00 Z5
N475 G68 X0 Y0 R288
N480 G00 X68 Y0
N485 G01 Z–5
N480 G03 I–20
N483 G50
N485 G00 Z5
N490 G00 Z200
N495 M05 M09
N555 M30


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