Smithy CNC Mills - Manual (Page 109)

Example 2 - Absolute Position G81
Suppose the current position is (1, 2, 3) and the following line of NC code is
interpreted.
G91 G81 G98 X4 Y5 Z-0.6 R1.8 L3
This calls for incremental distance mode (G91) and OLD_Z retract mode (G98).
It also calls for the G81 drilling cycle to be repeated three times. The X value is
4, the Y value is 5, the Z value is -0.6 and the R value is 1.8. The initial X posi-
tion is 5 (=1+4), the initial Y position is 7 (=2+5), the clear Z position is 4.8
(=1.8+3), and the Z position is 4.2 (=4.8-0.6).
OLD_Z is 3.
The first preliminary move is a traverse along the Z axis to (1,2,4.8), since
OLD_Z < clear Z.
The first repeat consists of 3 moves.
1. a traverse parallel to the
XY-plane to (5,7,4.8)
2. a feed parallel to the Z-
axis to (5,7, 4.2)
3. a traverse parallel to the
Z-axis to (5,7,4.8) The sec-
ond repeat consists of
moves. The X position is
reset to 9 (=5+4) and the Y
position to 12 (=7+5).
1. a traverse parallel to the
XY-plane to (9,12,4.8)
2. a feed parallel to the Z-
axis to (9,12, 4.2)
3. a traverse parallel to the
Z-axis to (9,12,4.8) The third
repeat consists of 3 moves. The X position is reset to 13 (=9+4) and the Y posi-
tion to 17 (=12+5).
1. a traverse parallel to the XY-plane to (13,17,4.8)
SmithyCNC Programmer’s Reference Manual: Mill Canned Cycles
SmithyCNC Programmer’s Reference Manual: Mill Canned Cycle 10-6