#68 G42 compensation applied at the wrong moment

[romain145]

Assuming the following code:

G0 X 166.548 Y 207.690 (Point 1)
G42 H03 (Cutter compensation)
F400
G1 X 170.649 Y 203.306 (Point 2)
G2 X 161.881 Y 203.306 I -4.384 J 4.384
G0 Z -10.000
F150
G1 Z -13.000
F400
G2 X 183.209 Y 224.634 I 10.664 J 10.664
G2 X 161.881 Y 203.306 I -10.664 J -10.664

The compensation is applied at the point 1 as shown in the picture G42_1. The green line between 1 and 2 represents the programmed path, and the red line represents the tool center path. The orange line is the tool radius (programmed in H03=6.000mm in my CNC).
The point 3 is where the problem happens.
Because the approach (1 to 2) is made from the top of point 2 the compensation will result in overcutting, an alarm is generated and the NC stops at the start of the block.

Solution 1: the compensation should be applied after the point 2.
Solution 2: the approach should be done from the other side (from "under" the point 2 in this case), to ensure the compensation is always applied on the same side of the movement.

I can give the complete Gcode, and the manual for the Fanuc 0-M controller documenting this issue.

[J-P]

Yup yup,
We know this whole cutter compensation is a problem.
Currently we are pretty much all working on it see ticket 59 "Enter and exit point is outside of compensated shape"
Since I see quite a resemblance with that one, and that one contains a lot of comments, I will mark this one as a duplicate.

But we are working on it ;)