I am getting a peculiar Z movement from mach3 (lockdown version) when running this code which is at the beginning of a job:

N60 G00 G20 G17 G90 G40 G49 G80
N70 G00 Z1.0
N80 X0.0 Y0.0 Z1.5
N90 M06 T1 G43 H1  ( Slot Drill )
N100 G94 S1000 M03
N110 X0.4375 Y0.1875 Z1.5
N120 X0.4375 Y0.1875 Z0.1181
N130 G01 X0.4375 Y0.1875 Z-0.015 F1.5
N140 X0.4375 Y0.2095 Z-0.015 F2.0
N150 X0.1655 Y0.2095 Z-0.015
............................

The Z axis initially drives to 0.5 inches  then drives up to 1.5"

Watching the DRO it ramps up to 1.5" and immediatly resest to 0.5" so the z movement reflects the DRO setting in its final position but does not get the chance to move to 1.5".

I have also noticed that a 1" Z error sometimes occurs in that the Z axis drives to 1.5" and then drives up another 1" so on the way down it is cutting air. On these occasions the DRO indicates 1" when it should be down to 0.

The common factor tseems to be this mysterious 1" that occurs.

Any ideas around that might account for this behaviour?

Alan

Well, for a Fanuc mill, you usually call out tool height before doing a Z rapid move as in:
O2047
N1 G20 G56 G90 G94
(OUTER PROFILE, .625" 2FL)
N2 T8M6
N3 S2139M3
N4 G0G56X-.6912Y6.7629
N5 G43Z1.H23M8
N6 Z.1
N7 G1Z-.1F2.
This start of program is what I've always used with success.

Have your first move and the G43 on the same line. You need to have the tool length comp active.

Brian,

Thanks, using my example code above in the first post would you put the G43 on line 70?

I have the tool length set to 1" in the tool data set in the CAM program. Should a further setting be required in Mach3?

regards

Alan

yes put the G43 H1 on line 70