Confused - G81 & initial plane

[mbam]

New to a machine with tool offsets, trying to get this straight in my head.

I have set SETZ 0 at the top of the travel

Used the utility to set tool offsets to workpiece, tool #8 is at -3.1320
Z0 does put the tool right on the workpiece.

Problem is at the end of the cycle, the next G0 Z1 causes Z to hit the limit. Is the tool offset canceled and the machine is trying to overtravel ?

Code below:

N68 T8 M6 (#7 TAP DRILL)
N69 G43 Z .25 H8
N70 M3 M8 S1000

N72 G0 Z.25
N73 G81 X18.6299 Y-7.19 R0.1 Z-0.35 F5.0 G98
N74 X17.0055
N85 G80

N87 G0 Z1

Thanks!!

[Shizzlemah]

I assume the machine overtravels down?

Your last line should read:
N87 G0 Z1.
not
N87 G0 Z1

If you enter X Y Z without the decimal, it will interpret in tenths, so Z1 and Z0.0001 are the same.

Other than that the code looks ok to my eye. Are you running in format 1 or format 2? The length offset should be in effect until calling H0 (or M6)

[mbam]

Yep, missed the decimal. No, it overtravels up. Using Format 1

[fizzissist]

Sometimes I find it real helpful to see examples not in the manual....

Here's my version of a hole pattern in Format 1 for a part I just ran, comments on the function in lowercase after the parenthesis. I don't use G43/G44. Top of the part is Z0.

G0 G90 X0 Y0 E1
T3 M6 (1/4 90DEG SPOT-------
S800 M3
G0 H3 D3 Z1. M8 (this moves the spindle down and initiates the H offset value
G83 G98 R0+.1 Z-.09 F2.5 Q.04 P.01 X.8503 Y-.8503 (1" above the part is the initial plane, .1" is the retract level ... the tool will go up to 1" above the part before moving to the next hole
X7.5248
Y-5.6498
X.8503
G80 (the tool will move up to 1" above here...
G0 Z2. M9 (turns coolant off and moves briefly to 2" above
G0 Z0 H0 M5
T4 M6 (