[choppero]

I have a PCNC 1100 making a rough cut with 3/4 rough/finish endmill. On the last cut Attachment 462290 the cutter is actually pulling the axis down so the final depth is deeper than the fixture top.
Crazy? I recheck the tool length and it is still the same. When I rehome the axis the tool will go to the correct height. for the final depth. This has started after running about 10-12 parts.
The material is 7/8 4140 annealed steel and the cutter is coated cobalt. The program is ramping the cutter at a 1 degree conventional cut.
Is it the cutter dulling? Is the cutter too large for the machine?
Oh ya, the spindle speed is 1000 and IPM 10

[popspipes]

Have you checked the Z axis coupler (lead screw to stepper) if this slips it could cause what you are describing.
The folks that assemble the Tormachs arent very good at torquing screws, at least that has been the case with my machine.

[choppero]

Where is the access. Recommended torque?

[choppero]

Have you checked the Z axis coupler (lead screw to stepper) if this slips it could cause what you are describing.
The folks that assemble the Tormachs arent very good at torquing screws, at least that has been the case with my machine.

I found the screws but a 1/8 hex bit is too big and a 3mm is sloppy. I gave all of them a hand tight with screw driver handle driver but if I torque them the bit will strip the socket head. I'll give Tormach a call tomorrow.

[popspipes]

I would suggest replacing the screws, many of them have a bit oversize socket and are relatively soft, I have found replacing them is the best option.

Mark the coupling and the leadscrew and stepper shaft then its easy to see if it has slipped or not.

[jwatte]

That's a pretty big cutter.
Are you sure it's pulling the Z down (missing steps? coupler deflection?) rather than getting tool holder pull-out?

[choppero]

I'm now sure that the cutter dulled enough to cause the coupling to slip. And the next time I run these it will be with a 1/2" rough /finish. Thanks for the tip popspipes