[sperman]

I spent the last week running a batch of parts. When it was all said and done, I ended up losing 20% of the parts, and I have no idea why.

Before I started the batch run, I spent some time optimizing the gcode, and tweaking the feeds and speeds. Once I started the batch, I didn't change anything, other than to take the finished part out of the vise, and put a new blank in. Every once in a while, one of the tools would cut about .050" too deep, but on the next tool the Z height would correct itself. I would take that part out of the vise, put it in the trash, and the next part would run just fine.

I'm at a complete loss on how to explain this. I hope some of you can contribute ideas.

Tormach 1100 series 3, with ATC running on Mach 3.

[SCzEngrgGroup]

Sounds like very likely tool holder pull-out - a not-very-uncommon problem with the Tormach PDB it seems. I don't see what else could "correct itself" on the next tool, unless you're re-homing between tools. A position loss (lost steps) would persist until the machine was re-homed, and would also likely get worse as time went on.

Regards,
Ray L.

[FuriousGeorge]

I agree with Ray, sounds exactly like pullout.

Best Practices for Preventing Collet Slip « Milling Around

Try tweaking the pressure on your PDB. Are you running with flood coolant? I've had pullout caused by coolant splashing tool shanks in the ATC.

The tormach white paper on preventing collet slip does a good job explaining all the issues and how to prevent it.

[Gerry Sweetland]

Sperman, not sure what you mean by " I would take that part out of the vise, put it in the trash, and the next part would run just fine." Do you mean when the part is finished you QC it and see the .05" over depth cut, toss it and put a new part in and run from the beginning, not changing anything and the next part runs fine?
Would it be tool pullout if the next part runs fine?
Gerry

[waltpermenter]

Sperman, not sure what you mean by " I would take that part out of the vise, put it in the trash, and the next part would run just fine." Do you mean when the part is finished you QC it and see the .05" over depth cut, toss it and put a new part in and run from the beginning, not changing anything and the next part runs fine?
Would it be tool pullout if the next part runs fine?
Gerry

Good point if he changes nothing except the part in the vise, a tool that pulled out is not going to magically reset itself.
walt

[David C. Allen]

OP, has "Tormach 1100 series 3, with ATC running on Mach 3."

ATC would be changing tools so the problem could come and go??

David

[waltpermenter]

OP, has "Tormach 1100 series 3, with ATC running on Mach 3."

ATC would be changing tools so the problem could come and go??

David

good point too if he is using the atc and changing tools. more data is needed. are multiple tools being used, if so what tool is causing the problem, is the toolholder itself the problem, ie shank undersize maybe?

[sperman]

Sounds like very likely tool holder pull-out - a not-very-uncommon problem with the Tormach PDB it seems. I don't see what else could "correct itself" on the next tool, unless you're re-homing between tools. A position loss (lost steps) would persist until the machine was re-homed, and would also likely get worse as time went on.

Regards,
Ray L.

Thanks Ray. I wasn't able to come up with an explanation that makes any sense, but yours does. I'll have to check the torque on my draw bar. I probably need to check the collet fit also. I know several people have mentioned that it only touches at the very end on their machine.

[SCzEngrgGroup]

Thanks Ray. I wasn't able to come up with an explanation that makes any sense, but yours does. I'll have to check the torque on my draw bar. I probably need to check the collet fit also. I know several people have mentioned that it only touches at the very end on their machine.

Also check the toolholder forks on the ATC - if one is loose, the tool will not be fully inserted into the spindle. If it were me, I'd sit and watch the thing, and stop it BEFORE each toolchange. When it stops, measure to see if the last cut was out of spec. If it is, then look at the toolholder, and see if it's fully seated in the spindle. Also watch and make sure each tool is fully inserted when the toolchange completes. If you do this, you should see if the problem follows a specific tool, or a specific ATC "slot", etc., ,or if the problem occurs when the tool is loaded, or due to pull-out. A few simple test programs doing heavy cuts with various tools should prove the point one way or the other. I'll bet you find the problem within an hour.

Regards,
Ray L.

[sperman]

I'm pretty sure I know which tool was having the problem, I just couldn't figure out why. Thanks again for the help.