Z travel increasing as the cut proceeds.

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Leo
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Re: Z travel increasing as the cut proceeds.

Post by Leo »

OK - seeing the process really helped me. I had to go back and read your original post. What was confusing me was the pictures you were showing. Those pictures do not show the problem, and I thought you were showing the problem. NO - that is just the beginning of the finish cutting, and that part is fine.

Now - I am even more on the control software. You have servos, so lost steps is out. It didn't sound like that anyway.

I had a somewhat similar issue with an older machine. Way different scenario, but the control software was faulty.

I wish I could help, but I have no idea where to go from here. I do hope the manufacturer can help you and I am sure all of us here would like to know what the solution is.

Just a thought - have you tried a different post? Gcode is pretty generic and standard. Some machines use differ code, but if it's a gcode machine - maybe a generic gcode post will work.

Good luck my friend.
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Re: Z travel increasing as the cut proceeds.

Post by martin54 »

I was thinking more along the lines of binding on the linear rails rather than something being loose, but that may well be picked up by the servos as with lost steps. Think as Leo has said this is beyond my knowledge so would also like to know what the solution was once you have sorted it out. :lol: :lol: :lol:

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Re: Z travel increasing as the cut proceeds.

Post by jarm2 »

If you look closely at the cut, it should be a straight line from the curved end into the rest of the part. It is tapering into the piece and the cut is getting noticeably deeper. The cut should only be .020 on the low points of the rough cut.
I agree it is likely the control software or the hardware picking up erroneous signals somehow. Thanks for all your help. It gave me some areas to check. Unfortunately, the problem is not solved yet. I will continue to pursue with the control folks and see if they can zero in on the problem. I do appreciate all the feedback and happy carving to all of you.
The post I am using is set up just for this machine and control combination so I need to stick with it if possible.
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SteveNelson46
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Re: Z travel increasing as the cut proceeds.

Post by SteveNelson46 »

It could be bit deflection. On your finish toolpath you have a raster angle set to 45 deg. Try setting it to "0" or "90" deg. to see if anything changes. Just a stab in the dark.
Steve

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Re: Z travel increasing as the cut proceeds.

Post by jarm2 »

Thanks for the additional info. I think I found the error per a suggestion from the control folks, I unplugged my pendant and cut a test file. It seemed to be cutting the way it should. I will cut a larger piece today and see if it continues. May need a new pendant. Got used to using it and will miss it, but at least I can keep cutting.
Bit deflection wouldn't account for the increase in depth. I am not sure why the pendant affected the depth change, but with it disconnected, things were back to normal. Once again, thanks to all who gave input. It was a unique problem to me and an easy solution once we located it.
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Leo
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Re: Z travel increasing as the cut proceeds.

Post by Leo »

WOW - I would never have guessed that.

Thanks for the info.
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jarm2
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Re: Z travel increasing as the cut proceeds.

Post by jarm2 »

It turns out the pendant wasn't the problem after all. I did a more complicated carving with more z movements and the pendant disconnected and it began going deeper again. From .25" above the piece on the finish pass at the deepest point(1.5" deep cut) it got low enough about 1/4 way into the carving to rub the collet on the material. I will be working with my control folks and scratching my head a lot. May be some type of interference caused by the VFD on the spindle or ????.
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Re: Z travel increasing as the cut proceeds.

Post by Rcnewcomb »

May be some type of interference caused by the VFD on the spindle or ????.
To rule that in/out with no material on the machine run the same job without the spindle running.
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Re: Z travel increasing as the cut proceeds.

Post by jarm2 »

I couldn't find the previous post on my z axis issues so I will start a new one. I did find the problem and it was mechanical, not controller or software. The folks at C&CNC were fantastic to work with and we were able to zero in on a clamp type coupling that was slipping by a few thousands each time the spindle raised, causing the bit to gradually go lower into the piece. Below is some of the steps we took to find the problem.
C&CNC
Your next step has to be to remove the motor and encoder and set it up so you mark a zero point on the shaft and a pointer (youcan mount a pulley with teeth or a disc with markings) and do a bunch of moves but bring it back to the beginning and pause long enough to check it . This narrows it down to the motor/encoder /driver . If its dead on then it HAS to be mechanical . The encoder controls the shaft position . You are gaining down even on lifts
You have to start out each time at exactly he same spot. and zero the DRO . In the code after you run a series of up and down you do a return to Z zero and an M1 pause to see how far off zero you are
ME
I recoupled the z motor. I cleaned and tightened the coupling as tight as possible. Running the z tests again seemed to show a slight .02 up movement this time with three test runs. It appears something in the coupling was allowing the unwanted movement. I will cut the long file tomorrow and see if it really is solved. Fingers crossed. I will probably modify the coupling with a flat spot on the ball screw shaft and an allen screw in the coupling. It was relying only on friction and although very tight, could possibly have been slipping. Thank you for all your help in searching for the problem. Sorry about not finding the coupling issue sooner. The cut tomorrow will let me know for sure.
With the coupling locked in place and the allen screw tightened to the new flat on the shaft, I am back in business. Thanks to those who offered suggestions and helped me find the solution.
Happy carving.
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Leo
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Re: Z travel increasing as the cut proceeds.

Post by Leo »

Yeah, that does make sense. Glad you found it, and thank you for posting the solution.
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Re: Z travel increasing as the cut proceeds.

Post by 4DThinker »

I also am glad you found the problem. By your description a loose/slipping Z coupler had to be the culprit if the depth change was consistent between depth passes.

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