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Y axis issues

Posted by oatridge 
Y axis issues
November 17, 2012 12:15AM
I have been consideraby frustrated with some Y axis issues. Part way through a print (never at the beginning) usually after at laest 10mm of layer, I get a sideways shift for several layers, that is one shift then another shift etc. It then come right, though of course shifted and procedes to the end of what is now a useless print. The Y axis seems free enough, there is no heating of the stepper or the driver IC (ramps board). I have changed the stepper, no difference, reduced the stepper current slightly, likewise and considerably reduced accelleration and XY jek figures. I thought that had fixed it as I seemed to be able to print OK but the problem came back. I had chrome Y rods with LM8UU and suspected that may have been an issue so I swapped the rods out for rolled silver steel. The problem persists. Anyone have any ideas? I am about to re-build with bronze bushes and back to the chrome rods, I have these on all the other axis with no issues.
Re: Y axis issues
November 17, 2012 12:53AM
Is the grub screw to loose? Is the stepper drivers overheating and allowing slipping?
Re: Y axis issues
November 17, 2012 01:30AM
Grub screww is ok, very tight and on a flat shaft. I'm not sure about the heatiung. The driver IC is onlky warm to the touch, my bexperience of electronics is that hot would still be Ok. It is worth noting thta it takes a while for this to occur (and I'm not there to check temperature) so it might be an issue, I do have heatsinks on Z and Y axis. Not on extruder or X where there are nio issues.
Re: Y axis issues
November 17, 2012 02:27AM
Is the hot end catching on the part? This might happen if your part is warping.
Does it happen on small parts and larger parts the same way?
Are you microstepping? Does it still happen if you drop back the microstepping to 1/4 stepping or less?
Mike P
Re: Y axis issues
November 17, 2012 04:55PM
I had this when I tried printing some Raspberry Pi cases, turns out my printer didn't like the recommended settings from the person who designed the cases, went back to my own settings which were not as fine and it printed perfectly. Another thing is to see what other electrical devices are on the same circuit. Even something like a fridge turning on and off can affect prints

Experimenting in 3D in New Zealand
Re: Y axis issues
November 17, 2012 05:38PM
Interesting with the part difference. I have only seen it on large parts. Things like the calibration tower print perfectly. I am using 1/16th microstepping, I'll reduce that and see if there is a difference. the printer is remote from any switching power source however I could always try a UPS and see if that had an effect. All good ideas to follow up. I am a little suspicious as initially I did not have any problems, I suspect something may have changed.
Re: Y axis issues
November 19, 2012 05:30AM
Y axis sorted. Noted after dissasembly tahr one of the LM8UU had missing balls. Repaced with chrome rod, new y table and bronze bushes. Very smooth now. The previous fault was intermittent and the table felt smooth. It was only after a late night long print that i noticed some lumpyness.
Re: Y axis issues
November 19, 2012 04:47PM
Hi Oatridge,
Were those LM8's imports from China?

Re: Y axis issues
November 22, 2012 03:12AM
Pleased you are sorted.

I had a Y axis problem occasionally on my Huxley, so I watched it through a few builds until I saw what happened.
The cable ties I had holding the hotend wires to the bowden tube occasionally caught on other cable ties I had holding the USB cable to the frame. If they held long enough, it skipped a few mm on the Y axis. So I have replaced nearly all the cable ties on my printer with cable tidy. End of problem.
Re: Y axis issues
November 24, 2012 05:49AM
On a quick comparison the LM8UUs directly from China are smoother than the LM8UUs from USA (China ??).
Re: Y axis issues
November 24, 2012 04:07PM
That's interesting Oatridge. I buy a lot from China and LM's were on my list anyway.
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