Z-axis motors grinding and out of sync

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Z-axis motors grinding and out of sync

Postby runninfarmer » Sat Feb 01, 2014 5:02 am

I'm having problems with my z-axis motors. I currently have them wired in series to my RAMPS board with a Vref of 0.7-0.8V. I found the default parallel configuration was worse. They're almost at full torque and they keep losing steps. One will also stall while the other continues to work, further causing the problem by putting all the weight on one side. The motors are 57 oz-in motors and I have the acceleration set at 10 m/s^2 and feedrate at 3-4 mm/s. Should I move to higher torque motors? Do I need a different power supply. Here's a video of them runnning on youtube and me shoing how they stop skipping steps when i lift the weight of the gantry off them:

https://www.youtube.com/watch?v=s_u5O6HjcBo

I appreciate the help!
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Re: Z-axis motors grinding and out of sync

Postby flickerfly » Mon Feb 03, 2014 1:42 pm

I've had some grinding on the Z-axis that turned out to be related to the max speed. I haven't yet completely solved my problem, but it isn't grinding on the Z anymore.

Check out this post for details: https://groups.google.com/forum/#!topic ... 2Y2MUSbkXg
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Re: Z-axis motors grinding and out of sync

Postby TLHarrell » Mon Feb 03, 2014 7:29 pm

When trying to debug a system, remove as many variables as possible and test each part separately. I would recommend disconnecting the motors from the system and try spinning the Z axis by hand to check for binding. Check that the vertical Makerslide are parallel and that the V-groove wheels operate freely but without any slop.

Until you test and verify that, simply adding more torque doesn't do much for you.
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Re: Z-axis motors grinding and out of sync

Postby Merfman » Tue Feb 04, 2014 2:25 pm

I had a similar issue, two things seem to have it working OK:
1) Loosen the Z-Axis connections to the gantry. This over-constrains the movement and gets bound up unless your
rods are perfectly straight (mine were not).
2) I had one motor turning slightly more powerful than the other so one would turn when the other would not, causing
further binding. I turned up the motor current just a smidge and with the other mod, it now works OK...
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Re: Z-axis motors grinding and out of sync

Postby flickerfly » Tue Feb 04, 2014 2:37 pm

My other issues appears to have been bed leveling. I had applied a mod (a bit of blue tack to the nuts and bolts) and hadn't level the bed in so long that I'd forgotten about the mod and really confused myself. :-) I'm all good again.
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Re: Z-axis motors grinding and out of sync

Postby runninfarmer » Thu Feb 06, 2014 8:46 pm

Thanks for the info everyone. I got fed up with the leadscrews and am converting my z-axis to belt drive. The belt drive is nice because my towers arent perfectly square with the gantry plates, so it helps correct for that. I'm also liking the belt drive a lot more due to ease of calibration because I like to have a max endstop for homing. The only isssue with it is the gantry falling when motors are powered off, but I'm placing rests in place for it. Once I have it fully configured I will post pics if there's any interest.
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Re: Z-axis motors grinding and out of sync

Postby Zat German » Fri Feb 07, 2014 2:46 am

I'm interested in seeing it. A belt drive system would be nice for homing Z at the top really quickly. The gantry with everything on it is pretty heavy though, you may end up needing beefier steppers.
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Re: Z-axis motors grinding and out of sync

Postby TLHarrell » Fri Feb 07, 2014 5:25 pm

I was considering the concept before of a belt driven Z axis. To eliminate the drop when the motors are not powered, I was thinking along the lines of a worm gear drive. The Z axis is the slowest axis anyway, and something on the order of a 1:4 to 1:8 worm drive should be quite suitable. The worm gear will have a small amount of backlash, but should not be a problem in this configuration.
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Re: Z-axis motors grinding and out of sync

Postby joeblow » Sun Feb 09, 2014 10:40 pm

I had the same issue and after many hours of frustration found that one of the jumpers behind the driver for the Z axis was not making a good connection. Simply rotating all the jumpers and all was good.
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