Z Gantry Hangup

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Z Gantry Hangup

Postby flickerfly » Thu Aug 01, 2013 2:34 pm

I have an issue with my Z-axis that when it goes to home bringing the gantry down quickly, it'll often hangup somewhere. My first thought was the threaded rod catching somewhere. I've also been thinking about getting new v-wheels as I believe I may have flattened them when I was first assembling. Maybe it's getting stuck in those grooves. A simple tap on the top will get it to settle back down, but if I don't catch it quick enough it sends the parts it floats on down to the stepper and seizes them making nasty noises.

Usually it happens just before the min endstop. I have seen it happen once or twice closer to the top, but I haven't printed many tall things at this point.

Is this a common problem with a known solution or do you have some other suggestions what I should check?
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Re: Z Gantry Hangup

Postby flurin » Thu Aug 01, 2013 3:54 pm

I had a similar issue.

Check the distance between the Z-Motor-Brackets and the Nut Plates right and left.
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Re: Z Gantry Hangup

Postby flickerfly » Thu Aug 01, 2013 3:59 pm

Thanks flurin
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Re: Z Gantry Hangup

Postby blah_59 » Thu Aug 01, 2013 11:38 pm

You might also want to make sure that they are still square and didn't get misaligned a smidge, it might just be binding on one side.
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Re: Z Gantry Hangup

Postby flickerfly » Wed Aug 07, 2013 2:30 pm

I'm growing more confident that it is the flat spot on the v-wheels. Where do I get replacements? I looked at inventables, but only saw ones that include the bearings. I don't need the bearings of course.
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Re: Z Gantry Hangup

Postby orcinus » Wed Aug 07, 2013 3:16 pm

Untighten the V-wheels, roll the gantry up and down a bit, then let the whole thing sit for a while.
See if that makes the "flat" go away.

See:

viewtopic.php?f=33&t=2139
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Re: Z Gantry Hangup

Postby lambinator » Wed Aug 07, 2013 5:17 pm

You could check the OpenBuilds parts store here: http://openbuildspartstore.com/wheels-bearings/ I've purchased some items from them in the past and they were very good to deal with.
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Re: Z Gantry Hangup

Postby flickerfly » Wed Aug 07, 2013 5:31 pm

Thanks lambinator. Are they using the same dimensions for their v-wheels? The ones I use currently are flat on the outside edges and those angle inward from the outside.

http://openbuildspartstore.com/openbuil ... el-delrin/

I think what I'm seeing isn't that I tightened my wheels too much, but that I put the upright makerslide too far apart and need to slide one in just a fraction. The flat spots are on the four inside v-wheels. I just remove the carriage entirely for now. Hopefully that'll resolve this. It seems like a good idea to have a couple spare v-wheels around anyway though so I'll look into that. I've heard of some guys seeing them split.
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Re: Z Gantry Hangup

Postby lambinator » Wed Aug 07, 2013 10:20 pm

I checked the wheels I received from OpenBuild with my OpenRail order and they are different than the ones I received with my Hadron kit from ATI. My ATI wheels are like yours with a flat on the outside but the OpenRail wheels have an angled outside edge. They both use the same bearings and the groove looks like it will end up in the same plane, but I measured the diameter of the inner V groove and the OpenBuild wheels are about 0.1mm larger. That might be fine if you used it on one of the wheels that use the eccentric spacer.

Hope this info helps,
Ross
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Re: Z Gantry Hangup

Postby orcinus » Wed Aug 07, 2013 10:54 pm

flickerfly wrote:I think what I'm seeing isn't that I tightened my wheels too much, but that I put the upright makerslide too far apart and need to slide one in just a fraction. The flat spots are on the four inside v-wheels. I just remove the carriage entirely for now. Hopefully that'll resolve this. It seems like a good idea to have a couple spare v-wheels around anyway though so I'll look into that. I've heard of some guys seeing them split.


Makerslides too far apart are basically the same thing as eccentric spacers too tight - except only for the outer V-wheels :)
In any case, if you still got flats, leave the wheels be for a bit, then roll them around, they should "heal" themselves.

And yeah, it's a good idea to have a few spares. I bought two extras just in case and it turned out it was a good call, as after a year of use, one V-wheel cracked on me.
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