Z-axis grinding

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Z-axis grinding

Postby Panopticon » Sun Oct 13, 2013 7:36 pm

An issue I that has been re-occurring since my Hadron build is not entirely resolved yet. The other day I replaced my Ubis hot-end with a shorter all metal hot-end, in doing so I had to re-adjust my end stop to a lower position on the Z-axis. As a result the Z-axis couplers will start grinding (painfully!) to a halt as the X-axis gantry is lowered to the bed. I'm led to believe this is a mechanical issue as I can manually turn the Z-couplers to lower the X-gantry down to the bed, as the gantry gets closer to the bed it becomes increasingly difficult to turn the Z-axis couplers to the point where I can not turn them. If I reverse and go up the Z-axis the couplers become easier to turn, and near the top there's hardly if any resistance. I've tried adjusting and changing out my Z-stepper drivers but the problem still exists, I even removed the Z-rods and Z-couplers and I can confirm that the motors spin without any problems. I've also started from the top and ensured the X-axis gantry is completely level before moving down and I still get the grinding halt towards the bottom!. I'm assuming the Z axis rods+couplers should turn with no resistance if I manually move them up and down anywhere on the Z. Any ideas on what the problem could be? I'm at my wits end! :cry:
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Re: Z-axis grinding

Postby cvoinescu » Sun Oct 13, 2013 11:21 pm

This can happen if the motor shafts aren't perfectly aligned with the holes in the nuts connected to the X axis. Try to loosen the screws holding the brackets to the aluminum profile, lower the Z as far as it will go, then carefully tighten the brackets in that position. Verify that it moves freely all the way up and down. Depending on the type of nut, it may help to loosen the nuts too when the Z is all the way down, then re-tighten them.
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Re: Z-axis grinding

Postby Panopticon » Mon Oct 14, 2013 4:01 pm

cvoinescu wrote:This can happen if the motor shafts aren't perfectly aligned with the holes in the nuts connected to the X axis. Try to loosen the screws holding the brackets to the aluminum profile, lower the Z as far as it will go, then carefully tighten the brackets in that position. Verify that it moves freely all the way up and down. Depending on the type of nut, it may help to loosen the nuts too when the Z is all the way down, then re-tighten them.



I think you're on to something! I loosened the two metric screws in the silver blocks that the z-threaded-rods go through. I started from the very top and the X-gantry came down without any grinding/stalling, however there was a lot of squealing (I guess that's the metal on metal). When the nozzle got to the bed, I manually turned the couplers to go back up the Z-axis and there wasn't much resistance. After verifying that I could turn the couplers without any hitches I went back down to the bed and tightened the 4 screws back in the silver blocks thinking I was in the clear. Now if I move the Z-axis/X-gantry up away from the bed using the motors it grinds and stops Hmmmmm. :?:

*You say that there's nuts located where I'm suppose to be making the adjustments, but I don't see any, just those black metric screws in the silver blocks,am I looking in the right place?
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Re: Z-axis grinding

Postby cvoinescu » Mon Oct 14, 2013 4:58 pm

Not sure which blocks you're talking about -- the Z nuts went through several revisions, and each manufacturer seems to have their own design and material choice.

I think the most likely cause is not the nut, but the motor itself being a little off, so loosen the screws that attach the Z motor brackets to the frame and see what happens.
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Re: Z-axis grinding

Postby orcinus » Tue Oct 15, 2013 2:07 am

The easiest way to align your rods is to put your ORD Bot on a flat, level surface, then prop the X gantry some way up (e.g. Z = 150ish cm).
Now loosen the adapter set screws and unscrew one of the rods until it's just above the adapter and let it "hang" off the nut.

Now unscrew the Z stepper plate and align the adapter hole with the rod, retighten the stepper plate, screw down the rod and tighten the set screw. Rinse and repeat for the other side.

Finally, don't forget the Hyneman's law:
When in doubt, lubricate!
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Re: Z-axis grinding

Postby Panopticon » Tue Oct 15, 2013 6:01 am

orcinus wrote:The easiest way to align your rods is to put your ORD Bot on a flat, level surface, then prop the X gantry some way up (e.g. Z = 150ish cm).
Now loosen the adapter set screws and unscrew one of the rods until it's just above the adapter and let it "hang" off the nut.

Now unscrew the Z stepper plate and align the adapter hole with the rod, retighten the stepper plate, screw down the rod and tighten the set screw. Rinse and repeat for the other side.

Finally, don't forget the Hyneman's law:
When in doubt, lubricate!



Thank you for the tip, I need some clarification though:

1. What is are the "adapter(s)"? Are they the silver metal blocks attached to the sides of the X-gantry that the z-rod goes through?
2. Set screws? (I don't see any set screws) in the adapter(s) if my guess above is correct.
3. I see no nuts either.

I sort of get what you're talking about, my parts/revisions may be different from yours.

I will try and post-some images / videos soon.
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Re: Z-axis grinding

Postby orcinus » Wed Oct 16, 2013 7:46 pm

1. "adapter" = the thing connecting your threaded rod to the stepper motor shaft
2. "set screws" = whatever is holding the threaded rod and the stepper motor shaft in the adapter (the early versions had set screws, flexible couplers usually don't have set screws, but screws that clamp the adapter to the shaft and rod)
3. "nuts" = the things attached to the X gantry, through which rods screw and convert rotation into translation of the Z axis
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Re: Z-axis grinding

Postby Panopticon » Wed Oct 16, 2013 11:51 pm

orcinus wrote:1. "adapter" = the thing connecting your threaded rod to the stepper motor shaft
2. "set screws" = whatever is holding the threaded rod and the stepper motor shaft in the adapter (the early versions had set screws, flexible couplers usually don't have set screws, but screws that clamp the adapter to the shaft and rod)
3. "nuts" = the things attached to the X gantry, through which rods screw and convert rotation into translation of the Z axis


Thanks for detailing the "things"! All clear now, I will try your adjustment recommendations. ;)
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