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Re: ACME screw upgrade for Shapeoko Z-Axis

Posted: Sat Jun 28, 2014 7:41 pm
by sullenx
I am not home right now, I will try it out and post a video with my setup. I did try tighting one screw at a time, it made it very smooth to to turn, but the wobble is what I want to fix. Nevertheless, it is 100% better than the stock, so worth It.


Thanks!!

Re: ACME screw upgrade for Shapeoko Z-Axis

Posted: Sun Jun 29, 2014 4:15 am
by sullenx
Hi Again,

I tried the suggestions here, but unfortunately have not helped me.

Please see the vids:

http://youtu.be/ROY6RoNOyEk
http://youtu.be/HgflI7X_pyE

I checked the coupling, the stepper shaft is almost touching the rod, so i made the standoffs a little bit longer, but didn't help much. I read online, that I'd have to cut the stepper shaft, but before I go there, I'd like to troubleshoot more basic stuff.

The lead nut is really really close to the Z maker slide. Do you think this is what is causing it, if so, how can i make it longer?

Overall, it runs smooth as you can see, but i don't know if that slight wobble is within acceptable range.

Thanks,
Manny

Re: ACME screw upgrade for Shapeoko Z-Axis

Posted: Sun Jun 29, 2014 12:38 pm
by Improbable Construct
There is definitely some wobble there.
I do not think that it is being caused by the nut.
Try cutting the screw down so that it and the motor shaft only extend into the clamping portion of the coupler.

If that doesn't fix it, I will send you a new one.

Re: ACME screw upgrade for Shapeoko Z-Axis

Posted: Wed Jul 02, 2014 7:01 pm
by twwaters
I was wondering if anyone had an idea as to when the "Shapeoko 2 - Acme Upgrade" will be back in stock. I would also love to get the NEMA 23 Z axis upgrade but that can wait.

Thanks!

Re: ACME screw upgrade for Shapeoko Z-Axis

Posted: Wed Jul 02, 2014 10:49 pm
by Improbable Construct
Acme screws will be back in stock next week.

Re: ACME screw upgrade for Shapeoko Z-Axis

Posted: Thu Jul 03, 2014 1:14 am
by twwaters
Thanks! I am sorry to hear about your wife's grandfather.

Re: ACME screw upgrade for Shapeoko Z-Axis

Posted: Tue Jul 29, 2014 9:02 pm
by eagletree
Improbable Construct wrote:Acme screws will be back in stock next week.
I grabbed one of these while it was in stock, but will the Z-Axis Nema-23 upgrade be available soon?

Edit, I just realized there is a thread going on about this in Assembly, I will watch that one. Sorry.

Re: ACME screw upgrade for Shapeoko Z-Axis

Posted: Tue Aug 05, 2014 3:51 pm
by tra
Has anyone figured out an anti-backlash solution? Mine is really loose inside the delrin nut, and deflects a lot! I'm considering going back to the M8 threaded rod at this point.

Re: ACME screw upgrade for Shapeoko Z-Axis

Posted: Tue Aug 05, 2014 4:05 pm
by WillAdams

Re: ACME screw upgrade for Shapeoko Z-Axis

Posted: Tue Aug 05, 2014 4:15 pm
by cvoinescu
What do you mean, deflects? The Z MakerSlide holds the Z axis in position in the horizontal plane -- the machine does not rely on the screw for that, so the leadscrew should never see any load that would cause it to deflect. The load on the nut should be only axial. If you are referring to, for instance, deflection of the tool tip, there are other parts of the machine that bend, twist and give quite a bit, significantly more than the small amount of backlash in the Z nut.

Assuming you're concerned strictly about the amount of backlash of the Z nut, you can try a few things. The simplest is to deliberately install the nut at a small angle to the leadscrew, as much as you can with the screw still turning relatively easily. The mounting holes should be wide enough to permit some mis-alignment like that, and it should reduce backlash substantially, at no cost. It would require more careful alignment of the screw, though.

If you don't mind modifying your nut, you could make a cut from one of the smallest sides all the way to the Acme threaded hole. This would also cut one of the M5 threaded holes in half; drill out one half to 5 mm, leaving the threads intact in the other half. Mount the nut with the drilled out hole toward the plate. The screw in the other hole is for attachment, the one in the cut hole is for anti-backlash adjustment. You could even use a longer screw with a spring on it.

There's at least one other way of cutting the nut that would give it useful anti-backlash properties, but it's more complicated to describe, and I'd need to test it to make sure it would work.