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Z Plate movement - solved (for me anyway)

Posted: Sun Jan 31, 2016 8:48 am
by apspurgeon
1.jpg
Pulling it apart
1.jpg (111.1 KiB) Viewed 1348 times
1.jpg
Pulling it apart
1.jpg (111.1 KiB) Viewed 1348 times
Hi all

Like many, I've had issued with Z plate movement causing chatter and poor cuts in the Y Axis.

I have the v-wheel as tight as they can go, and installed steel bars on the Z-Plate. However, I was still getting movement.

On closer inspection, I found 90% of the movement was caused by the bottom 2 v-wheels (closest to the waste board) where the plastic v-wheel was moving on the bearing. It would 'click' as it moved and the small movement of approx 0.5mm translated to approx 2mm at the tip of the cutting bit.

Both bottoms bearing/v-wheel assemblies have the problem, the top 2 are OK. I strongly suspect the bearing inners have loosen as these wheels take the most load under Y movement stresses.

Pulling the bearing assembly apart, there are 2 bearings with a washer sandwiched between them. This washer is now too thick as the v-wheel can slop between the bearings so they need to be a bit closer together.

Ultimately, new bearings are needed....but I don't have any. What is did do was cut some copper sheet to make a thinner washer (1mins work).

After re-assembling it all, both v-wheels are perfect. Zero movement of the plastic v-wheel on the bearing.
My Z-Plate moment is close to Zero even with significant stress.

If you have persistent Z-Plate moment check the video out.
https://www.youtube.com/watch?v=OWETzUwATOY

Pics of the fix below.

Re: Z Plate movement - solved (for me anyway)

Posted: Mon Feb 01, 2016 12:26 am
by twforeman
I measured my v-wheels and they are out of tolerance. The rib in the middle is too small, matched up with a washer that is too thick it causes the same issue you have.

See my details here: http://www.shapeoko.com/forum/viewtopic.php?f=37&t=7567

Re: Z Plate movement - solved (for me anyway)

Posted: Mon Feb 01, 2016 1:24 am
by apspurgeon
Hi there....I just saw that thread after posting this. Hmmm.....it's curious that only my bottom 2 v-wheel had the problem. I'll keep and eyes on it, just glad the movement is gone!!