Z Rails Worn

[Ken Sully]

I have talked to a couple of Bot senior users and they have not seen this problem.
The symptom: Going to z-zero my PRS Alpha and I noticed a stutter or what I would call a bump in the exact same place when the z moved.

What I found: After a lot of cleaning attempts and moving the z car by hand I removed the z assembly to see what was going on. I have found the rails to have an unusual wear on one side you can see the ware but can not feel it with your finger. When you move the bearing block it does not move smoothly along most of the track. Bearings feel fine ware is on the track. This unit has around 300 hours on it and I find it hard to believe this would fail this soon.

Going to call Shopbot Monday and may send the entire z-csr back to the factory.
Has anyone else had this problem? Or have any of you moved the z by hand to see if it moves smoothly?

[Ken Sully]

I ended up taking off the entire Z-Car and have discovered what was wrong.
My PRS has the wheels enclosed so they are hard to see. What I found is the z bearings were way to tight. This must have came this way from the factory. I found in the Bot docs an adjustment procedure that is supposed to be preformed or checked every 40 hours. I do a lot of 3D work. Both tracks (Z) were worn quite a bit one of them had a gouge it it which could not be adjusted out.

New z rails on the way, guess I will need to keep an eye on the movement of the Z from now on.