X axis is not accurate... Y and z seem fine

[chrisn]

X axis is not accurate:
I was running a very thin (.040") Aluminum part taped to an MDF backer board and using a .125" End mill (2 flute) running at about 1000mm/min (I know all these mixed units.. sorry) the part that was supposed to be 1.180" across in the X and it came out 1.135"

I did not realize it until I had a lot of parts... Damn.  Thought, I screwed up, but my layout if good. Reboot Axiom and cut one more... nope. Still off.

I'll put a piece of scrap even slower and report back but now I am running out of time so I am posting this now if case somebody has an idea.

Y and Z are fine at +/- about .004"
Lead screw is not sloppy

I'll setup a 1" dial and jog 20mm in the X and see if that reads accurate with no load..

Thanks
Chris
 

[garylyb]

That happened to me. It was the bolt on the end of the x axis that was loose.

Turn the machine off, and see if you can rock the x axis by hand, there should be almost no play. If there is, the bolt might be loose.

Take off the plastic panel on the gantry away from the stepper motor. You'll see the bolt at the end of the x axis.

[chrisn]

Garylyb,
You lead me to it. The ganty was good-n-tight. But as I was wriggling things for looseness I found the X lead screw would pull in and out - A lot!.
When I took the plastic cover off the side the nut for the lead screw was lying on the floor of that cavity. I put it back on and tightened it up a bit.

I used as much torque as I could muster with a wrench on the nut and my hand grip on the lead screw... I'll say "mot much" torque.

Anybody know if there is a technique and torque spec?

Thanks Gary!
Chris

[garylyb]

There is a hole in the lead screw near the nut. I put a screwdriver in there, and turned the wrench as much as I could. I don't know about a spec.

[chrisn]

I saw that. I should have looked closer. I thought it was just a center hole for the lathe (or whatever machine that makes ball screws).
Thanks