Z axis height not consistant

[Absolute Steve]

I have been having problems with a new machine I picked up. I am running servos and Wincnc. After setting it up I have everything working properly other then the Z axis wants to move up about .050 after a run time of about 30 minutes. It slowly trends upward as the program runs on, it is not just a sudden move. I have adjusted the revolution setting in the ini file for Z and it seems to be within .005 when I check the height. Is it possible that this needs to be closer than .005?
My table has been shaved down ans is level to the bit. If I cut only a couple of small parts I don't see any issues. It seems as though the more Z moves it makes the higher the Z axis will go over time. Any help would be appreciated.

Steve

[trevis1st]

I would check to make sure everything is grounded. It could be a loose cable. Also don't assume that because you plugged the machine into a receptical that should be grounded that it is. We had a similar problem with the drifting down, until I re-secured the grounding rod line.

[Butterknife]

Hi Steve,

What version of Wincnc are you using? It may benefit you to update your software. What brand of machine are you using? Also..., is it only on the Z axis that you are seeing this problem? Are you using steppers or servos?