Losing steps in Z axis!!

[Westozy]

Hi all,
I'm new to cnc machining although a machinist by trade. I have a pro built aluminium cnc mill which appears to be working fine except I appear to be losing steps in Z axis. I can engrave a few letters and the tool is climbing away from the material. after a few minutes of running the Z axis has crept away from the material about half a millimeter. I have checked the security of the toothed belt drive and pulleys all ok and the tool is not slipping in the chuck. My only idea now is a faulty controller card, could this be the problem? Does anyone have any other ideas? Help would be most appreciated! The error is consistant across all types of engraving.

Regards, Gwyn

[neeraj sharma]

is your axis moving up n down for every engraving,if so check backlash given in the ball screw or the endbearing locking.

[zeed]

Are you using mach3?
I had similar problem,the solution was setting dir puls in motor configuration to 5us.