erratic z axis

[endgrainguy]

After 100's of hours of flawless performance, my shopbuilt machine has developed a glitch whereby it, every so often, at 10-40 minute or so intervals , misses a z axis command. This may also result in lost steps in all directions. Then, after pausing feed and entering some manual z axis commands, it responds eratically, sometimes going up when i tell it to go down, or visa versa, -- but inconsistantly. After a while it returns to normal.
I"ve been running a Chinese 2.2 kw spindle for the last year, and the problem started after I had to swap it out yesterday back to a Bosch router (the spindle's water connecters sheared when I was redoing the water lines).
I really have no idea what's causiing the problem. What are the usual culprits in such a case? It seems nearly certain that somehow the spindle swap is causing the problem, but I can't understand how. I don't really have any idea what's causing the problem I"ve checked for friction and can't find any.

[vger]

It may be electical/electromagnetic noise. You might try putting an EMI filter in the power to the router just as close to the router as possible. Here is a link to one from Digikey
http://parts.digikey.com/1/parts/120...maw120522.html
They have others of course. I don't know how much current your router draws, but the filter current would have to be rated higher than the router startup current.

You might also try rerouting the power cord for the router along a different path than the machines signal lines.

Best of luck
Steve