I have finally managed to complete the new control system, (Mach 3 driving steppers through a UC300 motion controller) for my 1325 Chinese router and am generally delighted with the results. Everything runs much smoother and more accurately but................. I am plagued by occasional "clonking" from mainly the Z axis. I can only assume this is the drive losing or gaining steps and sounds the same as when the system is first turned on and power is applied to the drivers. It doesn't seem happen during program execution but very often does during initial homing or manually positioning for the start of job. Anyone any ideas where I should be looking first? Many thanks in advance. Bob.

Any chance of a video - it could be backlash, a loose coupling, belt jumping teeth, drive issue

Any chance of a video - it could be backlash, a loose coupling, belt jumping teeth, drive issue

Unfortunately there is nothing to see, I've checked the mechanical linkage, belt tension etc and all is well there, it does sound like an electrical issue as it's exactly as when the drive is first powered on.

Mine all clonk when powered-up, its the stepper motors stepping into a known position.

If its doing this same thing at other times it sounds like the drive is disabling/enabling or a power fault - check the lights (if any) on the drive when it does it.

Ok, I think I'll start by replacing the "Z" axis drive and see how it goes, maybe a faulty drive?

Could be, could be just loose wire etc

OK just to bring this back to the top, I've changed the Z motor and the driver and all is still the same 
Also checked the wiring and am sure all is good. Any further ideas where to look?

any chance of sticking a video clip up on youtube??

I'll give it a go but there really isn't much to see. Hopefully the sound if I can capture it will help. It's peculiar in that it only seems to do it when the axis is moving slowly, if I run it at rapid speed it appears to be OK.

Is it possible it could be something to do with the step per rev setting (currently 1600) resonating with something mechanically?

I doubt it, steps per is relative only to distance travelled and the drive system mechanically.

So, travelling slowly it clonks, how slowly?

No clonks at rapid speeds or fast moves?