View Full Version : Missing Steps + Stalling X-axis

26-08-2010, 11:13 PM
To cut a long story short; I've revived my CNC mill, from being sat on my bench doing nothing for around 9 months because of a damaged spindle.
I got a new spindle custom made for the machine, just fitted it tonight; switched on, booted up, and put the thing into first gear...

However: The X-axis sounded VERY ODD.
Took a closer look, and it is missing steps BADLY + stalling very often.

If I jog X+ and it starts to stall, giving it a little nudge tweak on the ballscrew brings it back into movement.
It does stall/jitter in both directions, but more so in one that the other.
Turning the ballscrew by hand doesn't mechanically feel that sticky; which is what has confused me.

I removed all the bellows, gave it a good clean (not that it needed much) and oiled all the ways and ballscrews. Ran it back and too, to let it soak in. And still the same.

If I send single steps, then it just jitters back and to on either step.

At the highest feed rates (1320mm/min) it doesn't seem to have this problem. Just anything less than this causes the issues...

SO: Is this a "bad stepper" one on it's arse? Or a mechanical issue?
It would be a *MASSIVE* pain in the arse to fully remove the X-axis and investigate in detail, so I'm not jumping to that immediately.

Anyone any ideas?

27-08-2010, 03:23 AM
You could try swapping your drivers around at least that would rule out those, also have you checked the software has had no changes again send the x signals to another axis to rule this out, im no expert but trial and error usually lights some lights


27-08-2010, 08:09 PM
check the earth for that drive, and as Rick has said swap the drives around to see if it's just the drive gone us.

28-08-2010, 09:34 AM
Hi Dan,

I had similar glitching issues:

It could be any number of things, but in my case I tracked it down to the power supply. It also occured at lower speeds, same as your problem. What drivers are you using? Are you microstepping?

31-08-2010, 12:50 AM
Many thanks; when I find time I will check over the next couple of evenings and let you know.


02-09-2010, 03:59 PM
OK, swapping the x and y drives over, dragged the problem with it.
So it's not the stepper, and it's not mechanical :)
It just means the X-axis driver is possibly goosed... I'll need to take the machine to bits and have a full-on gander...

To be continued...