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cropwell
09-01-2017, 12:04 AM
Hi Chaps,

I have a problem with my Z axis. I was doing a pocket to a depth of 0.8mm using a wire brush to put a texture on an ali sheet and clear odd a few burrs. It worked superbly until it came to do the outer 'finishing' run of the pocket, when the Z just drove down hard into the work. After recovering from that Oh Sh*t!!!! moment I tried to jog the axis upward, but no go, just some buzzy buzzy from the stepper.

I took the stepper off and wound out the screw (trapezoidal - MD machine) cleaned it all up checked all moved freely and re-assembled. Now it will jog up and down or just buzz at random. Jog direction is random.

Does this sound like a fried driver ?

Tomorrow, when I have cooled down a bit, I will swap over the drivers in the control box and see if the problem moves around with the driver.

Any thoughts anyone ??

Rob

Doddy
09-01-2017, 07:13 AM
Now it will jog up and down or just buzz at random. Jog direction is random.

Does this sound like a fried driver ?

Tomorrow, when I have cooled down a bit, I will swap over the drivers in the control box and see if the problem moves around with the driver.

Rob

Cooling down is always a good idea.

The bit that interests me is the random direction, and/or buzzing - I had this a couple of weeks ago with an axis on a 3d-printer. Turned out a core in the lead between driver and stepper had failed, so only a single coil was energising, you could coerce the motor to move in either direction with a bit of finger pressure.

In your case, could be driver, cable or stepper. I'd agree : check by substitution.


Curious bit: What caused the Z traverse in the first place?, it's not an obvious single point of failure with the resultant loss of Z control.

cropwell
09-01-2017, 11:01 AM
Curious bit: What caused the Z traverse in the first place?, it's not an obvious single point of failure with the resultant loss of Z control.
Yes - that is the strange bit, as earlier in the day I had drilled 4 plates with 388 holes in each one. without any glitch. Anyway, I have done some lead swapping in the control box and it seems to be the driver. The offending driver has been removed and the case opened, but no sniff of magic smoke. I have ordered a new driver, but will do some testing to make sure it is not the BoB.

My system runs at 48v and the drivers are M542H with a VDC input of 24-80V. Looking on AliExpress, most of the M542H drivers seem to be 12-32 or 24-50V. Anyway I have found one that says 24-100V input. I would go for better drivers, but the system isn't worth it.

Cheers,

Rob

cropwell
13-01-2017, 04:48 PM
Problem found ! Two broken wires in the stepper cable at the top of the Z axis. I was caused by the cable chain end working loose and so flapping the wires on the back of the connector.

Neale
13-01-2017, 05:22 PM
What did the man say? "To lose one stepper wire is a misfortune. To lose two stepper wires looks like carelessness!"

But these things happen. I'll be checking all my cable supports to make sure that nothing flexes where it ain't supposed to flex :smile:

Boyan Silyavski
13-01-2017, 10:56 PM
"To lose one stepper wire is a misfortune. To lose two stepper wires looks like carelessness!"


I have to prepare a special notebook to write down things like that

Neale
13-01-2017, 11:13 PM
Not original - it's based on a very well-known quotation from Oscar Wilde's "The Importance of Being Earnest". It's a good line, though!