Z axis slowly raising during cut

I thought I would throw this out there to see if anyone else has had this issue and if there was a resolution found.

During a cut, in this case a roughing pass for a 3d carve, my z axis slowly nudges itself up away from the workpiece instead of remaining in one position.
I can actually watch as the z axis leadscrew rotates in small increments.

I am running a 1st gen 1000mm machine with the original arduino gshield setup.

I have checked my wiring, belts, wheels,and even the gcode for z commands ( There are none where they should not be. and een checked grbl setting against a master setting file I keep just in case things go screwy. I have disconnected the usb and powered things down restting the arduino restting aside from grbl settings (larrym’s v1.0c (1ms) hex file)

At this point i am befuddled. this machine has never exhibited this sort of thing before.

Any insights or suggestions?
And yes I did a search before posting. but if one does not use the correct nomenclature, one gets BUPKIS.

Ok, my wild a** guess is as odd as your problem.

Remove the gShield from the Arduino. Plug it back in. Re-test.

This will, in effect, clean the gShield pins a bit.

If the z motor is unlocked could it possible do this, maybe through vibration?

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I was thinking along the same lies as you Larry, I was recently in there while setting up my laser so…

@ChrisRice, the z stepper should be in effect “locked” since it is in use supposedly holding a specified depth.
The Z’s stepper isn’t moving in any rhythmic pattern either. It’s a bump here, a couple there, etc but all in the same direction, up. Better than down I guess as it saves the material. But a project cannot be completed this way.

It’s almost as if there is a static charge building and releasing and only hitting the z.

I mess with it more tomorrow. to flustered about it tonight.

Don’t feel bad, the same thing happened to me earlier today. It was raising so slow that I had to stop the carve, and it was in a 2 stage cut. This never happened to me before in 2 years that I’ve had this machine. And it ruined my project because it didn’t raise all the way up and it moved to a different area dragging the bit across the already carved letters. I just gave up on it. I guess I wasn’t the only one having a bad day today.

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Ok, It was driving me nuts so I am back out in the shop.
I think I hae it figured out.
I am running an inventables 48v 300w quiet cut spindle.Have run it pretty hard off and on for the last three years it is my only replacement I have ever had since the infamous first batch of short lived spindles.

I recall what the symptoms were when the original died so I set up a simple test cut and sure enough with the spindle running I was getting the random z axis movement. Running an air cut with the spindle off and nothing was amiss. I reflecting on all of this I was getting some y and z shenanigans as well but not to the same degree as the z axis.

I opened up the spindle, discovered that the brushes are going away and the armature contacts were quite dirty. chucked the spindle into my wood lathe and cleaned the contacts, reassembled the spindle, those itty bitty little brushes are a serious pain in the ■■■ to get back into place. (sorry mods but it was warranted in this case) and put everything back togther.

Running a test carve now and tings are steady so far. I suspect electrical noise from the dirty armature was the culprit.
Since brushes for this thing are most likely unavailable I guess a new spindle is probably in my not too distant future.

Update, It worked for a while then went bonkers again. :face_with_symbols_over_mouth:

spindle replacement imminent!

could it be something to do with the steppers?

either settings or hardware related. low or losing torque by some means. just a thought

Worn brushes / dirty commutator sounds like a viable culprit for sure :slight_smile:
Happy upgrading and fingers crossed!

I doubt it has anything to do with the steppers since it doesnt present the problem when air cutting with the spindle off.
Also it was more prevalent depending on the load on the cutting edge, light loading had it only acting up a little bit , whereas heavier cuts caused more pronounced behavior.
After cleaning the armature, it worked great for a while then was even worse and not related to the cutting load at all.
I will probably go with a direct replacement of the spindle rather than an upgrade, I have been quite satisfied with it.
I have run this thing hard over the last 3 years and this is the first trouble I have had from it. And the cost to upgrade to a D611 or other trim router would be about the same or more. and then there is the noise factor. also My laser mount is designed for the size of the quiet cut’s mount,another expense.