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Grbl CNC Router Troubleshooting
01-31-2016, 01:48 PM,
Grbl CNC Router Troubleshooting
Hey all, hoping to pick the brain here for some input-

I recently updated my GRBL shield to 0.9j, and now my z-axis behaves somewhat erratically. It will sort of randomly reverse direction when issued a g code through UGCS. For example, if sent a G00 Z-1 F25 it will occasionally move in the positive direction instead of negative.

I've been trying to set up homing and a touch probe just so you have an idea what pins and settings I've been tinkering with. In addition, when the Z axis behaves and I try to home it, it tends to hit my homing switch and stop and buzz. I've played with the debounce setting without much luck.


01-31-2016, 11:36 PM,
RE: Grbl CNC Router Troubleshooting
Did it previously have 0.8 or earlier on it? The Z-limit pin changes when you move to 0.9, which may cause issues.
Have you checked wire continuity to the Z-motor? A dead/high resistance leg can cause some oddball movements.
Have you checked GitHub for any known issues with 0.9j?
Are you using a shield? And if so, which one?
02-01-2016, 09:49 AM,
RE: Grbl CNC Router Troubleshooting
There does appear to be large difference in settings between the versions, so you'd have to go through the setup files completely. Could also be noise or a bad ground when doing probes, disconnect the probe and make sure everything is working and then add in the probe. Good Luck!!
John Woj
IdeaMakers Designs, LLC
"I'm on the the verge of something" Breaking Bad

02-06-2016, 11:37 PM,
RE: Grbl CNC Router Troubleshooting
Apologies for not getting back to the thread sooner; I thought I had subscribed to it, but apparently failed.

I did resolve the issue (which ended up being a continuity issue- apparently jostled a z-axis connection to the stepper loose from my shield while I was doing the limit switches).

@Abearden- Yeah, I had upgraded from 0.8 before doing the limit switch install. I was pulling my hair out for a bit regarding the z-limit pin. I don't navigate github all that well, so I didn't discover the change right away.

I'm still tinkering with getting probing to work, but haven't really had a chance to get back to it, yet. I'm going to mill a custom touch plate to use for it at work.

Thank you for taking the time to make replies, I do appreciate it.

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