Bottom line up front: Z1 Motor experiencing drops mid cut; replaced SKR with Jackpot and unable to complete G38.2 probe without a huge drop.
I’ve been working to build a Lowrider V3 for a couple of years…life has gotten in the way. I was trying to chase down an issue by myself and failed and by the time I picked it back up, it looked like most people have moved on from the SKR Pro to the Jackpot. I had hoped that moving on to the Jackpot would solve my issue but it does not appear to have.
When I would attempt a cut with the SKR Pro, I would lose steps on the Z1 motor toward the cut surface to the point where I was concerned about a fire.
On the Jackpot, most of my movement tests have been uneventful and I was able to tram the X axis. However, now I am trying to do the squareness to see what adjustment I need to make to the Y pulloff value and at X0 Y0, the Z1 motor appears to completely fail and drop with a loud beep. I’ve captured a video of this behavior and linked below.
I’ve never seen that before - even if the stepper lost power from a bad connection I wouldn’t expect it to drop like that.
I think you might have the one in a million dud stepper motor.
Eliminate everything else first of course - power down and swap the stepper drivers from a working one, check and confirm continuity on the whole length of the wire - including during motion in case it’s an intermittent break.
I had issues when trying to check squareness that sometimes Z went down toward the cutting surface when moving to the next measurement point, which at least sounds similar to your problem on the SKR Pro. In my case I fixed it by checking wiring and crimping everything properly… Guessing it was a loose wire/ bad crimping (and not related to the board, skr pro) …
Thinking about this more, I was able to complete Z tramming with the probe so I know that some form of G38.2 was working.
I did some more testing last night: adjusted the Z endstops, redid the tramming. Interestingly I could get a successful probe if I used a more detailed command:
G38.2 G91 Z-124.9 F100
I’m wondering if this was successful because I slowed down the Z movement significantly from default.
I think you might have the one in a million dud stepper motor.
I thought so too but one of the things that I tried replacing before replacing the board was the stepper motor. Definitely a good suggestion to isolate potential faults. I’d be surprised if the stepper driver was the issue since I didn’t reuse the stepper motors from the SKR when I purchased the jackpot. Went all new
Guessing it was a loose wire/ bad crimping (and not related to the board, skr pro)
I’m hoping that it’s something simple like that. I’ll run through another set of checks on connections and validate in the next couple days.
My biggest long term concern is safety. I know that losing any steps on the Z1 motor will cause drag and friction and be a fire hazard. I’m curious if there’s any safe guards or detections that I can put in place to know if this is happening.
Genuinely, it’s been a fun puzzle to figure out, but the only successful cuts that I have made are the strut plates. I’m optimistic that I’ll be able to get this squared away and make something.
That’s a new one for me. I also run different lead screws on mine, dropping is impossible.
It looks like both sides are dropping at the same time. If so that’s not a stepper issue. Does it happen at the same point physically every time or is it happening at the same point in time? So if you probe from high does it run for 10 seconds and then drop, down low 10 seconds and drop or does it just get 2" inches from bottom and then drop?
But since the problem has been the same with 2 different boards, unlikely to be a board issue, which pushes it back towards either the build or the steppers…
Does it do it if you run it manually or only when probing?
As of right now, I am unable to reproduce the issue. Which is great, but also I am uncertain as to what the cause and resolution are. Unit is squared and trammed. I’ll update this thread should the issue return, but now I’ll be working on the fun task of learning how to generate some gcode for the Jackpot
For the fail to contact, in the probe window you can adjust how far you want it to go before it quits. Default IIRC is 40mm, so its 41mm above the touch plate it will throw that error. I usually just manually lower it until its in range, and then probe but you can also reset the default to a larger range.
