Mk3S+ not calibrating - totally useless  

Mk3S+ not calibrating - totally useless

I've been having problems with my printer not calibrating properly. I had a point in the past few months where I had to print new parts for the hot end and take it apart and reassemble it. Things worked fine until I left it printing a decent sized job overnight and the next day found it not all done because it ran out of filament. I tried to reset and ran into this issue. The printer just could not find the calibration points. It started with the front right point, then couldn't find the back right, then I tried again and it couldn't find the front left. While I need to get this up and running, there are other things I had to do, so I focused on other work and now I'm back on it.

My first thought was the SuperPINDA sensor might be out of place. I tried calibrating the Z axis - only Z, not the XYZ calibration. It went around to 9 spots and started okay, but when it gets to the front right spot, it pushes down on the bed and, if I can't shut it off fast enough, the printer seems to reboot. Since, in the calibration process, it asked me to check my nozzle, even though it was clean, I checked the hot end and realized there were several inches of filament in there - leftover from when the filament ran out. So I pulled that out and made sure the entire filament path was clean, then auto-loaded filament, made sure it was working, then auto-unloaded it and used a needle probe, again, to make sure the path was clear and used a lighter wire brush to clean any mess off the nozzle.

I still had the same problem: Trying to adjust or calibrate the Z axis resulted in the hot end trying to push the print bed down. (Through all the testing, there has been no metal sheet or anything like that on the bed.) I used these instructions to reposition my SuperPINDA. Now, when I try to calibrate the Z axis, it start pushing the bed down on the 2nd point, the middle front. I have a lot of zip ties around my shop and I don't know how sensitive the SuperPINDA sensor is and, since the instructions use the zip ties that came with the printer as a reference, I'm wondering if I could have use thicker ones without being sure about it.

Since it can't find the calibration points and can't detect the bed (well, in some attempts, it seems to), my guess is it's the SuperPINDA sensor, but I don't know.

What can I do to check that the SuperPINDA is working? What other troubleshooting steps will help here?

I really have no idea where to go from here to get my printer working again.