Load cell or Firmware Issue?
During the probing process the nozzle contacts the PEI sheet and dents it. This doesn't happen every print but now 4 times, once causing a lot of damage. I watch the probing process and shut the print down if it happens. I've performed the load cell test many times and it's never failed so this is leading me towards firmware. Anyone else experienced this? fw V5.0.0, 1 month old MK4
RE: Load cell or Firmware Issue?
Yes, my smooth plate is also covered in little dents. Not as bad as yours though! Mine are definitely caused by the bed calibration step as they are mostly in the same places on the plate. It's probably messing up the calibration step, so it might be something that gets worse each time the calibration runs. I'm a bit surprised that more folks aren't hitting this. I built my MK4 from the kit, so I wonder if I did something wrong?
RE: Load cell or Firmware Issue?
Yes, you probably did. Turns out even Prusa doesn't mention this, but the lower x axis bearing cover has a little cutout in it for the hotend to ride up into it. If you put the lower bearing cover on backwards, the hotend won't fit all the way into the nextruder, and when you calibrate the printer, the hotend will dig into the build plate. I had this happen to me. The software doesn't detect this. It's easy to fix: just unscrew the lower bearing cover and reverse it, then shove the hotend/nozzle up into the nextruder and tighten down the thumbscrews.
I am considering reprinting the lower bearing cover in PC+CF because it is so close to the hotend. I typically will sometimes print PC+CF for a strong part.
Senior Life member of IEEE.
RE: Load cell or Firmware Issue?
Good suggestion Steve. You mean Attaching the X-axis Clip? It would have been great if that was the problem. But I checked, and my bearing cover is on in the correct orientation. I also checked that the hot-end is seated fully in and oriented correctly.
I did some more research and found that most of my dents are actually just "moon craters" of extruded material that has adhered to the plate. I was able to remove it with some acetone and elbow grease. There are still some dents in the plate, but fewer than I originally thought. I'm printing with PETG on the smooth plate for adhesion. This worked great on my MK3S but I think it's not such a good idea on the MK4 due to the fact that the new sensor needs to touch the plate to calibrate.
Prusa did reach out and ask for pictures. We'll see what they suggest.