Originally shared by Patrick Ryan
Huh… my #printrbot just stopped moving in the -Z direction. Won’t home - a “home all” causes it to home the X and Y axes properly, then move the Z up, then up again. The auto-level probe light is off, but it’s acting like it’s sensing zero. Anybody seen this before? (It’s been working fine for years prior to this. New behaviour.)
The printrbots I’ve seen had the endstops wired normally-closed, so if a wire broke, they would appear to be triggered.
Hmmm… could be something along those lines, I guess. The Z “stop” is actually a Hall Effect sensor, and its light comes on if I wave a piece of metal close enough to the end, but I suppose if the signal line were broken it could act like that…
The pb sensors are inductive. But yes, lots of folks seem to have this problem with the wiring failing. They’ve switched to some other variants that may be more robust.
@Patrick_Ryan Also just double check that your start g-code has “G28;” and not “G28 X0 Y0;”. It’s likely not the cause, but I accidentally put in the “G28 X0 Y0;” on my printrbot metal simple assuming that the “G29” probe command after it would instinctively home the z axis while it was probing. It caused a similar situation, and since the sensor still works (still detects metal), then I thought I would throw this tip out there.
This is the normal response from the Marlin firmware when homing and the Z stop is already triggered. The fault is on the z sensor, wiring or the printrboard.
I’ve got no experience with the new PB’s so I can’t speak directly about how the inductive z home sensor is setup.
I think it’s gotta be the Z sensor, especially if that’s the way Marlin responds to a closed Z stop. Thanks for the input!
You can verify by sending an M119 to make the printer tell you the current status of the endstops.
@Ryan_Branch Printrbot has repeatedly instructed folks to use G28 X0 Y0 followed by G29. I don’t know if that’s because of something they modified in the specific variant of Marlin they were using or it’s just a mistake. G28 alone didn’t work for me as it introduced an unexpected position change in Y for some reason. I’ve been using G28 X0 Y0 followed by G28 Z0 and then G29 and this works well for me.
@Whosa_whatsis That’s a good idea - I’ll bear that in mind. I’m away from home for a couple of weeks now, so my troubleshooting is officially paused… 