Bed extends too far and belts grind

I finally got the part printed that I needed and everything installed OK. I’ve had problems with the probes being dirty so I gave the head and the probes a good cleaning. I go to reprint and the bend extends well beyond where it should be and doesn’t stop. The belt starts to grind and when it finally stops the printer looks for the probe pads in which it’s no where near.

I’ve been through the newest cura, the one before that and even the one that has came on the thumb drive. I have no idea how to fix this and the grinding scares me so much I just turned it off.

Any ideas would be helpful.

How did you clean the head? Did you by any chance use a wire brush while the heater was on?

Endstops not working (either always triggered, bed or head won’t move, or not triggering when at endstop), and/or seeing the probing sequence just immediately move to each of the four washers without probing downward to touch them – typically means a shorted wire or a blown mini-Rambo board. The usual cause of a blown board is shorting the heater wires to the heater block, either due to broken insulation on the wires or using a wire brush which penetrates the insulation and shorts it to the heater block. That runs high current meant for the heater into the low current circuit used for endstops, and can permanently damage the board.

Power off/on the printer, then use Cura controls to move the bed (Y) and toolhead (X and Z) a short distance away from their endstops. Then open a console and send an M119 command. The printer will respond with endstop status; they should all say “open” if you have moved everything away from the endstops. If one or more says “triggered” when not actually at the endstops, then you either have a shorted wire or a blown mini-Rambo (the odds of it being a blown mini-Rambo go up if more than one shows triggered).

I did actually. I saw someone say to clean the head with damp cotton cloth when the head was at printing temp. The stuff wasn’t coming off so I used a small wire brush that came with a 3d printer repair kit. Come to think of it, the problems did start after I cleaned the head with the brush. I messed up didn’t I?

Sounds like it -:(. But run the test I suggested above with M119 and see what it returns. Worst case, a new mini-Rambo is about $100. Kind of a pain to replace, not real difficult but takes some time.

Thanks a lot for your help. 100 dollars isn’t so bad. It’s an expensive lesson to learn but not one I will repeat.

Looks like I blew it.

Assuming that second M119, where y_min and z_max still show triggered, was reported after you moved toolhead and bed away from the endstops… Having two endstops falsely show triggered, coupled with it happening immediately after using a wire brush near the heat block, does point to a blown board. (If it was just one endstop, or no wire brush had been used – then I’d look for a wiring short or bad switch first.)

At this point, I would suggest you reach out to Lulzbot support via phone or email. They can set you up with a new mini-Rambo (about $100), and point you to a replacement procedure.

Thanks a ton for your help. Maybe I can get printing again soon.