I need help. My printer tries to home z by moving up instead of down. What is the M command to tell it to home the opposite direction? The video shows my printer homing x and y then trying z. I’ve put the metal right on the sensor and the light goes off so the probe is fine. I just can’t seem to fix this one little problem.
Sounds like the printer thinks the home switch is made. Maybe the contacts are shorted.
z motor wired backwards?
The z motor Is wired correctly and the z moves correctly. The printer just doesn’t home right.
What type of sensor is it? Mechanical, inductive, etc ?
I bet it’s a printrbot
It is a Printrbot plus with a induction probe. I have also tested a second probe and I had the same results.
The firmware might be wrong, homing can be in either direction depending on what is set in the firmware.
I don’t think home axis direction can be set with G-code, I’m pretty sure it had to be done in the firmware pre-compile. Luckily it’s also unlikely that is the problem unless you’ve switched the firmware from stock.
Have you made sure that the probe is triggering, and figured out where it’s triggering? Because “Home” for the induction-sensor models is (as far as I can tell) not at 0 but rather just above the point where the induction sensor triggers. So the motion I see in the video is what would happen if the sensor were triggering at the height that it’s already at.
two things i see as an issue…
- in the marlin FW, the Direction of Z is set to 1 not -1 … or…
- the mZ doesnt know what position its at…by typing M114, you get current position, then type G92Z50 it will think its at 50mm above the bed… then you can lower the nozzle keep changing the Z value in the G92 command till you can get it to the bed… once there with the PREHEATED nozzle just touching the bed, send G92Z0…be sure the inductive probe is lit…then raise the nozzle 10mm and do your probe calibration…
i had the same issue… both methods i had to do…