# Labists ET4 printer nozzle hits bed after automatic levelling

I use Slic3r to create G-codes for my Labists ET4 printer. Usually, no problem.

Now, as soon as I tried to start a print, the nozzle head went down as usual, but this time it went a bit lower than 0 and the machine made angry noises for less than a second.

It went back up again and heated the bed and the nozzle, only to go back down too strongly with angry noises again. Even left a little pokey hole on the bed.

I got scared and turned the machine's switch off and manually raised the Z axis with ease.

Never had this problem before and now I'm afraid to turn on my machine.

I've had the following setup for G-codes prior to today's incident and it had worked just fine:

G28 ; Home extruder
G1 Z15 F[travel_speed]
M106 S[max_fan_speed]; Turn on fan
G90 ; Absolute positioning
M82 ; Extruder in absolute mode
; Activate all used extruder
M104 T0 S[first_layer_temperature]
M190 S[bed_temperature]
G92 E0 ; Reset extruder position
; Wait for all used extruders to reach temperature
M109 T0 S[first_layer_temperature]


After this, I did try the auto levelling, however it still tried to plow into the bed, albeit not as angrily.

Here's other things to potentially consider:

• I haven't used the machine 10 days.
• It's been chilly in the room where the machine is.

So here's my questions:

• "What could cause a 3D printer to have an incorrect impression of Z-axis=0 even in absolute position mode?"
• "What can I do to fix it?"
• Please do the automatic levelling with the sensor attached, you will not damage the bed then. When you tried, please update the question that you tried it and it doesn't work, or ,if it does work post an answer and accept it after 48 hours! – 0scar Jan 24 at 11:42
• Hi @0scar! I added info. Unfortunately the auto levelling still had the nozzle attempt to burrow into the bed. Not sure what my next step should be :/ – B7th Jan 26 at 3:17
• That is quite strange, the sensor should have established the level seen from the top. – 0scar Jan 26 at 13:22
• So it probably is a build-up of molten carbonized filament, yes, that makes that the "nozzle + gunk" hits the bed after leveling. Heat up the hotend and remove all the additional material on the nozzle. – 0scar Jan 27 at 8:18
• This is not an Anet ET4 then! I've updated the question for you! – 0scar Jan 27 at 10:33