Oozing during mesh bed leveling
When printing PETG, the nozzle starts oozing during heat-up. I can clean it before print, but when the printer performs mesh bed leveling, some has oozed out again and this time wrapped around the nozzle.
This is a problem, since this blob will release somewhere along the first 10 layers, and mess up the print.
Maybe the slicer can insert some step right before the intro line and raise the extruder for the user to clean the nozzle?
Otherwise, maybe perform all of the bed heating, homing and leveling, before heating the nozzle and printing the intro line?
Best Answer by bobstro:
The easiest way to eliminate such oozing is to do a 2-step nozzle warmup.
- While waiting for the bed to heat up, only heat the nozzle up to a safe "no ooze" temp. I use 160C with PETG and PLA with good success. Technically, you could simply wait until later to do any nozzle warmup, but I find having the filament soft before homing avoids driving any hardened ooze into the PEI print surface at homing.
- Then do your mesh bed leveling.
- Only once you've homed and are ready to print, do the final nozzle warmup to actual printing temps.
I've got my documented gcode here that shows all of this in practice if you'd like to review it here.
Original Prusa i3 MK3S
RE: Oozing during mesh bed leveling
The easiest way to eliminate such oozing is to do a 2-step nozzle warmup.
- While waiting for the bed to heat up, only heat the nozzle up to a safe "no ooze" temp. I use 160C with PETG and PLA with good success. Technically, you could simply wait until later to do any nozzle warmup, but I find having the filament soft before homing avoids driving any hardened ooze into the PEI print surface at homing.
- Then do your mesh bed leveling.
- Only once you've homed and are ready to print, do the final nozzle warmup to actual printing temps.
I've got my documented gcode here that shows all of this in practice if you'd like to review it here.
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RE: Oozing during mesh bed leveling
That works very well. Thank you!
Original Prusa i3 MK3S
RE: Oozing during mesh bed leveling
I know I'm 4 years late (lol), but I just troubleshooted the same issue and wanted to share my solution, as it's fundamentally similar to Bobstro's.
Within the Start G-code section, I rewrote the "M104 S[first_layer_temperature]" line as a vector so I could multiply it by a scale factor:
M104 S{first_layer_temperature[0] * 0.9}
Here I set the scale factor to "0.9"; this way the nozzle heats up to 90% of WHATEVER the target first_layer_temperature is, so this fix should scale up or down with any kind of filament without the need to input an exact Celsius value. The scale factor 0.9 has been working for me on PETG, but if that's still too oozy for you and your filament, you can simply decrease the scale factor as needed (i.e. "0.85" or "0.8").
Alternatively you could use subtraction instead of multiplication. For example:
M104 S{first_layer_temperature[0] - 30}
This would heat the nozzle to your target first layer temperature MINUS 30 degrees C. If that's still too oozy for you, you can simply increase the value "30" as needed.
I also reordered select lines of code so that:
- the bed leveling test is conducted WHILE the nozzle and bed heat up (to save time),
- the nozzle will wait to heat up from 90% to 100% until AFTER:
- mesh bed leveling is complete, and
- the bed is at its target first_layer_temp.
NOTE: my printer has the MMU2S, so while your overall Start G-code may differ, the commands described above should still work.
Sources that helped me:
- Used this page to re-write "S[first_layer_temperature]" as a vector (and see examples of arithmetic operators in G-code):
- Used this page as an index for learning about G-code commands I didn't know: