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Unload / Reload Filament for tall prints  

Light Foot
New Member
Unload / Reload Filament for tall prints

I'm running into an issue with my MK3s+ w/ MMU2S. 

When my prints get to a particular height (say around 100mm), the extruder moves off the print, unloads the filament and asks me to press the button to load the filament.   Sometimes, it will unload again after 2 layers, other times it will be 30 layers.  Example:  The print of a spool holder in one color unloaded the filament over 30 times between 100mm and 128mm, when the first 100mm were fine.   I don't have issues with prints that are below a certain height.

Here's what I've tried for resolving the problem:  I've checked the filament is consistent.  I've tried different filaments (orange, blue, PLA & PETG).  I've spooled the filament so that it gets completely new filament (cut out filament between mmu and extruder).  I've cleaned the extruder gears.  My thoughts are that there's an issue with the flex on the tube between the mmu and extruder that is somehow causing a problem with the filament sensor.

 Has anyone experienced this and have any wisdom on how to remedy? 

Posted : 09/08/2021 11:20 pm
Reputable Member

The unload/load happens mostly when the ir sensor in the extruder doesn't detect the filament. Could be that the PTFE tube between the MMU and the extruder is pushing against the chimney with the ir sensor when the Z gets higher,


You could check that when you do a load to nozzle and move the Z up. Now check the sensor status on the LCD while moving the extruder on the X axis (may have to disable the steppers) Or simple put some pressure against the chimney while looking at the sensor status.

If the sensor status changes you have to readjust the ir sensor (move the chimney)


Or you could have a problem with a wire to the ir sensor. Try moving/bending the wires the go from the Einsy board to the extruder.

Posted : 11/08/2021 9:30 am