Filament keeps being unloaded during load cycle  

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CybrSage
(@cybrsage)
Honorable Member

This is what is happening:

Filament loads to the MMU2S, setting off the sensor.  The filament then loads to the extruder (MK3S), setting of that sensor.  Then the filament is pulled back the entire way to the MMU2S where the cycle begins again.

After three tried, it gives up with a MMU Error.

I am watching the sensors in the info window so I know when they change to 1 and back to 0 again.  What might be wrong?  Running 3.8.0 and 1.0.6.  I also have the Bondtech extruder upgrade, including replacing the extruder body and such.  I am using the chimney mod found here:

https://www.myminifactory.com/object/3d-print-prusa-mk3s-mmu2s-ir-sensor-mount-bondtech-bmg-89362

Best Answer by guy.k2:

Bunnies recommend some current limiting resistors rather than just the LED.

Here are more complete instructions for the LED indicator mod.

https://bunnyscience.dozuki.com/Guide/Bunny+and+Bear+(BNBSX)+MKS3+Geared+Extruder+Assembly/2#s84

This topic was modified 11 months ago by CybrSage
Posted : 07/09/2019 9:00 pm
david.a66
(@david-a66)
Honorable Member

you may want to monitor the sensors with a meter or do the LED addition to the IR sensor. even a short "0" on either sensor will start an unload cycle. you can watch the FINDA state by the built in red led (dim). IR sensor is harder 

Posted : 07/09/2019 9:21 pm
CybrSage liked
CybrSage
(@cybrsage)
Honorable Member

So you are saying it could be too fast for the LCD to pick up.  Hmmm...maybe do the indicator mode then.

Posted : 07/09/2019 9:25 pm
david.a66
(@david-a66)
Honorable Member

yep, there are times that the controller is not refreshing the screen waiting for an event

Posted : 08/09/2019 12:06 am
CybrSage liked
michael.t66
(@michael-t66)
Trusted Member

You can simply solder a LED with resistor to +5V and Sensor out (middle pin) and see what it is doing. ATTENTION: I just checked that on a bread board with a spare sensor and I might have recalled it wrongly. You need to check that yourself.

Although the LED might also be not quick enough to catch ms long signals it will give you an indication. Mine was on the limit as well and I needed to quick-and-dirty fix it. See my post. I will check on my second machine whether this is a general problem with the construction or rather a single phenomenon. Might be just manufacturing tolerances. 

The unloading you are describing can only be caused by the FINDA (run out of filament) or the IR (no filament in the extruder, hence not properly loaded). So either one or the other or both 😉

Posted : 14/09/2019 8:59 am
CybrSage liked
guy.k2
(@guy-k2)
Noble Member

Bunnies recommend some current limiting resistors rather than just the LED.

Here are more complete instructions for the LED indicator mod.

https://bunnyscience.dozuki.com/Guide/Bunny+and+Bear+(BNBSX)+MKS3+Geared+Extruder+Assembly/2#s84

Posted : 14/09/2019 10:42 am
CybrSage liked
CybrSage
(@cybrsage)
Honorable Member

Thank you everyone!  The Bunnies instructions includes links to the right parts as well, very nice!

Also, what is the current community recommendation on the heat break to use, as well as the ID of the tube in it?  Should they both be official Prusa ones (modified heat break and 1.85mm ID, or whatnot?

Posted : 14/09/2019 1:59 pm
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