Ramdom filament change request from the MMU2S unit  

RE: Ramdom filament change request from the MMU2S unit

Does this seem to you familiar?

https://forum.prusa3d.com/forum/original-prusa-i3-mmu2s-mmu2-assembly-and-first-prints-troubleshooting/how-to-fix-the-ir-filament-sensor/#post-169015

RE: Ramdom filament change request from the MMU2S unit

Is this message connected with a extruder move abit up and to the right side of the bed?

Could be some filament sensor misinterpretation - does it concern transparent filament or filament type independent? Could you provide as much as possible info? This can help yourself to look for solution and also other experienced users who are willing to help even they do not encouter your issue?

RE: Ramdom filament change request from the MMU2S unit

Had it, been there, .... It can be caused by the filament IR sensor flickering. Readjust the sensor, solder an LED on there. The LED tells you the whole story (I was really surprised when I saw my supremely calibrated sensor the first time with an LED as indicator, man, was I far away of what I wanted). Keep in mind that a non-robust adjusted sensor might trigger differently on different position of the extruder due to small deformations of the housing.

RE: Ramdom filament change request from the MMU2S unit

Hi,

The problem appear to come more often with a PETG white filament (non transparent) and a black PLA filament (this filament appear to be slightly thinner than the standard 1.75mm). Other than that everything is pretty standard.

I suppose we are talking about the IR sensor on the extruder.

@Michael-t66, where exactly should I solder the LED (and the load resistance I suppose). Is it ok if I place this between the ground and the output?

Thanks 

Luca

RE: Ramdom filament change request from the MMU2S unit

First: Yes, IR sensor on the extruder.

This is exactly what I was also experiencing, thinner filament and more misfiring. But the sensor can easily be adjusted to manage that. The easiest way was the LED idea (not mine), as well as a few tweaks to the position of the sensor. 

I do not have the correct link to the LED, but you might find it. One that is similar is: https://www.thingiverse.com/thing:3578659 . It is +5V and out. If you go for a standard LED connect a resistor in series to limit the current. I personally had some lilypad LEDs left over that have the resistor onboard.

RE: Ramdom filament change request from the MMU2S unit

I do not have the correct link to the LED, but you might find it. One that is similar is: https://www.thingiverse.com/thing:3578659 . It is +5V and out. If you go for a standard LED connect a resistor in series to limit the current. I personally had some lilypad LEDs left over that have the resistor onboard.

Thanks for the link and suggestion. I have plenty of standard LEDs lying around, I will test the mod by soldering the resistor and the LED on the wiring. If it works I will make it "pretty" later 😀

RE: Ramdom filament change request from the MMU2S unit

@luca-vicini

Just did another one

RE: Ramdom filament change request from the MMU2S unit

I know it is an old post but I faced the very same problem now.

I would like to add my small grain of sand. What I noticed is that the sensor is loose in its support (the chimney) no matter how much tight is the screw. It is the possible that, on the occasion of some fast movement of the extruder, the sensor moves and detects lack of filament, etc.

What I did, although I consider very valuables and helpful the proposal made in this post, was to sand a little bit the top of the chimney and add a thin paper washer between the top cover and the sensor.

This helps to keep the sensor quite steady in its place and now I do not face any problem.

Another solution would be to design the top of the chimney with less clearance with the sensor PB..

RE: Ramdom filament change request from the MMU2S unit

You're a lifesaver. I spent like an hour trying to fix this and you saved my print. Thanks, definitely gonna get an led!