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Filament sensor problems with MK3S extruder upgrade  

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hans.h9
(@hans-h9)
Active Member
Filament sensor problems with MK3S extruder upgrade

Hi, I am just letting the forum know of my problem with the filament sensor problems I had with my recent MK3S extruder upgrade (shipped 15th May 2019).

After completing the upgrade everything worked OK however the filament sensor did not function. From topics in this forum  I am not the only person having this problem.

I traced the problem to the lever that blocked the IR sensor when the filament was inserted, being too short by around 1.5 mm and therefore not blocking the sensor properly. All the parts were printed OK from the PRUSA supplied G code. All the distances for the sensor mechanism are defined by the printed parts,therefore this problem could not be due to faulty assembly.

I fixed the problem by building up the lever with some PETG filament with a temperature controlled soldering iron and the filament sensor now functions reliably. I have a detailed post how I did this under this topic in the forum under print problem sub heading.

I contacted PRUSA chat line to let them know about the problem, to be told that the problem had been solved however they could not tell me when or how it was fixed hence this post. 

Not being satisfied with the response and knowing that others are also experiencing faulty filament sensor on MK3S extruder upgrade I have contacted PRUSA via Email and hopefully this will reach someone in the company that is across this issue. If this problem has been fixed then I would like to see a procedure published by PRUSA on which part or parts need to be replaced to fix this problem.

If there is a PRUSA fix procedure out there already then let me know.

Hans

Posted : 31/05/2019 6:18 am
vintagepc
(@vintagepc)
RE: Filament sensor problems with MK3S extruder upgrade

I think the last time I saw this issue it was fixed by the user re-printing the arm, so either the STL has been tweaked or there was something up with the print/printer at PR that made it.

Posted : 31/05/2019 1:24 pm
hans.h9
(@hans-h9)
Active Member
Topic starter answered:
RE: Filament sensor problems with MK3S extruder upgrade

Hi 

Thanks for the reply. I printed the parts from the supplied G code (not .stl and my settings). All of the parts printed perfectly and the extruder assembled as per the instructions. To think that the only part that had miraculouly shrunk was the sensor blocking lever would be tantamount to being crazy.

I know that Prusa would have tested the upgrade before sending it out and my  parts printed perfectly so the only thing that could change is the the IR sensor chip may have been replaced with another version that was slightly shorter.

I would like someone from Prusa to take this up as I am not the only person with this problem. I purchase the MK3 about a year ago as a kit and it assembled and worked straight up. I purchase the printer as a workshop tool, not as a hobby. They have set a high standard and I now expect nothing less. 

Hans

Posted : 01/06/2019 2:34 am
hans.h9
(@hans-h9)
Active Member
Topic starter answered:
RE: Filament sensor problems with MK3S extruder upgrade

Hi,

I have imported the .stl files of the extruder body and of the FS lever into Turbocad and measured the distance from the top of the lever to the top of the body and the .stl file of the FS lever has been raised by approximately 1mm which should solve the problem.

It would seem that they tweaked the FS lever but did not modify the Gcode download for the the extruder parts. 

It is a pity that no where was this fix mentioned by Prusa. Could have saved me and a lot of others a lot of time. I still think something should be indicated by Prusa. 
I will Email them to see if they do something about it.

Hans

Posted : 01/06/2019 3:57 am
Cowwolfe
(@cowwolfe)
Active Member
RE: Filament sensor problems with MK3S extruder upgrade

I had issues with the upgrade from MK3 to MK3s where the filament sensor (fs-lever printed part) was not blocking the sensor.  When I wiggled the filament, I could see the sensor changing via the diagnostic screen under the Support/Sensors menu.  When I took the assembly apart and reviewed the design, I opted to modify the fs-lever to see if it would fix my problem.  I added a 0.5mm and 1.0mm extension to the fs-lever part to give it more coverage to get under the sensor.  For me, the 1.0mm extension worked best.  You can find my adjustment here: https://www.prusaprinters.org/prints/4419-mk3-to-mk3s-upgrade-fs-lever

I recommend that if you have an issue and try my replacement, to test the sensor assembly before you put the whole head unit back together.  Wish I had done this before I finished the MK3s upgrade.  Live and learn.

Hope this mod helps others.

Eric Z....
Posted : 14/07/2019 7:59 pm
mckibbin liked
mckibbin
(@mckibbin)
New Member
RE: Filament sensor problems with MK3S extruder upgrade

@eric-z2

Thanks Eric, I'm currently upgrading my 4 machines from MK3 to MK3s and experiencing the same issue. I was just about to make the same mod myself, but figured I'd check to see if others had the same issue. Thanks for sharing! 

 

Ryan

...
Posted : 03/06/2020 3:00 pm
mckibbin
(@mckibbin)
New Member
RE: Filament sensor problems with MK3S extruder upgrade

As a follow up... I ended up re-drawing the FS-lever in rhino and trying 8 different iterations after trying eric-z2's stl files, none of which were reliable in my machine. 

I then tried another color filament, green petg. I was using black previously. Green works flawlessly for me.

If you are experiencing this issue, try printing the lever arm in another color before re-designing. I actually arrived here by superglueing card stock to the lever arm and trimming it to size. I would have just used that part if I didn't need to build more printers. 

...
Posted : 05/06/2020 5:19 pm
JoanTabb
(@joantabb)
Moderator
RE: Filament sensor problems with MK3S extruder upgrade

Black filament isn't always Opaque to Infra Red. 

inf act the Black PLA that I currently isn't opaque to daylight!

as you have found, a different colour may be better...  e.g. red photo resist for ultraviolet light

 

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 05/06/2020 5:34 pm
jsw liked
Cowwolfe
(@cowwolfe)
Active Member
RE: Filament sensor problems with MK3S extruder upgrade

@joantabb

I printed in PETG Black and that has been working great.  Actually, at the time I upgrade to MK3S and made this STL all my upgrade parts were in PETG Black (from Prusa's upgrade kit).

I agree, not all materials are good with infrared.

Eric Z....
Posted : 05/06/2020 8:01 pm
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