Idler door screw compression and MMU idler screw compression
I've gotten the MMU2S to successfully print a few small items and now I am trying to get the printer to reliably extrude filament. I'm struggling with how much spring compression to use. For the idler door, if I tighten the screw down to be flush with the door surface as the manual suggests, there's too much force and I can't even get the filament in manually. The printer seems to to run ok with the screw backed out almost all the way but I'm worried that the screw will back out of the nut. I checked, I do have a M3x40 screw in there but was thinking of getting longer screw like an M3x45 or M3x50.
For the MMU2S idler screws, I keep seeing the idler move up and down when the idler is loading filament. I tried tightening the screws a bit but then the MMU2S doesn't want to load filament. Again, this is much looser than what the manual is suggesting. Anyone else having to use much less spring compression than what the manual suggests?
Re: Idler door screw compression and MMU idler screw compression
I found that the screw head needs to be about 2mm proud without filament and even then it struggles on the first load.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Idler door screw compression and MMU idler screw compression
Sounds like you have the same problem with the MMU2s firmware I had. With help from support we found that I was able to get the MMU2 to work with the 1.0.4 firmware here https://www.prusa3d.com/drivers/firmware-changelog/#mk3mk25multimaterial20
Re: Idler door screw compression and MMU idler screw compression
Hi,
For me it is the same after the MK2S/MMU2S upgrade. The compression screw on the extruder is a lot less under compression than before the upgrade, otherwise the filament is not loading (clicks etc.).
So out of 10 filament changes I have one where the filament is not loading correctly to the extruder and the print stops.
Therefore I am asking the same question, why it is so different to what is described in the manual.
Best regards,
David
RE: Idler door screw compression and MMU idler screw compression
I have the same problem. The spring seems to be very strong. I got to the point that the idler door would only move if the nut was hanging on to the screw by a thread and at the end of a print, when the filament retracted, the nut would be forced off and into the room somewhere.
I've reseated the nut so that it's sitting in the trap flush with the idler door and loosened the screw as much as I can. At the moment, I'm battling with either too much compression or none at all.
RE: Idler door screw compression and MMU idler screw compression
The MMU2S idler is supposed to move up and down a bit. When it rotates to "grip" filament (apply pressure to it) it will move up and then move back down when it rotates to allow the extruder gears to do the gripping.
When it's working, it's set right. Use the manual for a starting point, you're dealing with printed parts 🙂
RE: Idler door screw compression and MMU idler screw compression
i find the extruder door tension screw works will if it's flush with the nut or a bit tighter.
the filament should be moved to the bondtech gears by the MMU and the extruder motor should be spinning as the filament is loaded. the extruder bondtech gears should grab the tip of the filament and activate the IR sensor to tell the MMU that the filament has been engaged. the MMU should release it's drive on the filament and the extruder will feed some of the filament down ti the hotend then retract most of it and make sure the IR sensor stays activated. Then it refeeds it again and starts the purge cycle
RE: Idler door screw compression and MMU idler screw compression
I have the same problem. The spring seems to be very strong. I got to the point that the idler door would only move if the nut was hanging on to the screw by a thread and at the end of a print, when the filament retracted, the nut would be forced off and into the room somewhere.
I've reseated the nut so that it's sitting in the trap flush with the idler door and loosened the screw as much as I can. At the moment, I'm battling with either too much compression or none at all.
Sounds like you are talking about the extruder idler rather than the MMU idler, correct?
If so, you might look into re-printing the idler door. My door from Prusa acted similar to yours compared to my old MK3 door that I could get the bolt in flush on and still manually feed filament. I ended up reprinting the door and it fits much looser now and acts like my old MK3 door did.
RE: Idler door screw compression and MMU idler screw compression
You read my mind. I've just finished printing a new door and I'll try to fit it
RE: Idler door screw compression and MMU idler screw compression
my MMU screws are just under flush on the mmu
and my extruder screw is flush (not loaded) when loaded it sticks up abit.
I have a Prusa,therefore I research.
RE: Idler door screw compression and MMU idler screw compression
Movement of the idler cover is normal.
For me I've found that I want low tension on the cover. It needs a bit or it won't move the filament, but too much and it either bends the filament causing it to miss the tube on the other side or it will grind it down at the first hint of friction with the filament.
RE: Idler door screw compression and MMU idler screw compression
Movement of the idler cover is normal.
For me I've found that I want low tension on the cover. It needs a bit or it won't move the filament, but too much and it either bends the filament causing it to miss the tube on the other side or it will grind it down at the first hint of friction with the filament.
Agreed. I need a spring that isn't so strong.
RE: Idler door screw compression and MMU idler screw compression
Sounds like you are talking about the extruder idler rather than the MMU idler, correct?
If so, you might look into re-printing the idler door. My door from Prusa acted similar to yours compared to my old MK3 door that I could get the bolt in flush on and still manually feed filament. I ended up reprinting the door and it fits much looser now and acts like my old MK3 door did.
I've tried a newly-printed door. It's a little better but I still think the spring is too strong.
RE: Idler door screw compression and MMU idler screw compression
Perversely, I've tightened the idler more than I thought I needed and now I'm getting consistent extrusion. Go figure but I had to play around with the tension while the filament was extruding and it seemed to have worked.
RE: Idler door screw compression and MMU idler screw compression
I've found the depth of the screws is going to differ between systems. Whenever I have to open the MMU I use a procedure that works for me every time.
Tighten the screws to a bit above the unit, then have the MMU change to position 2, then 3, etc. If it starts clicking and doesn't proceed to the next number, I loosen the screws a bit and change selector to 1 and repeat procedure. I do this until it can successfully go to 5 with no clicking.
Make sure you go back to selection 1 after every time you loosen the screws.