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Finally got MMU2S to print  

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MileHigh3Der
(@milehigh3der)
Estimable Member
Finally got MMU2S to print

And of course, as I'm writing this, the MMU crapped the bed

Just on my second  print, but luckily have had no issues with the feeding of the filaments, one being PCTPE from Taulman.

Things I learned:

-I hate my MMU2s

--It wasn't designed very well for assembly and especially dissasembly.  The spindle in the directions talks about how weak it is.  Do yourself a favor and either print it out of a better material and/or the designs with a 'nut' as a bearing surface for the rotor selector.  If the spindle does break, you have to tear apart the spindle to get the parts out, or source them from somewhere.  You'll also wreak the spindle holder part getting it out.  Those recessed bolt need the round head key, and not just any round head one will work, you need the Prusa one, so don't lose it.

--Rube Goldberg would be proud of the mechanism.  I really wish it just used a motor per filament instead of the selector.

What I did to get it to work:

-Used foul language

-Replaced the spindle and noticed afterwards that they spindle bearings don't really press against the filament on the teeth.  this might have had something to do with the PC spindle I printed being a little 'low center' due to print warping, but 3 was the worst and 1 & 5 barely worked.  

-Reduced the height of the engagement surfaces between the body and the spindle holder to allow better engagement.  I took off enough material to see the infill.  Now there is a bit of airgap between the parts and the spring on the tensioner actually gives some play. (I think this was the key to getting mine to work)

-Larger tubing between the MMU and Extruder.  Like Big, really big.  Fat tips would get stuck here, or at least drag. I'll include the pics of the tubing and fest fitting.  Printed out alternate versions of the parts to just hot thread the parts right after printing.  MMU and Extruder head parts.  Maybe this was overkill.  I think I wasn't getting enough torque on the MMU filament feed.  But sometimes I couldn't get the filament to pull out. 

-I used smaller fest parts on the rear of the MMU.  I still haven't figured out a good filament handling scheme as I want to try to keep the filament in a dry box.

 

 

Posted : 27/03/2022 12:44 am
MileHigh3Der
(@milehigh3der)
Estimable Member
Topic starter answered:
RE: Finally got MMU2S to print

Posted : 27/03/2022 4:45 am
BaconFase
(@baconfase)
Eminent Member
RE: Finally got MMU2S to print

-Larger tubing between the MMU and Extruder.  Like Big, really big.  Fat tips would get stuck here, or at least drag. I'll include the pics of the tubing and fest fitting.  Printed out alternate versions of the parts to just hot thread the parts right after printing.  MMU and Extruder head parts.  Maybe this was overkill.  I think I wasn't getting enough torque on the MMU filament feed.  But sometimes I couldn't get the filament to pull out. 

You need to fiddle with temperatures and filament toolchange parameter settings and get those tips in working order. The slightly larger ID tubes that are normally suggested are only slightly larger because much bigger tips don't load/unload correctly as you've been experiencing. Not sure what you normally print with but this is a good starting point.

Also shouldn't need to lube the lead screws.

Posted : 28/03/2022 9:34 am
MileHigh3Der
(@milehigh3der)
Estimable Member
Topic starter answered:
RE: Finally got MMU2S to print

There is that approach, I’d rather tweak the hardware to work than tweak the settings.  That way I can run a lot of different polymers and brands with out doing software tweaking.   This tubing is actually bigger than I really wanted, but what I really wanted was clear tubing to be better able to diagnose issues.  This diameter is like throwing a hotdog down a hallway, it won’t work with true flex materials, but it works with PCTPE, which is as flexible as I need. I have some intermediate that I could use.

My tips are fine, slightly bulbuous, but I’ve only seen one that was stringy, and it dealt with it OK.  The failure I had was on a retraction,  it just didn’t retract for some reason.

I have an XL on order, and if that works out for multi material, I’ll keep the MMU as is until it dies and then go just MK3s.  Between sensor’s dying and parts breaking, it might not be that long…

Posted : 29/03/2022 6:09 pm
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