FLEX dead with MMU2s?  

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New Member

Thanks all for the responses and examples, i'll be looking into purchasing a mmu2s unit for sure.

Posted : 22/07/2020 12:59 pm
Trusted Member

If you get it to work it's a wonderful piece of machinery...

Greetings from Bruges,

Having problems with bed adhesion every morning......
Posted : 22/07/2020 3:15 pm
Active Member


I bought mine about a year ago with similar intentions: printing together materials with different characteristics to make print-in-place mechanisms.  Eg. a tough PETG chassis with PLA or ABS bearings, flex shock absorption and a gear train in place with soluble PVA separation so it's print, wash and go.

It's not practical.

You have to watch the MMU like a hawk - and I haven't even tried loading flex as per thread title.

Even if it were reliable enough to leave running unattended the print times with the repeated heating/cooling changes expand to many times those of printing the parts and assembling, and the wasted wipe material is excessive.

Unless all the materials can be printed at the same temperatures and survive a degree of mixing the MMU is useless.  I've removed mine and I don't expect to refit it.

If you just want to print multiple colours of the same filament it works fine - but even then it's limited by the stock available and in most cases it's better just to print plain and paint the object afterwards.

In other words: It works well for a limited range of cosmetic effects but not for anything functional.

Hth, Cheerio,

Posted : 11/08/2020 4:26 pm
Noble Member
Posted by: @diem

In other words: It works well for a limited range of cosmetic effects but not for anything functional.

Disagree on that. PLA+PETG is a very nice and usable combination. The only limitation is the original Prusa Slicer which does not handle real multi material well. But for that we have already Dribbling version or the parser script from the community.


Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram...
Posted : 11/08/2020 9:15 pm
Active Member

Congratulations @nikolai-r - clearly the MMU works in a manner suited to your projects.

For me the inability to manage print in place multi-material parts is the principal handicap.

With several small sub components eg. bearing rollers, standing on a plate alongside other materials adhesion is a nightmare; something is going to come loose or something else is going to stick so tight you risk bed damage.  Different materials don't cohere well, that's expected,  but when joining by shape there is enough bleed that delamination is common and when you don't want parts to join, stringing and blobbing wreck the print.

Don't misunderstand me, for those who want colour changes within one material, or those who use temperature matched cheap/soluble supports for expensive filaments and who can accept the doubled print time the MMU has it's place. It's an ingenious solution to a narrow range of problems and for some it may be ideal.

Perhaps I had unreasonable expectations, the MK3 is start and forget - once the first layer is down you can go away for hours, days even and come back when it's finished and be really surprised by a failed print - I expected the MMU to be as reliable with added function; it's not, not for me.

I will wait for Prusa to produce a triple head machine before I revisit multi-material printing.





Posted : 14/08/2020 5:25 pm
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