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Initial thoughts on MMU 2 and reported issues  

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JC
 JC
(@jc)
New Member
Initial thoughts on MMU 2 and reported issues

I have read a lot of reviews on the MMU 2 and there are not many that sing its praises and a lot of issues have been reported. However my experience is this.
I received and installed my MMU a couple of weeks ago, and was a wee bit frustrated at how difficult or seemingly impossible it was to get consistent prints, However I persisted to look at how this was put together in as much detail possible, as the design in general seemed to be pretty sound (as you would expect from Prusa),
I found that my main issue was inconsistent feeding which lead to missed layers, but it seemed strange that this could be the case if all the filaments were relatively equal in diameter and composition, so why No2 would feed OK a No1 wouldn't (consistently) could only mean an alignment or tension issue.
I found that the issue was indeed alignment (or to be more precise, tension) as there was a hairline crack in the idler to stepper shaft interface. The idler that is supplied is PTEG and is (in my opinion) just not strong enough to handle the forces being applied if the unit is assembled by a normal person, It would probably be adequate as long as you are (as you should be) extremely careful that you do not over tighten the clamping screws on the idler shaft and you ensure that the idler cover tension screws are no more than 1 - 1.5 mm below the surface . I must have slightly over tightened both (and I do mean slightly).
In my case I decided to re-print the idler in ABS. and paid close attention to the above when re-assembling.
My MMU is now very reliable and I feel comfortable leaving it on its own to do multi color prints using all 5 positions. (which has been up to 24hrs a day for the last week.
Of course I still have the usual issues from time to time with stringing causing the FINDA to trigger and halt, but that is easily remedied (though slightly frustrating). and I think I will find a way of limiting this with slicer tweaks for various filaments eventually, but in general it is very reliable.
So in summery (for my issues)
I have made no adjustments, calibrations or modifications from stock apart from some Slic3r settings and an ABS idler.
The assembly has been put together absolutely to the letter of the instructions but with and care and attention to the screw tensions (Remember this is only plastic).
All alignments are spot on.
I use all kinds of filament and a lot of cheap stuff as well (with no issues).

So I believe that if correctly assembled, the MMU 2 can work out of the box very well and I really like a lot of the benefits it brings with it (very easy now to change filaments e.g.)
I trust that Prusa has put a lot of time and investment into producing this so I would say that if there is an issue the first thing to check is the assembly and spend time looking for something fundamentally wrong with it. However im sure there are many improvements that can (and will) be made.
For me this would be an integration of the filament sensor as at present it seems a bit wasted.
a stronger idler assembly.
Non adjustable idler cover tension (though this would be less of an issue with a much stronger idler).
but thats about it at the moment. I think its great.
J.C..

Opublikowany : 26/10/2018 8:40 am
Peter L
(@peter-l)
Honorable Member
Re: Initial thoughts on MMU 2 and reported issues



So I believe that if correctly assembled, the MMU 2 can work out of the box very well and I really like a lot of the benefits it brings with it (very easy now to change filaments e.g.)

I generally agree with the "can" part of the statement, but would add "doesn't yet for many people."

There's a lot of very rapid experimentation going on now, with people working on changes to settings, slicing, and firmware, and there's been faster progress than I would have expected. I think most of the issues are solvable.

Many people are complaining that the MMU2 was rushed out the door half-baked, and I think that's a legitimate complaint.

On the other hand, Prusa has always been an "open source" platform, and I'm starting to appreciate the value of getting it into the hands of early adopters quickly. I suspect that Prusa working on its own would have taken months to get as far as the motivated hobbyists have gotten in a few weeks.

Opublikowany : 26/10/2018 4:56 pm
martin.m25
(@martin-m25)
Estimable Member
Re: Initial thoughts on MMU 2 and reported issues


There's a lot of very rapid experimentation going on now, with people working on changes to settings, slicing, and firmware, and there's been faster progress than I would have expected. I think most of the issues are solvable.

Many people are complaining that the MMU2 was rushed out the door half-baked, and I think that's a legitimate complaint.

After initial frustration I put mine back into a box and and have now again a well working single filament MK3.

What I expect from Prusa is: Clear upgrade instructions with new printed part files where necessary, new Slic3r PE, new firmware... so this thing works more or less out of the box as the MK3 would. I really don't want to watch through hours of videos or read through lengthy forum discussions before I can use the MMU2.
Let's see how long it takes to get there...

- Martin

- Martin

Opublikowany : 27/10/2018 6:08 pm
Peter L
(@peter-l)
Honorable Member
Re: Initial thoughts on MMU 2 and reported issues


What I expect from Prusa is: Clear upgrade instructions with new printed part files where necessary, new Slic3r PE, new firmware... so this thing works more or less out of the box as the MK3 would. I really don't want to watch through hours of videos or read through lengthy forum discussions before I can use the MMU2.
Let's see how long it takes to get there...

I'm guessing it never will, even if it works perfectly. Simply because the complexity of printing with five filaments at once means it's going to take a lot longer to learn how to use it properly.

Opublikowany : 28/10/2018 12:03 am
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