MMU2S not ready for public use  

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nils.t
(@nils-t)
Estimable Member

Personally in retrospective I find frustrating that most MMU2s problems are quite obvious and could have been adressed by PR with no extra cost. Basically, my with current knowledge I would never assemble the unit as delivered. There are some mods everyone seems to install at some point to get it working. PR could have included those in the design at little or no extra cost:

- some selector with improved path (optionally with magnet)
- wider diameter bowden tubes
- better quality idler door
- filament inlet with 5x pushfit connector
- ditch the buffer
- some sort of auto rewind spool holder
- several users reported issues with PTFE in hotend, why not include 50cm of material and a cutting/chamfering aid?

A lot of these things are obviously self-printable, or could replace printed parts already at the factory. I have not seen a post by a happy user who had not at least implemented one or two of those.

...
Posted : 31/07/2019 8:17 am
jason.n7 and CybrSage liked
CybrSage
(@cybrsage)
Honorable Member

While I agree with the sentiment,Prusa has been doing that.  The filament wallet you poo-poo is proof of that.  The people complained and Prusa agreed.  It does its job while still being cost effective.

I do think Prusa could adopt the most commonly used mods as new part revs, not sure why they are not.

 

This post was modified 11 months ago by CybrSage
Posted : 31/07/2019 12:55 pm
derek.a.austin
(@derek-a-austin)
Active Member

I'm a new owner of both printer and MMU and I must say reading this topic has me rather annoyed.  I now feel conned out of £269!  Was thsat cheap for a MMU, I don't know, Prusa has a reputation for producing an excellent printer, and it is, I tested it and ran several prints before attempting the MMU upgrade.

Once on I printed 2 small squres 15cm x 15cm x  3mm in 2 colours and it printed them perfectly.  I was over the moon, it was a joy to watch.

I moved on to a 4 colour print, it failed twice on the first layer after 2 colours.  I've tried everything I can think of to get this thing working, I thought loading to extruder would prove that at least it could load each colour.  I selected filament 1 and the selector moved to the right place but thr idler selected and subsequently fed filament 4 into freash air!  Noiw that's nothing to do with the PTFE tubing or shape of the filament end or the buffer or anything else, in my opinion thats firmware!

My bottom line, I can't get any filament to load no matter what I try, I now have a £1000 paper weight and to be honest that ain't funny!

Posted : 01/08/2019 11:26 pm
jason.n7 liked
Oregonerd
(@oregonerd)
Active Member

This morning I would have said "I'm with you!" Hours of futzing with this thing to try and get it to load. Then I read this thread. One fellow said something about 2.5mm ID tubing ( I could use a link/source please). Following that train of though I took mine apart this afternoon. I removed those short little tubes to inspect the bevel. Looking at the little tubes closely I noticed it was misshapen/ oval inside. Using a ejected filament end I found way to much resistance in all the tubes. Now I have none and it hasn't missed a beat since!

I drilled the tubes with a #45 drill bit and beveled the other end. Solved. Resistance in the path is the problem.

I also notice that the tube coming out of the selector in the air hose connector had a little too much resistance. I drilled that end of the hose for good measure. I believe the hose isn't quite long enough and bends a little too sharp almost causing a kink where it goes into the connector on the selector.

A nice touch on the selector bearing/gear assembly would be a quick release for cleaning... and a dust cover.

I am not an engineer or an artist. I am a bit of a designer that does a little of both....
Posted : 12/11/2019 1:22 am
joan.t
(@joantabb)
Veteran Member Moderator

I got mine from Ebay...

this seller has four colours 

https://www.ebay.co.uk/itm/PTFE-Polytetrafluoro-Tube-Transparent-Milky-Black-Red-Insulation-Various-Sizes/223582817566?hash=item340e930d1e:m:mNIXSnx2d83gvGOTaLhAwNQ

Note I have not bought from this particular seller, the seller I got mine from is currently not advertising, or at least I can't find them! 

 

there are revised models for the filament selector that slides along the front of the mmu2, on thingiverse, some revisions address the feed path through the selector, making transition from the main MMU body, across the gap into the selector, more successful, others add a magnet to ensure the Finda Ball drops more effectively when the filament is withdrawn, 

there are also models that allow the use of 10mm screw thread, 'Pass Through' pneumatic fittings on the rear of the MMU, to make the filament feed PTFE tubes more secure without squashing them.

regards Joan

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 : 12/11/2019 11:18 am
Oregonerd
(@oregonerd)
Active Member

JoanTabb: "there are also models that allow the use of 10mm screw thread, 'Pass Through' pneumatic fittings on the rear of the MMU, to make the filament feed PTFE tubes more secure without squashing them."

BTW that PTFE link won't send to the US.

I was just going to ask for that, because guess what happened... one of the feed tubes is pushing out of place during eject.

My Die maker friend owes me favors for inventing the control process for their Titanium injection mold machine. I'm going to have the short tubes turned in aluminum or brass or some such. Titanium is too expensive 🙁 

I still think the tube between the extruder and selector is too short, the bend out of the selector is too sharp = a bit more friction which seems to be the enemy of the MMU2. I'm thinking that a clear dust cover with integrated tube support and a longer tube for the MMU2 is in order.

Whenever a cable is used in a push - pull control mechanism, the cable manufacturer always insists the first x inches on each end are straight and have a limit on the radius of the bend.

Good news is after the rework I did I had one eject error in the 10 hour trial run + the tube feed being pushed out sometime while I slept.

This post was modified 8 months ago by Oregonerd
I am not an engineer or an artist. I am a bit of a designer that does a little of both....
Posted : 12/11/2019 5:55 pm
jason.n7
(@jason-n7)
Active Member

I'm about over this printer.. No matter how may tweaks i make... no matter how many forums.. i spend more time working on the MMU than printing.. seriously ready to sell this thing. I bought it to print not to troubleshoot ant tweak.. numerous tings that are problematic and i'm fairly technically capable... is this still worth the cost?

Posted : 17/11/2019 2:15 am
Oregonerd
(@oregonerd)
Active Member

@jason-n7

Life should be fun. Not frustrating. You might consider just using one channel to print in one color and revisiting it when other people come up with mods that make it work better.

This product is rough but it is pretty cool when it works. I printed a project after I though I had all the bugs worked out.  My partner works for a non profit and she hands the gear bearings out to graduating kids as fidget spinners.

It printed flawlessly for the first 20 hours and then started misbehaving with load problems in this 28 hour project. I nursed it along for 2 more days to finish it after coming home from work or waking up to find it stalled yet again. 

I will be ripping this thing apart and generating a wish list and fix list. 

I see it as more of a challenge.  I am determined to make it work more reliably.  Maybe the more tenacious among us here will come up with ways to make this thing work better. It's not the most elegant bit of engineering IMO. But I'll address that inn another post.

I am not an engineer or an artist. I am a bit of a designer that does a little of both....
Posted : 20/11/2019 4:35 pm
Scott
(@scottmg)
Active Member

After having spent months messing with my MK3S and MMU2S, it's fascinating to read these threads and realize I'm not the only one.  Fortunately this is a hobby for me, the printer itself has become a hobby, but I can understand other's frustration.  Many have had the same kinds of issues, and come to many of the same conclusions.

The first being that the PTFE tubes are way too narrow inside, particularly if you have filament that isn't perfect.  I haven't found 4mm OD 2.5mm ID, but I've been using these English units versions that have been very good: https://www.mcmaster.com/5239k25.   5/32 inch is very, very close to 4mm (like 3.97mm), and I haven't had any issues with it.

I'm also in the process of a complete redesign and rebuild of my extruder.  The original purpose was to make it easier to switch out the whole E3D hot end, to make nozzle switching a little quicker.  But another benefit was switching which screw the filament idler revolves around.  It's basically the same but rotates on the bottom stepper screw; my stack with the IR sensor is much shorter, and has been much more reliable. 

When I get time, I'm going to redesign (or print some of the existing designs), for the filament path through the MMU.  The filament path through the MMU adds more resistance than the entire rest of my setup.  I'm confident I can make it better.

FWIW, I've had enough hair-pulling days that I agree with the OP - this thing was not ready for end users.  Only ready for hobbyists who are OK with their printers being the hobby.  

Scott 

Posted : 02/03/2020 3:45 am
nikolai.r
(@nikolai-r)
Noble Member
Posted by: @scottmg

...Only ready for hobbyists who are OK with their printers being the hobby.   

I think that applies to every Prusa product and not limited to MMU units.

This post was modified 4 months ago by nikolai.r
Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram...
Posted : 02/03/2020 4:05 am
CybrSage liked
gernot.maxa
(@gonzomagx)
New Member

After 6 Months of frustrating working with the MMU2S I can say: It doesn't work properly, no, forget properly, IT DOESN´T WORK.
Three or four changes work, and then there is a mistake, one of what feels like twenty different ones. There is only one error message: "MMU needs user..." You have to find out for yourself what kind of error you have.
Imagine a car that only starts one or two days a month and outputs an error message: The car does not start.

With the MMU unplugged and the single firmware, the printer, like my second Prusa, does exactly what it should. He prints.

Posted : 03/03/2020 12:51 pm
armand.f
(@armand-f)
New Member

I think that PR should be ashamed of this terrible excuse for a multi-material unit.  I have been trying to get this thing working reliably for 6 weeks and the best print I have made is only 2 hours with a couple of interventions.  Reading these posts it seems like some users are happy when they get a print with"only several" interventions.  If a print needs an "intervention" and you are away or sleeping because the prints take many hours, the print is usually a failure.  There are so many different problems with this design that I don't think it will ever be ready for prime time.

I am an engineer very familiar with 3d printing having built several over the years with good success.  I bought the i3mk3 because of its great reputation and I was not disappointed...but it is not cheap.  After many hours of printing with the i3 I thought I would try the mmu2s even though I did not believe that the concept was particularly sound.  I believed in Prusa because of the volume of printers he sells, the performance of my i3, and the glowing reviews he received. 

So what happened with the mmu2s?...how could he release such a disastrous multi-material design?  I think he has left it for the community to figure it out.  Indeed many improvements have been published by the 3d printing community...without these "fixes" the mmu2s as delivered simply does not work and with the fixes, it will work maybe 1 out of 10 times.

I think this design is bad enough to turn off the PR community and tarnish the great reputation PR has developed with its i3 printer series. 

I really believe that his is a defective product and a refund should be offered.  My $300 mmu2s has become a door stop and  SLA printer I am about to buy, I will get from one of the many other brands...I can no longer trust PR.

Posted : 04/03/2020 2:47 am
armand.f
(@armand-f)
New Member

@roy-r3

Tried all of these fixes...still fail 9 out of ten times.  If your prints succeeds 99.9% of the time then you have a failure .1% of the time or 1 in 1000.  Have you done thousands of long prints 10+ hrs. to measure your failure rate?  I think not.

Posted : 04/03/2020 3:04 am
dick.v
(@dick-v)
Eminent Member

Ok, Armand-f, I do understand your frustrations!

If we took a close look at PR, this is the situation:
First off all I am Dutch and based in the Netherlands.
We admire the skills of the people of the Czech republic, they are mechanical engineers by nature!

There is only 1 problem;
At this moment only 2 economical business models are competing which each other;

The soo called Anglo-Saxon model and the Rhineland model.

- A) The US bullshit, "The winner takes it all, the loser standing small.
- B) The European model, looking after each other and taking care of each others local communities.

JP started with B and now tries to be A

To my humble opinion, wrong bed, nice try but the Corona Viruses took it over, let's return to innocence......:)

D.

Posted : 04/03/2020 3:38 am
nikolai.r
(@nikolai-r)
Noble Member

... and still there are plenty happy MMU2 user out there.

Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram...
Posted : 04/03/2020 7:09 am
CybrSage and gnat liked
robert.k71
(@robert-k71)
New Member
Posted by: @nikolai-r

... and still there are plenty happy MMU2 user out there.

And if there are any in Vienna, I could need (paid) help for my MMU2S.
I'm now tired of trial and error and thought about sticking my arm like John-H76
Posted by: @john-h76

Don't worry, you'll eventually get it to kind of work. If not, you have a $300 paperweight. I may just duct tape mine on my arm and tell people it's a Pip-boy. Either way, people will know you're a baller because your paperweight/Pip-boy will cost more than their fresh Jordand. 🤣 🙄 😭 

Posted : 04/03/2020 7:55 am
jason.n7 liked
jason.n7
(@jason-n7)
Active Member

@cybrsage

not all of them are "doing the job".. i've had nothing but issues. Prusa has some of the best support, but I have issues trying to print single filament with this, at this point wont attempt a job with multiple.

 

Posted : 04/03/2020 2:30 pm
jason.n7
(@jason-n7)
Active Member

@oregonerd

It is having difficulties on just one channel.. I do very little multiple material prints. I have a long background in manufacturing and didn't buy it to fiddle with it, i bought it to print. I'm not a mods type of person. My goal for this was fast material switches without manually loading and unloading. I've had to work more on getting it to take the filament that time in print. Just frustrating. Apologies, the frustrations aren't directed at you, have just had better success with my FFCP, which was much less.

Posted : 04/03/2020 2:36 pm
nikolai.r
(@nikolai-r)
Noble Member
Posted by: @robert-k71
And if there are any in Vienna, I could need (paid) help for my MMU2S.

Check for people around you here: https://www.prusaprinters.org/world

Contact them and I'm pretty sure you will find someone pretty fast.

 

@jason-n7

If you want help from the community, feel free to open a new thread and describe your issue briefly

Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram...
Posted : 04/03/2020 7:27 pm
gnat liked
armand.f
(@armand-f)
New Member

Just noticed that the MMU2s is not warranted like the other Prusa products...wonder why?

Posted : 05/03/2020 1:09 am
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