No problems with MMU2S  

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snaslund
(@snaslund)
Eminent Member

I have a MK3S and did some browsing here before purchasing the MMU for it.  It looked like there were a lot of problems but I decided to give it a shot.  I am glad I did because mine is working great.  I have printed about 20 objects with a total of several thousand filament changes and had one total MMU fault which cleared immediately.  Here is why I think the unit is working well.  Note that this is built per the manual with no mods and the stock buffer.

 

1.  Make sure the printer is working PERFECTLY before attempting the MMU upgrade.  That means all the calibrations especially first layer and extrusion multiplier for the filaments you use.

2.  Make sure you get the MMU parts completely cleaned up before assembly, especially any holes that the filament passes through.  Use a piece of filament to verify they are all clear.

3.  Make sure the IR sensor calibration at the extruder is good.  I played with this a bit to ensure the filament is detected every time.

4. Use good quality filament.  My tests were done using Prusament PETG and Atomic PETG.  I know Prusament is pricey in the US but I would recommend you get it to test with before you try others.  Do not buy from Amazon, the reseller is ridiculously overpricing.  Buy from Prusa direct.  You cant really complain effectively to Prusa unless you use their filament first.  I suspect many MMU problems are filament related.  I run right in the middle of their recommended temps.  Atomic has worked just as problem free for me.

5.  I did not tighten the buffer tubes at the buffer much at all.  I can still pull them out by hand which makes filament loading easier anyway.  There is a lot of talk about eliminating drag which sounds OK but there is no need to obsess about it.  I can easily pull filament through all the tubes until I feel it land at the MMU.

 

just wanted to reassure folks that the MMU can work well.

Posted : 28/10/2020 6:01 pm
mark.a19 and Lize liked
Lize
 lize
(@lize)
Eminent Member

Thanks for posting, I have the MMU which I haven't installed yet so helpful to get tips before hand.

Posted : 28/10/2020 8:04 pm
karl-herbert
(@karl-herbert)
Famed Member
Posted by: @snaslund

I have a MK3S and did some browsing here before purchasing the MMU for it.  It looked like there were a lot of problems but I decided to give it a shot.  I am glad I did because mine is working great.  I have printed about 20 objects with a total of several thousand filament changes and had one total MMU fault which cleared immediately.  Here is why I think the unit is working well.  Note that this is built per the manual with no mods and the stock buffer.

 

1.  Make sure the printer is working PERFECTLY before attempting the MMU upgrade.  That means all the calibrations especially first layer and extrusion multiplier for the filaments you use.

2.  Make sure you get the MMU parts completely cleaned up before assembly, especially any holes that the filament passes through.  Use a piece of filament to verify they are all clear.

3.  Make sure the IR sensor calibration at the extruder is good.  I played with this a bit to ensure the filament is detected every time.

4. Use good quality filament.  My tests were done using Prusament PETG and Atomic PETG.  I know Prusament is pricey in the US but I would recommend you get it to test with before you try others.  Do not buy from Amazon, the reseller is ridiculously overpricing.  Buy from Prusa direct.  You cant really complain effectively to Prusa unless you use their filament first.  I suspect many MMU problems are filament related.  I run right in the middle of their recommended temps.  Atomic has worked just as problem free for me.

5.  I did not tighten the buffer tubes at the buffer much at all.  I can still pull them out by hand which makes filament loading easier anyway.  There is a lot of talk about eliminating drag which sounds OK but there is no need to obsess about it.  I can easily pull filament through all the tubes until I feel it land at the MMU.

 

just wanted to reassure folks that the MMU can work well.

It is a variation to hear for once that the MMU2 can also work 👍 , which mine does by the way 😊 .
If you assemble it carefully, remove all burrs and fine tune it (including sensor and spring tension) and of course optimize the slicer software, there should be no problems. Some small changes regarding the cutting blade and rear PTFE seat I have changed and I am using 4/2.5 PTFE tubes.
What the MMU2 does not like is too much ambient heat. So I would not recommend to use over a long time it in an enclosure with e.g. 45 degrees C. ambient temperature. I tried it and after a few months of operation the MMU2 board was gone. In a cooler environment, I no longer had any problems in this regard.

 

 
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 28/10/2020 8:29 pm
Lize liked
Lize
 lize
(@lize)
Eminent Member

@karl-herbert

The ambient heat is interesting to know, I've recently finished a cabinet made from a computer server rack and am going to be printing ABS and running around 45C.  I'd been thinking of running disconnected for TPU but do you think that it would be OK doing ABS like that and the heat won't have so much an affect with the MMU powered off?

Thanks

Posted : 28/10/2020 8:38 pm
snaslund
(@snaslund)
Eminent Member

Here is more on my environment.  I built the Prusa Lack enclosure and I print PETG and PLA with the doors open.  My room itself is at 73 f.  I havent had problems so far.  I think the only reason I would run ABS is if smoothing is important.  For my usage, I think PETG is my favorite filament.

I mainly wrote this because I know from being in the IT industry is that people don’t post if everything works fine and I think that can give people the impression that the MMU is a bad product.  I have built several 3D printers over the years including a Rostock Max.  All of them needed tweaks but Prusa has been the best “out of box” experience.  I think it is a mistake to sell the MMU bundled with a new printer kit.  Too much to go wrong.  I think its critical to know you have built a great stock printer before you move on to the MMU.  Some people struggle just to get the basic printer working first.  Simple stuff like getting a good extruder calibration and first layer are absolutely critical or nothing further will work right.

 

Posted : 28/10/2020 9:30 pm
mark.a19 and Lize liked
snaslund
(@snaslund)
Eminent Member

As far as the MMU board being temperature sensitive, I had not heard that.  I suppose an enterprising person could extend all of the MMU cable out of the enclosure but I would try to confirm first that the temperature is really a problem. After all they designed the Lack enclosure and they run the MMU inside.  The electronics failure is too hard to diagnose as being temperature related unless Prusa sees this trend across many MMUs.  Some electronics experience a young death because the board had an inherent fault to begin with.

Posted : 28/10/2020 9:35 pm
Lize liked
Lize
 lize
(@lize)
Eminent Member

@snaslund

I agree, I've had my printer running for quite a while now and am happy with the set up, I bought both at the same time but purposely delayed adding the MMU.

I haven't tried ABS as I've only just finished my cabinet and would also stick with PETG but want to do smoothing for a range of planned prints.

Posted : 28/10/2020 9:37 pm
Lize
 lize
(@lize)
Eminent Member

My ABS projects aren't exceptionally large so think I will print some before I install the MMU and then will give it a go with the MMU in place but not used and chance that board failure doesn't happen.

Posted : 28/10/2020 9:40 pm
snaslund
(@snaslund)
Eminent Member

All motor drivers run hot because of the current they are handling so the question is whether the enclosure really makes the motor drivers hotter than they get anyway.  Prusa should have some data on the ambient temperature range of the MMU board.  If not, they should know the temp range of the touchiest component.

In my opinion I would look for an ABS alternative unless the smoothing thing or some other ABS property is mandatory.  Anything run at higher temperatures has a shortened life span compared to thing run at lower temps.

Posted : 28/10/2020 9:42 pm
snaslund
(@snaslund)
Eminent Member

@lize

I would run the wheels off of it right away.  You want to know if that MMU will die while under warranties.  I would ask Prusa support if its OK to run at 45C, keep the response, do your test.  If it fails, Prusa owns it.

Posted : 28/10/2020 9:44 pm
Lize liked
Lize
 lize
(@lize)
Eminent Member

I don't think the MMU2 should be a problem in a heated enclosure, the Lack modification instructions only mention that its better to move the power supply:

https://blog.prusaprinters.org/mmu2s-printer-enclosure_30215/

I've put the PSU in the bottom of the cabinet and when temperature testing if the top half gets up to 35C the bottom is around 10C lower.  I've ordered a heater bulb to try to get the temperature higher.

If the bottom half gets a bit too hot then I've got the option to heat insulate between the 2 areas or move the power supply outside with a connector.  I was trying to avoid having to disconnect it if I want to take the removable sides off although PLA prints fine with them on.

I might have a bit of time tomorrow so will run a small ABS print at the highest temperature I can currently achieve to see what its like 😀 

Sorry, got a bit off topic, will report back if I experience any problems post MMU install.

Posted : 28/10/2020 10:24 pm
snaslund
(@snaslund)
Eminent Member

Although it is weak evidence, Prusa recommended moving the power supply out of the enclosure but did not say to relocate MMU electronics.  Personally I would just ask them to state the allowable ambient temperature to avoid warranty problems.  Also, I have run a lot of ABS in the past with no enclosure at all so I would consider trying minimal heat in the enclosure and see how it goes.  Good bed adhesion and maybe a brim might be a better answer.

Posted : 29/10/2020 1:47 pm
Lize liked
Wojciech Penar
(@wheart)
New Member

In my case not the electronics failed due to temperature but poorly set IR sensor had problems with "softened" cheap PETG.

I'm using LACK enclosure (but table-top, not free-standing), with few customisations:

  • I've thrown away original buffer,
  • replaced PTFE seat at MMU rear with one with PC4 couplers - continuous tube between MMU and spool stand has large advantages and increases modularity
  • I use "self rewinding" filament spools together with custom stands (models on my PrusaPriters page, together with filament cleaner/spool-side PTFE fixture),
  • I moved power supply outside of the enclosure with detachable (6 pole connector) cable.

To the last point a few words of disclaimer: I'm using six pole Anderson Powerpole connector. Contacts are rated 4 x 30A for two 24V supply lines, 2 x 15A for PowerPanic (smaller contacts to make them easier to solder to thin PowerPanic cable) - in theory it gives LARGE margin for safety compared to infamous burning printers from PRC, connector is modular (so arranged in 2 x 3 layout, it fits hole intended for mains cable in original enclosure design - IEC plug) and can be connected only in one way (so minimizes risk of misalign). As there are spare cable wraps in MMU kit, I've used them to make whole thing looking nice 😉 Together with PC4 connectors at the rear of the MMU unit, it makes removing printer from an enclosure for maintenance (or enclosure clean-up) much easier.

Posted : 19/11/2020 1:50 am
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