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MMU2S loading/unloading getting worse with time  

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Martin Stoufer
(@martin-stoufer)
Estimable Member
RE: MMU2S loading/unloading getting worse with time

It is good/bad that my experiences so far with my MMMU2 match whats being described here. I printed out the sheep (2 color) and a modified Benchy (4 colors) and saw similar results.

On the sheep, I had two failures in the first 25% of the print. Both occurred during filament swaps and were cleared by pulling the filament and feeding in fresh before continuing. Once I understood the recovery process of MMU button presses, getting back on track was painless as the tip re-heated and the print continued from where it left off. 

As for the Benchy, I gave up after about 12% of the print. There were so many intended filament swaps that I was seeing failures 20% of the time. All were due to the new filament being unable to be retracted. In some cases, I had to re-heat the hot end in order to get it to release so I could work it back up the extruder tube with small pliers. I did see a minor amount of the PTFE tube sticking up here (<2mm) and wondering if my setup has come loose too. What exactly is getting jammed down there? I'm not seeing any real bulging of the filament as it comes back up.

While not mentioned before in this thread, I'm also noticing that both the extruder and MMU feeder gears are happy to just grind away on the stuck filament during extraction and any attempt to recover w/o pulling out the entire filament and trimming is a lost cause.

The only differential I have from these comments are the filaments are "old". They are bone dry but noticing some of them are becoming a bit brittle. I'm wondering if this too has set me up for failure.

Thanks to everyone who has posted here. It has helped me further narrow down the root cause.

This post was modified 2 years ago by Martin Stoufer
Posted : 20/03/2020 5:59 pm
DC
 DC
(@dc)
Active Member
RE: MMU2S loading/unloading getting worse with time

@martin-s61

At least in my case the filament is pretty fresh.  Less than 2 months old and storage in dry boxes with desiccant when not being used.

Posted : 20/03/2020 6:13 pm
gnat
 gnat
(@gnat)
Noble Member
RE: MMU2S loading/unloading getting worse with time
Posted by: @martin-s61

The only differential I have from these comments are the filaments are "old". They are bone dry but noticing some of them are becoming a bit brittle. I'm wondering if this too has set me up for failure.

Yes I too have noticed that as filament ages it gets stiff and brittle and that has a negative impact on MMU performance. 

MMU tips and troubleshooting
Stop SL1 tank leaks with a simple o-ring...
Posted : 20/03/2020 6:40 pm
michael.b103
(@michael-b103)
Active Member
RE: MMU2S loading/unloading getting worse with time

All my filament is stored in 5-gallon plastic paint cans with screw-on lids and a big pack of desiccant in a cotton sack with a tie string used for cooking (the kind to make bouquet garni, which is basically a sack of spices you can chuck into your stew/soup/whatever). 

Posted : 20/03/2020 7:43 pm
Martin Stoufer
(@martin-stoufer)
Estimable Member
RE: MMU2S loading/unloading getting worse with time

@michael-b103

I store all my filaments in a very dry open environment. Is it the concept of keeping them sealed in some climate controlled container better? Or does PLA simply have a shelf life that my stuff has now expired?

Posted : 20/03/2020 8:30 pm
DC
 DC
(@dc)
Active Member
RE: MMU2S loading/unloading getting worse with time

Here's a good write-up on what PLA degrades/changes:

https://www.matterhackers.com/news/filament-and-water

Posted : 20/03/2020 8:36 pm
vintagepc
(@vintagepc)
RE: MMU2S loading/unloading getting worse with time
Posted by: @martin-s61

@michael-b103

I store all my filaments in a very dry open environment. Is it the concept of keeping them sealed in some climate controlled container better? Or does PLA simply have a shelf life that my stuff has now expired?

Define "dry". It's somewhat hygroscopic, so it means it will pull moisture out of the air. The lower your relative humidity, the better.

It does not really "expire" to myknowledge. You should be able to heat it for a few hours at a low temp (~60C)  to drive off the moisture and get it back to usable.

 

Posted : 20/03/2020 8:49 pm
Martin Stoufer
(@martin-stoufer)
Estimable Member
RE: MMU2S loading/unloading getting worse with time

@vintagepc

It's not the moisture I'm worried about. I have a RH gauge in the room and it is always 10-12%. I have plenty of desiccant so I could store them in dry bags if the filament needs to be even drier. 

My major concern here is that some of the filaments themselves appear to be getting quite brittle. Others are still pliable and not apt to get ground down while in the extruder/MMU when a filament swap fails. 

Posted : 21/03/2020 8:04 pm
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