How to improve handling of Soluble Support Material on MMU2s - What is your experience?
The main reason why I bought the MMU2s upgrade was because of the possibility to include soluble supports. I was warned by the red red flags in many forums about this upgrade, but the possibilities were so many that I gave it a shot.
So far I have worked with PLA, and in my hands when using only PLA my results have been very good, and I cannot complain too much. Prints of 9h typically require me to make only a couple of interventions, but sometimes the printing goes on without incidents. With respect to the use of PLA I am very happy with the upgrade, multicolor is great and I would say it was a good investment.
It is with the handling by the MMU2s of the PVA from eSUN that I got really disappointed. eSUN is a brand I have used on multiple occasions, and the results are typically rather good, and their PVA filament is said to be on the better lot.
Using a freshly opened vacuum-sealed PVA spool, I had some initial problems of the filament at the extruder, but within two days of troubleshooting and studying these were resolved by adjustment the Idler tensioning screw and tweaking some settings in Prusa Slicer to account for the oozing (particularly high retraction distances and speeds were important). After this bottleneck was passed, all that remained were problems with the MMU2s unit that would not handle the eSUN PVA filament reliably. Filament load and unload failed constantly. From my experience at failing with the PVA from eSUN i got the impression that the material properties of the filament are not adequate for the hardware configuration of the MMU2s. The reason seems to rely on the mechanical interaction between filament and the Bondtech gears. Using the same MMU2s filament inlet with PLA filament results in no issues whatsoever. Adjusting the tensioning screws did not seem to reliably resolve the problems either.
I have now ordered some BVOH from Verbatim in hopes that this would be better. I will be posting here my experience once I have some further news.
In the meantime, it would be nice to know also some success stories, and if you had problems only with some filaments and not others, if success depended on the type of soluble support or if brand was relevant in your case. People often tend to voice their discontent, but it is important that people with positive experience (even if partial) to jump in. Unfortunately Prusa seems not to be handling this situation well enough and it would be nice to have some definite input from them too.
I also bought the MMU2S mainly to be ready if I need soluble supports. I also have a sealed spool of Verbatim BVOH ready.
The thing is, I don't currently have any models in the do-it queue that need such supports, and I have enough planned to keep the printer busy for at least the next month or so on the model railroad project.
I normally have the MMU2S disconnected, electrically with a mounted switch and mechanically with the extruder tube disconnected. However, I have run it in both the single filament and multicolor modes and I'm confident that it will consistently load and unload reliably.
Now I just need a model to test it out. 😉
So yesterday I tried for the first time some TPU (eSUN, A95). It is considerably less stiff than PLA, making it with respect to this more similar to PVA filament from eSUN. The MMU2s unit seemed to handle that much better than PVA - my BVOH is coming tomorrow, I'm really crossing fingers here!!
I forget which PVA I have, but I found the attempts to use it to be rather miserable.
- I had to resort to desecrating my smooth plate with glue stick to get it to stick to the plate.
- As my setup is not enclosed and humidity controlled I found I had to keep stopping the print and running the PVA through my dehydrator every 2-4 hours for 4-6 hours.
- As the filament picked up moisture it got more and more stringy which resulted in clogging up the FINDA.
- Even with incoming and outgoing purges set to 200 it was clear that there was still bleed between the PVA and PLA.
- After manually removing most of the supports, after soaking for 24 hours most of the remaining supports were still there.
I hear that BVOH is supposed to work better, but I think I'll play with mixing PLA and PETG to support each other instead.
The best tip I have is to limit the soluble support to a single layer between the object and traditional supports. That will save you some money on support material and limit the amount of time the PVA is being handled. Also, try to make a dry box for your PVA, it helps a lot.