Frequent clogging with Verbatim BVOH  

RE: Frequent clogging with Verbatim BVOH

the last time I used BVOH  I think I had to make the purge block bigger.

and I think I also made the layers bigger. it's been awhile.

but I am about to try pla and using petG for support material. 😀  why not try right?

RE: Frequent clogging with Verbatim BVOH

I tried PETG/PLA.

They are perfect as support for each other - if you get the printer working with it. 
The MMU does not like different nozzle temperatures (PLA starts stringing and clogs).

Make your Purge Tower big. I had problems with layer adhesion. Maybe because the PLA was not purged out completely and messed with the layer adhesion of the PETG.

I document everything here. I will add some more improved settings during the next two days.

RE: Frequent clogging with Verbatim BVOH

I have tried nearly everything I can think of to print with BVOH as support in my MK3S MMU2S - both as full support and soluble interface.  The problem seems to be that BVOH does not survive multiple filament changes.  Eventually strings or blobs create a problem and clog the extruded, sometimes so badly as to wrap around the extruder gear.  Sometimes I can rescue a print temporarily by unclogging and resuming only to have it need attention a few minutes later.  I can do multi PLA prints successfully so the MMU2S is otherwise functioning properly.  I can print with all BVOH (though why would I?) so the MK3S prints fine.  But when making multiple filament changes, BVOH eventually fails, then repeatedly fails.  I have tried different suggested print parameters — changing cooling moves, changing retraction amount and/or speed, changing print speed, etc.  The Verbatim has been dried — twice.  I had hoped that the change from MMU2 to MMU2S would help, but no.  If anyone has a solution I (we all) would greatly appreciate it.  I am eager to successfully print with soluble supports.

RE: Frequent clogging with Verbatim BVOH

First of all the purge volume should be high enough for bvoh. At least 100 mmm^3 (usually I use 140). Also it might help to dry bvoh in the oven (50-60°C for at least 3 hours). 

RE: Frequent clogging with Verbatim BVOH

Im am having these same issues.  I appreciate the advice, but there has to be a better way than putting it in the oven every time I want to print with BVOH.

RE: Frequent clogging with Verbatim BVOH

Did anyone ever figure out a solution?

RE: Frequent clogging with Verbatim BVOH

As you can read in this short string of comments, there has been no solution offered for this problem and it hasn’t received much interest from printers or Prusa.  Perhaps few other people are having a problem with BVOH or soluble supports.  Perhaps no one uses soluble supports — I sure don’t try anymore.  Perhaps there is a solution which no one is sharing with us.  I have stopped looking and experimenting for now, but am disappointed with lack of response.

RE: Frequent clogging with Verbatim BVOH

The sad thing is, I have friends with different printers who use soluble filaments all the time without problem.  This is really disappointing. 

RE: Frequent clogging with Verbatim BVOH

I have ran both Push Plastics BVOH and E3D soluble Scaffold, both run fine. I do have the loading/unload speeds turned down (especially with BVOH) and the Skinnydip version of PrusaSlic3r is a great help. https://github.com/antimix/PrusaSlicer

The Push Plastics BVOH is oversized to an average of 1.85mm(at least the spool I have) so I run it at .94 extrusion multi.

140 for purge volume is sufficient for both these filaments, and my GitHub has these profiles https://github.com/ironjoe13/Slic3r_settings/tree/master/filament

RE: Frequent clogging with Verbatim BVOH

Posted by: @ettore-b

Hi Everybody,

I'm trying to pritn with PLA + Verbatim BVOH and the BVOH is clogginv quite easily during the change PLA->VBOH

This is because the retracted BVOH filament hase sometimes a "ball" end

I'm currently printign with Slic3r standard PLA+Solubile suppoert interface

I also hear some "saw" noise when the BVOH filament is extraced during the BVOH->PLA change

Someone experineced something similar?

 

thanks in advance

 

best regards

 

 

Have you tried  changing the ptfe tube from mmu2s to the extruder? Prusa ones are 2mm inside diameter, but you can find 3 mm inside diameter tubes. Works for flexible and pva.

There is another problem, i have not this problem with my prusa, but i have it with a multiple extruder printers, if you leave the pva hot in the nozzle, it became stiff and clogs the nozzle, it can became rock solid. You must even disassembly the extruder to fix it.

Hope it helps

RE: Frequent clogging with Verbatim BVOH

My problem is very similar. I also have a bit of a theory formed and a proposed solution below. I am applying my theory on a print for the first time as I write this post, so no results yet, but thought I would share what I have learned while working through this issue.

Problem

I am attempting to print a fairly large model (~24 hours) using Prusament PLA and Verbatim BVOH. I can print pure PLA MMU2S prints, no problem. However, when I try the PLA and BVOH combo, it will go fine for a while and eventually it fails to load the PLA. It always fails to load the PLA, no unloading or loading issues with the BVOH.

The failure seems to happen after a relatively large amount of BVOH has been extruded. For example, there is a layer in my model where almost all of the layer is BVOH, and it tends to fail to load the PLA after that BVOH has been extruded. The failure also tends to occur more frequently as the print goes on, and will not happen for several layers if a lot of PLA has been extruded (I think this is because the printer has purged enough that whatever BVOH residue is left over in the nozzle has been pushed out).

When the failure happens, the PLA grinds in the extruder gear while it is being loaded. The MMU2S detects this failure and retracts the PLA all the way back and then tries again 3 times. After the 3rd attempt, it pauses the print and displays the MMU2S load failed message. On several of these failures, I have taken the failed PLA out and marked the ground-up spot with a permanent marker. Holding it up against the extruder, so that the extruder drive gear aligns with the marking, I can see that the tip of the filament was stuck half way down the heat break when it jammed. (Yes, I mean the heat break, not the heat sink. I am using a Mosquito, so the heat break is in plain view from the side.)

Theory

BVOH is building up in the nozzle over time, hardening (as I hear it likes to do), and eventually preventing the PLA from loading successfully. So, reducing the amount of BVOH used in the print as much as possible may help prevent this build up and so might increasing the PLA purge volume to push more of the left-over residue from the BVOH out through the nozzle.

Currently, I have resliced my print so that 4% of the print is done with BVOH rather than 11.3% (what I had before). I found these values using the "Feature Type" view on the plater after slicing. Since I was using the Soluble Interface print settings, the only feature type that was being printed with BVOH was the support material interface.

In short, my theory is that if the ratio of PLA to BVOH is large then the print will succeed. That is why I draw attention to having 4% of my print in BVOH which leaves 96% of my print in PLA.

Solution

If my theory is correct, I think these things may help and I am currently testing this:

Print Settings > Support Material > Support Material

- Reduce overhang threshold from 80deg to 35deg (reduce the amount of support material used in the first place)

Print Settings > Support Material > Options for Support Material and Raft

- Reduce interface layers from 3 to 1 (reduce the amount of BVOH used)

Filament Settings (for the PLA, not the BVOH) > Advanced > Wipe Tower Parameters

- Increase minimal purge on wipe tower from 15mm^3 to 20mm^3 (purge out more of the left over BVOH each time that the printer switches to PLA)

Note that the last thing I mentioned here, I am a bit on the fence about. Before making the first two changes I describe above, I tried a print that just purged more PLA. I had cranked it all the way up to 50mm^3 and found that the print actually did not make it further than the one before it. I have been giving each print 5 chances, meaning, I will intervene 5 times and then call it quits. For my problem, intervening means pulling the PLA out of the MMU2S after a failure and cutting it a new tip. Since I am on the fence about this particular change, but still believe that purging more when loading PLA might help, I have dialed it back to 20mm^3 which is much closer to the default 15mm^3.

RE: Frequent clogging with Verbatim BVOH

@karalt

You can also try this:

print a temperature tower, and set up the printer nozzle in the lowest temperature for your material. 

decrease the printing speed using the knob to 60% or less. 

RE: Frequent clogging with Verbatim BVOH

I've printed pretty extensively with BVOH with both PETG and PLA and not really had issues.  I've only used the verbatim bovh though.

RE: Frequent clogging with Verbatim BVOH

@mdjuan

Thanks for replying! I will try that next. Did you have a similar issue before trying that?

RE: Frequent clogging with Verbatim BVOH

@ssill2

I think part of my problem is my modifications. I am running a MK3S with MMU2S but the extruder is Bondtech and the hot end is the Mosquito.

This has made my printer infinitely more cooperative (and improved print quality) in every instance except the use of PLA with BVOH for some reason.

Prior to upgrading, I had a single successful PLA and BVOH print, but it was small and I never had success again despite making no changes to my settings. Perhaps it is the huge variations in ambient temperature where I live...

RE: Frequent clogging with Verbatim BVOH

well that makes sense.  I've got the stock extruder for the MK3S+ with the MMU2S addon.  I do have the standard upgrades to the MMU2S including:

The M10-PTFE connector pass-thru on the back
The selector that has the magnet in it

I also have have the mmu mounted horizontally as I found the ball bearing in the find would frequently think something was in the filament path when there wasn't.  Horizontally mounted the ball bearing moves up and down and thus the full weight of the bearing is in play to trigger the finda as it should be.

Other than that the most recent change, loosing the idler bolt on the extruder, seems to have done wonders.   I've not printed any soluble with it since the most recent change but I've done a 35h print with 1510 changes in it and I'm doing the same print again in different colors.

RE: Frequent clogging with Verbatim BVOH

For anyone who is interested in the outcome of what I tried, it didn't tell me much. At first, there was a spark of hope when I noticed that the print had only had two failures at the same point where the print before it had 5. However, it only made it 10 layers past the first print, failing for the 5th time on layer 76. At the end, it failed multiple times in a row despite cutting the new tips for the filament it was failing on.

Now I am trying to print with increased purge volumes on both the PLA and the BVOH. I have increased both to 150mm^3 per Joe Prints' post and if there is no (or low) sign of improvement I am going to try printing a temperature tower in each filament, setting the filaments to the lowest working temperature, and print at a low speed like Mdjuan suggested.

RE: Frequent clogging with Verbatim BVOH

I purge 200 when doing solubles.  you don't want to have soluble material end up in your model.  I also use 200 for most thing to prevent white from having other darker colors mixed in with it.  Not sure that solves your particular issue but I printed a huey that required a lot of supports and 200 definitely works.

RE: Frequent clogging with Verbatim BVOH

@ssill2

Cool! We have very similar mods to our MMU2S. I have the passthrough on the back and the selector with the magnet. I find both made a huge difference for me! 

I have not noticed the same problem with the FINDA, so I have not made the horizontal modification you described. I will keep that in mind incase I ever run into that problem.

IMO everyone with an MMU2S should have those first two mods.