What fixed my blockage / jamming issues
I am writing this to let people know what fixed my issues with jamming every time I printed with the new multi material upgrade. I tried everything I could find online and talking with Prusa support. This is what fixed my issue.
First off, I think I am the reason that I had issues in the first place. I say that because when I first put the multi material upgrade together, I cut my own piece of PTFE tubing that fit between the MUX and the hot end. "But Marty, why would you do that? Didn't you get a PTFE from Prusa in the kit? Why not just use that?" I did get a PTFE tube in the kit and I did try to get it installed the way the manual said but it just didn't "seem" to go in well. There was a gap under the MUX ( I thought it should be tight ) and the one bolt that holds the MUX down didn't just slide in. I had to screw it in from the far right all the way through. The bolt would slide all the way in if I didn't put the PTFE tube in... so that made me think something was wrong.
Since the online manual didn't say anything about the PTFE tube being special, I figured I could just cut it down so that it would fit better. Well after cutting it twice, I ended up cutting too much off. So I just grabbed another piece of PTFE tube that I had laying around and cut it to be a little bigger than what the previous tube was. Now the MUX fit down better, but I still had to screw the bolt in all the way.
Starting right away, I could not print without getting jams and since this was days after cutting the tube I didn't think it was that. I figured it was just a crappy upgrade that Joe built. ( I was wrong )
After trying everything from Retraction settings, tightening and loosening the extruder bolts, swapping nozzles, swapping heat breaks, changing the temp of extrusion.... on and on. It was very frustrating, but I was starting to figure out the issue.
I read somewhere about the PTFE tube needed to be chamfered on the outside at the bottom and chamfer on the inside on both the top and the bottom. So, I started to do that. After 2 or 3 different tries of chamfering, it seemed to go a bit longer in the print before jamming. But it would still jam every timer. Then I remembered reading about someone saying that the PTFE tube for the multi material is what "forms" the filament when retracted to be small so that it can retract back up into the metal sleeves in the MUX without issue.
Well, how what I supposed to know that the PTFE tube that Prusa uses has a smaller internal diameter than a common 2.0 mm PTFE tube that you can just by online. So I found a 1.8 mm internal diameter PTFE tube online and rushed it in. https://www.filastruder.com/products/capricorn-ptfe-tubing
Once I got that in, I did the chamfers, I tested the length to get to the point that I can just slide the MUX bolt in without threading it in all the way.
Viola, it works, and works awesome.
So, just be careful if you try to make your own PTFE tube. It NEEDS to have a 1.8mm diameter and NEEDS the chamfering.
http://shop.prusa3d.com/forum/download/file.php?id=6915
Joe, I am sorry I doubted you in my own mind.
Marty
Re: What fixed my blockage / jamming issues
And the moral of this story...
All the information is here in this forum. Read the posts and you won't suffer these issues...
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: What fixed my blockage / jamming issues
Well, how what I supposed to know that the PTFE tube that Prusa uses has a smaller internal diameter than a common 2.0 mm PTFE tube that you can just by online. So I found a 1.8 mm internal diameter PTFE tube online and rushed it in. https://www.filastruder.com/products/capricorn-ptfe-tubing
I tested this tubing for them for Capricorn to use with the MM upgrade. It does work extremely well but is just a little harder to get the chamfer correct.
Re: What fixed my blockage / jamming issues
I had the issue of the wrong size PTFE with the MM upgrade and support eventually posted a procedure to shorten the tube at http://manual.prusa3d.com/Guide/How+to+trim+PTFE+tube+-+MultiMaterial/497
Re: What fixed my blockage / jamming issues
TL; DR - Changing the PTFE tube is also what resolved my endless stream of headaches (along with flashing with latest firmware) , but my story was different.
In fact, I *had* already changed the PTFE tube with the one provided in the kit when I originally did the upgrade to MMU, but I never managed to get a successful print, despite trying all the approaches described by the original poster, and I was constantly having to resolve unsuccessful loading/unloading issues, jamming, etc.. It was a nightmare.
Then I ran into a jam that couldn't be resolved by any amount of heating, prodding with filament or needles, etc.. I removed the hot end altogether and discovered a small piece of filament jamming the PTFE. So I replaced the PTFE tube again with one that I had previous ordered from Prusa along with some other supplies. The only other change I did was to flash with the latest firmware (which I had been keeping up to date with along the way), but suddenly it was working, and I mean full-on working, with whole 5 colour prints with zero interventions. HALLELUJAH!
So the nightmare I went through was real and truly tested my grit. I came close to giving up on the MMU many times over, and barely believed in the dream anymore, convinced that at best I might be able to reduce the frequency of problems, but not overcome them altogether. But I can now attest to the fact that the MMU can actually work as advertised and I'm 10 successful prints in now.
The bottom line is that I don't really know what was wrong with my initial MMU installation/tube, but *somehow* changing the tube the second time is what made it go from "nightmare" to "as advertised"
I'm just hoping I didn't jinx myself be writing this 😉