Straight through heat break?
Just before I got the shipping notice for my MMU I ran into consistent clogs that appeared to be caused by the stepped heat break not liking all the retractions it was doing. I was going to upgrade my extruder housing and replace the heat break to a straight model, but the MMU came and I just couldn't let a box of parts sit unassembled...
As mentioned in other posts, the MMU is not going well for me and the latest issue is that after doing a bunch of filament changes with minimal printing (e.g. lots of retractions) it has now clogged up my hot end exactly as I was seeing before (though with filament that I did not previously have issues with).
I know the step in the heat break is there to help the MMU, but I'm wondering if it will run with a straight heat break. Part of this question is that I don't understand what benefit the step is supposed to have with the MMU. Has anyone switched to a straight heat break? Does it work? Better? Worse?
RE: Straight through heat break?
Gnat - my guess is it will run just fine; at least as well as it does with the stepped version. If you have any doubt, try the "other" heat break that has a step. With MicroSwiss's version the step is in the hot zone, rather in the transition zone. So retractions are a lot less likely to pull melt up the heat break - expand, cool, and jam.
RE: Straight through heat break?
I didn't realize that there was another stepped version available. I already have a replacement straight version from e3d on hand since I was going to install it expecting the MMU to still be another month or more out.
RE: Straight through heat break?
My understanding was the step was meant to help keep strings or slightly oversize ends from jamming on reload if your tips are not perfect.
Don't have an MMU (yet) so I can't speak to the actual impact, but in theory it would get worse with a straight through... or you might encounter other loading problems. But I could be completely wrong; couldn't hurt to try...
RE: Straight through heat break?
Heat break from MicroSwiss looks like this: the 2.2 mm step extends from the nozzle. Not exactly like the Prusa version which is 2.2 from the feed end. It may not perform the same function - but I have to ask why the extra machining step - why not drill the entire heat break to 2.2 mm.
RE: Straight through heat break?
Well I may be unfairly blaming the heat break. I ran the temp up to 280 to pull the nozzle and a big blob (roughly BB sized) fell out (before removing the nozzle). Even after removing the nozzle, however, the path is still blocked up. So I'm going to have to disassemble the extruder to see what is going on.
Really considering finding someone to print https://www.thingiverse.com/thing:3223513 for me and reverting back to the MK3 firmware (with this jam it kept happily thinking it was printing even though the filament wasn't moving the old sensor was smart enough to catch the jams for me).
RE: Straight through heat break?
I'm still sitting on the fence with my MK3S upgrade - it's in a box behind my printer. But my filament sensor is OFF, because of all the problems the sensor code has with corrupting the interrupt stack (at least when I looked at the code I saw what appeared to be obvious problems with how they handled the interrupt bits). Hey - here's an interrupt, what should I do first? Well, clear ALL the interrupt bits, of course - not just the one you are servicing. Anyhows ... I have some black PET somewhere. Live in the northwest, but first class goes anywhere. Let me know if you decide to make go that route. PM is working now ...
RE: Straight through heat break?
Well I may be unfairly blaming the heat break. I ran the temp up to 280 to pull the nozzle and a big blob (roughly BB sized) fell out (before removing the nozzle). Even after removing the nozzle, however, the path is still blocked up. So I'm going to have to disassemble the extruder to see what is going on.
Really considering finding someone to print https://www.thingiverse.com/thing:3223513 for me and reverting back to the MK3 firmware (with this jam it kept happily thinking it was printing even though the filament wasn't moving the old sensor was smart enough to catch the jams for me).
@gnat
Go with this one, it fixes the filament path alignment and makes for much smoother inserts/cold pulls:
https://www.myminifactory.com/object/3d-print-86329
RE: Straight through heat break?
@tim-m30 thanks for the offer, but if all else fails my local library will do it for me.
@vintagepc yeah that's the other upgrade I was gonna do, just couldn't remember the name when I made my post.
RE: Straight through heat break?
Ugh I am really unthrilled now that I've had to take the E axis apart...
So this is what I found. Turned out to be two separate pieces that were jammed in there. One (the small one) was wedged into the top of the PTFE tube completely flush. The longer one was jammed in the heat break. Neither came out nicely at all.
More irritating/disturbing/disgusting is that I found this:
The right is my old E axis with between 2000 and 2500 hours of PLA and 20 hours of PETG printing. The left is the new 3S E axis with a whopping 20 hours of PLA and 20 hours of PETG. I had seen a thread about this deformation shortly after the 3S upgrade started shipping, but at least when I stopped following it it seemed limited to lots of high heat hours.
I think that seals the deal for replacing the E axis...
RE: Straight through heat break?
Heat break from MicroSwiss looks like this: the 2.2 mm step extends from the nozzle. Not exactly like the Prusa version which is 2.2 from the feed end. It may not perform the same function - but I have to ask why the extra machining step - why not drill the entire heat break to 2.2 mm.
What I've found on my limited testing of the MMU2S, is that it seems that the glossy filaments are getting jammed in the bowden tube due to bulging/stringing when the filament gets extracted. Seems like if I stick with Prusament which seems to have a matte finish, I get flawless uninterrupted tool changes. And I have replaced the tubing with capricorn and put a c clip on the ptfe release ring on the heat sink.
I was talking to microswiss about their heatbreak with regards to the MK3S and how the protopasta HTPLA prints better than the Prusa stepped heatbreak.....which also comes on the MK3S with NO mmu. And this made me wonder if the MMU2S heatbreak would be stepped the opposite direction from the Prusa, would it tend to pull the bulge down to size on extraction.
Has anyone tried this micro swiss heat break on the MMU2S?
RE: Straight through heat break?
The region inside the heat break where the steps reside are in the cold zone: no plastic deformation should be expected. In the Prusa step case, the step is known to causes jams: it is that cold. I'd expect the MS to do the opposite: if the filament somehow expands in the larger diameter bore, you are not going to get the filament to unload in a friendly way: instead you'll have to push the thick spot out through the melt zone.
MicroSwiss:
RE: Straight through heat break?
The region inside the heat break where the steps reside are in the cold zone: no plastic deformation should be expected. In the Prusa step case, the step is known to causes jams: it is that cold. I'd expect the MS to do the opposite: if the filament somehow expands in the larger diameter bore, you are not going to get the filament to unload in a friendly way: instead you'll have to push the thick spot out through the melt zone.
MicroSwiss:
Yeah...I was at the ERRF show discussing this with MS and proto pasta and prusa. Micrswiss admit to have NOT tested it with the MMU. I have already ordered a couple of these heat breaks since I have an MK3S and also an MK3S/MMU2S. I kept going back and forth between booths discussing this LOL but my thinking was that if the filament was still hot in the hot zon, the bulge "might" get squeezed down by the narrow bore.
I'm really hesitant to tear either of these machines down since they are not necessarily broke. I do know my MMU2 is limited to prusament and I'm being told (at least) that the metal infused protopasta won't work in my MK3S unless I replace the heatbreak with, at minimum, a straight through E3D. Would like to hear from someone who has tried this.