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Rapid Accelerations Causing Broken Filament?  

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AbeFM
(@abefm)
Member
Rapid Accelerations Causing Broken Filament?

Since the MMU relies on coiling ejected filament, the material goes through many more bend/unbend cycles than it ordinarily would. For brittle filament, this means you're going to get breaks.

I'm getting a few filament breaks a day, across different physical channels and with differing filament brands/types.

I wonder if the moves of the MMU when feeding/retracting filament could be more gentle - and if it would help.

Is there a way to set low accelerations?

I maintain an informal list of San Diego, CA 3D printing enthusiasts. PM me for details. If you include a contact email and I can add you to the informal mailing list.

Posted : 04/10/2018 7:26 pm
PJR
 PJR
(@pjr)
Antient Member Moderator
Re: Rapid Accelerations Causing Broken Filament?


Is there a way to set low accelerations?

Not really. The lowest I can get away with is E4000 with interpolation off and 1/1 stepping.

Having said that, I have only have filament break once and that was with Galaxy Prusament neat to the end of a spool.

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…

Posted : 04/10/2018 8:25 pm
AbeFM
(@abefm)
Member
Topic starter answered:
Re: Rapid Accelerations Causing Broken Filament?

It is more common at the end of the spools. I think this is because the just-sitting-there style spool holders sometimes get pretty actiony - rocking around, tipping over, etc.

I'm using a non-traditional dead zone, but I've seen the breaks in the orange tube (~4), in the MMU (~3? hard to narrow down since stuff moves!), in my dead volume (2), and between the spool and the bowden tube inlet from the spool holder (~4).

I don't want to change the speed, just the jerk/accel

I maintain an informal list of San Diego, CA 3D printing enthusiasts. PM me for details. If you include a contact email and I can add you to the informal mailing list.

Posted : 04/10/2018 10:31 pm
Peter L
(@peter-l)
Honorable Member
Re: Rapid Accelerations Causing Broken Filament?


Since the MMU relies on coiling ejected filament, the material goes through many more bend/unbend cycles than it ordinarily would. For brittle filament, this means you're going to get breaks.

I'm getting a few filament breaks a day, across different physical channels and with differing filament brands/types.

I wonder if the moves of the MMU when feeding/retracting filament could be more gentle - and if it would help.

Is there a way to set low accelerations?

I'm able to get moderate success with some terribly brittle filament by hanging the spools above and a little behind the printer and getting rid of the brake mechansim completely. When the filament unloads, it just relaxes the long PTFE tube and doesn't coil the filament at all. This gives a lot less flexing on each cycle.

Posted : 05/10/2018 3:42 am
AbeFM
(@abefm)
Member
Topic starter answered:
Re: Rapid Accelerations Causing Broken Filament?

My first attempts at that worked until things got tangled. About the 5th time I tried adding divides. It works REALLY well, but the build is embarrassingly under developed and I want to make something more fancy with hinges and such before sharing it.. On the other hand I'd like others to benefit ASAP.

I do think with a cutter of some sort these could be made cheaply and included with the kit. They give you a great visual into what's going on. Perhaps I'll write it up more over the weekend. In the meantime I want to flash the MMU and Printer firmware to most recent betas.

The coils are effectively in free space, but they don't overlap or drag on anything. They become very insensitive to the spool mounting and position, and similarly I can move printing around while it's running without any issues.

Thee's a LOT of improvement to be made on aesthetics and packaging, but even as is it's reasonably easy to service (ask the guy who's had a few hundred jams) and eliminated a number of issues.

https://www.thingiverse.com/thing:3138950

I maintain an informal list of San Diego, CA 3D printing enthusiasts. PM me for details. If you include a contact email and I can add you to the informal mailing list.

Posted : 05/10/2018 9:15 pm
Paul Meyer
(@paul-meyer)
Honorable Member
Re: Rapid Accelerations Causing Broken Filament?

Very cool. Similar to this approach (which I'm taking inspiration from).

https://shop.prusa3d.com/forum/user-mods-octoprint-enclosures-nozzles--f57/mmuv2-first-impresisons-and-lackrack-setup-t24877.html#p109728

I just hit Home Depot to get some cheap acrylic to design my own. I'll probably design/build something like these while I'm at it: Cool Spool Holders.

Those two integrated (maybe wall mounted vertically above the printer?) will make for an effective and very cool looking approach. Still contemplating.

Posted : 05/10/2018 10:43 pm
AbeFM
(@abefm)
Member
Topic starter answered:
Re: Rapid Accelerations Causing Broken Filament?

I originally pictured this as a drum you would mount under the shelf the filament is on.

Right now I picture it as a 2" thick shelf the printer sits on.

It doesn't seem to be orientation dependent, it just comes down to how easy you want to be able to see/work on it.

I maintain an informal list of San Diego, CA 3D printing enthusiasts. PM me for details. If you include a contact email and I can add you to the informal mailing list.

Posted : 07/10/2018 4:19 am
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