peter.l22
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Is the MMU2 finally starting to come together?

Dec 01, 2018 4:45 pm

I had one of the first MMU2 kits shipped, and while it was OK, there were frequent print defects. I posted a list of failure modes at the time.

With the latest firmware updates it's starting to feel like the MMU2 is really coming together. Thin prints--ones with a few dozen filament changes--almost never fail for me anymore. Larger prints with hundreds of changes are also working most of the time for me.

What's everyone else been experiencing? I'm using mostly stock settings, firmware, and profiles. The only changes from stock I'm using are:
  1. Set the "Loading speed at the start" to 19 mm/s to better sync the bondtech gears with the MMU on filament load. This still needs to be tweaked a bit, but it's a lot better than the default setting of 3.
  2. Set the bowden lengths to be about 1cm long to reduce failures when the MMU2 loads just short of the bondtech.
  3. Adjust some of the default print temperatures a bit for some of my filaments

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PJR
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Re: Is the MMU2 finally starting to come together?

Dec 01, 2018 7:10 pm

Since I made changes to the extruder body and started using larger ID PTFE tubes, the only fails I have had have been the unusual ones (filament break in Bowden and top Festo undoing itself).

Other than that printing without problem or intervention.

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 or loss.

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daniel.a6
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Re: Is the MMU2 finally starting to come together?

Dec 01, 2018 7:59 pm

i had problems on the first day which was just setting the machine up and working out the kinks. i fixed some mechanical defects in the prusa parts. then after 1 hour of fighting with things i started to replace all the spool holders with pmeyers redesign on thingiverse.
on the second day i had 2 layer skips that was my fault because i didn't prep a new spool and just started printing. there was additional fine tuning of slicer settings.

since then i've had 100s of hours of prints that were successful in having no skips or jams.

there is a lot to be taken from that as i have a large table setup and i'm not attempting to cram into a IKEA table with PTFE routing, and i'm using a standardized PLA brand, hatchbox pla for everything and do not plan to really mix PLA from different companies.

i have not run PETG or BOVH yet.

in this time i have also made modifications to my MK3 MMU2 machine to try and address issues with my MK3 machine and in the process i broke a few parts that i needed to reprint on another 3d printer (MK2S) in PETG.
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kenny.b2
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Re: Is the MMU2 finally starting to come together?

Dec 02, 2018 4:38 am

PJR wrote:
Dec 01, 2018 7:10 pm
Since I made changes to the extruder body and started using larger ID PTFE tubes, the only fails I have had have been the unusual ones (filament break in Bowden and top Festo undoing itself).

Other than that printing without problem or intervention.

Peter
What size ID PTFE tubes did you switch to? I assume you replaced the tube between the extuder and the MMU2, the little ones between the selector and the bontechs and maybe also the ones running to the filament trays?

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PJR
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Re: Is the MMU2 finally starting to come together?

Dec 02, 2018 9:57 am

kenny.b2 wrote:
Dec 02, 2018 4:38 am
What size ID PTFE tubes did you switch to? I assume you replaced the tube between the extuder and the MMU2, the little ones between the selector and the bontechs and maybe also the ones running to the filament trays?
I replaced the filament feed and Bowden with 2.5mm ID PTFE. I also removed the lower Festo and gripped the Bowden with an amended extruder body, so the Bowden is a little longer and is a tight push fit into the extruder body, but the filament path has no ledges to cause problems. I made both changes at the same time.

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 or loss.

Mirar
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Re: Is the MMU2 finally starting to come together?

Dec 02, 2018 11:14 am

PJR wrote:
Dec 02, 2018 9:57 am

I replaced the filament feed and Bowden with 2.5mm ID PTFE. I also removed the lower Festo and gripped the Bowden with an amended extruder body, so the Bowden is a little longer and is a tight push fit into the extruder body, but the filament path has no ledges to cause problems. I made both changes at the same time.

Peter
This sounds like it could solve 99.8% of my problems. Where do you get 2.5mm PFTE?

The thing that saddens me most about the MMU is that it's not integrated with the MK3. It can't use the display or menu, it's doing silly LED blinking. The MK3 doesn't even know it's there if it had a boot failure mode. Also that the MMU reboots when Octoprint connects...

And things like temperature changes doesn't seem to be properly supported. (That's a slic3r PE problem though.)
Last edited by Mirar on Dec 02, 2018 11:31 am, edited 1 time in total.

flaviu.i
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Re: Is the MMU2 finally starting to come together?

Dec 02, 2018 11:14 am

I'm printing prusament blue and silver with bvoh at the moment. Blue works fine, with silver I get a lot of stringing (sometimes not from the beginning but after several hours of printing it starts stringing midprint), bvoh works 75% of the time.

Sometimes when I start the print the printer does "weird" things at the start and triggers crash detection. After restarting the print or the printer it usually works.

You can see that a lot of people doing “updates” to the system. There is even a custom firmware out which a lot of people are using.

Slic3ers pruge into infill is nice. But I need to set ramming temperature to get rid of stringing.

My MK3 printed without the MMU2 flawlessly for about a year.

But for 300€ you can have a lot of fun tinkering with the MMU2 unit so I think it is worth the money. But it is still a looooooong way to go until it reaches MK3 reliability (if it will ever).

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PJR
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Re: Is the MMU2 finally starting to come together?

Dec 02, 2018 1:26 pm

Mirar wrote:
Dec 02, 2018 11:14 am
This sounds like it could solve 99.8% of my problems. Where do you get 2.5mm PFTE?
eBay. Sorry, can't be more specific as I don't know your location.

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 or loss.

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TheSquall
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Re: Is the MMU2 finally starting to come together?

Dec 02, 2018 6:06 pm

PJR wrote:
Dec 02, 2018 1:26 pm
Mirar wrote:
Dec 02, 2018 11:14 am
This sounds like it could solve 99.8% of my problems. Where do you get 2.5mm PFTE?
eBay. Sorry, can't be more specific as I don't know your location.

Peter
Just to confirm, 4mm OD 2.5mm ID? This seems like it'll solve a lot of issues, so I'd like to look into this.

Did you chamfer the inside to 4mm, or just leave it as 2.5mm throughout?

Mirar
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Re: Is the MMU2 finally starting to come together?

Dec 02, 2018 6:55 pm

PJR wrote:
Dec 02, 2018 1:26 pm
Mirar wrote:
Dec 02, 2018 11:14 am
This sounds like it could solve 99.8% of my problems. Where do you get 2.5mm PFTE?
eBay. Sorry, can't be more specific as I don't know your location.

Peter
Stockholm. Basically this stuff then? https://www.ebay.de/itm/Ptfe-Teflon-Roh ... :rk:4:pf:0 (I am not affiliated)
https://www.aliexpress.com/item/2-5x4mm ... 43565.html

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