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  1. #21
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    IMG_20200902_232810.jpgIMG_20200902_232758.jpgIMG_20200902_232901.jpgIMG_20200902_232930.jpg

    Got it installed, took some 4+ hours of hw assembly and couple hours or so final calibration. Printed example gcode that ships with the driver package, worked fine after some initial issues. Haven't sliced anything yet, probably tomorrow.
    Haven't built the filament buffer yet, have to find a proper spot for the printer now that it and all the filament takes more room.

    AutoWiz, had similar issue I recall you had when feeding the filament to the extruder, it just kept feeding and created a blob. That was due to the extruder filament sensor not detecting the filament, had to adjust it properly. At least with Prusa printer the extruder filament sensor is required, don't know if that's how it works in the mainline Marlin.

  2. #22
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    Nice work, man. I am impressed with how fast you got that up and running. Can't wait to see some 5 color prints from that MMU2S.
    Last edited by AutoWiz; 09-02-2020 at 09:00 PM.

  3. #23
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    Alright buddy it has been a while, how fast can you reliably print with the MMU2S? In the beginning I thought we would have higher feedrates because of a literal dual drive from the MMU and the extruder but that is just not how it works. After the filament gets fed to the extruder the MMU goes to neutral and it is just and only the extruder motor pulling the filament through all the ptfe tubing and the mmu. I am on the fence between going with a volcano equivalent hotend and a 0.6mm nozzle because i have a large format printer connected to mine but IDK how fast I will be able to draw filament into the extruder. So what do you think from playing with yours? Do you feel like it could feed fast enough to warrant the extra melt zone for larger nozzles and layer heights or do you get the vibe that it will always be a slow printing thing??

  4. #24
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    Quote Originally Posted by AutoWiz View Post
    Alright buddy it has been a while, how fast can you reliably print with the MMU2S? In the beginning I thought we would have higher feedrates because of a literal dual drive from the MMU and the extruder but that is just not how it works. After the filament gets fed to the extruder the MMU goes to neutral and it is just and only the extruder motor pulling the filament through all the ptfe tubing and the mmu. I am on the fence between going with a volcano equivalent hotend and a 0.6mm nozzle because i have a large format printer connected to mine but IDK how fast I will be able to draw filament into the extruder. So what do you think from playing with yours? Do you feel like it could feed fast enough to warrant the extra melt zone for larger nozzles and layer heights or do you get the vibe that it will always be a slow printing thing??
    I haven't tried anything beyond normal print speeds. Actually haven't printed anything on the MMU setup since the first print, been busy with other stuff. Ordered some filament so once that arrives I'll be doing more testing.

    I've had 0.6 mm nozzle on the MK2.5S before MMU-setup and with normal print speeds PETG printed fine. Also 0.8 mm for some larger CF prints, worked without issues. But with MMU, not sure how much extra drag it would cause. I don't think it's noticeable unless going for speeds that are already straining the limits of the extruder setup. If you have a extruder with some gearing ratio, like Titan or BMG, I think the Bondtech gears and the extruder are capable of quite fast speeds as long as the heater block is beefy enough. The default MK2.5S doesn't have any gearing so the torque will limit the speeds. Personally I don't print fast, the regular speeds are fine for me. For larger prints I usually just use larger nozzle and layers, 0.6 mm nozzle and 0.25-0.4mm layers is a good compromise between speed and detail.

  5. #25
    Super Moderator curious aardvark's Avatar
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    what do you consider to be 'regular' speeds ?

    Mine are 75mm/s for fine prin5ting, 100mm's standard prints and 150mm/s for rough but structural.

    Only if I'm using flexible filaments do i drop down to 20-30mm/s.
    That said I haven't done much with pet-g yet.

    I think for something like a mumu I'd probably accept 50mm/s - anything much lower than that and even small multi material prints are going to take an enormously long time.

  6. #26
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    Quote Originally Posted by curious aardvark View Post
    what do you consider to be 'regular' speeds ?

    Mine are 75mm/s for fine prin5ting, 100mm's standard prints and 150mm/s for rough but structural.

    Only if I'm using flexible filaments do i drop down to 20-30mm/s.
    That said I haven't done much with pet-g yet.

    I think for something like a mumu I'd probably accept 50mm/s - anything much lower than that and even small multi material prints are going to take an enormously long time.
    50mm/s is what I use mostly. Default Prusa profiles use 60mm/s for inner perimeters, 15mm/s for outer. I haven't really felt the need to bump up the speeds, although I think there's some room for every machine I have. PrusaSlicer has some 100mm/s profiles, might try them some time to see if the speedup is worth it.

    PETG might have some limitations about speed, if I recall correctly I read somewhere that it might even fail to print properly after certain speed. I have printed some at 60mm/s as PrusaSlicer slices it and it turned out fine.

  7. #27
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    Hey Spegelius, Chris Riley just released another video for the MMU2S. Unfortunately it is with a Prusa machine so it is little help to me BUT, he shows a redesigned part for the MMU2S from Prusa and filament cut feature that we can enable. Take a look: https://www.youtube.com/watch?v=LpoCYmSb7wo&t=

  8. #28
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    Quote Originally Posted by AutoWiz View Post
    Hey Spegelius, Chris Riley just released another video for the MMU2S. Unfortunately it is with a Prusa machine so it is little help to me BUT, he shows a redesigned part for the MMU2S from Prusa and filament cut feature that we can enable. Take a look: https://www.youtube.com/watch?v=LpoCYmSb7wo&t=
    Quote Originally Posted by AutoWiz View Post
    Hey Spegelius, Chris Riley just released another video for the MMU2S. Unfortunately it is with a Prusa machine so it is little help to me BUT, he shows a redesigned part for the MMU2S from Prusa and filament cut feature that we can enable. Take a look: https://www.youtube.com/watch?v=LpoCYmSb7wo&t=
    Great, I?l have a look. Yeah the cutter is apparently a new thing, had a small issue while assembling it got it sorted (the blade wasn't in correct position). Haven't tried it yet, though.

    So I tried PrusaSlicer and sliced a custom keychain part I designed a while ago. For materials 2xPLA (white and light blue) + BVOH for soluble support interface. The slicing process was quite straightforward, there's a profile just for this kind of setup. So filaments 1 and 2 were PLA, 5 is dedicated for the soluble material in the profile, can be changed of course, but works for me.

    Loaded the filaments and started the print. For the first hour, everything went fine and the print looked good. But then the white PLA didn't feed properly and the extruder started skipping just when the filament was almost at the nozzle and that's a failure right there because the printer doesn't recognize this. MK3S might, as it has Trinamic drivers and should be able to detect missed steps.
    So for that one mishap I paused the print, did manual unload and load and resumed the print. It continued ok for a while until another jam and I wasn't babysitting the printer so fail it is.
    I kinda guessed that the MMU2S isn't that different from other solutions when it comes to loading performance with different filaments, there's just so much variance between different brands and even colors so it's just a matter of time consuming tuning each filament.
    In this case part of the problem is the extruder itself: it's a direct drive with the motor directly driving the Bondtech gear, so no reduction gearing so the torque is not very good. So either bump up the extruder amps or get a geared motor. Maybe something like this: https://www.thingiverse.com/thing:3626993 although I'm not too keen on replacing the stock extruder as it just so much extra work with firmware mods etc.


    IMG_20200917_184153.jpgIMG_20200918_085358.jpgIMG_20200918_085415.jpg

    Here's a video of the start of the print with the filament priming:
    https://drive.google.com/file/d/1MOX...ew?usp=sharing

  9. #29
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    Ok after some time brooding about the failures (and interlude with kitchen renovation), two things for fixing the failed feeds:
    - Prusaslicer has and option to raise extruder motor current during the filament change. I tried this and no more skipping. However, now the print failed because the extruder gear had grinded through the filament and I had to do a manual intervention, which kinda fixed the print but after that there were missed layers. So more extruder power is not the complete solution, but does help in some cases
    - apparently the PTFE tube inside the extruder should be less than 2.0mm. Saw a post about this in Prusa FB group. While setting up the MMU2S, I didn't change the original PTFE tube thinking that the provided parts are the same as the one I already have. Maybe changing the tube would fix the feeding. The idea with the smaller ID is that it forms the tip bit smaller. I'll check the new PTFE tube if they really are smaller than 2mm

  10. #30
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    The new PTFE tube that came with the MMU2S kit indeed has bit smaller ID so I swapped it in the extruder. Luckily the current Prusa extruder is actually quite easy to dismantle enought to get to the hotend.
    After swapping the tube the print finally finished without jams, although the MMU2S unit needed some attention couple of times; seems that FINDA didn't trigger when pulling filament out or something. Probably need to adjust it slightly.
    Dissolved the BVOH overnight, most of it was gone by then. However, some bits were left that didn't dissolve and had to be removed manually. Probably had some PLA in them because I didn't have enough purge for materials to be fully purged and there's some mixing happening. In previous tests, BVOH needs to be purged at least 80mm, otherwise it starts to affect PLA and especially PETG strength.

    IMG_20200929_143928.jpgIMG_20200925_185127.jpgIMG_20200929_143912.jpg

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