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MMUv2 First impresisons and LackRack Setup
 
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MMUv2 First impresisons and LackRack Setup  

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The_Ball
 The_Ball
(@the_ball)
Active Member
MMUv2 First impresisons and LackRack Setup

I had quite a few problems with my MMUv2, however now it's printing fine.

Problems found:

  • Hobbed gear quality. This seems to be a common problem where the hobbed part diameter varies between gears causing the number of rotations needed to reach the extruder to vary between which "port" is selected.
    One of my gears would not even fit on the shaft and the teath of one gear were strangely machined. Prusa sent me three new gears which looks like they are from a newer machining process and of better quality.
    By arranging the gears by smallest diameter (hobbed part) so that the smallest diameter gear is for "extruder 1" which is used for bowden tube calibration the other possitions will go too far and grind a bit of filament when reaching the extruder.
    There is an upcomming MMU firmware which will allow calibration of each gear.

  • In the PETG extruder body the hole before the bondtech gears was too tight and sometimes the filament "plug" would get stuck here on load/unload. No problems after I expanded this hole with a 2.5mm twist drill.

  • The PTFE tube from the MMU to the extruder is too tight. When a filament plug with a stringer is formed, this stringer can fold back and cause a jam in the tube. Replaced with a 4mm/2.5mm PTFE tube.

  • The filament brake system has potential for tangling, if any filament twist is induced during printing the filament will cause loops which are crimpt tight when a load is attempted.

  • The vacuum formed filament spool holders are "crimped" and too tight where the bearings should fit. Not a big fan of these spool holders anyway so they'll end up in the thrash. Thanks for the nice bearings though.

    • LACK Rack Modification

  • "External MMU" / Longer PTFE tube / Firmware
    I wanted easy access to the MMU for maintenance and inspection, so I moved it on top of the LACK Rack. I replaced the PTFE tube with a longer 4mm/2.5mm tube and modified the firmware to reflect the new length. The calibration procedure only allows for 200 steps of length adjustment so a firmware mod is necessary.

  • Filament Damper
    I designed a filament damper to accept the slack generated by the filament unload procedure. Because of the extended bowden length the amount of slack generated is significant.

  • Smaller Spool Holders
    The five spool holders supplied will not fit with the MMU on top of the LACK rack. I've designed a smaller spoolholder with PTFE tube holder. I've also used the MMU to print labels that identify what I have loaded on each spool holder.

    • Posted : 30/09/2018 11:33 pm
    The_Ball
     The_Ball
    (@the_ball)
    Active Member
    Topic starter answered:
    Re: MMUv2 First impresisons and LackRack Setup

    Prints

    Posted : 30/09/2018 11:35 pm
    The_Ball
     The_Ball
    (@the_ball)
    Active Member
    Topic starter answered:
    Re: MMUv2 First impresisons and LackRack Setup

    Layout:

    Posted : 30/09/2018 11:53 pm
    Jorg
     Jorg
    (@jorg)
    Estimable Member
    Re: MMUv2 First impresisons and LackRack Setup

    Looks very nice!
    It is one of the first examples I see where the MMU is not on the printer. And it gives perfect access to the buttons.

    The idea of the filament damper is very nice (and it looks cool :)). How difficult is it to load filament with it?

    Posted : 01/10/2018 10:41 am
    The_Ball
     The_Ball
    (@the_ball)
    Active Member
    Topic starter answered:
    Re: MMUv2 First impresisons and LackRack Setup

    I have a little tool I help the filament through with, however I'm changing the desing (picture below) so I can pull one of the sides down like a "bridge" which will make the filament thread through without problems.

    Posted : 01/10/2018 1:07 pm
    Jorg
     Jorg
    (@jorg)
    Estimable Member
    Re: MMUv2 First impresisons and LackRack Setup

    Clever modification!
    I'm still planning on how/where to put my printer but want to be prepared if I ever decide on an MMU. This idea is a great one, and opens up more options.

    Posted : 01/10/2018 4:03 pm
    Paul Meyer
     Paul Meyer
    (@paul-meyer)
    Honorable Member
    Re: MMUv2 First impresisons and LackRack Setup

    Sweet! I've got my MMU2 on the printer, but I think I'll need to make those filament guides just because they look so gorgeous!

    Posted : 01/10/2018 4:28 pm
    stephen.c14
     stephen.c14
    (@stephen-c14)
    Active Member
    Re: MMUv2 First impresisons and LackRack Setup

    Can we expect to see these files here or on Thingiverse? Thanks for your quality efforts.

    Steve

    Posted : 02/10/2018 12:20 pm
    The_Ball
     The_Ball
    (@the_ball)
    Active Member
    Topic starter answered:
    Re: MMUv2 First impresisons and LackRack Setup

    Thanks! Yes I will be uploading the design files to Thingiverse once I clean them up a little.

    Posted : 02/10/2018 10:03 pm
    Jan
     Jan
    (@jan)
    Eminent Member
    Re: MMUv2 First impresisons and LackRack Setup


    Thanks! Yes I will be uploading the design files to Thingiverse once I clean them up a little.

    Cheers mate, would very much appreciate that!

    Posted : 03/10/2018 5:09 pm
    robert.m28
     robert.m28
    (@robert-m28)
    Eminent Member
    Re: MMUv2 First impresisons and LackRack Setup

    Nice work mate,

    That is really impressive, I like how visual it is!

    Is your Bowden to main extruder much longer like that?

    This is my take on the Lack issue, although if I had some acrylic laying around your design looks the part 😀
    https://www.thingiverse.com/thing:3128344

    Posted : 04/10/2018 11:10 pm
    AbeFM
     AbeFM
    (@abefm)
    Member
    Re: MMUv2 First impresisons and LackRack Setup

    Oh, hey! You had the same thing I pictured!

    https://shop.prusa3d.com/forum/hardware-firmware-and-software-help-f56/rapid-accelerations-causing-broken-filament--t24956.html#p110400

    I made something a lot less pretty (but works just great). Mine has a lot fewer parts, I originally wanted to all all that stuff but don't think you need it.

    A row of small bearings would work, but actually, so would a single short length of PTFE stuck though - JUST enough to get it to take a bend, and with so shallow a bend, there's no appreciable drag.

    The other side should be a triangle.

    I think this could be made quite nicely. I'd REALLY like to see a book - with each sheet folding over, so it's easier to work on. In practice, since I added slots so I can pull out tubes as I need to work on them, I have no problems.

    I'd love to join forces, if you'd like. I want to make something simple that Prusa could pick up with and use. I'd rather see all the spools hanging from a single pole than on rollers, but it's irrelevant to what we're doing.

    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 4:11 am
    joe.w6
     joe.w6
    (@joe-w6)
    Eminent Member
    Re: MMUv2 First impresisons and LackRack Setup

    Great design! Did this ever hit thingiverse? I recently got my MMU (still can't get it printing correctly, the MMU keeps failing me). However this would help me tidy up my space!

    TIA

    Posted : 15/12/2018 3:15 am
    BamBam
     BamBam
    (@bambam)
    New Member
    Re: MMUv2 First impresisons and LackRack Setup

    Is this Design somewhere on thinkiverse?

    Posted : 02/01/2019 1:35 pm
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