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Prusa Mk3 Front Z-axis frame brace/stiffener/reinforcement with M8 threaded rods
 
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Prusa Mk3 Front Z-axis frame brace/stiffener/reinforcement with M8 threaded rods  

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DockGuy
 DockGuy
(@dockguy)
Member
Prusa Mk3 Front Z-axis frame brace/stiffener/reinforcement with M8 threaded rods

Solid feet and a paving stone helped reduce noise/vibration on my Mk3 improving both print quality and print speed capability. But there is still vibration at the top of the main frame. My Mk2s printers have triangulated Z-braces based around M8 rods which helped reduce vibration:
https://www.thingiverse.com/thing:1656945

My plan is to replicate this stiffening scheme for the Mk3. My recipe for each side of the printer, but primarily the control-board side which flexes more than the PSU side is below.

Prusa Mk3 Z-axis frame brace/stiffener/reinforcement BOM (per side):

  • top bracket from Mk2 Z-brace: https://www.thingiverse.com/thing:1656945 (zSolid_top_right.stl or zSolid_top_left.stl)

  • ~105mm length of 3030 extrusion or printed equivalent https://www.thingiverse.com/thing:2838381

  • 3030 brace https://www.thingiverse.com/thing:2322856 (combo of corner brace and flat brace for sheer/tension/compression strength across multiple axes and planes) OR

  • 3030 simple right-angle brace or printed equivalent: https://www.thingiverse.com/thing:2503636 AND

  • 3030 simple metal flat plate brace or printed equivalent


  • 2 drop-in M5/M6 T-nuts or printed equivalent: https://www.thingiverse.com/thing:2762571 (drop-in to eliminate the need to disassemble Mk3 printer)

  • 4 slide-in M5/M6 T-nuts or printed equivalent: https://www.thingiverse.com/thing:2621682 (slide-in for added durability compared to drop-in for added 3030 extrusion)

  • 6 M5/M6 8mm screws

  • ~450mm M8 threaded rod

  • 4 M8 washers

  • 4 M8 nuts

  • 2 M3 25mm screws

  • 2 M3 lock nuts

  • 2 M3 washers

  • housing to adapt threaded rod to 3030 extrusion at 60° angle with bracing on two sides of extrusion todo: complete design of this part!

    • Benefits of this approach:

  • Proven method to stiffen frame on Mk2 - ought to translate well to the Mk3

  • Uses off-the-shelf parts

  • Does not require disassembly of printer except for the brackets holding the top of the Z smooth rods

  • Keeps printer easily portable I.e. not fastened down to table

  • 100% reversible

    • Drawbacks of this approach:

  • impacts ability to use storage bins hanging off front 3030 extrusions

  • impacts accessibility of print bed

  • many parts in BOM

  • increases footprint of printer which may impact enclosure fitment

    • Related projects:

  • https://www.thingiverse.com/thing:1656945

  • https://www.thingiverse.com/thing:2874500

  • https://www.thingiverse.com/thing:2970524

  • https://www.thingiverse.com/thing:2984143

    • Posted : 16/12/2018 8:54 pm
    DockGuy
     DockGuy
    (@dockguy)
    Member
    Topic starter answered:
    Re: Prusa Mk3 Front Z-axis fraame brace/stiffener/reinforement with M8 threaded rods proposal

    Mockup in CAD

    Posted : 17/12/2018 1:38 am
    Martin_au
     Martin_au
    (@martin_au)
    Reputable Member
    Re: Prusa Mk3 Front Z-axis frame brace/stiffener/reinforcement with M8 threaded rods

    I'd be interested in having reverse Z-braces, behind the Z-axis tower.

    Posted : 18/12/2018 2:47 pm
    DockGuy
     DockGuy
    (@dockguy)
    Member
    Topic starter answered:
    Re: Prusa Mk3 Front Z-axis frame brace/stiffener/reinforcement with M8 threaded rods

    I'd be interested in having reverse Z-braces, behind the Z-axis tower.

    I looked at this, but in my estimation it would increase the footprint of the printer even more than front braces since the angle of the main rod would have to open up about 75-100mm beyond the rear of the printer to ensure proper clearances. This would involve an extra 3030 extrusion joint increasing part count and make enclosure fitment even more problematic.

    Still, I prefer all bracing to be on the rear for aesthetics and easier accessibility of the print bed, so I may design for that too.

    Posted : 20/12/2018 6:14 pm
    DockGuy
     DockGuy
    (@dockguy)
    Member
    Topic starter answered:
    Re: Prusa Mk3 Front Z-axis frame brace/stiffener/reinforcement with M8 threaded rods

    See jitx's Z-brace with fewer parts and a more elegant design here:

    https://www.thingiverse.com/thing:3321711

    Posted : 30/01/2019 4:25 am
    DockGuy
     DockGuy
    (@dockguy)
    Member
    Topic starter answered:
    Re: Prusa Mk3 Front Z-axis frame brace/stiffener/reinforcement with M8 threaded rods

    I abandoned the aforementioned approach and instead am using a modified einsy box with built-in stiffener and printed T-nuts. The left side of the chassis is just as stiff as the right-side now. Perfect. Have no idea if it improved print quality, but should help the chassis stay aligned during maintenance at least. I see no need to add rods to triangulate/truss the top gantry any more.

    Re-use all your einsy box components and just print this:
    https://www.thingiverse.com/thing:3476970

    Or re-print all einsy components to have the hinge on the other side:
    https://www.thingiverse.com/thing:3424832

    Posted : 06/04/2019 9:58 pm
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