High-Temp Magnetic Buildplate

Discussion in 'Tool heads & ToolChanger' started by Joe Pomo, Dec 14, 2020.

  1. Joe Pomo

    Joe Pomo Well-Known Member

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    Update: The bed + magnets are still working fine after a couple of months. I like the textured PEI. Some prints just pop off after cooling. Also, mandala roseworks has a magnet bed option for the TC:

    https://www.mandalaroseworks.com/shop/mrw-products/magbed-for-e3d-toolchanger

    I'm not sure if this sits on top of the existing heated bed, or if you're supposed to supply your own silicone heater. Either way, it looks really nice.

    Original Post:

    We modified the Tool-changer's HT bed to use a spring-steel sheet.

    Comparison Image.jpg

    Parts:
    - 45 Samarium Cobalt Magnets (Magnet Dimensions: 1/2" x 1/16")
    https://www.magnet4sale.com/smco-magnets-dia-1-2x1-16-samarium-cobalt-magnets-608-f-temperature/

    - Textured PEI sheet from Th3d Studio
    https://www.th3dstudio.com/product/ezflex2-flex-plate-smooth-or-textured-pei-coating/

    - Loctite SI 506 Red RTV Silicone Adhesive
    https://www.henkel-adhesives.com/us/en/product/flexible-sealants/loctite_si_596.html

    Cost Breakdown (w/o shipping):

    45 SmCo magnets: $32

    Th3D Studio PEI sheet: $25

    Loctite Silicone RTV: N/A

    Machining Time: N/A

    ----------------------------

    Procedure:

    We had our machine shop mill a grid of 45 circular pockets into the plate (dim: 13.2mm diameter, 2mm depth). I wanted to use an ASMBL spindle-tool to make the grid, but I wasn't feeling feisty enough at the time!

    Then we cleaned and filled the pockets with a small dab of silicone adhesive (approx the size and shape of a half-used pencil eraser). Then we added the magnets and pushed each into a pocket until it was below the lip. We let the plate cure for ~48 hours. I used an Xacto knife to clean off the excess silicone after curing.

    ----------------------------

    Performance:

    It holds the sheet well. Probably a print collision could make it slide a bit. We also put our Prusa's sheet on and had better pulling force. The prusa sheet is a little thicker than the Th3D plate.

    I compared the bed heightmaps before and after installing the magnets and they are comparable, so any new 'thermal expansion' deformation due to the pockets was not an issue in this case.

    I heated it to 120C and the pull-force didn't seem to change.

    ----------------------------

    Longevity:

    We used a similar embedded-magnet buildplate design on an Intamsys HT printer. That buildplate has around 100 printing hours at temps at 160C and the magnets are still in place with no perceivable change in the pull force.

    ----------------------------

    Notes:

    We chose samarium cobalt (SmCo) magnets because of their high-temperature rating (>300C). They're around twice the cost of similar neodymium magnets but only ~half the pull force. You can also find HT-grade neodymium magnets but the SmCo's size fit the bill for thermal performance.

    We happened to have the high-temp RTV silicone already, but other versions are readily available in small tubes at hardware stores or on amazon. SDS says wear gloves and don't get it in your eye.

    Th3d studio had some 255mm x 300mm textured sheets on sale. They are one-sided, so you can add an adhesive-backed smooth PEI sheet to the other side if you want. I used our local makerspace's sheetmetal shear to trim the sheet to the correct dimensions for the E3D heated bed.

    In the future, I want to add some pins or M3 set screws to the back of the heated bed for more repeatable placement like the heated bed found on Prusa printers.
     
    #1 Joe Pomo, Dec 14, 2020
    Last edited: Feb 15, 2021
    garethky, HamJ, tg73 and 2 others like this.
  2. Paul Arden

    Paul Arden Well-Known Member

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    Amazing work. I really wish E3D has this as a standard option for the HT beds.
     
    tg73 likes this.
  3. John Meacham

    John Meacham Well-Known Member

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    Oh wow. I absolutely loath the clips used to attach the glass bed (I hear the ping ping ping of them popping off one by one from the other room and just know my print is ruined) so got a PEI spring steel bed that uses the adhesive magnetic sheet and really enjoy it. But i know it is limiting my max temp. I would probably be willing to buy a bed modded like this.
     
    Olle Wreede likes this.
  4. Peely

    Peely Member

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    I've been uing Ziflex magnetic sheets for a while and am blown away by the durability, part adhesion and then how easy the part comes away post print. They support temps up to 150 degrees.
     
    HamJ likes this.
  5. HamJ

    HamJ Member

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    Thanks for the hint! I've got the Ziflex and it really does the job well...

    Nevertheless, great work on modifying the HT bed! If I had access to a mill, I would probably do the same ;-)
     
    Joe Pomo likes this.

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