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What's the "Acrylic bed" exactly ?

Discussion in 'Troubleshooting' started by polylac, Aug 23, 2013.

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  1. polylac

    polylac New Member

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    On the PLA-only model is a acrylic bed.

    Is this just a ordinary PMMA plate?
    Or is it something else that goes under the term "acrylic" which is a bit unspezific.

    I'm wondering because PMMA is only temperature stable to 85°C (long term) oder about 125°C for short time. So how can you print on this directly?

    On the other hand there are other "acrylics" stable up to 165°C.

    Does anyone know something about this? (Otherwise i ask the Robo Team directly).
     
    #1 polylac, Aug 23, 2013
  2. Printed Solid

    Printed Solid Volunteer Admin
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    IMO, it doesn't matter. I don't advise printing directly on the bed. Also note, the acrylic bed is for printers without a heater. If you have the ABS model, you get borosilicate glass.

    I've heard of people printing directly on acrylic beds, but I don't think it's a good idea. I've accidentally melted a little hole in the acrylic bed of one of my other printers. I've also gotten prints to stick so hard to tape or glass or whatever that I'm practically chiseling them off.

    Blue tape is cheap and easy to apply and reduces the chance that you're going to damage the bed.

    Plate glass is also cheap and pretty much eliminates the chance that you are going to damage the bed (although you have the risk of breaking glass).
     
    #2 Printed Solid, Aug 23, 2013
  3. polylac

    polylac New Member

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    Hi

    thanks for the answer.
    (on the robo site they say you can print directly, but i never wanted to anyway).

    I wanted to build some heat bed on my own, but it seems that on those whith a heated bet, the heat bet is only attached to the acrylic plate so this seems to be stable to temperatures at least 100°C.
     
    #3 polylac, Aug 23, 2013
  4. Harry

    Harry Team ROBO 3D
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    Hey polylac, for the ABS version, the Heatbed is actually not on Acrylic but a sheet of Birch Wood. It goes BirchWood, then the HBP, then I put Boro over the HBP so I don't damage it (The HBP). There is no Acrylic on the ABS version. And with it being on the Birch, for Vapor Polishing, I actually put and got my heat bed up to 120C the other day.

    As a side note, the only difference in the versions I believe is the "build platform" itself, the ABS version has what I described the PLA version has just a sheet of Acrylic. I'm sure it would be possible to contact the RoBo team and see if they would be willing to offer an upgrade (After purchase, like for people who got the PLA version and then months or even days later decided they want the heated bed) to the heated bed, which would really only be two new parts, the heated bed and a sheet of birch.

    - Let me know your thoughts!
    - HV
     
    #4 Harry, Aug 23, 2013
  5. polylac

    polylac New Member

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    hey harry

    ah oke, couldn't see that on the picture.
    Yes I know i asked what's the difference and they told me only the heated bed (and 100$ ;))
    Now they put on an boro glass too.

    I'm going to ask them about the material properties.
     
    #5 polylac, Aug 23, 2013
  6. CAMBO3D

    CAMBO3D New Member

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    The melting point of acrylic is around 175F nothing near the hotend temperatures of 190c-230c for pla printing. So yeah don't directly print to acrylic unless you want a warped bed. Even on the abs model the heat from the heatbed caused warping issues in the acrylic so that's why robo choose to use birch for abs model.
     
    #6 CAMBO3D, Aug 23, 2013
  7. polylac

    polylac New Member

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    @cambo

    thanks for that piece of information about the change from acrylic to birch.

    but the melting point is 320F (160°C), 170F is approx. the long term exposure limit.
     
    #7 polylac, Aug 23, 2013
  8. CAMBO3D

    CAMBO3D New Member

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    Your probably right about the melting point, i just got those numbers from mcmastercarr website, doing a quick glance but definitely there's enough heat in the heat bed to warp the acrylic if not melt it.
     
    #8 CAMBO3D, Aug 23, 2013
  9. polylac

    polylac New Member

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    i looked it up on wikipedia and google. (ordinary acrylic = PMMA)
     
    #9 polylac, Aug 23, 2013
  10. Harry

    Harry Team ROBO 3D
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    @cambo that is why RoBo used Birch not Acrylic.
     
    #10 Harry, Aug 23, 2013
  11. polylac

    polylac New Member

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    @harry, that's what he said.... quotation: "Even on the abs model the heat from the heatbed caused warping issues in the acrylic so that's why robo choose to use birch for abs model."
     
    #11 polylac, Aug 24, 2013
  12. polylac

    polylac New Member

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    so the robo team answerd my request.

    the PLA model has "basic off the shelf acrylic"

    thank's for all answers, I'll look how i can arrange that (and post the solution)
    when my printer arrives.
     
    #12 polylac, Aug 24, 2013
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