• Re: 3d printing

    From Computer Nerd Kev@21:1/5 to Dan Purgert on Fri Feb 23 11:37:55 2024
    Dan Purgert <dan@djph.net> wrote:
    On 2024-01-31, john larkin wrote:
    Does anyone here do 3d printing?

    I want to make some small fixtures to hold a part in place on a PCB as
    it passes through our reflow oven. I was planning to machine it from
    aluminum and steel, but it would be cool to 3D print it if some
    material would stand the temperature, maybe 250c peak.

    250C might be a bit much to ask, as I think most "heat-resistant" 3d-printable thermoplastics (PEEK / PEKK / PPSU / others) are only good
    to around 200C (+/- a bit).

    One solution is to use the 3D printed part to make a mould for
    casting the final part in another material. JB Weld epoxy claims it
    "can withstand temperatures up to 550F when fully cured". That's
    305C. I've 3D printed a part in ABS, then pressed it into a
    cut-down disposable plastic cup filled with silicone sealant. Once
    the silicone is fully set, the cup can be flexed to release the
    plastic part, leaving a perfect mould into which the epoxy can be
    poured. I found it worked very well for a higher-temperature
    application, but JB Weld is quite brittle so it wouldn't suit all
    applications.

    I've also done aluminium casting using the Lost Wax process, but
    with 3D-printed ABS instead of wax. The basic idea is to put the
    3D printed object (painted with a paint containing bits of ceramic)
    in a bucket full of fine, dry, sand, and pour in moulten aluminium
    which melts out the ABS while simultaneously filling the resulting
    cavity in the sand. That worked well sometimes, but it's not easy
    and there are a lot of details to fiddle with, not least building
    the furnace!

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