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Thread: Experimenting with DEC handles and knobs

  1. #11
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    A moulded part typically will have much better finish. I reckon you could probably 3D print a good permanent mold though. (It will need polishing.)

  2. #12
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    My son is at university where he set-up some very expensive 3D printers - so the service came for free for me! The university also paid for the standard filament to be used. He is now back at the university doing a research project looking to recycle plastic waste into filament for 3D printers - and is also working at the university part time supervising undergraduates.

    The way he did them you can't see the print lines on the external surfaces and there was very little finishing to do. The surface finish you can see is just as good as an injection moulded part.

    I have seen the colour information somewhere - one of the many documents on Al's or Vince's site somewhere. I will see if I can track it down again.

    An entire directory of DEC Standards - http://www.bitsavers.org/pdf/dec/standards/!

    Just (re)reading http://www.bitsavers.org/pdf/dec/sta...dard_Dec82.pdf. Especially table 5-1 right at the very back.

    Dave
    Last edited by daver2; September 30th, 2018 at 01:14 PM.

  3. #13

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    Quote Originally Posted by Roland Huisman View Post
    So this weekend was for experimenting with silicone and plastics...
    ...After mixing the silicone I put it in a vacuum chamber to let all the air out...
    Nice job. A company I worked at a few years back used this technique to make their specialised products and we made our positives on a hobby-type CNC mill. I'm assuming you also evacuated the resin just before pouring? We did use a high-vacuum pump.
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  4. #14

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    Quote Originally Posted by paul View Post
    I'm assuming you also evacuated the resin just before pouring? We did use a high-vacuum pump.
    I've done that with the silicone. I've evacuated it before and after pouring.

    I would like to do that with the PU too. But I've got not enough time to do this two times in 6 minutes.
    So I want to ask the PU supplier if they have slower curing material. Then I can do it in two stages.
    And a faster pump with a lower end pressure would surely help too. I'm working on that.

    Quote Originally Posted by daver2 View Post
    I have seen the colour information somewhere - one of the many documents on Al's or Vince's site somewhere. I will see if I can track it down again.
    Just (re)reading http://www.bitsavers.org/pdf/dec/sta...dard_Dec82.pdf. Especially table 5-1 right at the very back.
    Thanks! are there any conversion tables for those colour numbers?

    Regards, Roland
    WTB: Dec TU56 / Case for Altair 8800

  5. #15

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    From our painter at the university I've got a colour reference book.
    I think I've found more or less the right colours for the knobs.
    These are RAL 2000 and RAL 2001

    16 RAL 2000 2001.jpg

    The magenta handles are really close to RAL 4004

    17 RAL 4004.jpg

    The green handles are a bit different from the RAL colours.
    RAL 6025 is the closest which I could find.

    18 RAL 6024.jpg

    I will check at the supplier if he can make these colours in a small volume.
    They say that they can make all RAL colours... Well, lets see what they can accomplish
    WTB: Dec TU56 / Case for Altair 8800

  6. #16

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    Quote Originally Posted by Roland Huisman View Post
    But here is my problem. A little pin on the knob is a little hole in the negative.
    When there is air in that hole the PU can not reach that place. Here you can see
    what happens. That little pin on the left one is disappeared at the right one.
    The cause is a little bit enclosed air.

    Attachment 48342
    I've had that problem. What you need is a (thickish) pinhole in your mold
    to allow that region to fill with resin. Otherwise an air bubble gets trapped
    there, and pumping can't really get rid of it.

    I actually didn't bother with the pumping, but as a result had to be quite
    careful about venting the molds so that every region could be flooded
    with plastic.

    Vince

  7. #17
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    Here's how the pros do it - https://www.youtube.com/watch?v=BFqNP8VqoPs
    Strange Parts has many cool videos about manufacturing in China - worth a look.

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