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Re: Holding thin styrene sheet from which to cut shapes

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  • David
    Right, well, the MDF is what we call a bleeder board, so as I said before, you dont want to use it for building the bottom or sides of the fixture, because
    Message 1 of 11 , Aug 31, 2005
      Right, well, the MDF is what we call a bleeder board, so as I said
      before, you dont' want to use it for building the bottom or sides of
      the fixture, because you want the draw only on that top sheet.

      I think the bleeder board works best if you have a "very good" vacuum
      source which of course also depends on the volume...not that I'm
      saying not to try it, but if it doesn't work then it would be easy to
      go with a harder board.

      Anyway, the 1/4" holes... I think they give a good surface area and
      it's a handy drill size to grab around here. The smaller the holes,
      the more you have to drill. Bigger but fewer might be even better,
      but then again if a bigger holes "let's loose" it decreases the vac
      volume quicker than a smaller hole... again, the importance (or not)
      of this depends on the total vacuum you are able to get and that's
      just so full of variables... well, yes, experiment!

      One other thing to be thinking about is where your chips will go. In
      a perfect world, you wouldn't think you'd get chips inside your vacuum
      fixture, but if you go with the 1/4" holes, it's likely that you will.
      A screen should be employed in the line to catch these before they
      go into your pump. (I do this by cutting a piece of screen to fit
      inside one of those 2 piece pipe unions... easy to pull apart to clean)
      Of course, if you get the bleeder board to work, then you don't have
      to worry about it.

      Finally, about the material and cutter. I agree with Ron Ginger that
      material can get sticky, and that's why you'll do well to try the "O"
      flute bit. It really makes a clean cut and gets the chips away. A
      little air on the cutter while running is really helpful, too.

      Oh yeah, last thing I remembered ... Downcutting is not good with the
      material because you're pushing chips under the sheet -- that's
      another thing about the O flute... it's a straight cutter and pushes
      the chips away, not down or up. I have tried some cutters that were a
      helix "O" flute, but I didn't like them.

      Yeah, I know, I'm blathering on and on... anyway, again, good luck,
      let us all know how it goes!

      --- In SherlineCNC@yahoogroups.com, "Andrew Wells" <andrew@m...> wrote:
      > David
      >
      > thanks for this
      >
      > The disks as 1.5" OD, with a 4mm centre hole. I've worked out that I
      can cut 11 disks (one row of 5 and one of 4) from a 10" wide sheet.
      The styrene sheets come in 30" wide, so this works out fine.
      >
      > I have an imperial mill, so generally think in inches, but the final
      product needs a pressfit #8 wire guage hole, hence the 4mm works fine.
      >
      > My vacuum source (the BloVac) is infinitely adjustable based on the
      volume of air that you put through it, and claims to gives up to 3" of
      Mercury vacuum.
      >
      > I am surprised about the 6mm holes - I was planning to use smaller.
      >
      > Years ago I built a vacuum forming jib (1" draw over a 8" x 6" size)
      and it worked fine and had lots of ~1.5mm holes.
      >
      > Ron Ginger has just posted suggesting using 1/4" MDF without holes!
      I can see some experimenting coming on!
      >
      > rgds
      > Andrew Wells
      >
    • KM6VV
      Hi Andrew, 2mm thick cuts on a Sherline mill? You might try double sided tape. I don t see how you could use a chamber on the mill! Another way would be to
      Message 2 of 11 , Sep 4, 2005
        Hi Andrew,

        2mm thick cuts on a Sherline mill? You might try double sided tape. I don't
        see how you could use a chamber on the mill!

        Another way would be to use a few toggle hold downs. Temporarily release a
        clamp until the cutter clears it.

        Alan KM6VV


        Andrew Wells wrote:

        > I have an application where I want to cut lots of disks from 2mm styrene.
        >
        > I have it set up and working fine, except I have to manually hold down
        > the styrene otherwise it climbs up the mill and "tears".
        >
        > I can't make the spindle reverse so that's not a solution.
        >
        > What I have been thinking is to make a vacuum holder.
        >
        > I envisage making a chamber from MBF, with lots of small holes on the
        > top surface (excepting along the cut paths). I'll mill the cut path
        > patterns into the MBF top surface, using a bigger diameter mill, so
        > that when I come to produce the disks the mill wont be cutting into
        > the MDF.
        >
        > I have an Australian gadget called a BloVac which can create a bit of
        > suction from a compressed air feed, or I can connec to the shopvac.
        >
        > Before I embark on the wordwork required for the chamber, has anyone
        > got any advice/experience in trying to do this sort of thing?
        >
        > rgds
        > Andrew Wells
        > Auckland
        > NZ
        >
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