vacuum forming
from the notes of Professor Ted Selker

Vacuum forming is wonderful for making a short run of manufactured shells that can hold technology or.... anything. It is the technology used to make the plastic packaging that products hang in, it is the technology that is used to make some golf carts and many electronics enclosures. It is the poor man's injection mold, slower and not as fancy as shapes with molds sometimes costing as little as 1/1000 as much.
Vacuum forming is a craft, easy when done right, with a lot of little things that improve any project. It is easy to start and complete a project in 1 hour (with design, construction of buck, placing buck, We have an excellent rudimentary book that I would like to tie to the vacuum forming machine: "Do it yourself: Vacuum Forming for the hobbyist."

Vacuum forming can be done with any thermoplastic.

Make Buck
Vacuum forming is done over a convex buck.
Concave areas can be pressed in
  • By making a hole through the buck to such air to that spot
  • With a felt eraser while molding

    The buck has to be strong enough to be stood on.
    The buck has to be able to be heated for 30 seconds by the material it is forming without deteriorating.
    The buck has to have a way of coming out of the formed object.
  • A small "draft" of even one degree can be sufficient
  • Bucks that unscrew or otherwise come apart work well
  • Blowing it off before the form is solid can work

    Heat Plastic
    The heaters that are needed are turned on (two knobs for 12 inch molds) The top piece is a heater that needs to be rolled over the part to be molded when in use.
    The heater has many knobs that are turned to activate the heaters that a diagram shows.
    If the material is 0.2" thick or more, start with a full or 6 setting on the knobs you are using.
    The buck is put in the machine in a way that lets air suck around the edges
  • If big the machine has stand-off bumps that hold it up
  • If small the buck might need to be supported by a many holed base
  • peg board works well
  • green scotchbright works
  • washers work as standoffs too
    The buck is lowered with a handle to where it won't get overheated while the plastic is being heated
  • use the red handled large lever on the right to lower the buck
    Open the plastic clamping area with the funky clamps left and right (easy to pinch your fingers here)
  • A set of plates are often in this area for holding 13.5 inch square material or 26.5 inch moldings
  • Take them out (carefully)
  • The 12" or 24" forming takes an extra 1.5" material to hold the seal while molding.
  • Take the protective cover off of your PET, ABS, Polycarbonate, Vinyl, Acrylic or whatever.
  • Clamp it in place so that no air enters.
  • If it is summer, you are likely to get bubbles in your molding unless you preheat the plastic on 1 or 2 for 20 minutes

    Pull Plastic
    Pull the heaters over the plastic
  • 0.1 inch plastic will take on the order of 45 seconds,
  • 0.25 will take on the order of 2 minutes
  • the plastic will bulge (top is hotter than bottom and it expands) then droop (both surfaces are hot)
  • Test the plastic for a rubberiness by poking it with a felt eraser
  • pull back the heaters, poke it, if hot enough, pull the heaters back over it for 5 seconds

    Pull the mold!
  • Push back the heaters,
  • Push the mould button & pull the red lever to pull the buck into the plastic (don't stand on the lever!!!!)
  • Rub the parts that aren't sucking into place with the felt eraser - this can improve things

    Remove the part
  • If you have no undercuts, let the vacuum run until the part is hard (30 seconds for thin, 1.5 minutes for thick molds) (recomended)
  • If you are worried about it sticking stop the vacuum early, open the clamps and take out the buck while the plastic is soft (not recomended)
  • If you are really worried blow the mold off with the release button

    Turn off the heaters

    Trim the edges
  • use the scroll saw or band saw to tirm off the flanges
  • Use the sander to finish the edges.

  • Using one part to make another, One can leave a molded part on the buck to make one that fits inside another.
  • Wood filled foam, wood, plaster, plaster covered styrofoam, string, metal, sturdy plastic things, even lego all make good bucks.
  • Finish the buck carfully, molding can pick up even wood grain

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