Hot wire foam cutting for polystyrene pattern making

Written by kasandra rose
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Hot wire foam cutting for polystyrene pattern making
Polystyrene patterns can be used for casting. (Hemera Technologies/ Images)

Hot wire foam cutting produces a solid, smooth-edged pattern piece when used on polystyrene foam. Lost foam casting uses pieces of polystyrene, cut into the shape of the desired part, to cast unique aluminium pieces to order. Just cutting the polystyrene with a knife won't produce the smooth precise part needed by home mechanics and automobile and motorcycle speciality shops. After burying the polystyrene pattern in the sand, hot, molten aluminium, poured into the sand, burns away the polystyrene, filling the void with the cast aluminium.

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Things you need

  • Hot wire foam cutter
  • Polystyrene
  • Marking pen
  • Hot wire detail cutter

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  1. 1

    Glue styrofoam sheets together if a thicker part is required.

  2. 2

    Design the part you wish to fabricate. Draw the desired pattern on the top of the styrofoam sheet with a marker. Sometimes a two-step cutting process is necessary if the design includes small details.

  3. 3

    Turn on the transformer attached to the hot wire cutter and set it to the desired voltage. This will vary with your particular hot wire cutter and with the styrofoam density and thickness you're using. Use a bit of trial-and-error experimentation to find the voltage you need for your project.

  4. 4

    Cut the pattern out of the styrofoam with the hot wire. Cut at a moderate speed -- move fast enough not to melt the edges of your pattern, but not so fast that you press into the styrofoam and tear or deform it.

  5. 5

    Push the styrofoam into the blade if you have a table-mounted hot wire cutter. Push the blade into the styrofoam if you have a handheld hot wire cutter. With a handheld cutter, you must also pay attention to keeping the wire perpendicular to the styrofoam.

  6. 6

    Turn off the transformer.

  7. 7

    Once the bulk of the cut is done, detail any secondary cutouts onto your pattern with the marker.

  8. 8

    Plug the hot wire detail cutter into the transformer. Use the detail cutter to gouge out small sections to match the pattern to your design following the guide marks you made on the styrofoam. If necessary, continue to work back and forth from your design to your pattern.

  9. 9

    Turn off the hot wire cutting tool between uses.

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