THERMOFORMING

Thermoforming is the process of forming and shaping plastic by using heat. There are primarily three methods of thermoforming. They are mechanical thermoforming, vacuum forming, and blow or pressure forming.

MECHANICAL THERMOFORMING

This process of thermoforming is used to form very accurate parts. It is also the most expensive for industry because it requires very accurate and matching molds to be made. This makes the initial cost of production very high.

You will be required to do two projects in this procedure. One will be a simple manual formed plastic tray and the other will be a box that requires you to use a matched mold to form the parts. The box will also require you to use processes that you have already done – fabrication and lamination.

PROCEDURE

TRAY

  1. Determine which of the shapes you want to make
  2. Cut a piece of acrylic plastic to the size indicated on the mold
  3. Sand and buff all edges
  4. Pre-heat the oven to temperature
  5. After it is up to temperature, remove the masking paper from the plastic, place the plastic in the oven and leave it in for 4 to 6 minutes. Do not overheat the plastic. It will blister if it is left in the oven too long and becomes too hot.
  6. Remove the plastic with leather gloves and place it in the mold you have chosen
  7. Working quickly, use the wooden former to apply steady pressure and continue to shape the tray by hand. Keep at this process until the plastic cools
  8. Remove the plastic from the mold. If it did not form to the proper shape, repeat steps 5, 6 and 7
  9. After the tray is properly formed, clean it up, place your name on it and turn it in. No follow up worksheet is due on this project

(0ver)

BOX

  1. Using the plans as a guide, cut the curved part of the box to size
  2. Sand and buff only the two short sides
  3. Remove the masking paper and as with the tray heat the plastic to forming temperature.
  4. Place the heated plastic in the mold and form it to shape
  5. If the piece does not form properly, reheat and reform
  6. Remove the formed piece and sand the curved edges smooth on the disc sander
  7. As per the plans, cut two ends for the box. Sand and buff all four edges of both pieces
  8. Carefully cement the two end pieces onto the curved piece keeping them flush with the top
  9. Cut out the lid for the box and sand and buff all four edges
  10. Cut two pieces of plastic ½” wide by 4 5/8” long. Sand all four edges of both pieces
  11. Cement the pieces onto the bottom of the lid, centering them from both ends and keeping them 2 11/16” apart (outside to outside)
  12. Design and create a laminated knob, then cement it onto the top of the lid
  13. Place your name on the box and turn it in along with the follow-up worksheet for mechanical thermoforming (projects 4)