DIY Thermoforming Plastics

Make complex plastic models by thermoforming plastic.

Thermoforming plastics are a class of plastics, called polymers, whose molecular alignment allows them to be easily heated and pressed against or inside a mold. This simplistic material handling works well in environments where temperature, toxicity or mechanical risks are unacceptable. For this reason, and ease of use, thermoforming plastic is well suited for DIY projects. While pressure and mechanical processes work well, vacuum thermoforming works best for small DIY projects in home or school environments. A highly versatile thermoplastic former -- the heart of the system – can easily be assembled at home.

Things You'll Need

• 3/4-inch plywood
• Tape measure
• Framing square
• Straightedge
• Pencil
• Circular saw
• 6-inch circular rubber gasket
• Rubber cement
• Power drill
• 1 1/2-inch hole-saw bit
• 1 1/2-inch PVC pipe
• Reciprocating saw
• Vacuum cleaner or shop vac
• Small aluminum screens
• Utility knife
• Heavy scissors
• Sponge rubber weather stripping
• Rigid thermoplastic sheeting
• Aluminum screening material

Instructions

Make the thermo-former and frames

1. Measure and use a circular saw to cut a ¾-inch by 30-inch square piece of plywood for the platen -- the vacuum work surface. Connect the opposite corners with a straightedge and a pencil to locate the center of the board.

2. Glue a six-inch circular rubber gasket or circle of rubber from an inner tube to the center of the board. Use a power drill and hole-saw bit to drill a 1 1/2-inch hole in the center of the board on the rubber side. Begin the cut gently so that a circle of rubber is removed before the bit starts to cut wood. The result is a hole through the rubber and the board that are exactly the same diameter.

3. Apply rubber cement to the outside of a two-inch piece of 1 1/2-inch PVC pipe. Insert it into the hole in the platen so that the pipe is flush with the upper, rubber side of the board. Connect the hose or coupling from a household vacuum cleaner to the 1 1/2-inch PVC pipe.

4. Select two aluminum screens that are less than 24-by-24 inches. The smaller the screen size, the easier they will be to work with. Remove the screen material with a utility knife and smooth the edges flat with a gloved hand. Measure the screen frames to get the exact length and width.

5. Draw the dimensions of the screens on the side of the board with the rubber added to it. Use heavy scissors or construction snips to cut one-inch wide strips of sponge rubber weather stripping. Cut the pieces to fit the dimensions of the screen that has been transposed onto the platen. Pull off the adhesive-covering strips and carefully stick the strips to the board.

Thermoforming Plastic Models

1. Fold several thicknesses of aluminum screen material to a size that will exceed the dimensions of the intended mold. Place the folded screen material in the center of the platen, over the center hole. The screening allows the air to pass under the mold and out the hole. Select a convex mold -- a figurine or other three-dimensional object -- and place it on the platen.

2. Measure and cut a piece of thermoplastic material the size of the screens that were chosen. Cut the plastic with a utility knife and insert it between the screens. Use manuscript binder clips every four inches around the screens to bind them together.

3. Place the bound screens into a conventional, 250-degree oven. They should be resting on glass or metal supports that will elevate them but not touch the plastic. Allow the plastic to begin to sag slightly -- a 2-inch sag over a 12-inch span is typical.

4. Connect and turn on the vacuum to the platen. Remove the screens from the oven and carefully place them on the platen so that the edges rest squarely on the weather-stripped rectangle. The vacuum will immediately begin removing the air between the plastic material and the platen, escaping through the screen material that is under the mold. In several seconds the vacuum will have removed all the air, creating a partial vacuum. Allow the vacuum to continue to run for 30 seconds and then shut it off.

5. Allow the stretched plastic to cool for 20 minutes after the vacuum has been released. Remove the screens from the platen and take the clips off the screens.

Tips & Warnings

• Wear goggles and hearing protection when working with power tools.

• Use caution when handling hot plastic.

References

• "Plastics, Composites and Polymers"; Richard Wool; 2005

Resources

• Read this Article in Spanish