Drape Molding Using Recycled Silicone Liners
How many of you have a box of old liners sitting in a corner collecting dust? Well, dust off that box. Now, covered and uncovered silicone liners have a new use. Traditionally, to drape mold a socket or AFO, we would cut a ½-in. piece of Plastazote to the size of the top of the cast, then slide it over the tube for the vacuum and try to seal it so that it would not leak. This would seal the plastic onto the ½-in. edge of the Plastazote. This article will show you how to skip the Plastazote and use recycled silicone liners instead.
There are two methods for using silicone liners—one for covered and the other for uncovered.
Covered Liners
Cut a small hole in the bottom of a covered cushion liner and turn the liner inside out. Slip the liner over the tube for your vacuum station and then insert the cast. Pull the liner about 1 in. over the edge of the cast. The cover will act as a vacuum wick. If the liner does not stay in place by itself, use a staple gun to secure the liner to the cast. For the final step, wrap a few layers of electrical tape on the edge of the liner and staples, if used. Some liners have oils in them that prevent the heated plastic from sticking, so the electrical tape helps to hold the plastic in place (figure 1).
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| Figure 1. Cast ready for vacuum forming. | Figure 2. Nylon over vacuum tube for vacuum wick. |
Uncovered Liners
For uncovered liners, a vacuum wick needs to be added (figure 2). Before pulling the liner onto the edge of the cast, a nylon should be extended from the tube to the cast. Leave the nylon long, and after you have finished wrapping the electrical tape over the liner, cut the nylon ½ in. past the edge of the liner (figure 3).
The Drape-Molding Station
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| Figure 3. Nylon extended over top of cast and held in place with tape or staples. | Figure 4. Quick-change vacuum station. |
We use our drape-molding station infrequently, so we have mounted it with wing nuts for easy removal. It also features a quick disconnect so that we can switch the drape-mold tube to a blister-molding station easily. The drape-molding station is made from basic hardware parts that are welded together. A ⅜-16 nut is welded to the top of a 1-ft. long, 1-in. threaded pipe and drilled through, then taped. The tube is capped at one end with a reducer from 1-in. to ¼-in. pipe thread to accept the quick disconnect. The pipe is then welded to a base that consists of two ⅛-in. steel plates. The base plate is 6-in. wide and 5-in. deep with holes in the corners. The upright is 4-in. tall and 5-in. deep (figure 4). The drape-mold station is connected to a foot pedal for vacuum.
Editor's note: The parts list for the foot-pedal design can be found in the article, "Outside-the-Box Solutions for Low-Cost Shop Equipment," The O&P EDGE, August 2005.
Craig MacKenzie, CP, RTP(c), is the president of Evolution Industries. He can be contacted at