VacuumForming

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Around two years ago I purchased a vacuum forming table called "The Formicator".  Up untill my R/C Shuttle project, I never had the need to form anything,and the former sat ready to be used.  When I was designing the ET and SRBs for the Shuttle I thought it would be a great time to form a few parts for the project, ie, external tank nose and tail cone.  I then hit a few web sites and gathered informatin about the process.  I learned from my research that it is difficult to draw the plastic over a mold more then around 3 to 4 inches.  Because the nose on the ET was to be around 7 inch long, I then decided to make the nose cone from two pieces (two halves) and glues them together.

The two molds were made from 1 inch balsa, and sealed with 3 coats of polyester resin (Fiber glass resin).  I did not sand between the coats, but if I make any more molds I think I will.  I also learned not to use any plaster (wall putty) for filler.  Even coated over with the polyester, the heat from the molding process made those spots bubble.  It is better to use the resin to fill any miner dents and imperfections.

The plastic used was 1/32 thick polystyrene, also called styrene.  I got a 4' x 8' sheet and cut it to the correct size to fit the Formicator.  Picture shows plastic in the Formicator.

Oven temperature was set at around 325.  It took a few minutes forthe plastic to sag at this temperature, but I found that at a higher temperature the plastic stretched too much and caused wrinkels in the plastic.

It took a few trys before I got the process down. If you look closely you can see some of the wrinkes mentioned above.