Vacuum Forming

Vacuum Forming Jig Components

A simple vacuum former is just a wooden box with a hole suitable to attach a vacuum cleaner for the vacuum source, an upper perforated surface to support the pattern, and a frame to sandwich sheet plastic between . 

The version shown here is made from 1/4 inch plywood and 1 x 1/2 inch wood for the sides. It took no time at all to assemble, but I did use a jig saw and power drill. As long as the box is basically airtight, it really doesn't matter how you make the joints. The hole for the vacuum cleaner is fitted with a heavy duty self adhesive foam. The internal joints were also filled with wood glue and the thing all nailed together.

If your making a larger version, several internal braces for the top surface may also be in order. The frame for the sheet of plastic is held together with wing nuts and bolts. You need to hold the sheet firmly in the frame , so you may need more than 4 bolts if you want to form larger plastic sheets. You want to make the frame bigger than the box top, so that the bolts clear the top of the box with room to spare. 

Vacuum Forming a part from Wood Pattern

The pattern in this case was made from balsa wood, primed, filled, sanded and that loop repeated until the pattern was perfect. The resultant vacuum formed plastic will be no better than the original master, so if it isn't straight and true, neither will your copies be. The styrene was then cut to shape and sandwiched between the 2 plywood frames.

The pattern is mounted in the center of the perforated box top with double sided tape. The frame and sheet is then held over a  burner on the kitchen stove, or in an oven, and heated evenly until it starts to sag. 

When the plastic starts to sag turn on the vacuum cleaner, after it has been attached to the box, and I slam the frame and sheet as firmly and evenly over the pattern and hold it there till the plastic hardens.   

You then cut out the part you need and get on with your project. Note that you use much more sheet plastic than the final part. 

Cast Plaster Pattern

Here is another pattern technique. In this case the original vacformed part  was in a tinted acetate. I wanted a clear version, so a pattern was made by pouring fine plaster into the inside of the original part, letting it harden, then trimming it to shape. The yellow part in the image at left. Acetate sheet was then used to form a clear part.

Note that you cannot vacform clear styrene sheet, it just doesn't work.