One of our favorite things about Hackerspaces is people tend to spend a lot of time building tools, or repairing/upgrading older ones. This is a case of the former. The vacuum former.
[Adam] wrote in to tell us about this vacuum forming machine which he and few other members built for FizzPOP, a hackerspace in Birmingham, England. The device is used to suck hot sagging plastic around a mold. This is accomplished in two parts, the vacuum table and the heating mechanism to put the sheet of plastic into that sagging state.
The vacuum part of these tools has been easy to DIY for a long time. Pegboard makes for a very good table surface, with some type of vacuum motor (usually a shopvac or two) in an enclosure below the surface. This design adheres to that common formula.
On the other hand, the heating mechanism is more difficult to solve. The plastic is unwieldy and fragile when hot so a frame is very common. Following the example of commercially available models, the FizzPOP crew built a frame that slides along four vertical rails (envision table legs) extending above the vacuum surface. These legs also hold up the heating element. Often this is a nichrome wire array, but not this time. They went with an array of 70 halogen bulbs in a 10×7 orientation. A PCB was milled for each, with a system of bus-bars connecting them all. The trial run showed that the intensity of the bulbs made hotspots directly below each. But a bit more testing helped them solve the issue by keeping the frame further from the array in the heating phase.
The team’s 13-seconds of fame are found after the break. A black sheet of High-Impact Polystyrene (HIPS) is formed around a compilation of tools spelling out the name of the hackerspace.