I have access to a "Zero Gravity"* thermoforming machine (chinese, so has its problems!), and we are wishing to make some small deposits to be hung from a metal frame, nothing too fancy, so I have designed my first female mould:
I would really appreciate any professional feedback about this mould - it is to sit on and be trapped between the material sheet and vacuum platform (which has 3 holes where the vacuum is sucked out, corresponding to the 3 "holes" on the bottom of the mould) - the mould is made from 35mm MDF, and designed (hopefully!) to withstand both the vacuum pressure from the atmosphere, and the pressure required by the platform to force it against the inner seal, just below the outer seal where the material is clamped. As yet I have to draw in all the screw holes, but basically will be 5mm wide 100mm long screws all around...

thanks for all and any advice!!


Now there’s a real trick without being in outer space. This somewhat improperly described technique requires a whole new type of thermoforming machine and is very popular in Europe. Essentially what you need is a machine that has a bottom platen that is contained within an enclosed box that you can inject a mild amount of air pressure. On this platen you mount a standard male vacuum-forming mold that is capable of protruding out of a hole in the top of the box. On a frame that merely goes up and down via some mechanism on the side of the machine (essentially a top platen), you mount a clamp frame similar to the ones in the above techniques. This clamp frame has a sealing mechanism on the bottom of it that seals over the hole in the top of the box that the mold is contained within. The hole can be sealed over by lowering the clamp frame and pressing it against a seal ring on the top of the box.
Here is basically what happens in the process. A movable top and bottom oven is rolled out over and under the clamp frame with the plastic sheet in it. The plastic is heated to the proper temperature and then the ovens are rolled away from the heated sheet. Next the clamp frame is lowered over the seal on the enclosed box with the mold in it. At this point the proper amount of air pressure is injected into the enclosed box and the plastic sheet rises up in a standard billow bubble. This can be either controlled manually, by time, or by an electric eye at the side of the machine. When the bubble is just the right height, the mold from inside the pressure box is extended up into the bubble. When the mold is fully extended, a seal is made around the edge of the mold base, the bubble is allowed to settle over the mold, the air is turned off and the vacuum is applied to the mold, usually very slowly. When the part is cool enough, the air eject is turned on and the part is demolded. Because the mold is trapped inside the box, the air eject is very efficient and difficult parts can be demolded quite easily as the seal is actually under the clamp frame. Hence we get the name zero gravity as the blown bubble merely floats above the mold until the air is released and the vacuum is applied.