First I think I should go over why my old machine didn't work and why the new machine works a whole lot better. With my other design the plastic was heated while sitting above the oven, I did this because heat raises and I thought this would heat the plastic more effectively. As you see I underestimated how effectively this method actually heats the plastic. The plastic got to hot, sagged to much, touched the coils and caught on fire. The new design holds the plastic below the oven so that when it sags it falls away from the coils. It might not heat the plastic as fast but the heating process is much more controllable.
Step 1: The New Base
Materials needed for the Base:
1 1x4x8ft lumber
2 1x2x8ft lumber
4 1in angle brackets
4 5/16in-18 x1.5in hex bolts
4 1in wood screws (for the angle brackets)
The pdf has drawings for the oven and the new base. The base parts are VF-09 to
VF-14. There is also an assembly drawing of the base with all the parts labeled. The angle brackets were drilled and tapped to 5/16-18 threads for the hex bolts. This is so you can clamp frame to the oven while the plastic is being heated. To take the frame out once the plastic is heated you have to loosen the 4 bolts pull the frame forward and off the bolts and then just lower it onto the platen.
Step 2: Changes to the Frame, Platen and Oven
With this design I made the oven and the platen removable because these are the things I might make changes to in to future. So if I ever want to redo the platen, maybe with an aluminum surface, I'll I'd have to do is take the old one off and build the new one to fit in the same manner on the base. This makes upgrades very easy.
Step 3: Test Run 2
The plastic formed pretty well but it could be better. I think I need to let it sag a little more. On one side it pulled out of the frame so I'll have to put some spacers on the frame to clamp the plastic tighter. I also need to experiment with different shapes to figure out how to avoid the webbing that happened at the corners. The shop vac worked pretty well but this could be upgraded too. Overall this is a good start though. I want to make some body parts for my motorcycle and I have a few other ideas. I hope this was enough info for you to make your own vacuum forming machine and if you have any questions just post and I see if I can help out.