This is the redesign of the vacuum forming machine I built this past summer. Here my first design Vacuum Former and if you look at the last step you can see why I redesigned it. If you don't know what a vacuum former is check out the links on the first step of my other instructable. I'm not going to go over everything again but you can use my other instructions to build the oven, platen, and frame. Only minor changes where made to these parts and a different base was made.
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
The new base was made to hold the oven upside down, hold the platen directly below the frame and hold the frame in place while the plastic sheet is being heated. The base was made from standard lumber you can get from Lowes or Home Depot. I nailed it together with a nail gun but screws could be used too. It also has some small angle brackets and hex bolts. Here is a list of everything you'll need.
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
Starting with the oven, I added extensions to the short ends so that they would fit it the new base. This is because I wanted to be able to take the oven off when moving the machine. The oven is heavy and makes the whole thing a little top heavy and being able to take it off makes it a lot easier. I added four short extensions to the bottom side of the frame. These parts sit on the bolts on the base. I added some of the same balsa wood that I used to separate the layers of the platen to the bottom of it. The platen sits on the risers on the lower part of the base and the balsa wood pieces locate the platen on the base.
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
I cleaned up and tested the oven and put everything together for another test. This time I had a fire extinguisher ready just in case. The plastic took about five minutes to heat up and sag about 1.5in. The oven smoked a little because of the soot and ash still in it but I think that will eventually burn off. I put some left over pieces of wood on the platen to make a tray organizer for a desk or tool box drawer.
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.