Okay… so it’s more “PART 1-ish”. Our first attempt at vacuum forming was a pseudo-failure/success. We managed to get most of the vacuum forming system built… which was enough for one night… but it really didn’t turn out like we had hoped. Myles designed and built the vacuum table, Chris built the frame for heating and holding the plastic sheet, and I sealed and tweaked the system. But like I said… the first pass stunk. But, even though it didn’t work well… and I ended up with a molten pool of plastic on the bottom of my oven… we could see what changes we needed to make.
1. Change the material from 1/8″ Acrylic to 1/16″ Polystyrene
We switched to a plastic that was typically used for vacuum forming. It isn’t the type that I want to use for the final design, but at least we can fix our vacuum process.
2. Control the heat in the oven to prevent burning
We’re using a gas oven that heats up either ‘Flame on!’ or off. This created super hot blasts of air that bubbled and burned the bottom side of the Acrylic. To fix this problem we heated the oven to 500 degrees and then shut it off. We then put the plastic in and the burning problem went away.
3. Construct better frame to get a better seal during the vacuum process
We made a frame out of the scrap wood in my yard. It was thin and made of several pieces screwed together. Chris purchased some 3/4″ press board and made the top and bottom frame single pieces. Plus, he put four through bolts to hold it together. This also provided a much better seal on the vacuum table.
4. Seal remaining air gaps in the vacuum system
Even with the improved frame, there still was a problem with the vacuum. I tested it by assembling the frame with the plastic sheet that would eventually go in the oven. I then placed the frame on the vacuum table and turned on the vacuum. I then could tell where the leaks were. First, I needed to counter sink the bolts holding the frame together. Next there was a thin layer in the plywood. I used Aluminum tape and patched that up. Once all the leaks were patched, it really sucked!
Here you can see the results… not too shabby!
Next steps… We’re going to try thicker Polypropylene but heat at a lower level. This plastic has a better finish and one that I’d like to use as a finished product.