Step 8: The First Test
Now is its time to test. I got a sheet of .020in. thick Polystyrene from a hobby store. This is a little on the thin side for vacuum forming, but it all depends what you are making. A normal thickness would be between .040 and .080. A thinner material can be formed with more detail but needs to be watched closely while heating. This is the problem I had with my first test. I turned of the oven and let it preheat for a little bit. I cut out another piece of hardibacker to be a cover for the oven while it was heating. Then I put the plastic in the frame placed it over the oven and put the cover on top. When the plastic starts to heat up it will start to warp, then it will start to sag. Usually you can determine when to form the plastic by the amount of sag there is in it. But this learning has to come from experience, your first couple of times might not turn out so well. Due to my lack of experience the first time I used the machine the plastic heated up a lot quicker than I expected, saged to low, touched the coils and caught on fire. As you can see from the pictures it melted all over the oven. This ruined the oven but I can be cleaned up and used again. I don't the time to do it though. I'm living away from home for the summer and won't be able to work on it for a couple of months.
So at least for now I learned a lot about how a vacuum forming machine works and how it could be put together. I might try to change some parts of the machine to make it a little more solid and heat the plastic more evenly. If there is one thing I can tell you about build a vacuum forming machine here it is, when you are testing for the first couple of times have a fire extinguisher ready to go.