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Project 2: Vacuum Forming Machine Construction
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------Design Lab Vacuuformer ------------------------------Vacuuformer from The Prop Builder's Handbook -----------------Vacuuformer from the web site mentioned below
Overview:
For this project, three other classmates and I built a vacuum forming machine for the architecture department. We started this project with only a vague idea as to what a vacuum former was, or what a massive undertaking we had just signed up for. To form our design we used instructions from The Prop Builder's Handbook, by Thurston James, a web site of someone who built one, and knowledge from viewing the vacuum former in the design department on campus. With this combination of information we started on a basic design by first building two tables using MDF sheets and 2X4s, and attached casters to make it mobile. We then began work on the two separate tables
Part 1: The Oven
The first part of our system was an oven, which heats up the plastic until it is soft and pliable so that the vacuum pump can easily form to a mold. The oven uses coiled nicrome wires attached to a power source at six points, as the heating element. The wire is wound around ceramic posts in a pattern design for even heating. Also the edges of the oven are sloped in and insulated to improve evenness of heating. During heating an insulated top is put over the plastic to further improve heating.
Part 2: The Vacuum Table:
The other part of this project was the vacuum table. The major piece to the vacuum table is the forming area, which was formed by using a sheet of plywood topped with a sheet of aluminum (for smoothness), which raised above the MDF table, with plywood strips to create a void. Holes were then drilled in a consistent pattern on the upper surface to allow a vacuum to pull evenly across the surface by simply evacuating the void. To accomplish this task we made a vacuum pump system which allowed us to first evacuate a tank to pre-charge the system to get a good initial pull. The vacuum table also includes a moving frame which holds the plastic and moves it from over the oven to the forming table. This frame was welded together and bracketed into place.
Part 3: Using the Machine
To use the machine you first preheat the oven, with top on. Then clamp a 2' by 2' sheet of plastic into the clamping frame and place it over the oven, placing the insulated top on top of it. During heating place your mold on the forming table. When heating is done you should be able to feel the bounce in the sheet all around the edges. When this occurs turn on the pump and precharge the tank to about 23 inches of Mercury. Finally rotate the heated plastic onto the mold, push it down, and release the stored vacuum pressure. Below is a video of our final product.
What I Learned:
This project had numerous problems throughout the construction, mainly due to our lack of knowledge about many of the factors which went into construction. This led to a good amount of learning from our mistakes. For example, in making the vacuum pump system we learned a lot about plumbing, including the importance of unions and, of course, flexible tubing. Also we learned a lot more about the importance of an air tight seal and the usefulness of a caulking gun. The oven had much larger problems. Since none of us knew much about electricity and wiring we had someone else handle that part. After the initial wiring up we were unable to get the plastic hot enough to melt. To solve this problem we covered the oven walls in insulation strips and added another connection in the wiring to increase voltage. Aside from all this I would say the most important thing I learned is that sometimes projects can take way longer than you would ever have guessed and despite any amount of planning you will forget things.
I would have to say that this project really taught me a lot and made me take pride in my work and definitely helped to make it a very enjoyable though insanely busy semester.