molds  &  forms... the fun & messy stuff !

a conglomeration of things learned by megan during how to make almost anything, fall 2001
                                      megan[at]media.mit.edu

using the vacuum form machine    >> or read about making rubber molds

1. turn on all the heating elements to be sure you get even heating. if you are conservative, and only forming with the smaller size plastic, feel free to omit the perimeter elements (3, 4, and 5). be sure to push the heating tray back off the forming table, so that it can heat up without burning you, or making the metal frame too hot before you put your molds in.

2. lay your object inside the machine, through the opening and on the tray. raise the lever on the right to make sure the object fits entirely inside the opening. if it's too large, read below for instructions on how to remove the small frame so that you can use the larger sheets of plastic.

3. if it fits, you should next pad your object to get a good flow of air from below.. either place it on 3-4 small legs (made of clay, wood chunks, something rigid) so it resembles a table, or place some spongy material below as a flat base. there should be some sheets of this material in the drawers under the workbench (second drawer from top, on the right). it's important to have a good flow of air in order to get a close fitting form.

4. lower the base far into the machine. the deeper you go, the less heat your object will have to withstand as the plastic warms.

5. next you'll need to grab a sheet of plastic. there should be some piles of it, cut to size, underneath the vacuum form machine. these sheets are more expensive to cut to the square dimensions, so please do not use these in the laser cutter!

6. take off the blue wrapping, from BOTH sides of the plastic.

7. raise the top section of the table, and place the sheet of plastic on the white sealing rubber border. close the top and clamp both sides down. adjust the tension on the clamps if it seems too loose.

8. pull the heating element over the plastic and let it sit for about 30 seconds to start warming. then start to check it periodically until the plastic has sagged about 4 inches in the center. it should be warm to the touch. if you don't wait long enough, the plastic will cool too quickly and you won't get a good mold. however, be careful not to wait too long or it will sag all the way down to the object in the bottom, which means many wrinkles might form in your plastic. ew.

9. when the plastic seems ready to mold, grab the eraser hanging from the machine, or throw on a pair of cloth gloves so that you can help press the plastic to your mold for a better fit. this next set of instructions needs to happen fairly quickly, so read carefully before proceeding.

10. push the heating element back off the plastic and raise the lever on the right of the machine completely to the top, so that you object presses into the plastic. do this fast, and then press the vacuum button (green) so the suctioning starts. suction for a short time (~3 seconds) or until your plastic just fits your object, then press stop (red).

11. use the eraser or your gloved hand to press down the random areas that might need a little help. press the release button (orange) to push the plastic back off your object. if needed, try a few spurts of vacuuming and releasing until you are happy with the results. do these last two steps as quickly as you can because the plastic will start to cool and your molds will get less and less accurate.

12. when you are done, lower the lever so your object recedes back into the machine. unlock the hinges and take the plastic off the machine. it might be hot still, in which case you should let it cool for a minute. but basically, you're done. turn off the heating elements, grab your object and your plastic mold, and have fun!

important things to remember

1. vacuum forming with foamcore or other paper products is generally a bad idea. it sticks to the plastic.

2. acrylic can be pretty wimpy, too, depending on the shape of your object.

3. try not to hold the vacuum for too long.. might pop your plastic. try it in spurts.

4. if done well, a form will pick up a LOT of detail.. so be careful about what you use on the surface of your objects. even thin layers, like innocent scotch tape, will show up.