Press forming

Warning

The following uses an electric stove burner to heat plastic. It is recommended for adults only, or with adult supervision. Perform the following at your own risk. Working within a few inches of burner could cause major burns.

Press Forming is another way of forming parts without a vacuum. Some parts can be pressed formed while others will need to be vacuumed. Press forming the parts requires you to make what I call press plates. Press plate is made from 3/16 to 1/4 ply. You will need a top and bottom plate. To determine the size of the plate lay the part down on the ply. You want to leave at least an inch all the way around the part. Now trace around the part. At this time you can trim plates down to size. Mark the plates as top and bottom. Screw the plates together from the top. Now cut the part out of the plates. Cut about 1/16inch to the outside of the line, this will give room for the plastic to pull. I cut my plastic to the size of the plate. Now make a plastic sandwich by installing your plastic between the two press plates and screw together. I try to install the screws closely around the part to be pulled. Most parts need to be raised at least 1/4 inch above the tabletop and be mounted sturdy. I hold the plastic sandwich over a stove burner set on high until the plastic is very flexible. At that time bring it over the part a press it down over the part. Hold it until it cools. Unscrew plates remove plastic and install new sheet.

Plastic
I use the clear stuff from SIG. Come in three thickness. I use the middle one.

Tips
I hold to the outside of the plate while I’m heating it. I recommend use a small set of needle nose vice grips to hold the frame while heating it.  I also recommend using an oven mitt on your other hand.  Because you are stretching the hot plastic over the part it is better to have one hand pressing down while the frame is still in the vice grips. When bring plastic off the heat move as quickly as possible to part and form it. I place the part as close to the stove as I can. Hold that part for at least 345 seconds to allow it to cool.  Remove the plastic too fast will allow the hot plastic to change shape and draw back.

If your first part dose not turn out good, so what. The one I made did not. Sometimes you can add some heat and reform it. As with everything you will need to try a sample or two to get the feel of it.

This is the molds I have made for my parts.
This is the molds I have made for my parts.
This is a frame with a part formed in it.
This is a frame with a part formed in it.
An example of some parts that have been made by this step
An example of some parts that have been made by this step
Part still in the frame.
Part still in the frame.
Several parts that have be formed and removed from frame.
Several parts that have be formed and removed from frame.

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