With your sheet plexiglass clamped securely to your work surface under a straight edge that defines where the bend will be, it is time to heat your material. The object of heating the sheet is to heat it evenly along a line just in front of the straight edge of your clamped jig. To make sure you apply heat evenly, pass your heat source at an even, slow speed along the line of plastic in front of the jig, keeping it far enough away that the heat source will not singe your wood jig. Try to keep the heat source at a right angle to your sheet of plastic / plexiglass. If you turn your heat source as you pass across the acrylic, the heat won't be evenly applied across the entire width of your sheet.
You will have to work on several test strips to establish what speed and how close you should be to your sheet material. In the pages that follow, I've shown several problems that can occur.
While you are applying even heat along the bend line, press gently up on the sheet of material you are bending. There will come a point when the material will move easily upwards as it reaches a molten state. You should be able to feel this point evenly along the full width of the strip you are bending. It should not be softer on one side than on the other.
When you feel that your sheet is allowing you to push up evenly on it, remove your heat source and set it safely aside on a stand or heat resistant surface -the end of your tool will be very hot! Holding the sheet material evenly with both hands (both in protective gloves) push the sheet up gently bending it against the line of the jig as shown in the photo above. You must use two hands to do this with an even pressure, or your material will twist slightly as you bend it, unless you are working with a very thin, narrow strip.
When you have your sheet at the correct angle or have bent the curve you want (for a window or the front of a curved bakery case, which may not be at 90 degrees), hold the plastic gently in place for a few seconds until it sets up again. Allow it to cool still clamped in the jig as shown.
Note: You can use the same heat tool you use to bend plastic, to seal and neaten the cut edges of any plastic parts. Run your heat tool gently back and forth along a cut plastic edge to soften it just enough that it turns clear.