From this site: working with acrylicBending:
In my opinion, a heat gun used for stripping paint ($25) works best when trying to bend acrylic. With a pencil, mark where you want to bend the Plexiglas. Place that line on an edge that you can bend it over. Then, with two people, one holding the heat gun and the other bending the acrylic, move the heat gun slowly, back and forth across the line. You wonít have to heat both sides, just the outside. Stay far enough from the acrylic so that it doesnít melt or bubble. You can start out at 4 inches away and work your way towards the acrylic until you find a distance you find works best. When the Plexiglass gets soft, you will see it start to sag, but you will need to keep heating slowly. Donít rush this part. Gently, start bending the Plexiglas downward. When you get the desired bend, remove the heat, and hold it in place until it cools. If you want to speed this up you can either direct a fan on it, or drip water over the bent edge.