I make Laser Tag equipment for a hobby. And I sometimes need to make clear acrylic domes for the sensor electronics to be housed in. To accomplish this, I buy A4 2mm clear acrylic sheets off ebay, which I then cut with the laser cutter at Hack Oldham into 6 pieces.
I then put a sheet into the oven at gas mark 9 for about 2 minutes. The time for each piece seems to vary (I think this is because as I take the pieces out of the oven, the temperature drops as the door is opened.) I know when they sheets are ready for forming as small bubbles begin to appear at the edges of the sheet:
My neighbour is a pattern maker and he made me these molds for the domes. They are made of a weird resin/clay composite and have a draft angle to aid removing the molds from the cast. The draft angle is common on molded/cast parts and it’s why the sides of your butty box/margarine tub always slope…..it would be very difficult to remove from the mold without it.
I use a piece of MDF which has a turned aluminium shim to push the softened acrylic sheet over the mold.
When soft, the acrylic sheet is simply placed over the mold and the shim pressed down over it to shape the sheet around the mold.
When set, the sheet now looks like this:
I then use a hole saw to cut the dome out of the sheet using a a piece of wood to allow the dome to be cut from the underside:
And the rough edges are sanded with a bench linisher:
To leave them looking like this:
Here they are attached to a sensor hat with the electronics and 3D printed plastic mounts: