Thermoforming Acrylic Domes

Thermoforming Acrylic Domes

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:

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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.

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I use a piece of MDF which has a turned aluminium shim to push the softened acrylic sheet over the mold.

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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.

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When set, the sheet now looks like this:

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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:

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And the rough edges are sanded with a bench linisher:

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To leave them looking like this:

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Here they are attached to a sensor hat with the electronics and 3D printed plastic mounts:

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