When I created my first CAD drawing of the lid of my bowl, I gave it an inner, smaller lip which would sit around the wall of the bowl to hold the lid in place. I decided that I could also use a silicon seal to ensure the lid doesn’t come off easily when the food is being heated.
To achieve this inner lip, I decided to use two layers of laser-cut acrylic, one smaller than the other. One would would fit inside the lip of the bowl and one would sit on top of it.
The lid of my bowl piece had to have a part in the middle that looked like a halogen bulb which would heat up the food. I decided to make this part out of silicone so that the silicon would hold the two layers of acrylic together.
Silicon Casting from a two part plaster mould
Unfortunately, the finish of the plaster mould wasn’t quite good enough because it had picked up too much of the detail from the polystyrene balls I had shaped to create the original mould. I learnt the hard way that silicon is impossible to finish once it has been cast so I made the decision to re-make the part.
With not enough time to re-silicone cast, I decided just to turn a part on the lathe out of engineering foam.
Here is my finished perspex lid. I’m very happy with how neat the finish of the turned part is and wish that I had had enough time to do another silicon cast from this much neater part. This photo shows the two layer perspex and also the silicone seal I attached.