Casting plastic

For this explanation I am using the probes for my final project as the example, to cover making them for my final project, and I documented this part best with them.

When casting plastic we used Smooth-Cast 310, which produces a white plastic when it is done curing. To make the red and black probes for the final project, I had to use coloring, SO-strong from the same manufacturer.

Turns out the cocktail picks I have in the picture are excellent for measuring out the amount of colour, dip the tip into the small jar of color and you get some of the colour. More importantly the amount of colour you get is essentially the same each time, making it possible to estimate fairly accurately how much you have used. Meaning you can essentially say you used 4 picks of red and 2 picks of black.

First we need to mix the plastic we are going to use, it comes in two parts. Essentially they are mixed 1:1 ratio when it comes to volume. If it is easier to measure weight, the ratio is 100A to 90B.

Once you have mixed the two parts, you can use the toothpics to mix the colour into the mass. You do have to remember that this plastic by default is white, meaning if you dont use enough red, you can get pink.

Using old soda bottles is a good idea for mixing the plastic, because after it hardens essentially any container you use to mix it in cant be used again, and by cutting the old bottle in half you get two containers for mixing your materials.

First I tried to just tape up and clamp down my mold, but since I had made such small silicone molds, the thing leaked BAD. The initial version failed, epicly. Then I used hot glue to seal the mold better, this was tricky because once cooled the hotglue doesnt really stick to the silicone, but when it is hot enough it fills every little crack that could leak. Once the hotglue was around the seam, I taped the mold up, locking the hotglue in place.

Then I just peeled off the hotglue and opened up my mold to see how it had worked out. turns out the cable had not been in deep enough, and I had to cut off bit of the finished probe, to reveal the metal part of the probe.