A12 - Moulding and Casting

Brief

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• Design a mold around the process you’ll be using, produce it with a smooth surface finish, and use it to cast parts.

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Creating the mould

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Since the first 3D design week, I had gained more experience in OnShape so designed my mould using that.

I had the issue of the sensors degrading due to moisture in the back of my head from similar projects shared on the Core Electronics forum some time ago...

So I wanted to design a sealed resin enclosure for the Electronics on the soil sensors.

I measured the soil sensor, and designed the following:

xxx TODO: animation of making primary

Our process

We were using the SRM20 again, now to mill 3D parts. We would need an STL, where the shape would be the final part produced on the mill.

The whole moulding process would be: Create the 'primary mould' - the original, create a silicone negative, and finally, cast our parts in said silicone.

Milling the primary

The STL was loaded and a toolpath was created using the default settings.

xxx TODO: collage of slicing settings

The final result had no observable imperfections :o

Creating the silicone negative

We mixed the 50/50 silicone, then poured it into the milled primary. Making sure to add a release agent (Vaseline).

We allowed 30 minutes for it to set, although upon touching the silicone it still seemed wet so waited another hour.

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Casting the final product

With the silicone mould now complete we could encase the sensors in resin, making them far more waterproof.

Not designed in was slits for the wires and body of the sensor. Those were cut in using a sharp craft knife (not cutting towards myself). (they ended up being a bit jagged :( )

The sensor was inserted then resin poured ontop.

xxx TODO: Video of putting in resin

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