Sunday, 21 August 2011

Prototyping ‘Carbie’ - Personal Energy Monitor for Kids


The ‘Carbie’ badge design consists of an internal recycled plastic ‘skeleton’ with a silicon overmoulded body. The following series of images depicts my attempt at completing the overmoulding process.

First things first - I did some silicon tests. In this picture, the trusty CNC machine is machining out a one piece foam mould of the badge form.

Silicon is poured into the mould and left overnight to set.

Hey presto… the following day the silicon is pulled from the mould. Appears to have worked quite well.

     I went to FabLab in Ardwick, Manchester to get the badge’s internal plastic skeleton 3D Printed. It’s amazing to watch the machine print in plastic.

In all its glory.

Here’s the skeleton and the two parts of the mould. I decided to use Cibatool instead of blue foam for this two parter as it’s a much tougher and more robust material.

Snug fit

‘10 parts silicon to 1 part accelerant’… my silicon mixing station. It’s not the easiest stuff to work with and can make quite abit of mess (or maybe that’s just me).

Lots of bubbles are created when you mix the silicon with the accelerant and in this case some green dye. You therefore have to ‘de-gas’ the mixture in an air pressure chamber. The pic shows the bubbles pulling the mixture to the surface of the container. It’s basically like boiling a pan of water - you have to keep an eye on it and make sure you release the pressure as it reaches the brim, otherwise it’s game over man.

With the skeleton sitting safe and sound inside, the mould is clamped and the silicon is poured into the top. The pressure from the clamps helps to stop the material from ‘flashing’ - seeping through the join of the mould.

I drilled three outflow holes at the base of each of the badge’s toes. This is so I can make sure that the material has passed throughout the mould and has not got all clogged up near the top. When I was sure it had made it’s way through (i.e. it’s visibly draining out), I plugged the holes with some nylon rod.

Next day… the silicon has definitely set so it’s time to crack the thing open…

… which proves to be bloody hard work. I have to make use of a chisel as i’m no Geoff Capes.

Say hello to my little friend.

Needs some cleaning up but pretty pleased with this attempt.

From the rear. It did flash abit even with the clamps - note the thin layer of silicon around the toes.

It’s a bit rough and ready but it proves the process can work. Chuffed to mintballs… as they say.

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