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Assignment: design and make a 3D mold, and produce a fiber composite part in it.

After working with composites passionately during a week, we present to the rest of the class our experiences and insights. But this time was different. We need to pass Neil's test. Hold up with both hands your masterpiece — this composite thing you created with love, sweat, blood and tears, and without thinking twice — and slap it against something harshly, with anger. It should endure the hit.

How much suffering and anguish in so little time. Somebody had to stand up and say something.



password: fab

:-)

The design is the first step of this assignment. In my case, the shape doesn't need to be really complicated, just need to have space inside enough to "hide" the electronics.



Once the design is done, I sit down with Ferdi, our jedi master (aka instructor), to prepare the G-code I need to mill the piece using the Precix. I am going to use high density foam as a material for the mold. The features of the design let me mill using only a roughing strategy, using a drill with a flat end.



This is the resulting piece.



Next step is to produce the fiber composite part. I prepare a working space and I gather all the material I am going to need.

list of material used: — thin sheet of protective plastic, similar than the one that you use to protect a room while you are painting the walls — an special plastic with tiny holes on it — roll of plastic used in the kitchen — breathing textile — fiber/fabric — epoxy — containers for the mixture — stick of wood as a spatula for mixing — protective gloves — the mold

I cover the table using the plastic that comes in a roll, to keep the mess under control. Put the gloves on.

Now it is just about layers of materials. Protective plastic, special plastic with holes, mold and kitchen plastic. Time to mix the epoxy. 50% - 50%. Spread the mixture over the fiber generously. Put the one layer of fiber with epoxy on the mold, and the second one with the direction of the fibers perpendicular to the other. A layer of the holed plastic, the breathing textile and other sheet of protective plastic. And we put the sandwich inside the vacuum.

In this moment, the instructors tell me that I need to put some material around my piece if I want to reach the inner edges. I use some leftover pieces of foam.



It need 6 hours to dry and harden.

I had a leak of epoxy in one spot.



This is the resulting piece.



Some close ups for the imperfections. Accumulation of epoxy, wrinkles, leaks...



It is a tricky technique, but I am sure that using a counter mold would help to get better results. The high pressure inside the vacuum rounded the corners of the mold.



I cut the surplus material, and that's it.



Now it's time to do hack some electronics.

I bought a sound machine like this one, but with "f" based profanities. The plan is hack the machine to activate certain sounds when the composite piece is hit. Because I don't have so much time, I am going to use an Arduino with a breadboard for the connections. A piezo to detect the hit, and transistors to substitute the pushbuttons of the machine and activate the sound through the Arduino. Because the machine has male and female voices, the idea is to put cables for the two voices, and maybe using a switch, change the gender of the composite.



I made a selection of 4 expressions for each male and female voices. Depending the threshold of the hit, activate a certain sound. Three levels of agressivity, and an extra expression when you hit the composite several times in succession.

	level 1	level 2	level 3	after a bunch of knocks
female voice	what the f*ck!	f*ck you!	for f*ck's sake!	unf*ckingbelievable...
male voice	f*ck off!	f*cking hell!	now we're f*cked...!	oh... go f*ck yourself...

When I start hacking the toy, I realize that the circuit is more complex than I expected. It's something similar than the Charlieplexing thing that Neil's explain us during the output devices week. With the countdown running, I decide to make it work one sound at least and try to assemble everything.

I put everything inside the composite piece. The Arduino is powered by a 9V batt. I close it with a laser cutted piece of transparent acrylic, and done!

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