Friday, 2 March 2007

Resin Casting Tutorial: Part IV

(versión en Español)


One of the main concerns when considering resin casting is how to avoid bubbles in the resulting pieces. There are different techniques to help remove bubbles, some of them involving pressure changes. Either for degassing the resin in its liquid form and/or compressing it when is inside the mold, reducing the bubbles size.

Another method, that I personally prefer as I work with open molds (as you probably noticed, I do not build pour spout or air vents, we'll see why in the next part), is to remove bubbles with vibration.

Making something to vibrate is fairly easy. Just unbalance a rotating axle adding some excentrical weight. For doing this I just took an old computer fan, removed the case and blades and glued a nut on a side. Once the motor rotates, the small nut will make it vibrate. I then play with the amplitude of the vibration adding bolts of different lengths. Finally, I glued the fan to the tray.

To build the tray, I bought a cheap wooden frame and fixed the tray with four springs. This is to allow the tray to vibrate freely. I also built a box with polistyrene (I didn't had any wood at hand) and added a switch.

Here it is the final result. It can vibrate big molds like the one in the pic and get rid of more than 90% of the bubbles, although you'll need to remove some of them manually (this is why open molds are so convenient).

You can see below the mechanism working:

I suppose that I will someday build another table, with a more powerful motor and frequency and amplitude controls. But, for the moment being, this small tray does the job.

Next time, we'll see finaly how to cast. See you then!