So why all this? When casting resin in a (RTV) silicone mould at room pressure it seems you're up against mainly one problem: Bubbles. You'd do anything to get rid of them. From complicated vent systems in the molds that i've seen to the nice thingy below: A vibration table that will shake out the dreaded little bubbles.
The LEGO construction you see on the table is there as a test object - it will be used as a box to pour the silicone in (THIS WILL NO HAPPEN ON THE VIBRATION TABLE! ITS REALLY ONLY MERELY A PLACEHOLDER THERE). After the silicone mold has vulcanized(?) and is ready to be filled with liquid resin to cast it is placed on the table, the resin is poured and then the table is switched on.
I've tried to put a little work in the construction of the table, yet still keep it a quick hack. I have not yet acquired a jack for the power, so currently i'm holding the wires on my power connector manually ;>. This WILL be changed ;P.
As for the construction, its a simple rectangular frame which is miter-joint for extra stability and better looks ;P. The wood used is some cheap three-layer composite material sourced in the waste-bin of the local DIY-store.
Additionally i have mitered the top edge and the edge of the "floating" table plate.
This allows for more play for the table and thus a larger range of weights that can be put on it without restricting the vibrational ability...
The "Floating" construction is made using pull-springs in each edge:
On the frame side they're simply hung on simple wood-screws...
On the table-plate side they're mounted using a long screw driven through the plate itself. The mouting ring of the spring is then fastened between two hexnuts.
For the vibration mechanism itself we went for a old computer fan that has been stripped of ... nearly everything. I've preserved a few struts to mount the motor on. To create a imbalance large enough to vibrate a big block of silicone i've glued a large screw to the outer runner of the motor and added weights (hexnuts) until i was satisfied. The position and weight of the nuts can be used to adjust amplitude and frequency of the vibration.
For fastening the motor on the table i've gone the simple way and clamped the struts of the frame between two screws.
Nice jack and switch to come ;P.
So, how good does it work? To be honest - I DONT KNOW! We haven't got the resin and silicone yet, so i can't test. But the basic principle is there, and it vibrates nicely. Check out this bad, crappy, short video for a functional test using ~1L of water ;P.
I'm really looking forward for the rest of the equipment to arrive so i can test the construction ... and hopefully report back with more ;P.