This subject was published - more extensively - in Modelspoormagazine nr 55.

Air-bubbles are often the cause of bad resin castings. Especially when using multi-part molds this is a severe problem. The risc is reduced with this vibration-tool.

Small air-bubbles are hard to avoid. When mixing the components of resin, air is trapped within the mix. Shaking the mix lets the bubbles reach the surface. Vibrating the mold with its setting content is the best way to do this.
As I sometimes use double-sided molds, a vertical clamp is nescessary. This is integrated in the device

The drawing shows the construction concept. Its dimensions aren't very important, the pieces of scrap MDF I had determined the size of the tool.
As the toll should vibrate freely, a suspension was constructed using some springs and rubber placeholders I found in my drawers.

The fixed part of the clamp is glued and screwed at a straight angle. The clamp inside should be flat, so screws must be sunk flat with the wood surface.
The moveable part of the clamp is composed of two sturdy L-shaped profile pieces. We drill two corresponding holes, in one profile wide enough to let an M5-bolt move freely through it. In this profile, we also drill two smaller (3,2mm) holes. The other profile is tapered to hold an M5-bolt and two smaller holes are drilled in its bottom part.

The small holes of the first profile are used to drill corresponding holes in two MDF plates, which will become a small and a large movebale clamp part. These holes should be sunk, so a pair of 25mm M3-bolts can be fitted without disturbing the flat wooden surface. These bolts are secured with two M3-nuts each.

Aligning the parts, the exact place for the fixed party of the clamp vise can be determined. Drill corresponding holes in the bottom MDF-plate.
The double vise is constructed of two M5-rods with corresponding nuts and one hand-vise nut (this isn't the correct name, I know, help me!)

Both profiles are now connected to form a double vise clamp. To secure the moveable part, a nut is glued to the rod using a drop of cyanoacrylate glue. the fixed part of the vise can now be attached to the wooden bottom plate using M3-bolts and nuts.

The device should vibrate freely, so we need a loose suspension. This is composed of a not to strong spring, a rubber placeholder and some small construction parts. This way each corner of the bottom plate is supported.

For the actual vibrating we use a small electro-motor. The excentric part is recovered from a piece of electrical connector. Its metal part is very suitable, as it has some M3-type holes in it. Fix it on the motor axle and try it out. It should vibrate enough, but the motor shouldn't heat up to much. Experimenting is nescessary.

This vibrator can now be fixed firmly underneath the bottom plate. A small adapter delivers its power. Be careful to construct it well: electricity can be dangerous.
Our device is ready to use. Use a gutter-shaped piece of cardboard to protect the clamp mechanism from spilled resin.