Sunday, March 23, 2014

09 Plaster Production Molds Nº 6

One of my very best plaster molding tools is a molding table vibrator. I made mine from a used AC Electric Motor that I found at a flea market for a few dollars many years ago. I used machine bolts and nuts to attach it to my plaster molding table. I plug it in to turn it on, and I unplug it to turn it off. One day I may even make an on/off switch for it? Click on any image to enlarge it.

It is not a very big motor. The black body of the motor is about 5 inches long, and it is about 4 inches in diameter. What makes it vibrate is an eccentric disk made of steel, attached to the shaft. The disk was made from a piece of 1.75 inch diameter scrap bar stock, found at a salvage store. It is about 1/2 inch thick. A friend with a drill press made the hole. The hole was drilled off-center. This is what makes the table vibrate when I am pouring plaster.

This is a diagram of the disc with the eccentric hole. The more off-center the hole is, the more it vibrates.

Once I mix my plaster, and right before I pour, I turn on the vibrator. I turn if off after filling the mold. Using this vibrator, I hardly ever see any air bubbles next to the patterns in my molds. The plaster is vibrated as it is poured, and fills in all spaces. I always seal around all edges of the coddles with clay when using the vibrator.

Another way to vibrate a mold is by tapping it with a small hammer, or other stout object. Once a mold has been poured, patting the top of the plaster with the flat of my hand can also release air bubbles.

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