Open wagons from homemade resin castings
- Thread starter ge_rik
- Start date
Never come across the air-blowing idea before.... I used to cast a lot of resin (mainly filled polyester rather than urethane) as part of my wargame model business, but gave the resin side up a few years ago to concentrate 100% on the metal side of things - much faster and easier; resin is a messy, slow and unpleasant business.
In my experience there are three basic ways of removing bubbles - vacuum, vibration and poking! Last first, if you are casting in a transluscent resin and you can easily see the parts of the mould where air gets trapped, just prod around in the poured resin with a length of wire and you'll get a lot of the worst bubbles out. This is the easiest and least equipment-heavy method for small amounts of home casting.
Vibration can be used, with the filled mould placed on a shaker plate, but the most effective is vacuum - for which of course you need a vacuum chamber and pump. Some manufacturers do the reverse, and use pressure rather than vacuum to force the resin into every nook and cranny of the mould, but this generally needs bigger and more expensive equipment.
My method of choice for small to medium production runs was a vacuum chamber, with the resin vacc'd twice - once after mixing the filler into a bucket of resin, to draw out all the air that you've trapped in the mixing process, and then once again with the filled moulds to get rid of any bubbles trapped in fine detail.
Jon.
Never had much trouble with bubbles using polyurethanes. My mix was the consistency of milk and any bubbles just floated to the surface were they usually popped or could be encouraged with any old object.
