On 9/27/2013 9:27 AM, Erik Friesen wrote: > Has anyone here done much polyurethane resin pouring? I have been trying > to fine tune the process. Current process uses silicon moulds. > > #1. Does it work to use aluminum moulds? > > #2. Could it work to use high vacuum to eliminate air bubbles? I would > envision using some type of fill funnel and a pulling a full vacuum, then > opening the entrance to the funnel with some type of rod/oring seal. > > The current material I am using sets in about 10 minutes, the gel time is > around 50 seconds, so its all static mixed.
I do quite a lot of it in silicone molds. http://partsbyemc.com/catalog The process I use for both casting the resin and the molds is to do it in a pressure tank. The pressure forces air into solution from which it cannot escape once the resin or silicone is cured. Pressure also pushes the resin and silicone into every tight corner, which simple casting often fails to do. I've tried using vacuum on the silicone and resin before casting it but still got bubbles. Silicone tends to get small bubbles just beneath the mold cavity surface, mostly on vertical or nearly vertical areas. When using quick gelling and setting resins, vacuum is too slow. Can't get the air out quick enough to have time to pour it. A basic pressure casting setup can be had for around $200 using a pressure pot (for painting) and a small compressor from Harbor Freight. Unscrew the pickup tube from the underside of the lid, remove the paint outlet on top and replace with a pressure gauge. Don't do anything with the pop-off valve that's already installed. Install a 1/4 turn ball valve between the regulator and the lid and you're done. 60 PSI is high enough. For small castings as low as 40 PSI will work. I have several tanks from a small one from Harbor Freight up to a 24" diameter by 30" tall one. A short overview on how I make silicone molds. http://partsbyemc.com/pub/mold-making.htm That's the process I developed over time, after starting out using other methods that were more difficult, took longer, and didn't produce the quality of castings I needed. Shiny surface corrugated cardboard, a hot glue gun, a very sharp knife, a Dremel with cutoff wheels and ogive and cylinder shape grindstones, a pressure pot and an air compressor are all the tools one needs to do high quality urethane resin castings. What has been done by some with vacuum is to place the mold and resin into a vacuum chamber then remotely pour the mixed resin into the mold. With next to no air in the mold cavity the resin should flow into every tiny corner and crevice. It'll also more easily flow into the tiniest gaps between the parts of the mold. ------------------------------------------------------------------------------ October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60133471&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
