Hello Everyone I do not know if anyone in the forum has tried this before, but I intend to experiment with raw expandable polystyrene beads, and if anyone has tried what I am going to attempt, any input would be appreciated. Basically, my intended experiment boils down to this, I want to create eps patterns like the big boys, such as the auto makers, but I want to do it on a much smaller scale. Instead of creating and processing xps or eps patterns time after time, with a hot wire foam cutter and other various tools, I would like to create several rigid aluminum molds, and fill them with expandable polystyrene, and have the polystyrene take the shape and contours of the aluminum mold. After many hours of research into working with eps and xps, I came across this video, which leads to believe that it can be done: After watching this video, since the author provided no source for the raw materials, I went on a quest to find a small quantity of raw expandable polystyrene beads to experiment with. Once again, after many hours of research, I came across the Industrial Arts Supply Company, located in Minneapolis, MN. The Industrial Arts Supply Company sells raw expandable polystyrene beads in 5 lb. and 25 lb. quantities. The Winter 2020 catalog for the Industrial Arts Supply Company lists a price of $19.50 for the 5 lb. quantity and I believe this should be plenty enough raw material to experiment with. The Industrial Arts Supply Company and their catalog can be found here: http://iasco-tesco.com/ and the raw expandable polystyrene beads can be found on Page 43 of their Winter 2020 catalog. However the end of the catalog has a 2022 date included. Any input is welcome and appreciated. Bruce
Hi Bruce, I do like experimenting! Do the moulds have to be aluminium or could they be 3D printed? Lee
There is another discussion about this here and some pictures of successful castings made: http://forums.thehomefoundry.org/in...molds-to-make-eps-patterns-for-lost-foam.842/ Also, I think DavidF tried to get some of the beads several years ago to try something like this, but it didn't really work out. I seem to recall his beads were duds or something. Might have been before this forum existed, back in the alloyavenue days. If you have found a reliable source of good beads, that's great news! Jeff
It can certainly be done. If you haven't already, you should read this thread. http://forums.thehomefoundry.org/in...molds-to-make-eps-patterns-for-lost-foam.842/ After reading that thread, in short, you'll gather I don't think it is very practical for the hobbyist. If you want to make a lot of copies of a part, it merits discussion, but unless the part has complex coring and parting lines, you'd be far better off using a hard pattern and conventional sand casting because the effort to tool the molded pattern and control the pattern making process will far exceed what is required to tool and conventionally sand cast copies. Finding a source of raw pre-expanded material is problematic. It has a very short shelf life because the blowing agents quickly diffuse out and degrade the material. Commercial sources will be uninterested in providing hobby level quantities. Members here have reported the small quantity eBay sources that pop up from time to time deliver depleted material that won't expand 8/10 times. One member here had an acquaintance that used molded eps in a production business setting, but short of that, it's a tough problem for a hobbyist. You might join a duck decoy forum and search for sources there. A few of them mold their own polystyrene decoys but most buy them or use urethane. Best, Kelly
Lee - Most of the videos I have seen pertaining to eps talk about using aluminum molds. I suppose it has something to do with the thermal conductivity of aluminum, because steam is utilized for expanding the beads and I am sure it has something to do with the cooling as well. At this moment, I forget what the melting point is of PLA and ABS plastics, so I am unsure whether 3D printed molds would hold up. Jeff - At this point, I am uncertain of the quality of the beads, but for $20, I will take a gamble and at least try it. Kelly - As I said in my last response to you within the sand thread, I certainly respect your input. However, I am one of those stubborn, hard headed men, that likes to experiment, improve my experiments as I go along, and I am not afraid of failure, but I always strive for success. If it can be done successfully on a small scale, I am a man well suited for the challenge. I make miracles happen in my small and primitive workspace EDIT: That is providing I can gain access to some good raw materials as you pointed out.
I tried using aluminum filled resin for a flat backed mold. It didn't stand up to the boiling water and warped. Thinking about this new type of epoxy resin.. Heat cured it has a temp range to 350*f. all the other specs look good, 2lbs $60. EPOXACAST_670_HT_TB.pdf (smooth-on.com)
When I was a kid, like 60 years ago, they sold a toy the was aluminum molds with expanding plastic beads. As I recall the mold was installed in a frame that held it together and heated it. Made toy soldiers and tanks and such
Long ago, I worked for a contractor that made styrofoam coffee cups. His setup was making "cup makers" that popped out about 4 cups a minute, the more he made, the more they made. The machine used aluminum molds, opened and closed with air pressure. The molds had a water jacket, which used both steam and cold water. The beads took a bit of heat to expand. (they held boiling coffee, after all.) I don't know the exact temp. The beads were raw, about like sugar. You had to be careful with the stuff. If spilled, it could make concrete like ice!! We moved the beads with pvc water pipe and air, but it would gain a static charge which made it float in the air, climb walls and act alive. Used a vacuum to deal with spills. The density was controlled by how many beads were placed in the mold before steaming it. Linked timers controlled the whole process. I think a person could do it in a small shop.
I had one of those, it made rubber bugs too. Also had a Toy Foundry that would cast little metal airplanes out of Bismuth or some other "Special" low melt metal. But, I was way more dangerous with my Chemistry set. Way too dangerous for the kids today.
