Brady Watson
08-29-2004, 08:42 PM
About a year ago I bought some USG Rayite 100 machinable media. It is a gypsum based hybrid powder that can be mixed and cast to the exact size you need. There isn't much info on the web about it besides USG's data sheets, so here's my experience with it. If I recall, it was about $110 for a 50# bag from a supplier in Ohio.
You have to weigh the water and powder before mixing. I needs to be exact. I used an old broiler pan that measured 9X12X1.5" deep. I waxed it with bowling alley wax as a release and poured the slurry into it. An hour later I flipped it and it popped out of the mold. I had it sitting out in the sun...but it was so hot that I could barely hold it. Smoke was actually coming off of it when I demolded it! They said to wait 3hrs before machining, so I waited 4.5 and carved it with an 1/8" ballnose. I drilled and screwed it to the spoilboard.
I realized that at a depth of 1", the material was not totally cured, although it was machining well. I think it is supposed to be that way because it did harden after being exposed to the air for 20min or so. It threw off a combination of small and medium sized chips. Not really dust...but not soap carvings either. It did machine as easily or easier than 15# foam. The problem is, as it mills the semi-moist chips will stick to the finish surface of you don't have strong dust collection. I had to use compressed air to unweld the chips from the finished surface. This is probably why USG recommends that you use fans or something blowing on the material while it is cutting. The once hard clay-like surface hardened pretty quickly.
The surface did show machining marks (expected) even at 10% stepover. They did buff down smooth with a scotch pad. The edges are crisp and the surface is solid except for 3 or 4 pinholes. You are supposed to vibrate the mix to eliminate bubble entrapment...I gave it a good tapping and most of the bubbles broke.
5185
5186
Here's my mug carved about 4X5" and 1" thick. I used Poser 5 to create the face, add the beard and scaled the Z down in Rhino. I used Millwizard for the 3D and PartWizard for the profile pass. Just goes to show that if you do your homework/research to find solutions and invest the time to learn, you can do some neat things on a budget with the right combo.
The surface is very hard now and it is also very heavy for the size. I imagine it is about 1 full pound. I think it is perfect for larger vacuum mold tooling and even machining masters for molding and casting parts. USG also makes Rayite 200M-S which is meant to be sprayed over a foam core, built up to thickness and then machined. The downside is you need specialized spray equipment to use it...I bet some experimentation with a drywall hopper gun would work if it came down to it.
I will be testing a 2 part liquid plastic next to see how well that machines. It looks promising so far, but I haven't tried anything other than hand machining with it.
-Brady
You have to weigh the water and powder before mixing. I needs to be exact. I used an old broiler pan that measured 9X12X1.5" deep. I waxed it with bowling alley wax as a release and poured the slurry into it. An hour later I flipped it and it popped out of the mold. I had it sitting out in the sun...but it was so hot that I could barely hold it. Smoke was actually coming off of it when I demolded it! They said to wait 3hrs before machining, so I waited 4.5 and carved it with an 1/8" ballnose. I drilled and screwed it to the spoilboard.
I realized that at a depth of 1", the material was not totally cured, although it was machining well. I think it is supposed to be that way because it did harden after being exposed to the air for 20min or so. It threw off a combination of small and medium sized chips. Not really dust...but not soap carvings either. It did machine as easily or easier than 15# foam. The problem is, as it mills the semi-moist chips will stick to the finish surface of you don't have strong dust collection. I had to use compressed air to unweld the chips from the finished surface. This is probably why USG recommends that you use fans or something blowing on the material while it is cutting. The once hard clay-like surface hardened pretty quickly.
The surface did show machining marks (expected) even at 10% stepover. They did buff down smooth with a scotch pad. The edges are crisp and the surface is solid except for 3 or 4 pinholes. You are supposed to vibrate the mix to eliminate bubble entrapment...I gave it a good tapping and most of the bubbles broke.
5185
5186
Here's my mug carved about 4X5" and 1" thick. I used Poser 5 to create the face, add the beard and scaled the Z down in Rhino. I used Millwizard for the 3D and PartWizard for the profile pass. Just goes to show that if you do your homework/research to find solutions and invest the time to learn, you can do some neat things on a budget with the right combo.
The surface is very hard now and it is also very heavy for the size. I imagine it is about 1 full pound. I think it is perfect for larger vacuum mold tooling and even machining masters for molding and casting parts. USG also makes Rayite 200M-S which is meant to be sprayed over a foam core, built up to thickness and then machined. The downside is you need specialized spray equipment to use it...I bet some experimentation with a drywall hopper gun would work if it came down to it.
I will be testing a 2 part liquid plastic next to see how well that machines. It looks promising so far, but I haven't tried anything other than hand machining with it.
-Brady