2011 Christmas Ornament
I wanted to create something special for this Christmas. I actually created several things like the cookie stamps and a couple of Lithophanes. But this was going to be something I have never done before.
I have been mulling over the idea of using CAD/CAM for making casting molds. I have machined molds in aluminum for making pewter castings and have shown some medallions (they look like coins) over in the THMS Blog. What drove this project was I was originally thinking of using pewter for this project.
For one I started too late and I really wanted to test the concept by making a mold in wax first and using polyester resin. None of this have I tried before. This is the polyester resin version, so the pewter Christmas ornaments will have to wait for next Christmas. I already have some cool ideas for that one.
As you can see to the right I have completed 10 ornaments. These were just to be a learning experience and they were. But they didn't turn out too bad if I say so myself. Family and a few friends will receive these. Gloria has already claimed one for herself. I also have a white unpainted one shown farther down below.
All the finished ones received a coat of chrome paint , then a coat of Candy Apple Red.
|This is the rendering I produced in Vecric Aspire software. It is just a computer drawing but looks very realistic. I am not going to get into the detail about CAD/CAM/CNC. If I can draw it, I can make it... but there is a lot more to it that that.||This is the finished CNC carving done in the blue wax. It looks just the same as the computer version. One of my concerns was if I could produce a smooth enough surface for casting. EVERY detail will come through. This was the proof of concept. It worked OK!|
|I purchased the casting resin at Hobby Lobby. There are lots of sources on the web and If I get seriously into this work I have already determined my suppliers. I am thinking of machining positive models, then using silicon rubber to cast the molds. Watch for the fun later.||The mixture for this polyester (plastic) resin is 50/50 by weight or volume. I first used water to find out the mold would hold 15cc or ML of liquid. Here I measure 7.5cc of the part "B" ...or was this the one for my drug test?...|
|Next I poured 7.5cc of part "A" on top. The instructions say to use two measuring cups then mix into a third. Surely the best way but this isn't rocket science. This works fine.||After mixing with a popsicle stick for no more than a minute it turns crystal clear and is very thin.|
|Here you can see how thin it is and how easy it is to pour. Note too how clear it is. I don't always pour left handed but I did have to hold the camera.||Wearing gloves is recommended and I highly suggest they be used. I don't always follow best practice. Do as I say and not as I do. I did do a lot of hand washing but still no excuse.|
|About 5 minutes after the last picture you can see the cloud forming. It starts in the deep middle and spreads to the edges in about 15 minutes overall.||This is just to show the progression. Using an open back mold helps me see what is going on with this resin cure.|
|It has been 20-30 minutes after the mix. The shop and material is about 60 degrees so I am sure the process is much slower than it would be in hot weather. I am picking slightly ot the edge.||I can get a fingernail grab and peal/pop the casting out of the wax mold. The nice thing about wax it needs no prep for casting resin.|
|The casting is still a bit flexible but returns to its cast shape. In other words, bending and pulling the soft casting does not distort the casting. It already has a memory. I lay it on a granit flat tile and wax paper until it gets hard.||Still on the tile, sans the wax paper, you can see how smooth the surface is and how it picks up all the detail.|
|Here is is hours later. Just a solid piece of plastic that looks like it was bought at the craft store. That's kind of an insult but so true. There is not much reason make something that can be purchased because of mass production much cheaper that it can be made at home. This however is an original!||I sprayed Testor's Chrome paint as a first coat. Then after it dried I applied Testor's Candy Apple Red. FWIW, the Testor's rattle cans are junk. The shop is cool as I said, so I warmed them in hot water. The paint still came out like splatter paint. It was impossible to do a nice mist coat. I did my best.|
|The back is plain. When I do the pewter, I am planing on a closed mold with detail on both sides. Stay tuned (for about a year)...||Here are all ten finished just in time for Christmas.|