John in Oly, WA Posted February 27, 2017 Share Posted February 27, 2017 I finally finished my heat treat oven. Took a few months to pull all the research together, do a lot of head scratching to figure out the electrical circuits and other details, and then acquire all the parts and pieces and put them all together in the right order. Fired it up yesterday on it's initial oxidizing run. Took it to 1950F. My thoughts are to use it to melt metal for casting, as a burn out oven for the molds for casting, fire smaller ceramics in it, as well as heat treating blades. All in all, an interesting project. Quote Link to comment Share on other sites More sharing options...
Latticino Posted February 28, 2017 Share Posted February 28, 2017 Looks like you did an extremely professional job. Looks like you even have an SCR on your electrical circuit. Does the chamber maintain good stability at setpoint? I assume that you are planning on using it for melting non-ferrous metals. Most Nichrome wire heating chambers I've seen don't last long at the temperatures needed for steel/cast iron... Quote Link to comment Share on other sites More sharing options...
John in Oly, WA Posted February 28, 2017 Author Share Posted February 28, 2017 Thanks Latticino. Just don't look too closely at the welds or my sheet metal work. I don't have a brake, so I was bending the sheet off the edge of my table saw. In the initial oxidizing burn, I was a bit concerned as it reached the higher temps. At one point I watched the display go from 1798f to 1820f, back to 1805f, to 1792f, 1788f, 1796f, 1802f, then continue progressing upward again. it was set to reach 1945f and it bounced around from low 1940s to 1958f and back before signaling "complete" and returning to idle. I was beginning to wonder if my thermocouple was not functioning as well as it could be. I have no experience using thermocouples though, so I'll keep watching it and see how it does. It was also a "canned" cone fire to 04, so I need to look at the program and see if there were any built in plateaus that might explain it. The next firing, I'll set my own program to hit a critical temp and hold for a period of time to test the temp stability. You are correct, aside from heat treating blades, melting bronze, brass, aluminum, maybe venture into silver. The element is the Kanthal A-1 wire, but I don't see me casting iron or steel in the foreseeable future. Quote Link to comment Share on other sites More sharing options...
bobasaurus Posted February 28, 2017 Share Posted February 28, 2017 John, it sounds like maybe the D gain of your PID controller is a bit high... over-reacting to the slope of the temperature rise? I want to build one of these myself someday. Where did you get the insulated firebrick? Quote Link to comment Share on other sites More sharing options...
WoodnMetalGuy Posted February 28, 2017 Share Posted February 28, 2017 It's a ways from you, but I got some recently from Continental Clay in north Minneapolis, MN. -- Dave Quote Link to comment Share on other sites More sharing options...
John in Oly, WA Posted February 28, 2017 Author Share Posted February 28, 2017 Thanks Bobasaurus, I'll look into that. I bought the fire brick from Seattle Pottery. Fairly local to me so shipping wasn't too terrible. Look in your area for a pottery supply. Quote Link to comment Share on other sites More sharing options...
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