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Old 12-10-2012, 07:53 PM
Chris Marriner Chris Marriner is offline
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Join Date: Apr 2012
Location: Palmetto, FL
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re: Crucibles and wire melters

Pete -
The horse is on it's way - but fear not!!! I forgot to mention the controller... 3 button Orton - programmable up and down... I have it programmed up 75 degrees per hour - so hopefully the 30degrees isn't a problem... and I missed the soak at 1100... (Fingers crossed - I will build those in for future firings) (See the ramp I'm using at end)

The pyrometer was only to see how well the inside of the crucible was heating...
The thermocouple for the controller is in the "firing chamber" with the elements - so I'm guessing that it won't read the same temp as inside the crucible... until it reaches that stabilization point... Glad to hear it has no insulating properties - and the difference between reflective and latent heat... sounds normal.

Elements are recessed into a t slot in the brick to hold them in place without pins or insulators. The crucible is approx 1.5" from the elements... a little more in the corners of the octagon...

Should there be a gap to allow the heated air from the elements directly into the air space where the crucible is?? or is minimal gap better to reduce the work of the elements??

Melting Spectrum System 96... I know... but it's what I had...

Another thing I'm worried about is heat loss when opening the port to gather... but I guess once the crucible and the glass reach the magic temp - that it will probably retain heat pretty well and its only a few seconds per gather...

75/hr to 2200
hold for 4 hours
down 30/hour - 2000 for squeezing
hold 2.5 hours
up 50/hour to 2125 - working temp...
Indefinite hold... Then I can switch programs to cool down...

Then a separate program for cooling at 50/hour after scraping the pot. Do I need to slow around 1100 on the way down??

I just popped the lid to take a peek and the glass is getting soft!! (and everything still looks intact!!!)

SORRY FOR ALL THE QUESTIONS!! and thanks for the SPEEDY answers.

Originally Posted by Pete VanderLaan View Post
It sounds like there is no controller on the furnace which makes it really dicey. The pot should be brought up at 45F per hr until you hit 1000F and then hold for four hours. Then go to 1100F over four hours and then hold at 1100F for four hours. Then go back to 45F per hour until it starts to glow. Then just turn it up.

It sounds like this particular horse has already left the barn.

Electric furnaces have thermal planes, there's no way around the fact. It's part of why I like it turned up slowly. The pot has zero insulating capacity. You are just seeing reflective heat versus latent heat. You don't say how close the pot is to the elements. Too close is bad. I like about 1.5 inches clearance.

In my opinion, Trying to run a furnace with a pyrometer is a recipe for trouble.
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