With the New Year I am starting my mini electric kiln project and would be grateful for your recommendations or even guidance.
For the time being I am calculating how long and how thick heating kanthal wire I need. Preliminary results are, that I need 20 meters of kanthal wire of 1 mm (or 0.04") diameter.
This should support 1600 W input power and max. kiln temperature of some 2000°F. The kiln size is 3x4.5x12". Quite challenging is to calculate the diameter of the heating spiral so, that it can be accommodated in the side walls of the kiln. The heating spiral must be stretched so that its threads do not touch each other.
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Simultaneously I am considering suitable PID temperature regulator.
Jan
Please make two Jan. We want one as well. Used to make temperature cycling chambers using nichrome wire, a temperature thermistor and an 8032 processor to keep track of it all. What's the difference between kanthal and nichrome?
Thanks Mr. Scott, it is a very nice compilation of useful ideas.
(01-05-2018, 04:15 PM)EOU Wrote: [ -> ]Please make two Jan. We want one as well. Used to make temperature cycling chambers using nichrome wire, a temperature thermistor and an 8032 processor to keep track of it all. What's the difference between kanthal and nichrome?
Thanks for your confidence, EOU.
An explanation why Kanthal is a better heating wire than Nichrome is here
https://www.linkedin.com/pulse/why-kanth...jia-alloys
I hope it is correct.
Jan
Mr Jan, do you wrap the wire around a dowel or something to make an electrical coil? I can't imagine trying to manage 20 meters of wire...
Paragon sells coils, and they aren't expensive. I don't know what they're made of, but I believe the top end is 2200°F.
I have a couple kilns because nobody made one with coils in the ceiling when I bought my first, an Evenheat, which did almost everything except heat evenly.
My very good friend, Mr Ed Fowler has been the Paragon spokesman for many many years. I tried to bend every ear within reach to design a better kiln. Paragon finally did, about 1 1/2 years ago, and I bought the first one. It's so superior to anything else I've seen I can hardly believe no one had ever thought of putting coils in the ceiling. Makes all the difference in the world.
The problem with knife kilns comes from having coils on the sides and back wall, but the end with the door has none. Impossible to heat knives evenly that way.
With the new Paragon, it was shocking to see every speck of steel the exact same color. No matter what I tried, the old kiln could not do that.
here is another link
http://www.duralite.com/store/scripts/pr...roduct=108 they have elements in stock , a 115v 1600watt is $29. these folks and Joppa Glass also sell all the connector, rods, insulators, and such to make a kiln.
Mark:
For my second furnace I looked at lab furnaces rather than modified pottery kilns. i found a used one of these with controller
https://www.lindbergmph.com/light-indust...ox-furnace for a very low price. has elements top, bottom, and walls. the elements are embedded in special compound so they are not exposed to the air and can't flex. works fine. just need it to get above freezing here so I can go to my shop and use it.
Mr. Mark am Mr. Scott thank you very much for your input. Appreciated!
Mr. Mark, 20 meters (or 22 yd) of kanthal wire can be coiled to some 0.8 meter (or 0.9 yd) of closed heating element with the outside diameter of 10 mm (or 0.4"). The installed length after stretching is some 2.5 meters (or 2.7 yd).
For Kanthal A1 the max. wire temperature is some 2550°F but the max. kiln temperature is limited to 2350°F because the element in the groove is hotter.
The Web of Paragon Ind. is a very good source of information and inspiration. Mr. Mark I envy you that Ed is your friend. Please let me know what kiln model do you have? The idea to put the heating elements also in the ceiling of a narrow knife making kiln is new for me! Until now I thought that the heat generated by the elements in the side walls rises to the ceiling. I have to reconsider it carefully.
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Jan
Thanks a bunch, Mr Jan! Being an HEPK Mastersmith (actually the 2nd) under Mr Ed Fowler is a tremendous honor to me. I don't care about the ABS, they don't care about me, and they don't get my membership dues. I don't care about the knives they make, or what the ABS has come to stand for. Mr Ed Fowler was a Founding Member, directly under Mr Bill Moran, who not only directly Taught Mr Ed Fowler how to make knives, Mr Bill Moran Started the ABS with the help of his wife and Mr Ed!
My Paragon is a "220V 24" Double Barrel". It has 11" Inside width, with state of the art control, also wi-fi capable. I can heat treat anything, but I only heat treat knives I've forged. When I design a knife and have them waterjet cut, I usually get 150 blanks to grind. Brad Stallsmith, at Peters HT, heat treats M4 and S35VN for about $2/blade for 50 blades. They are Exactly to my specifications.
In actuality, the temperature difference at the top of the kiln to the bottom is negligible, even in brand x. The difference from front to back in brand x depends how close the tips of the blades are to the back wall. With a recommended distance of 1", the temperature difference is enormous. Judging by color, probably 200°F minimum, at 1500°F. Most guys don't harden their tangs anyway, but I sure do. Since I draw the whole blade, except for the edge, drawing the tang is nothing
Brand x lists outer dimensions, so they call mine 18" long, but interior length is about 13" total, with "usable" length of 12", but this puts the points of the knives 1" from the back wall coils. I've tried a 1/8" thick plate 1" from the back wall to act as a baffle. This does not work, and reduces length capacity by 2", because I still kept the tips 1" away from the baffle. Baffles are surprisingly ineffective in my experience.
I talk to brand x reps at the Blade Show every year, and it's like they've never seen their kiln in use. They told me to start with a cold oven, and set for low ramp. Like I said, it's like they know absolutely nothing. Nothing!
Really? Start with a cold kiln? So I have to wait several hours for the next blade or next cycle? Idiots. Everyone knows that's not just impracticable, it's dead wrong. Always start with your kiln at temp. The faster you can heat blades the better. That's why salt pots are much better, but they are expensive, take a lot of space, and they're very dangerous. Few people use them for those reasons. Induction heating is virtually exclusively Industrial, and the only other method I know of.
Paragon, on the other hand, shows Interior dimensions, so they aren't trying to fool anyone. Coils in the ceiling work PERFECTLY. There are coils on the sides too, but I don't think they make too much difference. I always made sure to rotate the knives on each heat cycle in brand x, because I know it has to make some difference when the blades are only 1.5" from the coils. With the Paragon, it doesn't matter, since it's twice as wide and twice as long. Height is the same. The price difference was negligible for me, but now the 2x bigger, 220V, much heavier duty, Paragon is about 40% more expensive. I don't know the price difference on similar size kilns, but brand x had to lower their price a Bunch. They still don't put coils on the ceiling anyway, so it's positively a no-brainer, unless you do small knives one at a time.
I never would have thought size mattered so much, but it's Very Clear now. The Paragon works perfectly, and I only use brand x for tempering. I don't mind if the tips are a point tougher (softer). I couldn't care less how much electricity it takes, I just want my knives exactly the same temperature when I'm running critical cycles.
I was totally blown away the very first time I used the Paragon. Seeing the exact same color from tip to tang was Shocking!
Mr. Mark, thank you very much for your detailed answer. You helped me to make further step in my decision about furnace design.
Jan