I have a chance to pick up an old front loading Paragon kiln, 110 V rated for 2000 degrees, for $100. All it has in terms of controls is an on/off switch. What would I need to add to make it useful for heat treating? I'm thinking a thermocouple and some kind of controller? Can anyone be more specific?
Kiln construction/upgrade?
- Thread starter jkf96a
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JRNP
Well-Known Member
Sounds like a great deal! But you will need to spend a little more money to get it right. For bare minimum you will need to get a thermocouple (k type $5 maybe), a process controller capable of displaying temps in our target range ($60-$100 Allied electronics Automation direct ), and a heavy duty relay (I prefer solid state $20-$30}. This will give you good control of temperature but you will not get the multi stage ability of the kiln controllers. Honestly I have an evenheat with the rampster controller and never use more than 1 step any way. Most of the process controllers have ramp control and alarms built in so you will have more than enough control. If you need a wiring diagram you can PM me and will draw some thing up for you, this my area of expertise
JRNP
Well-Known Member
You might want to think about installing a door switch to turn the power off when you open the door just in case. You will also appreciate having a rack that holds the blades in a stand up position. Tracey sells one that does a good job. BY the way a spare TC is a good idea.
Any advantage to buying a ramp controller, which costs about 2.5 times as much as the standard PID? What could I do with it that I couldn't do with a regular PID and a watch? Also, specify a "heavy duty" SSR... 25 amp, or bigger? It's a 110 volt oven, don't know how many amps it draws, but I'd guess only 15 to 20.
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JRNP
Well-Known Member
You have done your research!2thumbs I see no real advantage to the ramp controller in knife making but others may have different opinions on that subject. Its just a nice option, more useful if you play with glass or ceramics. By heavy duty I was referring to industrial type mechanical relays generally referred to as contactors witch are just very beefy mechanical relays. As for the SSR 25 Amps will plenty big because you are not likely to have a 110V circuit capable of more than 20 any way. The SSR is quiet and will out last the Mechanical relay many times over as long as it is not over heated. I can not be sure what your heater will draw but if you use a mechanical relay be sure it is rated for a greater amperage than the heater. Have got any pictures of the new toy I am curious to see what you've got there.
Got it all in hand. Turns out it's more of what I'd call a "cup kiln." Front loading, relatively square interior, about 7 inches square. Really too small for most of what I want to use it for, but it will work for several styles of blades I make. Got the PID, SSR, and thermocouple in the mail today, haven't tried to hook it all up yet. My brother tested it, and it works. He heat treated some 1080 blades with it, just using the color to judge temp.
JRNP
Well-Known Member
Tutorial
Sounds like great material for a tutorial! I know its not knife making but others might be interested in building a similar controller for their own home made ovens. Make a parts list and take few pictures to post in the tutorials forum.2thumbs I am exited already and its not even my toy.
Sounds like great material for a tutorial! I know its not knife making but others might be interested in building a similar controller for their own home made ovens. Make a parts list and take few pictures to post in the tutorials forum.2thumbs I am exited already and its not even my toy.
JRNP
Well-Known Member
Ya that reminds me, I should give one more word of advice. FUSES!!!
You don't want to buy those parts again.
JRNP
Well-Known Member
The circuit breaker will protect the heating element and the SSR but a 20 amp fuse wouldn't hurt between the line and the output side of the SSR. I would highly recommend putting a small fuse between the line and the PID. Maybe 1 amp just to make sure that a short or a wiring mistake doesn't ruin your day. The input for the SSR should also come from after this fuse. This will ensure that when a part fails and some day one will, it will not damage any other parts.
Got it up and running. Heat treated 6 blades a couple of nights ago. The PID was keeping the temp within about 10 degrees plus or minus of 1450. Haven't tried anything other than the default program on the PID, and haven't tried higher temps yet. I did use it to temper a blade at 450 for nearly two hours, and it held +- about 20 degrees at that range, more fluctuation that I'd like to see.
JRNP
Well-Known Member
Try checking the set up on the controller, some have adjustable tolerances or ranges. You may need to do some tuning. Another thing to check is your insulation, if it has any cracks or the door does not seal properly you will lose heat very fast. You could also try adding some mass to kiln when you are running it. Try using a hard fire brick in the oven and the extra mass will help buffer the temperature changes. Last thing to check would be the thermocouple placement. if it is to close to the heating element or the door you will have problems The best place is usually at the center of the kiln at the top and should protrude into the kiln a little. If it is touching the brick or even to close to it you will get fluctuations because the brick will be slow to heat and cool.