DIY Heat Treat Kiln Project - Score !!

[Vermillion]

In what little bit of free time I have had lately, I have been experimenting with 410 Stainless. I own a small Majestic propane knife kiln I purchased off Ebay, which will do small pieces up to about a elbow or knee cop. But thats about as far as I can go.

A new computer controlled kiln can run from about $3,000 up to $7,000, and the really nice industrial units can go up from there

I have seen quite a few old Pottery kilns on Ebay, but these are typically "pick up, no shipping" and I have never seen one in my area. So go for as little as $200-$300, but need work.

I have known for years that my Aunt had a Pottery Kiln since the mid-70s, but she hasn't used it for a very long time. It has literally been stored in a Barn. I had no idea what condition it was in. Everytime I mentioned it, she pretty much ignored me/blew me off. Last week I decided to ask her again and to my suprise, she has agreed to a "long term loan".

SCORE !!! It is a Paragon A88B from the mid 70's and needs some serious reconditioning. It is big enough to do helms or even breast/backs.

http://www.paragonweb.com/A-88B.cfm

So I plan on reconditioning it, and adding a digital temperature controller.

I'm taking pictures so that I can share the project with the archive.

More news later.

[Kenwrec Wulfe]

I just recently went through this myself. I had a kiln that I wanted to add more temperature control to, so I replaced the coils and added a digital temperature controller and high-temp thermocouple.
Ended up completely rewiring the entire thing with new coils, wires, digital controller, switch, thermocouple and SSR. I have an old 70s 5 coil GARE kiln. If you run into any issues, let me know. Would be happy to help.

[Johann ColdIron]

Nice!

I still lament not picking up the pottery kiln I saw in a local thrift shop...for $50.

[whonew]

Hey! What controls [digital?] are you using? I have 2 pottery kilns sitting waiting to updated for heat treating.
Les

[Vermillion]

Guys, I've started a blog at http://verms-projects.blogspot.com to document what I'm doing (figured it was easier than building a webpage).

Kenrec, Nice ! I'll keep you in mind. I'm an digital control engineer by training, but work more day to day as a computer engineer. We'll see how much I remember ! Did you use a single SSR on the nuetral leg of the 240v, or did you use two of them ( 1 on each leg of the hot side).

Reportedly, on mine the upper two elements are not heating, but the lower two are working. It might be a bad switch or connection in the controller box. I'm presently building a new floor plate (mine was rusted completely out) and some kiln cement to be delivered so that I can repair the physical damage before I start screwing with the electricals. Not to mention I still have to wire up 240v service to my garage.

Johann, you'll kick yourself for a longtime on that Hell, you could have sold it on Ebay for more than that. I've been searching for 4 years for a reasonably priced kiln that I didn't have to drive 500 miles to get.

whonew, I bought the individual parts from this seller on Ebay. http://stores.ebay.com/coldfusionxelectronics
You can buy a complete set from this seller for $60
http://www.ebay.com/itm/PID-Temperature ... 1c253cb821

I spent about $25 more, but got a slightly upgrade temp controller, a 90Amp SSR (instead of the 45Amp in the kit), and I purchased a heat sink as well. The kit does not have a heat sink, but I would highly recommend one. Reportedly these cheap chinese SSR's can overheat and catch on fire, so its always better to buy one that is rated for more than you actually need, use a heatsink, and mount a computer fan in your controller box. I saw some posts from one guy who built a temperature controller for his hot tub. It overheated and almost burned down his house.

Whonew, if you don't have training/experience with 240v circuits and control circuits, I would recommend finding someone who does to help you. 240v's can kill you easily and if you wire up a circuit wrong you can burn your house down.

[Kenwrec Wulfe]

Kenrec, Nice ! I'll keep you in mind. I'm an digital control engineer by training, but work more day to day as a computer engineer. We'll see how much I remember ! Did you use a single SSR on the nuetral leg of the 240v, or did you use two of them ( 1 on each leg of the hot side).

I just used one SSR. The kiln is a 240v, 30a, so I used a 60a SSR (yea, I overengineered...) on one of the 2 hot lines (the kiln was wired with 2 hots and a ground, no neutral...)... I also made my own aluminium heatsink for the SSR.

I was thinking about building a new kiln from scratch at some point for my next kiln and using a mercury switch instead of an SSR, simply for the life of the switch. Given the number of interactions that occur with a kiln, the SSR will likely die after a couple/few years. My big concern with the mercury switch is the heat from the kiln. It only gets up to about 120* or so in the housing, and I would have fans set up to cross-vent, but mercury is partitularly tempermental ( ) with heat.

[Kenwrec Wulfe]

whonew, I bought the individual parts from this seller on Ebay. http://stores.ebay.com/coldfusionxelectronics
You can buy a complete set from this seller for $60
http://www.ebay.com/itm/PID-Temperature ... 1c253cb821.

I bought from the same guy.
I have that controller. It is a chinese made controller and the instructions for it kinda suck. It looks like they were a direct translation from chinese, rather than an intuitive one. Despite the instructions, it is a nice controller. Once you understand the settings and what they do, the functionality is quite detailed and specific.

[Vermillion]

kenrec, you probably know this already, but the old style connector with no nuetral will not pass inspection if on you have to have one for some reason. Just a friendly FYI


Mine is a 240v 45 amp which is suppose to have 8 gauge wire, which is impossible to find so far withoit spending a fortune. I need about 50 ft to wire my garage and at 4 to 5 dollars a foot is steep

[Swamp Stick]

I was thinking about building a new kiln from scratch at some point for my next kiln and using a mercury switch instead of an SSR, simply for the life of the switch. Given the number of interactions that occur with a kiln, the SSR will likely die after a couple/few years. My big concern with the mercury switch is the heat from the kiln. It only gets up to about 120* or so in the housing, and I would have fans set up to cross-vent, but mercury is partitularly tempermental ( ) with heat.

Building an electric kiln from scratch is a PIA from what I understand. You destroy router bits and routers in the process. Making the ends (lid/bottom) is not easy. K23s are at least $4-5 each in the quantities needed to make a kiln the size you will want. I would not want to experiment with $100+ worth of brick per end just to try and learn how to do it. Learning how to wet the bricks and just how much thinset to use takes a bit of experience. I'd talk to Olympic up in GA and ask how much for a "shell" or at the very least the lid and bottom (basically the same thing).

I ran two custom 36H x 23W zone control kilns for years. These kilns probably fired 150-200 times a year so they got ridden hard and put up wet. Each kiln had 3 temp controlled zones, so that is a total of 6 SSRs between the two kilns. I did not have a heat sink on them either and never lost one. Now I was running two hot legs out of three phase (208v?) instead of 240v. That should not make a bit of difference to the number of times the SSRs cycle though. I did fry two boards though and if I ever pull those kilns back into duty (probably), I will be removing all of the electronics off of the kiln and making a control box that mounts on the wall next to the kiln. I would encourage you to think about that concept if you have concerns about how hot the electronics are getting.

I can't comment on the mercury switches, I am unfamiliar with them for use in industrial applications. I just know them from the old AC/heat switches, and I expect that is a different animal.

You know for being an over glorified light bulb sometimes these things are a pain in the fundament. I still have not figured out a way to keep the elements from burning through right at the cable/element connection every year or two. Easy fix until you run out of slack/extra and have to take a torch to unwind some element just to get more slack (while trying not to break it!). That always happens when I have a deadline for some reason.

Bjorn

[Swamp Stick]

Vermillion, we had twin 100'+ runs of 6 gauge installed and inspected. So yeah, that gets pricey. I would like to point out that if you can ground out your permanently mounted throw switch properly (which I highly recommend having one even if you have a wall plug) you can get away with 3 conductors instead of 4. That helps with the cost some.

Bjorn

[Kenwrec Wulfe]

I was thinking about building a new kiln from scratch at some point for my next kiln and using a mercury switch instead of an SSR, simply for the life of the switch. Given the number of interactions that occur with a kiln, the SSR will likely die after a couple/few years. My big concern with the mercury switch is the heat from the kiln. It only gets up to about 120* or so in the housing, and I would have fans set up to cross-vent, but mercury is partitularly tempermental ( ) with heat.

Building an electric kiln from scratch is a PIA from what I understand. You destroy router bits and routers in the process. Making the ends (lid/bottom) is not easy. K23s are at least $4-5 each in the quantities needed to make a kiln the size you will want. I would not want to experiment with $100+ worth of brick per end just to try and learn how to do it. Learning how to wet the bricks and just how much thinset to use takes a bit of experience. I'd talk to Olympic up in GA and ask how much for a "shell" or at the very least the lid and bottom (basically the same thing).

I have heard it is not the easiest process, but it is something I still want to do at some point. I have this DIY bug that I just cant shake, and after rebuilding the one I have, I want to improve upon that and just build from scratch.

You know for being an over glorified light bulb sometimes these things are a pain in the fundament. I still have not figured out a way to keep the elements from burning through right at the cable/element connection every year or two. Easy fix until you run out of slack/extra and have to take a torch to unwind some element just to get more slack (while trying not to break it!). That always happens when I have a deadline for some reason.

Bjorn

In the old coil wiring, and when I did my more recent rewire, the coil termination was located just inside the outside edge of the K23 brick wall of the kiln, where it does not get as hot as the rest of the coil. I have never had one burn out at the termination point. every coil I have had go bad has been at some point within the kiln where the wire is repeatedly heated and becomes brittle.

[Swamp Stick]

Because I want to is a good reason!

While I have had many burn out inside the kiln on old beat up kilns from the wires sagging and then shorting against each other, I'm talking on the outside of the kiln right at the connector where you are talking about. I suspect it is from galvanic action and fumes from the kiln. It takes years to happen, but I usually get one every year. Not really a big deal most of the time, but it always seems to happens when I need stuff yesterday. I often have to abort the firing and "loose" a day. Grumble grumble, grouse grouse!

Bjorn

[Tom B.]

As discussed in this AA thread making at least one 120v and one 240 volt digital controller are on my to do list.

Take a look at the thread I linked to above it has some good discussion and a few good links.

Tom

[Jurgen]

I wouldn't expect an SSR to wear out if it is properly heat-sinked and not run near its maximum current. I'm guessing the SSR I used for my kiln is probably over 1000 hours of kiln run time. I'm running it at about 70% of rated current, with minimal heat sinking.

Jurgen

[Kenwrec Wulfe]

SSRs have moving parts and so will wear out....its not an if, its a when. Everyone I have ever seen has been rated to a certain number of cycles and after that is when it fails. Most I have seen rate over 1,000,000 cycles, but if you figure that you are having a cycle as often as every 1/10 of a second to a few seconds...that is a helluvalota cycles per use of your kiln.

That is why I am looking at a mercury switch. They are usually rated to 100 times the number of cycles as an SSR.

[Vermillion]

Most of my parts have come in now, and my family is going to the beach next week without me (my job sucks). So I should get some work done and I will post some updates and pictures.

[whonew]

anyone have a wiring dia. for adding a new/digital controller to an older kiln? Or does the new controller come with one?
Les

[Jurgen]

SSR stands for solid-state relay. It has no moving parts. If you don't overstress them(too much current, resulting in too much heat) they will last longer than a mercury switch or a mechanical relay by a long shot. Given my run time and mine is easily over 2 million on/off cycles.

Jurgen

[Albrechtthesilent]

Sorry to thread jack; but since it looks like you guys know your $h!t about these controllers, can they be set up to ramp down such as for annealing? Most of the time the descriptions on kiln controls mention the ability to be programmed to ramp up (which seems to be what the market is concerned with), I was wondering if they could be programmed to ramp down too.

I'd like to be able to throw some pieces in the kiln which (for example) are work hardened, plug in the program, turn it on, and continue work the next day on the pieces. I think that'd be a handy feature. In larger pieces that tend to warp during heat treatment, it's be nice to anneal them before treating them to help address warping, and hopefully reduce or eliminate it during the treatment. I also (at some distant time in the future) would like to just try re-tempering aluminum just to see if an acceptable level of temper can be done in a non-professional environment.

Thanks,
Albrecht

[Jurgen]

Generally they can ramp up or down with or without hold times between stages. More expensive controllers tend to allow more stages to a firing cycle so you can perform more complicated cycles.

Jurgen

[Vermillion]

Whonew, that is tough as it will be individual to each brand and type of kiln.

Typically you will have two wires providing power to the controller, either 12 volts DC or 110/120 volts AC. n youill have two wires to a Type K thermocouple, which is your thermometer. Then you have two wires to your solid state relay or SSR, which is the on off switch to the kiln. Where the SSR goes into the existing wiring ( in series) is what would be different from kiln to kiln.

What brand and model kiln do you have ??

[Baron Alcyoneus]

If temperature affects the SSR, couldn't it be mounted further from the kiln, or insulated from it a bit more?

[Jurgen]

You don't generally mount the SSR on the kiln itself. SSRs produce about 1 watt of heat per amp of current they are controlling due to losses in the semiconductors. That is the heat you need to get rid of.

[Tom B.]

anyone have a wiring dia. for adding a new/digital controller to an older kiln? Or does the new controller come with one?
Les

try this link I think there is a diagram there.

Tom

[Kenwrec Wulfe]

SSR stands for solid-state relay. It has no moving parts. If you don't overstress them(too much current, resulting in too much heat) they will last longer than a mercury switch or a mechanical relay by a long shot. Given my run time and mine is easily over 2 million on/off cycles.

Jurgen

I was thinking electromechanical.... you are correct. Sorry for the blunder.