Kiln help please:)

kungfumo

kungfumo

Joined
Aug 21, 2006
Messages
533
Okie dokie I just got this kiln for free.99 from my paw, and I bought a few things to get it in order for in house heat treating:D

I know most don't like to use a kiln since it has such a large enclosure and will take forever to heat up. I turned it on its side so that it would not have to be loaded from the top. I think I may have solved the large capacity problem by filling it half way with kiln bricks?:confused: I will raise them off of the bottom so that it doesn't interfere with the elements. Any comments on this, whether it will work or not?

the next thing I need some help in is wiring. I bought a PID and it came with a K type thermocouple.
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I'm thinking that the thermocouple that came with it will not work since it doesnt have a long electrode to go into the kiln? will the one thats already in there work?
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The next thing I am wondering is if there is a way to wire the PID into the existing wiring and get it to run with out having to yank all of the other stuff that is there for getting it to work?
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Thanks for any help guys.
Jake
 
I dont have much to add but am very interested if it will work.
Good luck Anthony
 
Thanks man, I really don't want to have to tear this thing apart to scavenge the pieces. Just hoping that by filling up the majority of air space I will be able to get it to ramp up quickly.
 
Set the thermocouple that you have aside for some other project. You need a type K thermocouple probe. Either get one with a ceramic sleeve, or use a ceramic sheath.

If you are not familiar with wiring this type of circuits, get someone who is to come over and help you re-configure the wiring so it can be PID controlled.
 
Ah, I thought something looked weird. The fleabay add said that it had a K type thermocouple:barf:

Guess I will buy another one.
Thanks,
Jake
 
Before I say a word, please know that working with this type of stuff is really dangerous and if you dont know much about electricity you can get yourself hurt(ask me how I know). I would recommend finding someone that could help you out if you are confused, the information that I am offering is just advice and should be taken as just that. I am only speaking from experience of having actually built my own HT oven.

That is a mess of wires, are you using 110 or 220? This would give us a better idea of what you are dealing with as far as wattage output and what you plan on doing as far as powering the unit. From the looks of it the elements in there are of a pretty small gauge which is why there are so many of them. Also from looking at it the 3 elements the unit does have are independently controlled via the knobs on the panel, these are going to have to be removed and those elements are going to have to be ran in a union as one element(that is how I would do it) in order to be properly controlled by the PID that you have, if there is a way to wire the PID to the analog controls it is WAY over my head, but I dont see how it would be possible as the SSR needs to have direct access to the Element and one of the hot legs of the power supply. Once you get some more info on the electrical stuff I can maybe point you in a general direction.
 
What are the inner dimensions? I hope it is not that big. Another suggestion if the space is big is to wire it for 220. 110 will take a long time to warm up a big space. This puts it into perspective. My inner space is 7"x5"x15". It gets to 1200 in a few minutes on 220.
 
Aside from the good advice given above about getting help if you're in over your head, I'm going to add in that turning it on it's side is probably not the best idea.For one, you've now potentially shifted the heating elements around which could have damaged them. They do become quite fragile after the first firing...This is also a good reason not tp put stuff over top of them (like your new "floor", which may also cause premature burnout of the elements under it by overinsulating them and making them cook themselves...).

As to filling up the extra space with firebrick, this will not speed up the heat up time. The firebrick will take much longer to come up to heat than air and will really slow things down in heating up. On the good side, that much thermal mass inside the kiln will give you very stable temperatures once you're up to temp...

Not trying to be a buzzkill, just trying to save you some heartbreak...

-d
 
Thanks for the help guys. Its not that I dont know how to work on wiring, I was just hoping that some one here would have done the same thing and would chime in with some advice, which seems to be working great:D

When I turned it on its side I did it by and and was very careful as I surely know how brittle those dang little electrodes are:)

I'll keep that in mind about the extra fire brick, I assumed that it filling the dead air space would make it faster in heating? weird.

The kiln is 220 and I want to keep it that way.

So if I just yank the old set up and wire it to the PID and SSR will it hurt the steel I will be heat treating if it take a bit of time to ramp up to temp? I will be using CPM154CM, CPMSV30, O1, 1095, S7. I'm assuming that the ramp up time isn't that critical, its the hold and acctual temp that matters from what I have been reading.

Thanks for all of the help guys.
 
Slow ramp times won't be a problem.
Wire the coils to run on 220V directly. Take the power wires to the coils and attach them to the SSR ( You want a 220V SSR, BTW). Wire the SSR control line ( something like 24VDC), to the PID. Connect a type K ceramic sheathed thermocouple ( the little type K provided won't work for a kiln/oven) to the PID TC connections ( observe polarity). Connect the PID to 120VAC, and the SSR to the 220VAC incoming line. Place power switches and fuses in the PID circuit and the SSR power input. Double check everything, and power it up for a smoke test.

One thing about using an open coil kiln or oven is the risk of severe shock should a blade touch a coil when inserting or removing it. Many folks place a safety switch in the 24VDC control line between the PID and the SSR. It should be a spring loaded or roller type microswitch that opens when the door is opened, as a manual switch is just too easy to ignore flipping.
 
You are quite welcome.

Now, back to that screw stud TC that came free with the PID. Many of us have some of these sitting around and think they are useless....not so.
Take an 10X3X1 block of aluminum. Drill a 1" deep hole centered in the 1" side, and tap it for the stud. With the TC screwed into this block you have a large mass TC unit for your tempering oven . In many cases, a small hole drilled in the proper spot on the back of the oven will allow the TC cable to exit.
Place the block in the oven and place the blade on the block. The TC will read the heat of the block's mass, not the air, and the blade will evenly be tempered by the surface convection of the aluminum.

A toaster oven can be made into a highly accurate tempering oven this way. Here is an old thread on building a tempering oven. The aluminum block is not mentioned, but is an improvement on the plain TC used in this build.
http://www.bladeforums.com/forums/showthread.php?t=599423&highlight=PID

Here is an old thread on a project similar to yours:
http://www.bladeforums.com/forums/showpost.php?p=5008952&postcount=24
 
Aw man thats cool, I may have to use that:) thanks. I ordered another thermocouple yesterday and I should be able to get this thing up and running in the next week or two.
Thanks for every ones help:)
 
Ok So I finally got the kiln wired and working:) PID controller works and everything went together without a hitch.

I have a question on programming the PID. I set up the auto tune and let it run, checking the temp with a temp gun, it was very accurate. Problem lies in that the kiln took 20min to get to 175 deg. That seems really slow :thumbdn: I’m tempted to mess with the "P" to get the PID to ramp the temp up faster but I'm not sure what the best plan of action would be to get what I want. I researched and it seems that the "P" will get it to ramp more aggressively, but I also don’t want to over shoot the desired temp by more than a few degrees.

The kiln has 6 elements in it and should have no problem getting to 2200. The elements are about 16-18 gauge and curled about 1/4-3/8 round. if that helps at all.

Oh and before you ask, silly me never actually turned on the kiln before I switched everything from manual to digital. So I have no idea how fast it ramped before.
Thanks,
Jake
 
When I check the voltage from one side of the element to the other I get 240v but if I check from one side and work my way inward I get less and less voltage until I get to the other leg and its back to 110v. Shouldn't it been 240 all the way across the board?:foot:
 
This is called voltage drop, and is part of electrical engineering and design.

When you put the meter probes on the input to both sides of the coil, you are reading the line voltage with no resistance. When you move one probe to a point along the coil, you are reading the voltage through that amount of resistance, thus the voltage is lower.

If you call the two coil posts A and B, the reading from A-B is 220VAC. If you keep one probe at A and move the other 1/4 up the coil from B, the reading will drop to about 165VAC. At 1/2 way around the coil it should be 110VAC...etc.
 
Thanks man that makes sense:)

Here is some of the issue: the kiln has 6 seperate coils, originaly they had them paired up in 2's. I had originaly jumped them to make one long coil and then put a leg of 110 from the ssr on one side and the other 110 leg from the pid to the other side. This did not give me very much power at all, but it would get to a set temp and then shut down like it was supposed to.

I rewired it now so that the first coil has the original 110 leg from the ssr on one end and the 110'from the pid on the other, then I jumped them to the other coils down the line. This heats up much faster now, but it will not shut down when it hits the set temp.

I messed with some of the factory set pid settings last night before the rewire, thinking that it was slow because of the low settings, I cranked up the pid settings about 2 settings. Would this be why it would go over the programed temp by 45' or more, the pid shows no out flow of power but I can still pull 240 off of the coils, so it's not shutting down? I have no temp hold now.

Are both legs of the 220 supposed to go to the ssr then to the pid? Or only one to the ssr and one to the pid?

Thanks this is a bit confusing:)
 
Look at the schematic posted at the top of the thread here.
http://www.bladeforums.com/forums/showpost.php?p=5008952&postcount=24
Look at the PID, SSR, and the buss bars. Ignore the numbers, your PID might be different. but either way, a pos and neg go from the PID to the low voltage side of the SSR. One high voltage leg goes from buss bar to SSR, then out other high voltage tap on SSR to one leg of elements. The other end of elements goes to other leg of buss bar.

If you are powering your SSR with 220 then you need two completely seperate legs from buss bars to power the PID. those two have nothing to do with the lines going to the SSR and elements.

I hope I am not confusing you.
 
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gixxer said:
Look at the schematic posted at the top of the thread here.
http://www.bladeforums.com/forums/showpost.php?p=5008952&postcount=24
Look at the PID, SSR, and the buss bars. Ignore the numbers, your PID might be different. but either way, a pos and neg go from the PID to the low voltage side of the SSR. One high voltage leg goes from buss bar to SSR, then out other high voltage tap on SSR to one leg of elements. The other end of elements goes to other leg of buss bar.

If you are powering your SSR with 220 then you need two completely seperate legs from buss bars to power the PID. those two have nothing to do with the lines going to the SSR and elements.

I hope I am not confusing you.
Click to expand...

You sir bring forth the awesome, that fixed it:) thank you very much!!!
 
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