Large ceramic shell burnout kiln for lost wax - Zapins

Discussion in 'Furnaces and their construction' started by Zapins, Jan 3, 2019.

  1. Jason

    Jason Silver Banner Member

    I keep a leather apron permanently parked on top of my anvil. If I put it away, I won't wear it. I have many pairs of jeans that have been set on fire from sparks when cutting steel. A speed control is a good idea Mark. I recently polished some granite and needed to slow things waaayyy down. So I used a light dimmer switch. While I would never hang that on my dewalt grinder, I have no problem slowing down a $14 hf cheapie angle grinder.
     
  2. Zapins

    Zapins Silver

    Tig welded up the propane pipes so they fit around the kiln. There will be two burners. One in front one behind. Facing opposite ways. I think I'll make the flames come out under the stainless floor. So the heat stays even throughout the chamber. Hopefully the stainless can take the punishment.

    I also came up with a new idea for the door lock. Will make it tomorrow and post when it's done. Should work very nicely. It is also very simple.

    I'm really close to finishing it. Just a few more details and finished!
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    Last edited: Jan 11, 2019
    Tobho Mott likes this.
  3. Jason

    Jason Silver Banner Member

    There ya go... No more fittings. Cut and weld. Saves money!
     
  4. Zapins

    Zapins Silver

    I got more stainless to make a more substantial rack. Now I'm wondering where to place the propane burner? Below the rack so the flames pass up under the stainless floor or above the rack so the flames don't directly touch the rack?

    Apparently 316 starts to creep at 1700F but I dont have a temperature controller pid yet for it. 900 F is hotter than my extruder pid go so I'd need to order a new pid and probe to keep the temp at that range. Or I can just do a melt out in the kiln and do a full burn out in my electric kiln?
     
  5. Jason

    Jason Silver Banner Member

    Looking back at your photo with the rack, it looks like you don't have much choice. Above.

    Barry's has 2 burners came in on the sides above the rack, one high, one low. One towards the back and the other towards the front. Probably helps spin the heat through the chamber.:confused:
     
    Last edited: Jan 18, 2019 at 10:43 AM
  6. Zapins

    Zapins Silver

    I'm looking into a PID for the kiln so I can set it at 900 F or whatever and just have it open a solenoid to do that for me.

    I'm having trouble finding a PID and thermocouple combo that will do that for a reasonable price though. Anyone got some advice? I've been checking ebay and amazon listings for about an hour now and they almost all go 0-400C or the description is too vague to really be sure what I'm getting.
     
  7. Zapins

    Zapins Silver

    I have an extra LCD PID REX-C100 Temperature Controller with SSD and heat sink. I think I might be able to reset the range on it to accept a K type probe? This guy http://castboolits.gunloads.com/sho...er-Schematic&p=4352006&viewfull=1#post4352006 said to reset the PID range you do:

    I think this PDF for the PID also mirrors these instructions on the 2nd page: https://www.mpja.com/download/rex-c100.pdf

    Calibration of REX-C100 PID:


    K type Probe setup on REX-C100 PID:


    This guy used a REX-C100 PID and made a kiln controller:



    I think all I need is just the K type thermocouple? Then I can reset the PID I already have and go from there? Not sure if I need the special cord for the thermocouple in the picture with the yellow end?

    The probe I'm looking at doesn't have a part number, but is called "NEW High Temperature Type K Thermocouple Core Ceramic Kiln Probe 2372°F"

    https://www.ebay.com/itm/NEW-High-T...ln-Probe-2372-F/173526344518?var=472215010753
    [​IMG]
     
    Last edited: Jan 16, 2019 at 8:16 PM
  8. Al2O3

    Al2O3 Administrator Staff Member Banner Member

  9. Zapins

    Zapins Silver

    I just looked over that thread. Very impressive build! I don't think I understand all the wires, your setup looks a lot more elaborate than mine. I also didn't see any names/part numbers of the components so I'm not sure if we have the same components.

    Is your controller the same type as mine? A Rex-C100 PID? Did you just pick up a K type thermocouple like I linked above and connect it or did it have to be a special type for that PID? Does the thermocouple need to be connected with the special wire and yellow plastic connectors to the PID or will it work with any wire as long as it gets to the PID?

    I went ahead and ordered the thermocouple & wire since it was only $16 it won't be a big problem if it ends up not working but any advice would be helpful!
     
  10. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    I scanned your thread but I'm assuming this is for some other electric kiln not the gas fired burn-out in the title of this thread kiln...correct? Otherwise I don't understand what you are controlling in the fuel fired box.

    I don't the think the brand of PiD or so called fuzzy logic matters for simple temperature control. They all do pretty much the same thing and you already have noted that some are temperature limited....and the range can be re-set. For a K-Type TC used in air, I'd just recommend the thickest gauge TC wire for durability and ok to have a sheath to protect it from chemical attack, depending upon what you are cooking, but it slows down response time a bit.

    I have a number of other features and instrumentation to control heating elements and monitor operating status. Strictly speaking, you only need the PiD, TC, and SSR (and heat sink). That would be the minimalist approach. I don't recommend it.

    I would have an SSR for each separate heating element in the kiln but you can run them all off of one with a sufficient rating. I would however add a main power contactor, start stop switch, and circuit breaker for safety. I have status LEDs on the panel so I can see what has power applied. This allows you to remove power from the kilns without powering down you PiD so if you have a program running and need to access the kiln you can do so without the electrocution hazard.

    Best,
    Kelly
     
  11. Zapins

    Zapins Silver

    I probably should have explained what I wanted to do first haha. Sorry!

    I want to make a propane powered kiln that uses two small pilot lights to keep the kiln burning and then one solenoid to add more gas into the kiln to maintain a specific temperature.

    SVseeker made one a few years back that seemed to work well so I am loosely copying his design.



    This is his setup. There is a T in the line that allows gas to bleed around the solenoid and go into the furnace to fuel the pilot light,this line has a needle valve on the back of it so the flow is very low and won't heat the furnace up to operating temperature on its own. Then the second line on the bottom has the solenoid in it and is connected to the PID. That way the temperature can be controlled.

    I think this setup is a simple solution to how to operate my kiln, I was just concerned the thermocouple wouldn't be able to communicate with the PID or the PID wouldn't have the ability to accept different inputs. The description of the PID on ebay is bad, it says 0 to 400 temp range but doesn't say it can be reset for different inputs.
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  12. Peedee

    Peedee Silver

    What are you doing to prevent a 'boom' if you loose the pilot light?
     
  13. Zapins

    Zapins Silver

    Bring a second pair of undies.

    Not sure, was thinking about that. There should be 2 propane pilot lights, hopefully that prevents it?

    Outside of that not sure. Open to ideas.
     
  14. Jason

    Jason Silver Banner Member

    Personally I wouldn't waste the time or money sticking a pid on that thing. Now if you are burning out exotic resins I could see that. For wax? No way. Full tilt from the time you light the wick.
    I would put a pair of theromocouples and a couple of cheap meters on it somewhere. Good enough to tell if you have even heat. Preheating it would be ideal and sliding in the shells in one go would be the best. If you are going to crack a shell, it's in the first 2 minutes. After that, you could melt that wax out with a friggen candle. You know zap any slow heat ramp up is asking for trouble.
    Hot, Hard, Heavy and FAST wins this game. (or boiling water)
     
  15. Zapins

    Zapins Silver

    I see what you are saying Jason, but I have an extra PID controller from my extruder machine build. I needed 2 PID's for that project and figured I might as well buy another kit for a future project and save on shipping. So all I need is a solenoid and a K type thermocouple which aren't expensive.

    The reason I want the kiln to be controlled is the stainless will start to creep if it goes above 1700 F for too long. I don't think this is going to be an issue if I max out the flames and burn the wax out for a few minutes, but it certainly will be an issue if I keep the propane cranked up at max and close the box up and bake out the molds for 1-3 hrs. Also, for the baking/burning out part Remet recommends the molds are held at 1600 F for 2 hours for a proper burn out. I've always just winged it when it came to burnouts, but it would be nice to eliminate another variable and get better castings with a more repeatable process. Especially since it doesn't really add much more cost to the already expensive build.

    I cut a vent hole in the ceiling and caulked the internal edges of the furnace so fire won't leak out.
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    I used caulking and stuck fiber blanket over the exposed steel tabs inside the furnace to protect them against the flames. I also added fiber blanket over the steel brace that sits at the bottom of the front door.
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    I welded on a handle for the bottom left bay door where my hand is. I will add springs to prevent the doors falling down too quickly and getting damaged on the legs of the frame.
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    I also removed the old 1/2" stainless steel 316 bars and installed new 3/4" thick 316 stainless bars. I'll be chopping up the 1/2" frame and welding it in to make a nice mesh between the thicker 3/4" bars. I've also got 3/4" schedule 80 (316) tube to make a scaffold inside to tie the molds to so they don't fall during burn out.

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    And finally, I remade the hinges. These work very well and hold the front door tightly against the frame without space for flames to escape. The door rides up on the incline then catches in the groove at the top. To open the door all I need to do is lift up on the front door handle and that disengages the lock.
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    Last edited: Jan 18, 2019 at 6:31 PM
    joe yard likes this.
  16. Zapins

    Zapins Silver

    I drilled the holes for the burners out. Tomorrow I'll install the floor and burners. Then coat with satanite and fire this bish up. Looking for a monday test burn.
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    Maybe I went overboard welding the entire edge of the panel on. But when it is ground down its going to look great.

    I'll add the other panels soon.
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    My welds improved after switching the polarity on my welder from flux core to solid core...
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    Jason likes this.
  17. Jason

    Jason Silver Banner Member

    That weld looks like a winner. Yeah I would not have run full length welds, but wire and gas is cheap. Call it training.:D
     
  18. Zapins

    Zapins Silver

    Well. I would have had it finished tonight but the power just went out so here's what I managed to do today.

    I do hope it comes back on soon or my 25 gallons of slurry is going to freeze.

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  19. joe yard

    joe yard Silver

    Hi Zapins
    It is a bit scary using a pilot light without a way to verify that the pilot is lit.
    A suggestion would be to use a separate PID for verification of the pilot light. And another for kiln temperature control.
    Wire the second PIDs output in series with the first. The first PID would have a thermocouple probe directly in the flame of the pilot light. You would then set the first controllers temperature to just below the temperature reading of the pilot light flame. Then wire first PIDs output in series with the second PID.
    The second PID controller thermocouple. Would be the one that controls the kiln internal temperature. If you you the two outputs in series from the PIDs to the solenoid valve.
    No gas other than that supplied to the pilot light will pass Unless both the set point of PIDs are met.
    In such a small enclosure if only one solenoid valve is used and the pilot is out. It will supply pilot gas. I would suspect it would eventually build up to a dangerous level.
    I would consider using 2 solenoids. One for just the pilot lights gas and the other for the main heat gas.
    Joe
     
  20. Jason

    Jason Silver Banner Member

    How about a optical flame sensor? Flame goes out, and out goes the lights and cuts the power?
    The F-16 had one in the tail pipe. It looked to see if the afterburner was lit or not. It told something somewhere the status of the AB. Bet I could find one if we could figure out how to wire it.
     

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