Which PID to buy? (and other questions)

Well, I am buying stuff to build the oven. I thought I found 9 x 4.5 x 2.5 firebrick for only $0.73 each! I was overjoyed. I redesigned the oven to accommodate the smaller size brick and set out to purchase my bricks. Come to find out, they thought that structural fire brick and insulating fire brick are the same thing. They even tried to convince me to buy when I told them it was not what I need. Well, you can bet that I will not be calling Elgin-Butler brick company any more. 3 hours driving time and 1/2 tank of gas blown out for nothing. <<not happy>>

I am going to use 9 x 4.5 x 3 bricks like I originally designed and I am buying them here: http://www.tflhouston.com/
 
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Sean Cochran said:
Looking forward to it.
Remeber its useless without pics. ;) :)
Click to expand...

I plan to post complete plans, including parts lists. This weekend I will most likely get the box and the shell made. I will not get the good stuff (PID and heater and all) until next week. I procrastinated too long ordering it....

I am using 30 bricks. The new version is 7.5" x 7.5" x 12" inside. I had part of a sheet metal skin made using 24 gauge galvanized. The total for the skin will be about $100. I will pay about $80 for the bricks. $25 for the mortar. The other stuff comes to about $171.00. That does not include wire and switches and a box for the PID. I probably have most of that stuff. I am also using my own heat sink for the SSR. That puts the total cost at around $400. Wait till you see the cool door I am putting on it. You lift up and it rests on top of the oven. When you close it, gravity holds it against the oven. It was a lot easier to design than I though it would be. It should be relatively easy to fabricate, too.
 
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I got my PID yesterday. I also have the heating element, the SSR, and the thermocouple. I still need a box and some wire, a couple of switches and lights. I was also thinking of putting alarms on the oven, since the PID already supports them. It looks like I could easily put another $100 in the wiring and stuff.
 
I've been reading, with interest, your thread on building an oven. I work with, repair and rebuild the control systems on laboratory benchtop and free standing ovens (mostly Limberg Blue-M) in my work. We have ovens from very small to big enough to hold multiple 55 gallon drums at a time. I've never considered the complications and thought that goes into the actual structure of the oven because I only work on the electrics and electronics. I find your discussion on the building of the structure interesting.

We have modified our ovens to have a seperate controller strictly for overtemp shutdown as ours run unattended 24/7. This involves a second different type controller and a second seperate thermocouple. We also use a power relay controlled by the alarm contacts on the controller to shutdown the incoming volt source if the oven exceeds a specified temperature. If you are present while your oven is running, you shouldn't have a problem.

I'll continue to follow this thread and offer my experiences from what I've run into.
 
Well... I finally got around to buying the rest of the stuff I need for the oven. I spent about $45 at http://jameco.com on switches and indicators. I got double of everything that I need in case I screw it up. I also spent about $25 at http://iseinc.com for high-temp wire and ceramic wire nuts. I still need a back cover for the oven, which I will have made from sheet metal, and a control box, which I will also have made.

I was going to use fibreglass rope for the door insulator, but I cannot find it locally and it is too expensive if I have to have it shipped. I was wondering if anyone listening has a piece of ceramic wool they can sell me cheep. I hope to get it finished next weekend or the one after that.
 
chucktilbury said:
So here is what I am buying for the oven:

1. http://tflhouston.com.
25 K23 firebricks. I only need 16 for the actual design, but I am getting extras to play around with since I have never seen them before. $2.25 per brick + tax. Nice people, BTW.

2. http://duralite.com
1pc. 4000W 240V Heating element: DURA005681 $25.25
2pc. 2 way terminal blocks: DURA005078 $5.00 each
1 bag of shoulder bushings DURA006252 $10.00

3. http://auberins.com
1pc. PID with 30 steps ramp and soak SYL-2352P $78.00
1pc. Thermocouple TC-K-KLN $26.00
1pc. 25A SSR RS1A40D25 $15.00

5. Ace hardware
1 qt. refractory cement. Ace item #40987 $7.00

6. Lowes Building supply
1 roll aluminum flashing. item #12539 $12.00
1 bag of rivets $10.00
1 bag of backup rings for the rivets $2.00
1 bag of sheet metal screws $4.00

7. I will supply the following from my "stock"
1pc. Heat sink for the SSR
steel bar stock for the door and stand
Hookup wire to connect up everything
Switches for the heater lockout

8. Other stuff that I have not discovered that I need yet :)
$100.00

That brings the total cost for the oven to around $350. Did I leave anything out?
Click to expand...

As much as I have been looking,I don't have a clue how I missed this.
After I read it all through,I think this should answer most of my questions.
Thanks for doing this Chuck.

God bless,Keith
 
In case anyone is interested, I have posted my CAD drawings as JPG files on my web site. I should get it fired up this weekend God willing. I still need to develop and post the schematic.
 
I posted the rest of my pics and the schematic. http://chucktilbury.com/pages/gallery.php?dir24=/Heat+Treat+Oven

I still need to work up the parts list for the controller box. I will post that too. The oven works just fine. It went from 85F to 1450F in 40 minutes flat. It pretty much worked the first time, but I made a couple of mistakes.
1. I need to put a heat sink on the SSR.
2. I also failed to lay out the front and just did a "I have done this dozens of times and I can guess close enough" type mistake. It works but it's not pretty.
3. The outer shell gets scalding hot. I will probably discard the current shell and make another one with a blanket around it.
4. I really need a gasket on the door. I have not really figured that one out yet. Koa wool?
5. I used sta-cons (bell shaped crimps) to assemble much of the wiring. Next time I will use terminal blocks.

I also added a couple of features that I have not seen elsewhere.
1. I use a 20A circuit breaker instead of a fuse.
2. I put an alarm on the controller so it can call me at the end of the process. To do that, I needed a source of 12V DC, so I put a transformer and a rectifier in it. I will also use that to drive the fan when I add a heat sink. I have an old CPU fan that I am planning to use.

After I get the heat sink on the SSR, I will FINALLY be able to heat treat something. This started out to be a $300 project and could have probably brought it in for that. As it is, I am up to about $500 and still counting. ;-/

Edit: forgot the link.
 
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