Heat treat furnace

[Highpower]

Made some more progress on the furnace. I got the chamber and outer shell all back together with no pieces left over so I guess that's good. Yesterday I wanted to make a new face plate for the new controls. I don't have any aluminum sheet so that was out. I have a few pieces of galvanized steel sheet metal, but I didn't want to use that either. Luckily I did find a few small pieces of 16 gauge 316 stainless I had left though. That'll do....  

I don't have a sheet metal brake either   so I had to make do with my SWAG press brake instead. First use actually since I put it together. It's far from perfect but I think it's "OK". Rather plain looking, but again - it'll do.
Views of old and new:

   

   

After that I attached the heat sink and SSR (with heat transfer grease) to the lower back panel with a couple of screws. Easy enough. The lower shell as you can see is VERY well vented.

   

I got a late start today but worked on getting everything wired together. One thing that bugged me was that the furnace itself had no circuit protection at all. It's rated at 6.3 amps but I'll be running the furnace on a 20 A circuit. So just for a little piece of mind I screwed a double fuse holder to the bottom plate and popped in a pair of 10 amp ceramic fuses for the 240 V line coming in on the cord. Just in case. I've got it all wired now EXCEPT for the new thermocouple. I called it quits for today.

Now the hard part comes. The leads on the thermocouple are much larger than I expected them to be. 16 gauge SOLID wire. Somehow I have to attach these to the teeny-tiny #4 terminal screws on the back of the PID controller....  

   

[DaveH]

It's looking good Willie  
 
Dave

[dallen]

what are you going to do with the old analog gauge out of the old panel?

[Highpower]

(12-13-2015, 09:20 AM)dallen Wrote: what are you going to do with the old analog gauge out of the old panel?

Originally I thought I would install it on one of my lead furnaces for bullet casting. If it works.... I don't know, I haven't tried connecting the thermocouple to it and testing it yet.

But then I thought if I'm going to go through the trouble of attaching it the the lead furnace anyway, I might as well put a PID controller on it as well and take advantage of the tighter heat control too.

If you want the analog gauge it's yours David. Just PM me with a mailing address.

[Highpower]

   

Got the new thermocouple installed and proceeded to set the parameters on the PID controller. It had me befuddled for awhile because it would bring up two different parameters at the same time - one on each digital display, and I didn't know which one I was setting!  

I fiddled with it for some time and finally figured out the upper display was for the setting currently being adjusted, and the lower display was just showing the next parameter that was going to come up afterward. Once I knew that it was smooth sailing.  

Running the "autotune" routine and the furnace is warming up.

   

Reached the temperature set point (1500° F), and autotune is still running. (Fine tuning the response.)

   

Autotune completed and switching back to normal operation. Temperature dropped 1 degree while doing that, but the output to the heating element came back on and quickly recovered.

   

And yes, believe it or not the furnace actually still works!  

   

[DaveH]

That is beautiful  
Great job Willie  
 
DaveH

[TomG]

SWEET! 

[Highpower]

Used furnace: 200 dollars.

Modern upgrade parts & misc hardware: 175 dollars.

Having a bunch of metal geeks to help steer you in the right direction with one of your hare-brained ideas..... PRICELESS.

[Hawkeye]

Nice work. I've been working on getting my used oven running, too. On Saturday, I ordered a similar PID controller. It's good to see how well it works.

[Vinny]

Good Job Willie!