Chapman HT oven WIP

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dmcmd

Joined
Jan 1, 2026
Messages
31
Hi guys,

Been away for a while on various projects, but my heat treat oven is coming along, so I thought I'd share since you guys are a pretty helpful bunch. I still have a number of weeks before I'm done because my life gets in the way of working on it.

Let's get started:

First, I used T Taz brick design.
I'm using 12 awg coiled kanthal wire, so to get enough of that in and get the oven down to 18 amps, I had to make the wire go three lengths down the sides of the oven. I made router templates to cut the K23 bricks to make the coil groove. I made 3 sets of templates: 1 for a 3/8' straight bit, 1 for a 5/8 ball end bit, and 1 for a 3/4 v groove bit.

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Sorry I don't have any close ups of the v groove bit profile. But you can kind of see what I did with the v groove. I cut out the tops of the coil grooves with it so that I can just drop the coil in, rather than having to slide it through all the bricks.

Here's all the bricks set up like they're going to be in the oven:

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Next, I started working on the frame. The way this is going to work is: I'm making a frame inside a frame design. So all the bricks will sit in the interior metal frame made out of 3/4" angle iron. The bricks will be able to be loaded into the frame from the top. Then, I will have 2 layers of 1" ceramic wool on each of the 5 sides of the oven (not the front obviously), and there will be 18awg sheet metal that slides in from the rear holding the ceramic wool in place.

Here's the internal frame:

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Hopefully you can see how this box is going to work. The back will be a 1.5" angle square cap that fits over the angle long edges. I'll get some more of the frame done tomorrow so it will be more clear.

Let's move on to the controller. I decided I didn't want to use the crappy PID controllers everyone uses. I have somewhat of a background building my own PID contollers, so I decided to make one for this oven.
My controller is a raspberry pi 4 connected to an esp32 that is connected to a max31856. All of my electronics are in somewhat of a disarray so I won't show you pictures of the contactor, SSRs, and power supplies yet, but I will when it's time.
For now, let me show you some screenshots of what the PID controller can do (I named it "STEELHAUS", BTW):

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I don't know if you can tell from the pictures, but the PID controller allows you to autotune it for multiple different temperatures, and then when it's controlling the oven, it will use the correct tuning for whatever temperature you set. It will also move between tunings as the temperature changes.

You can put as many programs in as you want and you can tell the controller exactly how you want the oven to heat up.

The program is accessible from any internet connected device anywhere in the world, and it responds on your device exactly how it would if you were touching the computer itself.
 
Here's a couple of pictures of the computer. I haven't done all the wiring yet, so it's kind of ugly right now. I'll fix that up in good time...

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That's all I've got for tonight. I'm going to keep working on the box tomorrow and hopefully get the stand and possibly the control box done this weekend... We'll see.
 
Scrolling down thru the photos I am really impressed with your design and quality of workmanship..... Then I saw the Raspberry Pi controller. I'm blown away with that. I played around with the Pi 1 and 2. I'm not a real coder by any means, so when I saw your screens and what you can do I'm REALLY IMPRESSED!!! I'm impressed (using that word too much:) with your coding ability.

GREAT WORK!!! Thank you for posting this.

BTW, would you mind sharing the details, manuf, model, etc of that display? Looks pretty big.

Ken H>
 
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Ken H> said:
Scrolling down thru the photos I am really impressed with your design and quality of workmanship..... Then I saw the Raspberry Pi controller. I'm blown away with that. I played around with the Pi 1 and 2. I'm not a real coder by any means, so when I saw your screens and what you can do I'm REALLY IMPRESSED!!! I'm impressed (using that word too much:) with your coding ability.

GREAT WORK!!! Thank you for posting this.

BTW, would you mind sharing the details, manuf, model, etc of that display? Looks pretty big.

Ken
Click to expand...
It is a “Roadom 7” Raspberry Pi Screen”. Search that on Amazon. It’s the $59.99 one.

And don’t worry - all electronics stuff will be coming to this post when it’s ready.
 
Here's today's progress. Now you can see what my plan is for the outer frame. I made a back cap that will be screwed onto the 1.5" angle iron rails. Then I cut 18 awg sheet metal panels for the sides and the top. These panels will also be screwed into the angle iron rails to hold them in place. So to remove the panels, I will just unscrew the back cap and then unscrew whichever panel I want to remove, and then slide that panel out the back. If I remove the top panel, I'll be able to replace the elements and the bricks. The side panels cover the wiring, and the back cap covers the thermocouple. There is no need to remove the bottom panel; that's why that one is welded in place.


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This weekend I'm going to be working on the door. Honestly, I don't have a great plan for the door yet. It's really the only part of this oven I'm not sure how I'm going to build. My current plan is to make a frame that holds some fire bricks, and then figure out a way to cover those bricks with ceramic wool. So the plan is that the ceramic wool will be sandwiched between the front walls of the oven and the fire bricks in the door.

I'm interested to hear if anyone here has a door similar to that. Does anyone have ceramic wool as the first layer on the door, or does everyone have brick-brick contact in the front of the oven?
 
My EvenHeat oven has only brick for the inside of door and it works pretty good. I suspect your idea of a iron frame holding the bricks will work good.

I spent a good bit of time today looking at that Pi 4 with “Roadom 7” Raspberry Pi Screen” - boy those sure do interface nicely. I WILL be following this thread to learn as much as I can about the wiring/coding.

Ken H>
 
Looks awesome! I want to know more about the raspberry pie thing too!!
 
same here. I wish I could change my evenheat controller over to something like that!
 
dmcmd said:
In reality you probably would be able to. I’ll show you guys what I did pretty soon. I need to get the oven built first so I can build the control box.
Click to expand...
you could sell conversion kits if yours works out. They would be a hit!
 
Linus Knives said:
same here. I wish I could change my evenheat controller over to something like that!
Click to expand...
That is my future plans also - I really like that 7" display. I've added a similar HDMI 7" display to my SV08 3D printer. That's simple once it's be mainlined to Klipper. Just plug cables in:)

I used a R-Pi 1 & 2 years ago in small projects, but no real programming was involved. I've done much more with the Arduino.

Thank you dmcmd for starting this thread, and providing info for the controller.
 
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