Heat Treat Furnace Build

[dulltool17]

Thermo Fisher SCIENTIFIC. I'm the Manufacturing Engineer for Chiller Production, but spent a bit of time this afternoon with the MFE for the Furnace line. They build a long one with a chamber I'd estimate at 6" diameter x 50" long. It has three separate elements. I have no idea what the specs are or pricing. I was told that the smallest, with about a 5 x 5 x 5 interior goes for a grand. I've not seen Scratch & Dent items. YOu might find one on E-bay.

If you're going for 6' long, maybe the JBolt route would be viable. Definitely needs multiple elements, probably with independent control. Not an undertaking for the faint of heart...

 

[Linghunt]

Thermo Fisher SCIENTIFIC. I'm the Manufacturing Engineer for Chiller Production, but spent a bit of time this afternoon with the MFE for the Furnace line. They build a long one with a chamber I'd estimate at 6" diameter x 50" long. It has three separate elements. I have no idea what the specs are or pricing. I was told that the smallest, with about a 5 x 5 x 5 interior goes for a grand. I've not seen Scratch & Dent items. You might find one on E-bay.

If you're going for 6' long, maybe the JBolt route would be viable. Definitely needs multiple elements, probably with independent control. Not an undertaking for the faint of heart...

Thanks for the info. The JBolt direction is probably the most economical method. I keep an eye out on used equipment site when I remember. That is how I got my current tube furnace that is 37" length capacity x 3 inch diameter. I recall getting it for about $1K without controls. This one has 3 thermocouples, but only need to control off of one from measurements and testing. I had the controls already from my attempt to building one from an old tool box inside a salvaged Hoffman cabinet.

Multi-section ovens and controls can be tricky. I had project with an inline continuous feed 3 section furnace used to heat large glass circles around 24 inch diameter that were pressed to a spherical curves for computer monitors. This was pre autotune days. I sure learned a lot about PID loops on that job. I bought and studied a book just on PID's. The biggest fix I did was changing out the K thermocouple wiring. I discovered they used multiple types of wire and also aluminum terminal box in various locations. It was a great learning project, but a nightmare of a job. I was total cherry back then too that didn't help.

Today's controls are so much better. I got stuck with a PID tuning application that other engineers gave up on. I messed with it for a while and didn't get anywhere. I figured I needed to try anything as long with it was different. My fix was to make the bandwidth ranges of the PID variables vs constants and I changed those at diffferent stages of the ramp and steady state. It worked and surprised them that I fixed it.

 

[jbolt]

I did a few more tweaks to help with the electronics enclosure cooling.

I added 1" standoffs between the enclosure and the enclosure mounting straps.



I also added a 60mm 220vac fan to the bottom of the enclosure. A 80mm fan filter cover covers the 70mm x 50mm cutout for the SSR I did not use. The fan comes on with the contactor.
I got the fan from mouser electronics. p/n OA60AP-22-1WB

 

[jbolt]

Attached is an initial setup and quick start guide for the SOLO SL4848-VR controller. I didn't find the manual very intuitive for someone not familiar with PID controllers so I'm passing along what took me a few sessions to figure out.

 

[Linghunt]

Is the fan blowing out of the box or sucking air in?

My "general" picky thought process for cooling fans: Suck air into the enclosure, you now have a slight pressure gradient in the box, cracks or gaps from different holes or the door will have air flow out of these. Most of the air will go out the vent, so this is being real picky. Filter the fan so you don't suck "dirty" air into box. Heat rises, so fan on bottom, vent on top. Don't forget to change filter or blow it out on some schedule.

What you have here is more than good enough. My Oven has no filter , and the vent is on the side, I built with what I had. My box does collects dirt, I blow it out when I remember

Aside: I got an extra cooling fan on my phase perfect converter and no filter. I didn't have one to fit the fan I had from salvage and just went with it. Manufacturer has a fan as well hooked to a thermal switch, and no filter.

 

[jbolt]

The fan draws air into the enclosure.

Sent from my SM-G955U using Tapatalk

 

[brino]

I bought and studied a book just on PID's.

Is it a book you'd recommend?
Or do you have other resources you could point to?
Thanks,
-brino

 

[Linghunt]

Is it a book you'd recommend?
Or do you have other resources you could point to?
Thanks,
-brino

Let me look, I got it here on my shelf.

 

[Linghunt]

Is it a book you'd recommend?
Or do you have other resources you could point to?
Thanks,
-brino

If you have a technical background and understand Laplace transforms etc, then it's good. Without the a high level of mathematics it will read Greek. The Math is not hard and illustrated well, but without having seen them before is the point.

Here are some samples of the authors writing style. There are 4 old controller referenced in the book, That section is interesting but junk. Book is 1988.

Found this one , (my 1st EE boss gave it to me when he retired) This is a small handbook from 1980. Still good today since math and physics doesn't change. I took one internal page picture. This type stuff is hard to read.

http://www.linghunt.com/ForumPosts/books/EM_SHIELDING_BOOK1.jpg

http://www.linghunt.com/ForumPosts/books/EM_SHIELDING_BOOK1.jpg

http://www.linghunt.com/ForumPosts/books/EM_SHIELDING_BOOK1.jpg
I think I have some other material not so Math based. Let me know how this reads for you.

 

[brino]

Thanks @Linghunt
Electromagnetics was my most difficult class.
PID looks interesting. I wish I knew more control systems theory.
-brino