A small trick for tempering accurately in Evenheat kilns...

That's a great tip. Thanks Aaron.

 

Great tip! Thanks.

 

I have better Tip.

Wanna good precise kiln?
Buy a better - industrial or lab kiln
My PEM-1 muffle kiln 2,5kW is for 1200*C and with TAIE PFU-48 ( 2 programs with 8 steps) after AT for 800*C, this have overshoot +/- 1*C
Evenheat and Paragon are Hobby level kilns.

This PID is with a fuzzy logic.

or if you want to use evenheat or paragon, just don't use their controllers.

 

Aaron, ask people in IZO or KEPKA in Poland, they also making kilns for export.
In size for knifemakers (like 150x 200x 450mm chamber) you will pay max 5.000$
From IZO you will get even with PLC control and touch screen.
Put be prepared to pay about 1k for sea-shipping.

 

My self made HT oven uses a really nice PID controller (http://www.automationdirect.com/adc...ss_Controllers/1-z-8_DIN_Size_(SL4896_Series))

The nice thing about it is that you can calibrate it at four temperatures, if I recall correctly I used 250C/500C/800C/1050C
It's like having four controllers in one since the oven knows how to accuratelly get to these set points and not overshoot, and if you are not using exactly one it uses the closer one.

Great advise, again if I recall correctly by Timgunn1962.


Pablo

 

I made the plans and WIP for my oven public, days ago I posted them here at shop talk, a repost from british blades from years ago.

[edit] here is the link: http://www.bladeforums.com/forums/showthread.php/1314585-Heat-Treatment-Oven-WIP-PEU


Pablo

 

I have a cheap 24" Sugar Creek kiln that only over shoots 3-4 degs when tempering, then settles down to 1 deg.

But I also have a smaller Paragon that over shoots 40 degs, then settles down to 20 after 15 minutes. This one I just set 20 degs lower than I want. Works fine, but not ideal.

 

You need the entire oven's mass to be at tempering target anyway. So it should sit at temp for a good 1/2 hour before placing the blades inside.
By that time, the over-shoot will be smoothed out.
It's not an issue.

 

What Karl said. Overshoot shouldn't be an issue if you understand it.

 

They speak the truth!

It's also important to bring the oven to temp before putting blades in for hardening, overheating can be an issue for the same reasons then as well.

 

Good tip Aaron, crazy timing, I had the same epiphany recently. I had always left the 9999 Ramp as well, and would get that temp jump right off the bat.

Having only one oven, how quickly should the first temper occur? As quick as possible from what I understand. It takes about 40 minutes+ before my oven cools down enough to stabilizes below my target temp and I can start a cycle. Does this fall within the window of time for the first temper? I haven't found anything definitive on this.

 

Hey Arron, I like your YT vids. Your down to earth approach makes others feel like they can make basic (but nice) knives too.

 

Aaron... This could come off as dicky but please know that it is not my intent.

Kilns have ramp speeds for a reason. We should be educating ourselves on their use and take advantage of the controller. We should also have a grasp of basic metallurgical and heat transfer principles. The last thing would be to familiarize ourselves with the steel we use, with regard to it's chemical composition.

Maybe, I am just having a problem with the chosen title of this thread(OCD and all)... "A small trick for tempering accurately in Evenheat kilns...". It sounds as though kilns need a "trick" to work right. To me, it is like starting a trick thread for a drill press... only to tell us you discovered that changing the RPM to suit the bit size improves performance. Something that anyone who uses a drill press should already know.

IMHO, this thread should be titled... "How to properly use your kiln's controller."