Self build heat treatment kiln

izafireman

Well-Known Member
Can anyone possibly point me in the direction of any self build heat treatment oven plans please?

I am looking to build one as in the UK they are hugely expensive and I have the contacts who could help me build one, just need the plans for one.
 
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izafireman

Well-Known Member
Thanks Ken, really appreciate your help. Something I have always wanted to do as at the moment get my steel heat treated in bulk commercially, at least if I have my own oven I will be able to use other steels and I have no doubt learn much more.

I contacted one of my pals who works as an engineer for BP thinking it would be a difficult build but he replied that it was an easy build for him, I have no doubt he will over engineer what he makes and possibly think of some improvements on any designs.

Many thanks

Pete
 

izafireman

Well-Known Member
Ken , have you made of these units yourself?

Reason I ask is regarding the PID model shown in the link, does that have the capability to remember several different heat treatment cycles as I know some PIDs do. Or are there other models I should look at. I am hoping to build the units out of stainless as I think that would look good and also wont rust in my workshop over winter.

I also found this easy to cut lightweight sheet which is what I line my wood burner in my house with, very easy

 

KenH

Well-Known Member
Nope, I never built one myself. Waaay back when I first got involved in knifemaking the wife decided I needed to be making her kitchen knives of SS, so I needed an oven. I placed an order for the EvenHeat oven. It's worked just fine.

"IF" you want a PID controller that seems to be the best around: https://www.kilncontrol.com/shop/conversion-kits/

OR, a step down from that but has been around for a LONG time:
https://shopevenheat.com/index.php?main_page=product_info&cPath=100_106_128&products_id=1481

Or with fewer features at less cost (this is the one I have):
https://shopevenheat.com/index.php?main_page=product_info&cPath=3_12&products_id=1479

Here is a link that gives a brief description of each controller.
http://www.sunshineglass.com/rcol/b_fusing/kilns-ramp2.htm
 

izafireman

Well-Known Member
Thanks Ken I will have a look at these later and making a kiln for the kitchen knife reason also and to give me more flexibility.
 

Gliden07

Well-Known Member
Nope, I never built one myself. Waaay back when I first got involved in knifemaking the wife decided I needed to be making her kitchen knives of SS, so I needed an oven. I placed an order for the EvenHeat oven. It's worked just fine.

"IF" you want a PID controller that seems to be the best around: https://www.kilncontrol.com/shop/conversion-kits/

OR, a step down from that but has been around for a LONG time:
https://shopevenheat.com/index.php?main_page=product_info&cPath=100_106_128&products_id=1481

Or with fewer features at less cost (this is the one I have):
https://shopevenheat.com/index.php?main_page=product_info&cPath=3_12&products_id=1479

Here is a link that gives a brief description of each controller.
http://www.sunshineglass.com/rcol/b_fusing/kilns-ramp2.htm
Are those controls all self contained?? Other than the relays to control the heating elements?
 

KenH

Well-Known Member
The only one I've used is the Set-Pro which sure looks like it's a single complete unit - and I think it includes the relay because I can heard the relay clicking as it goes ON 'n OFF, and the sound seems like it's internal to the Set-Pro box. It would be best would be to contact vendor.
 

izafireman

Well-Known Member
Had what might be good news this evening as my father who is a retired electrician said he has a PID controller made by a company called Omron which although 20 years old is brand new and was used to control the temperatures on wrapping machines on a production line in a factory. Hopefully it will be ok , if not I will buy one of the other units.
 
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izafireman

Well-Known Member
Thanks for all the replies so far. The PID my dad found isn't suitable so as I can get some decent controllers over here what should I be looking for as in criteria for a Kiln? Max temp, number of programmes I can create, ramp up and soak....but what else please.

Also I am going with a solid state relay so once again what should I look for when I buy that …..everything will be 240 V

Finally I will need a heat sensor, what should I ensure with that?

Thanks gents , really looking forward to this project and what I will be able to achieve once it is complete.

Edit ,,, Today whilst researching a tempering conversion for my toaster oven I found one of these used by someone

https://www.amazon.co.uk/dp/B01MY2B6BR

Not sure if it will be good enough for the heat treat oven but if it is it comes with the relay etc, just would need to get a higher rated probe.
If this one turns out to be too basic there are loads more on the net as I don't think I can afford the Evenheat models and they are in the US and I am UK.
 
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timgunn

Well-Known Member
I’d avoid the Inkbird. There’s a thread on one of the forums where the OP has one and can’t get it to display over 1000 degC. There also seems to be a bit of a question mark over it’s auto tune, and It’s a pretty basic controller anyway.

I use Automation Direct Solo 4848vr or Omega CN7823 controllers. More expensive, but have ramp/soak capability. Both Omega and AD (through their UK outlet Lamonde) have good, patient, tech support in the UK. The controllers are the same with different badges so I tend to buy whichever works out cheapest at the time. Omega have the advantage of selling thermocouples too, so there may be a shipping saving to be had. It is definitely worth talking thermocouples with Omega’s tech sales people. I use typeN, rather than typeK but they can tell you the pros and cons of the various types.
 

izafireman

Well-Known Member
I’d avoid the Inkbird. There’s a thread on one of the forums where the OP has one and can’t get it to display over 1000 degC. There also seems to be a bit of a question mark over it’s auto tune, and It’s a pretty basic controller anyway.

I use Automation Direct Solo 4848vr or Omega CN7823 controllers. More expensive, but have ramp/soak capability. Both Omega and AD (through their UK outlet Lamonde) have good, patient, tech support in the UK. The controllers are the same with different badges so I tend to buy whichever works out cheapest at the time. Omega have the advantage of selling thermocouples too, so there may be a shipping saving to be had. It is definitely worth talking thermocouples with Omega’s tech sales people. I use typeN, rather than typeK but they can tell you the pros and cons of the various types.
Only just saw this reply, I will look at what you advise as have been looking at other models today which were the Omega CN7500 which has 8 separate segments with 8 ramps and 8 soaks per segment and with a type K thermocouple is rated to 1300c I think they said, higher with other thermocouples it also has a +/- 0.25% accuracy over the whole range from 0c- 1300c.

They do other thermocouples so what would be the best to go for as for as the max temp I would need?

I don't know how many segments would be needed but I though 8 might be enough as that's 8 steel types covered. I am also not sure of the max degrees C I would need......I would imagine 1300c plenty???? This unit is £91 and the SS relay is £21.

If I needed more accuracy the next model is their platinum range....a whopping 99 segments each with 8 ramps and 8 soaks.
Accuracy with a type K thermocouple is 0.4% over the whole range, but this unit is £166.

I am guessing the first unit would surfice?....Their customer supor was superb!

I need to call them and chat about other thermocouple for the first unit as the accuracy can be increased.

Cheers

Oh and I emailed Inkbird and they were very honest about their unit not having the range and also said they would pass on my comment as to why don't the do ramp/soak units.


 
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timgunn

Well-Known Member
I think the CN7500 series is "just" the 1/32 DIN version of the CN7xxx range of controllers. I have used the 7200, 1/4 DIN (96 x 96mm) and 7600 1/8 DIN vertical (48mm wide x 96mm tall) versions. I like the 7200 best because, being twice the size, it's easier to see the display from several feet away (and there's less tendency to fat-finger the buttons), always a consideration for an old codger. If/when I get to build an oven to keep, it'll get a CN7223. Most of the ovens I've built have gone to knifemakers younger than me and use the CN7823. The 78xx is the 1/16 DIN (48 x 48mm) version and that's the most common size for PID controllers. It therefore gives the most adaptability and I feel it's worth the extra 8 quid over the 24 x 48mm 75xx.

Knifemakers seem to be tidy individuals and may be a tad obsessive about keeping the wiring neat. However, it is a really good idea to leave an extra inch or two on the wiring to the back of the controller so that you have the option of changing it out later. Different models may have different depths behind the panel and different terminal layouts. A couple of inches extra on the wiring will accommodate this.

The Omega CN7xxx and Automation Direct Solo series controllers have the ability to autotune at 4 different temperatures and to automatically select the PID values for the autotune temperature nearest to the setpoint. If you make a control box with plug-in connections for the power out to the elements and for the thermocouple, you can use the same control box for an Austenitizing oven and for a tempering oven (which could be a mildly-modified toaster oven).

Plug in the tempering oven and run autotunes at, say, 100 degC and 499 degC. Plug in the Austenitizing oven and autotune at, say 500 degC and 1000 degC, set the controller to autoselect the nearest PID terms.

Now you plug in the Austenitizing oven for the high temperature stuff at 500 degC-plus (normalise, Austenitize), quench, plug in the tempering oven for the low-temperature stuff (sub-500 degC temper) and avoid the need to wait for the hi-temp oven to cool to lo-temp.

The CN7xxx has plenty of capacity for ramp/soak profiles for most of us. It is not very user-friendly to program though, particularly compared to the controllers on the likes of the Evenheats and Paragons. Not necessarily a problem, but something to be aware of.

My preference for a thermocouple would probably be an Omega TJ1NNXL-IM30U300

The TJ means it's a transition junction probe, with the extension cable fitted by Omega. This removes, or at least greatly reduces, the possibility of the user connecting it up wrong.

The NN means it's a typeN: originally developed as a "better type K" for high-temperature applications to overcome the "drift" that affects typeK thermocouples which spend much time above about 1000 degC.

The XL means it has the proprietary "Super Omegaclad XL" sheath, claimed to be good to 1335 degC (NOTE: if buying from anyone but Omega, you'd want a Nicrobell sheath, normally considered good to 1250 degC).

I don't know what the IM denotes (maybe mineral insulated?)

30U means 3.0mm outer diameter and an ungrounded junction.

300 means 300mm long. You might be ok with 150mm, but the 300 lets you bend it on a decent radius outside the oven and means that the Transition Junction does not stick out very far. For me, not losing a couple of inches of bench is worth the additional cost for the extra 6" of thermocouple. YMMV.
 

izafireman

Well-Known Member
I think the CN7500 series is "just" the 1/32 DIN version of the CN7xxx range of controllers. I have used the 7200, 1/4 DIN (96 x 96mm) and 7600 1/8 DIN vertical (48mm wide x 96mm tall) versions. I like the 7200 best because, being twice the size, it's easier to see the display from several feet away (and there's less tendency to fat-finger the buttons), always a consideration for an old codger. If/when I get to build an oven to keep, it'll get a CN7223. Most of the ovens I've built have gone to knifemakers younger than me and use the CN7823. The 78xx is the 1/16 DIN (48 x 48mm) version and that's the most common size for PID controllers. It therefore gives the most adaptability and I feel it's worth the extra 8 quid over the 24 x 48mm 75xx.

Knifemakers seem to be tidy individuals and may be a tad obsessive about keeping the wiring neat. However, it is a really good idea to leave an extra inch or two on the wiring to the back of the controller so that you have the option of changing it out later. Different models may have different depths behind the panel and different terminal layouts. A couple of inches extra on the wiring will accommodate this.

The Omega CN7xxx and Automation Direct Solo series controllers have the ability to autotune at 4 different temperatures and to automatically select the PID values for the autotune temperature nearest to the setpoint. If you make a control box with plug-in connections for the power out to the elements and for the thermocouple, you can use the same control box for an Austenitizing oven and for a tempering oven (which could be a mildly-modified toaster oven).

Plug in the tempering oven and run autotunes at, say, 100 degC and 499 degC. Plug in the Austenitizing oven and autotune at, say 500 degC and 1000 degC, set the controller to autoselect the nearest PID terms.

Now you plug in the Austenitizing oven for the high temperature stuff at 500 degC-plus (normalise, Austenitize), quench, plug in the tempering oven for the low-temperature stuff (sub-500 degC temper) and avoid the need to wait for the hi-temp oven to cool to lo-temp.

The CN7xxx has plenty of capacity for ramp/soak profiles for most of us. It is not very user-friendly to program though, particularly compared to the controllers on the likes of the Evenheats and Paragons. Not necessarily a problem, but something to be aware of.

My preference for a thermocouple would probably be an Omega TJ1NNXL-IM30U300

The TJ means it's a transition junction probe, with the extension cable fitted by Omega. This removes, or at least greatly reduces, the possibility of the user connecting it up wrong.

The NN means it's a typeN: originally developed as a "better type K" for high-temperature applications to overcome the "drift" that affects typeK thermocouples which spend much time above about 1000 degC.

The XL means it has the proprietary "Super Omegaclad XL" sheath, claimed to be good to 1335 degC (NOTE: if buying from anyone but Omega, you'd want a Nicrobell sheath, normally considered good to 1250 degC).

I don't know what the IM denotes (maybe mineral insulated?)

30U means 3.0mm outer diameter and an ungrounded junction.

300 means 300mm long. You might be ok with 150mm, but the 300 lets you bend it on a decent radius outside the oven and means that the Transition Junction does not stick out very far. For me, not losing a couple of inches of bench is worth the additional cost for the extra 6" of thermocouple. YMMV.
WOW TIM...….thanks for the in depth reply, most of that has gone right over my head :)) so I will have ti sit down and also send it to my father and pal who will be helping me with the builds. Really appreciate this.

Cheers

Pete
 

izafireman

Well-Known Member
Timgunn , above are the images I couldn't upload in the PM......not sure how to do that. So is that unit any use for a tempering oven or useless as most likely one segment?
 

timgunn

Well-Known Member
One segment, but that's ample for a tempering oven.

It's even good enough for Austenitizing many steels. The biggest limitation of not having ramp/soak (or at least ramp) is that you probably won't be able to anneal air-hardening steels. Most Carbon steels will anneal if you switch off and let them cool with the oven.

I think the E5CS probably has the input type set in hardware, giving limited (or perhaps even no) input choice. I'm too tired to read the manual properly ATM. If yours will take a suitable input, and has a suitable output, you may be fine with it.

If you can get the full part number, that should give all the information needed. I'll take another look once I've slept.
 

izafireman

Well-Known Member
One segment, but that's ample for a tempering oven.

It's even good enough for Austenitizing many steels. The biggest limitation of not having ramp/soak (or at least ramp) is that you probably won't be able to anneal air-hardening steels. Most Carbon steels will anneal if you switch off and let them cool with the oven.

I think the E5CS probably has the input type set in hardware, giving limited (or perhaps even no) input choice. I'm too tired to read the manual properly ATM. If yours will take a suitable input, and has a suitable output, you may be fine with it.

If you can get the full part number, that should give all the information needed. I'll take another look once I've slept.

Ok will try, many thanks

Pete
 
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