Arduino, thermocouple, firebricks, and heating elements?

Kevin Zito

KNIFE MAKER
If I know how to program an arduino to do pdi control, is it feasible to make a halfway decent HT oven for far less money than an even heat or paragon? I see that the heating elements they sell are like $55.
OR
is this realistically a complete disaster waiting to happen. Thanks!
 

C Craft

Well-Known Member
It is feasible. You got to have some knowledge in electrical, have the ability to tunnel the brick for the heating elements and I would look into what that $55.00 is as well! That sounds light on price. I have several tutorials/WIPs on building your own. I will see if I can dig them up and you can do some reading!!

OK I have been trying to open 15 -20 old links I had. The problem is most of them are too old and no longer work. Go to search here on KD and search for heat oven. Some of the links I had are from here. Go to bladeforums.com and do a search. If you are not a member you can still see some info as a guest. Do a google search, or Bing, https://www.bing.com/search?q=homemade+heat+treat+oven&FORM=QSRE4 , here is another https://www.bing.com/images/search?q=Plans+for+Heat+Treating+Oven&FORM=RESTAB click on the pics and often the info is still out there you just have to find a way into it!!

There is a ton of info to sift thru. I have all those links and now most won't open or the pics were lost in the Photobucket BS but the info is there and it can be done if you have enough of a want to!!!

Almost all of the components can be bought on line!!
 
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KenH

Well-Known Member
Kevin, rather than use an Arduino I'd get one of those $20 to $30 PID controllers off ebay to control. Of course with an Arduino you could perhaps have 2 or 3 different programs and select the one you wanted with a button. If you're really good, you could use an Arduino Mega with a touch screen display and make it really fancy.

Here ya' go - F or C display for $22 shipped: https://www.ebay.com/itm/110862594914?

Here's a thread you might like to read thru: https://www.bladeforums.com/threads/heat-treat-ovens-some-basics.1022992/
 

Gliden07

Well-Known Member
Kevin lots of vids on You-Tube too. There was a gent on there that made a tool to groove the soft refractory bricks with a block of wood a piece of mild steel with a slot (so he could adjust the depth) with a bolt through it (real simple layout).
 

C Craft

Well-Known Member
Kevin when it comes to PID controllers go with http://www.auberins.com/ easy-peasy, easy to understand, easy to set-up. IMHO

Just because I throw information at you, you need to pick out what works for you!

PIDs can be easy to program or frustrating to point of screaming!! I am just mainly trying to give you something to reference " how to by"!!
Pick the things that are the best and combine them into your build if you decide to go that way!!!!
 

C Craft

Well-Known Member
One thing to keep in mind in all this is safety. Those coils are ready source electricity and accidently touching a blade to one is well,............lets say a real bad day! A HT oven must have a safety switch so the power has to be off before the oven opens! The direction the door opens is something to think about as well and having a counter weight is a plus at the door when you have a handful of hot knives! Take a look at this one. 1525437039349.png You have to think where is that hot door when you are reaching into the oven and that door will stay hot for a while! This one the door flips up. 1525437365785.png Which to me sounds a better idea to me about getting it out of the way. This one has a spring system to keep it up while you are in and out of it!!! 1525437473108.png Here is a side mount door with a counter weight, so there is many ways of doing it! You just do not want to accidently come in contact with that hot door!!

Any and all electric connection need to be enclosed to avoid electrocution. Also a little planning ahead on how the power enters your cabinet is good as well. I remember a thread where a fellow had an oven he built and it was up and seemed to be working well. He had penetrated the cabinet with his electrical leads on some home made brass rods. The oven got slid back on the bench accidently and the 220V touched the metal the shed was covered in. He lived the oven fried and he learned a valuable lesson.

Do your planning ahead and it is feasible to do! :)
 

Kevin Zito

KNIFE MAKER
You all make some very good points. Thanks for resources as well. I’m gonna research this fully. I want something really small ... if it can do 5 - 8 inch knives at a time, that is plenty. Later, I can move up. I simply hate sending my blades off for HT. That is a pain.
 

latticino

New Member
If that is the size you need then I suggest you keep your eyes open for a used enameling kiln. With the addition of a thermocouple, PID controller and contactor (and microswitch for the door) it is pretty easy to repurpose one as a heat treat oven.
 

Andre Grobler

Well-Known Member
You all make some very good points. Thanks for resources as well. I’m gonna research this fully. I want something really small ... if it can do 5 - 8 inch knives at a time, that is plenty. Later, I can move up. I simply hate sending my blades off for HT. That is a pain.
You almost WILL have a heat gradient front to back in the oven... make the oven at least twice as long as the longest blades... and i am hesitant to havbe 5 blades in the oven at a time, as the radiation will almost inevitably be irregular if some blades are shielded from the elements and others not, or one side of the blade is shielded and another not... or closer to the one element than the other... but I worry about a lot of things that may not need worrying about...
 

timgunn

Well-Known Member
None of it is particularly difficult, but the differences between poor HT ovens and very good HT ovens are not necessarily apparent to most people, though some can quickly become apparent once the mistakes have been made.

Much of the value in an HT oven from the big names is that they've made the mistakes over the years and corrected them. Doing it yourself can get expensive if it needs to work as well as the commercial offerings. My second oven was certainly considerably better than my first and I'd like to think that my seventh and eighth (which were built at the same time and could join together to make one 56" long one) were actually pretty good.

One of the things I learned pretty quickly (with a datalogger and an assortment of thermocouples) was that overshoot on tempering is a big problem if you don't take precautions to overcome the effects Andre mentions. A slow ramp to setpoint will pretty much eliminate the problem, so I'd regard ramp-soak capability as very worthwhile.

Overshoot tends not to be a significant problem at Austenitizing temperatures, so if you temper in a different oven, ramp/soak may not be a factor.

The small size you are looking for makes 110V almost essential, since it is difficult to get a short enough element using a reasonably thick wire on 240V. Going too thin with the wire will give a short element life.

As Latticino says, a used enamelling kiln is probably your best bet. I'd build a completely separate control box for it and use a 48mm x 48mm PID controller with SSR(s?). That way you can use it for other things. The controllers I use are either Omega CN7823 or AutomationDirect Solo SL4848VR controllers with pulse DC outputs to drive SSRs. As far as I can tell, they are the same controller with different badges and I buy whichever is cheapest at the time. Auber don't have a UK presence so I have not tried theirs. Those who have seem to consider them good.

Using an Arduino instead of an off-the-shelf controller could probably work well. Whether or not it's a good idea in this case is really down to how familiar you are with process control. The tuning is key to operation and most of the off-the-shelf PID controllers have pretty good self-tune capability. I'm old enough to remember tuning PID loops manually on pneumatic controllers and know that the controller itself is only a small part of the picture. If you can program an Arduino for ramp/soak and tune it well, it should be good.

TBH though, I'd be inclined to take the view that in asking the question you have indicated that you probably don't understand process control enough to do it well yet. If you need it to "just work", don't do it. If you want to learn, and are happy to make some mistakes to learn from, go for it.
 

Kevin Zito

KNIFE MAKER
Again you guys have hit on some really important points. Looking more and more like another $11-1200 is needed for the budget.
 

Gliden07

Well-Known Member
Again you guys have hit on some really important points. Looking more and more like another $11-1200 is needed for the budget.
When funds permit I'm getting me an Evenheat. $1400.00 set up the way I want. I am getting the door off function for safety and I read an article saying that the coils will oxidate by opening door and exposing to the cool air? Kinda made sense to me?
 

C Craft

Well-Known Member
Kevin, its the little things that kill you! And I ain't gonna preach on safety, cause I have already been told on another forum I am too old to be relevant!!

I will tell you this and most electricians will probably back me on this one! 220 Volt will knock you so hard, you will think you just went 10 rounds with the heavy weight champ but, most times it will knock you loose! However that little ole fellow 110 Volt will grab on and hold till sweet death is about to enter the picture.

Ovens are not that complicated it is the electronic side of it that need a fair amount of thought and time put into it. Back to your original question. Is it feasible to make a halfway decent HT oven for far less money than an even heat or paragon The short answer would be yes. Think of it this way it is nothing but a frame with a skin, and firebrick for insulation. However the safety side of the door the shut offs, and how the electronic work is the very most important part to get right!!! It is also the reason the sell them from the big companies. They have over the years been thru all the trials and tribulations and heart breaks where they thought they had it figured out. Believe me with law suits like they are today, they better have it figured out!!

However if you do decide to build yourself re-search it well. and here is a piece of advice a seasoned maker once told me, if you think that you can only have need for a small capacity oven, build it for twice that big.
However the down side to that is just like heating a house that extra space has to be heated! Then he laughed and told me or you can do like me, I am about to build my fourth oven I have had since I started!
The first one was too poorly done, the second was too small and the third was not efficient and so I am about to hit the mother load and build my fourth, "the mother of all ovens". He stood, there silently for a minute and laughed again and said, I just hope I don.t have to add one of those bad words after mother, ........................... with this one!!
 

scott.livesey

Dealer - Purveyor
look for other sources. go to sites and look for used lab furnaces. these are furnaces designed to heat quickly and evenly in addition to lasting for years. they are not pottery kilns with a different name. at the same time, look for a used front door pottery kiln. a big decision is how big your knives will be. a 36" deep furnace is kinda silly if the biggest blade you plan on making is 16"(12" blade with 4"full tang). unless you have some back round in electronics and electrical installation/maintenance, I would advise against trying to build one. just too many things that can go wrong and most of the things that can go wrong will kill you.
 

scott.livesey

Dealer - Purveyor
a used lab furnace example https://www.ebay.com/itm/General-Sigma-Lindberg-Bench-Top-Laboratory-Oven-Box-Furnace-51894/122959835332?hash=item1ca0fa30c4:g:P0sAAOSwYNxafhv4 chamber is 9x9x14", heats to 2050F, if you find one close, you can save on shipping. just a thought.
this is another way to go when starting out https://www.ebay.com/itm/PARAGON-E9S-ELECTRIC-KILN-120V/292548763623?hash=item441d43dfe7:g:LIsAAOSwHLFa63kG paragon still makes an E9 kiln. I got mine for $250 delivered. only goes to 1650F so you are limited to high carbon steel. but $250 is a lot less than $1500.
this is similar to the lab furnace I bought https://www.ebay.com/itm/LINDBERG-FURNACE-OVEN-51442-1200C-WITH-CONTROL-230V-NIVC/302137081799?hash=item4658c5ffc7:m:mb4OWMQvXyAchCwg0cD7WbQ 5x7x16" is plenty big and 2200F is plenty hot. I found mine for less than this and picked it up myself instead of shipping.
good luck
 
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Gliden07

Well-Known Member
I was thinking about building my own but as Mr Craft said he's getting ready to build his 4th oven. I don't have the time to build what I want now never mind 4 ovens (no offense C Craft)!! Still building my forge. Have to get my anvil finished up want to start moving forward with my forged stuff and want to up my game with better finishs on my stuff! Gotta say enough is enough I'm gonna buy mine! Hope it works out for you, if you do decide to do it I will follow along and cheer you on!!
 

C Craft

Well-Known Member
However if you do decide to build yourself re-search it well. and here is a piece of advice a seasoned maker once told me, if you think that you can only have need for a small capacity oven, build it for twice that big.
Not I, this was another maker talking to me! I personally have built a lot of my own equipment but I always try to build it as save as I know how to. Now the fact that the seasoned maker was building his fourth,............ IMO that in its self says a lot!!!

I also had another maker when I was asking details on building something, (can't remember at this moment what it was, but the advice stuck)!
He told me I learned to think about it like this, would you rather be building equipment or building knives!!
 
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