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Amoled
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Any interest in Tube Furnances?
Hey, I am building 5 Tube Furnances in the near future, is there any interest of getting one, because I dont need 5 Tube Furnances but only one or two
I can say you the price for it later, and also will post the process of making one in this forum. Just want to know if there is general interest in
tube Furnances.
Greetings
Amoled
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JJay
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Perhaps. It depends on price, quality, maximum temperature, size, durability, etc. I've built several low-quality tube furnaces. The thought of
building a high-quality one has certainly crossed my mind, but the materials can be expensive and require ceramics skills to work with if you want
high durability and high temperatures.
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Melgar
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Sure. Would prefer to trade reagents and/or equipment for one, if possible, as I'm short on cash right now, and have too much chemistry stuff.
The first step in the process of learning something is admitting that you don't know it already.
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Amoled
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Yeah, it will take some time, but theoretically I also would trade equipment.
I will do my best to provide good quality, but I don't know, whats your expactation of good quality and high temperature. 
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JJay
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1300 C, usable in both vertical and horizontal configurations, capable of regular use for years with minimal maintenance?
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Melgar
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I guess it should be able to get pretty close to the maximum safe operating limit for the heating element (kanthal, I'd imagine?), without burning
out. And you should run it for at least a few hours at its high temperature to make sure it all works. I guess as long as the temperature can be
measured with a thermocouple, and the power can be adjusted, that should be fine. You should probably just make a k-type thermocouple built in. I
have two thermocouple readers already.
I don't mind fixing it on occasion, and it should probably not be completely sealed up for that reason, unless absolutely necessary. I probably have
to fix the stuff I made myself more than anything else, so I wouldn't demand higher standards from others.
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Amoled
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At the moment it's just planned for horizontal use, but should be possible to change this,
As for now the material that were planned for the furnance would withstand around 1200°C-1300°C, but also this should be no problem, and I should be
able to get materials that are just slightly more costly, but can withstand 1500°C, but another material for the heating coil must be used. The size
would be around 400/450mm
[Edited on 10-11-2017 by Amoled]
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macckone
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Quartz tube will work up to 1200C, Kanthal A1 wire up to 1400C, so 1200C max
assuming reasonable loss in transmission into the tube. This combo is actually
cost effective.
For higher temperatures you can go to aluminum oxide 1700C but then
heating stuff becomes more of an issue and you are probably going to want to
go to flame heating. Molybdenum heating elements can go up to 1850C
they are quite pricey and dont wrap around the tube well.
At extra high temperatures you will want to go to arc furnaces.
K type thermocouples also max out around 1200C so planning on
a tube furnace that goes to 1200C is reasonable.
Going to higher temps gets exotic and expensive.
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violet sin
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Are you using a commercially available piece for reference? I picked up a desktop vertical model for 80$ used at the pawn shop. Lind
sola-basic. It is a two piece set, oven and controlled box. Quite heavy when you stack one on the other and cary around, but not impossible. I'm
not saying this is pertinent for price, but construction is pretty bulky and industrial feeling. You could use it to beat up a geo metro, and I bet
it would still function.
On the other hand I have seen a bead-makers kiln from an old Stanley toolbox, ceramic fiber mat and a quarts heater element from a room heater.
It got hot and worked for borosilicate.
So it doesn't HAVE to be able to take on a small auto head to head and still be useful. Though with hight temp, more protection/safety would be
most important. This illustrates how having already seen a real model, the knock off may look wimpy. If I hadn't seen the real one, I bet that
toolbox/fiber mat version would have been way more impressive. Home projects versions may be not hold up to experienced users expectations.
I am not discouraging you from building at all, quite the opposite. It's hard to improve your vision if you never make one. Best of luck building,
favorite way of learning.
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macckone
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22mm id tubing can be had for around $35
Kanthal wire is pretty cheap $10.
Insulation can be had for $15.
The real expense is the controller and that is something
that is expensive to buy.
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NEMO-Chemistry
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Quote: Originally posted by macckone  | 22mm id tubing can be had for around $35
Kanthal wire is pretty cheap $10.
Insulation can be had for $15.
The real expense is the controller and that is something
that is expensive to buy. |
Can i ask what kind of controller are normally used, and what kind are you thinking of? Ive had an idea for a long time, its from something I did at
school two years ago.
While it didnt involve temperature, I might have a reasonable solution for a controller, no idea how accurate it would be though.
In a nut shell we did some stuff on light and light detection, but it crossed my mind that with 3 different leds, it just might be possible to measure
pretty high temps.
I guess its a bit like a IR method used in IR thermometers but simpler.
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JJay
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| Quote: Originally posted by macckone | 22mm id tubing can be had for around $35
Kanthal wire is pretty cheap $10.
Insulation can be had for $15.
The real expense is the controller and that is something
that is expensive to buy. |
The controller is the easy part 
I'd just use an oven dimmer (this one for example, although Sulaiman can surely find a better one: https://www.ebay.com/itm/4000W-AC-110V-120V-SCR-Voltage-Adju...), perhaps with an Arduino with a temperature probe and a relay.
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macckone
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Jjay, that will work as long as you don't need close tolerance control.
For close tolerance work, you need a PID controller.
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JJay
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I am a human PID controller
But yeah, digital control of the dimmer would be nice....
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Melgar
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Just program in some fudge factors with an Arduino, and I bet it'd work as well as any PID. Possibly even better, since you'd be calibrating it to
your specific hardware.
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NEMO-Chemistry
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There are loads of Arduino PID libraries around. Chances are you wouldnt be far off.
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JJay
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By adding an LCD module to the Arduino, the controller could emit helpful messages such as, "Decrease power to 30%," and "Turn the power on dummy."
You can get some dimmer-like action out of a relay by cycling it on and off, but I like to avoid that as much as possible. I hadn't given much thought
to what would go on the Arduino, but you could use a recurrent perceptron library or something if you really wanted to be hardcore and lazy at the
same time.
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Amoled
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I wanted to work with a PID-Controller, coz I never really worked with an Arduino, only with a Raspberry Pi, and an Arduino seems to be somehow
completly different, I think I should look into all this Arduino things, because all these project I've heard of, you could possibly do, sound very
interesting.
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Melgar
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| Quote: Originally posted by JJay | | You can get some dimmer-like action out of a relay by cycling it on and off, but I like to avoid that as much as possible. I hadn't given much thought
to what would go on the Arduino, but you could use a recurrent perceptron library or something if you really wanted to be hardcore and lazy at the
same time. |
Lots of circuits do that, except they use MOSFETs instead, because they don't have any moving parts. The main advantage of relays is being able to
isolate power sources, and also to easily switch AC.
I've had to take multiple undergraduate and graduate classes on control systems, and they're often quite sophisticated. For example, your
thermocouple is presumably outside of the tube and your object in it, right? Say you want to program it to heat the object to a certain temperature.
Most heating devices would heat until the thermocouple read that temperature, then maintain that temperature. But it could take a lot longer for your
object to reach that temperature. So you could initially overshoot the temperature based on the size and material of the object (entered at the
beginning) and then stop heating at a certain point such that the object's temperature will be rising as the tube's is falling. So you reach your
target temperature much faster that way.
Another way you can do that is mechanically, so that your thermocouple is an adjustable distance from the tube. That way the thermocouple temperature
more closely matches the inside of the tube. Less control, but a lot easier.
But Arduinos could also have programs to, say, gradually increase temperature over an hour, hold it there for three hours, then gradually decrease it
back to room temperature over the course of an hour. Or cycle temperatures, even. Or program it to turn off if it detects flammable gases. Or hook
up an outlet, so you can plug something into the the outlet, that the Arduino can turn on and off. Say a fan, or an ultrasonic wave generator.
The first step in the process of learning something is admitting that you don't know it already.
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JJay
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I kind of assumed solid state relay (I think they are based on MOSFETs, but they might as well contain powdered goblins for all I know). I don't like
them cycling on and off because of the uneven heating and erratic magnetic fields. I am a competent programmer, and I personally would not use a
recurrent neural network to address temperature changes, but that's one way to do it....
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Melgar
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| Quote: Originally posted by JJay | | I don't like them cycling on and off because of the uneven heating and erratic magnetic fields. |
You really have to do it that way though, or with a PWM system. Reason being, a component doesn't generate much waste heat in either the
totally-closed or totally-open states, but if you try and partially close the component... well, now it's a resistor and is wasting a lot of heat and
probably burning out.
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JJay
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Pretty much... I mean, you could probably use a DAC with op-amps and diodes, but I'm not about to attempt to put together a circuit like that given my
level of experience.
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NEMO-Chemistry
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Triacs are used with AC, pref one with zero point crossing detection, that way you can safely switch upto 50 or 60 times a second (depending on
country).
I got a circuit for a pic micro with a decent triac switching circuit, its no big deal to swap out the pic for Arduino.
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macckone
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Buying an off the shelf PID controller would be ideal if you have unlimited funds.
However an arduino, k-type thermocouple, and a triac with a zero crossing detector could be cost effective.
k-type thermocouple - $10
arduino - $25
call it another $15 for other parts
That is $50.
That puts the whole project at about $110.
Of course scrounging and getting some of this stuff for free is possible.
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yobbo II
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Sticky here
https://www.sciencemadness.org/whisper/viewthread.php?tid=97...
Pids can be had for cheap.
https://www.ebay.co.uk/itm/Digital-LCD-PID-REX-C100-Temperat...
This one is supplied with k type but will probably work with lots of different types of tc
Check with seller. You set the type of tc in the controller.
Below iss better than k type. A bargain imo. K type will give trouble if continously run at 1200c
https://www.ebay.co.uk/itm/225mm-WRP-100-S-type-Platinum-Rho...
Yob
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