Damn, these are expensive. We can do better than that…
Hey guys, a burnout oven is a useful bit of kit if you’re into Lost Wax Casting and
Lost PLA Casting, or even if you’re looking for a Pottery Oven, though they’re not cheap.
But you can make one MUCH cheaper, especially if you make use of a programmable PID.
Today I’ll be converting my electric furnace into a burnout oven. I’m going to be taking
a quick look at the CAL 9500P unit and showing how it can be used to Step, Ramp and Soak,
which are extremely useful functions. Now I’m not going to be telling you how
to make an electric furnace here, because I’ve already covered all that in other videos,
AND for this tutorial you will need an electric furnace.
I made my electric furnace out of Grade 28 insulating firebricks. Again they’re not
cheap, but they’re nice and light, so they’re easy to work with. Cutting these precisely
is simple if you follow my short video guide. Next you’ll need heating elements - resistance
coils. Now you can buy these, but you’ll save a bundle on MUCH better quality if you
make your own. I used Kanthal wire and made these with a simple jig. Look out for this
video tutorial on Coil Elements where I show you how to build the jig and use it. I also
cover all that nasty maths and make it easy with a free online calculator.
Building the furnace was much easier than you’d think. You really don’t need building
skills or a certified electrician to do this. Just common sense and a safe working practice
will do the job. And these video tutorials cover everything in FULL.
Now I was a little ambitious with my furnace build. I incorporated a lifting mechanism
to raise the furnace for easy crucible access, but this really isn’t necessary. A simple
box construction would do the job for you, with a lid made from lightweight insulation.
I ran my furnace with a simple PID controller and it still works great. Tap in the temperature
and sit back and wait. But that’s not how a burnout oven works.
Burnout ovens need much more control. This can be affordably achieved using the CAL 9500P
process controller. There are other units out there, but this was the one I went with.
Again it’s not cheap, but with a bit of shopping around I got mine from here at a
great price with excellent service. It’s a 1/16 DIN controller, so it fitted
perfectly into the opening left in my old control unit.
Wiring it up was an absolute doddle with these screw terminals. And the wiring was basically
the same as with my other PID, with only the terminal numbers changing.
I will admit the instructions baffled me a little initially, but I got there. For my
purpose, the initial configuration of the unit went like this.
Input type for me is a Type K Thermocouple. I know that doesn’t look like a K but it
is. My Unit preference is Celsius, though Fahrenheit
and other units are available. The main output is a Solid State Relay so
I chose SSD for Solid State Relay Driver. And that was as much information as I needed
to put in, so I ignored the unit for 60 seconds as I puzzled over the manual and it thankfully
took itself back to the default display. What it now needed was a program. The CAL
9500P allows up to 31 programs to be stored, and each program can be thought of as a burnout
sequence. This is the recommended burnout sequence for
the investment plaster I use, so this seemed an obvious choice for my first Program. So
let’s do it. From the default display, press the Up & Down
arrows at the same time for 3 seconds. Down arrow.
Star and down Arrow for Level P which is how we add programs.
Up Arrow, and this is Program 1, which is perfect, so Up arrow.
Now Run is exactly what it sounds like. Should the Run Program be on, off or on hold? The
default is “off” and we’ll keep that so Up Arrow.
“Fail” is in case of power outage, and what the unit should do next. For now I’ll
select Continue. I’m not interested in this, or this, but
Seg 1 is needed. Each action can be thought of as a segment
– a doing point if you like. The very first thing we need to do is get
the temperature up to 230 within an hour. Now we could ramp this, but it’s not indicated
as being necessary, so I’ll start with a Step.
So Type is Step. The Temperature of that Step is 230.
EoP I’m not interested in. That’s segment one finished, the first instruction,
so let’s add segment 2. Well on the diagram a 3 hour soak is recommended
here. So Type is Soak.
The Soak Interval or duration is 3 hours which is 180 minutes.
EoP still not interested. Add another segment and this time we want
to Ramp the temperature all the way to 730 degrees but, importantly, at a rate no faster
than 150 degrees an hour. So… Type is Ramp.
Ramp rate per hour is 150. And the target temperature is 730.
Hbu and EoP I’m not interested in, so it’s on to the next segment.
The diagram tells us once we’re at 730 it needs to Soak at this temperature for 4 hours.
So… Type Soak.
Soak Interval is 4 hours which is 240 minutes. EoP ignore.
Add another segment. This time the diagram tells us to drop to
our casting temperature and gives this as 630 degrees. It’s not bothered about the
rate of the drop, so we can just Step this down. So…
Type Step. Step target temperature, 630.
EoP none, and add one last segment. This last bit is just for me. I’m going
to allocate myself some time to get everything ready and I know what I’m like, so I’ll
add a Soak time of 2 hours, which is plenty, even for me.
So to exit the Program Level, hold the two arrow buttons for 3 seconds and return to
the main display. Now, a Program has been added, but how do
we run the program. Well I expected something easier, but it seems to run a program you
need to do the following. Hold the two arrow keys for 3 seconds.
Down Arrow. Star Down Arrow to Level P.
There’s Program one which is the one I want, so Up Arrow.
And Star Up to turn Run On. Now press and hold the two arrow buttons to
execute the program and return to the main display.
It takes a few seconds whilst it has a think and you can see it’s saying Soak 230, which
is effectively what we asked it to do. I’m surprised it doesn’t say Step 230 and then
Soak 230, but ultimately it’s the same thing in this case.
And the irritating flashing green light indicates that everything is on. So the Solid State
relay will have triggered and the coils will have been energised.
And it works. It takes a bit of getting used to, but the
CAL 9500P allows me to convert my furnace into burnout oven.
Just one last tip, remember to vent. Plaster, for instance, holds a lot of moisture which
doesn’t fully disperse until around 400 degrees Celsius, so I wedge a small metal
flat bar under the lid until I reach 400. This venting helps extend the life of the
coils. I just want to say that this video wouldn’t
have been possible without the support of my Patrons. It’s through their kind donations
that I’m able to bring you builds like this, so if you think you could spare the price
of a coffee each month, then please take a look at my Patreon account.
And that’s it folks, an electric furnace made into a burnout oven with a programmable
PID, for hundreds as opposed to thousands, which is a significant saving.
Hope you enjoyed this one guys. Take care and thanks for watching.