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.