Hey guys. I keep getting requests to do a Lost Resin
Casting guide, also known as Investment Casting, covering all the steps and equipment needed to
turn a 3D print into solid metal, such as bronze, silver, gold or whatever, so that’s my aim today.
I’ll also be looking at ways of saving money, as this can be a very expensive technique,
but fortunately I’ve developed a few low cost budget solutions that may help.
As you’d expect, this process begins with a 3D resin printer, but model and brand really doesn’t
matter. Honestly any resin printer will do so choose according to your budget and needs though,
of course, the better the print quality you can achieve, the better your metal castings should be.
The magic ingredient for Lost Resin Casting is the resin itself. Ordinary
resins just won’t work properly, so a specialised Castable Resin is needed.
I’ve tested a number of castable resins and so far at least, my personal favourite based
on affordability, printability and casting results is Siraya Tech Cast.
It does a great job and doesn’t break the bank, but like all things, it’s a personal preference.
A printed pattern needs to be encased in specialised plaster
and to hold this we need a metal flask. There’s two main sorts of flask, perforated
and solid. Perforated are much more expensive and require costly vacuum systems as I’ll cover
in a moment, but for those on a budget or with smaller needs, these solid flasks are
nice and cheap and can be used with my homemade vacuum system, which I’ll mention in a moment.
Specialised casting investment plaster is needed and this you really shouldn’t skimp on.
This is NOT plaster of Paris.
It’s a special blend of plaster is actually porous, allowing a vacuum to pass through it.
This plaster needs to be carefully weighed and mixed
according to the manufacturer’s instructions, so an accurate set of weighing scales is also a must.
The 3D print gets attached to wax sprues. I use a Wax Pen for this as it precisely melts
the wax giving the user control. There’s a thick central trunk and often smaller branches, which
gives us what is commonly called a casting tree. The Wax trunk sits in a rubber or silicone base,
though I’ve had great success with printing PLA bases.
The weighed investment powder is then mixed with distilled water, working within specific
temperatures and time frames stipulated by the plaster manufacturer. It then needs to be vacuumed
before being allowed to rest usually for not less than 90 minutes before going on to the Oven.
Vacuuming the mixed plaster is critical as is ensures proper consistency and removes unwanted
trapped air, and ideally you’ll need a vacuum chamber and vacuum pump. These are very expensive,
but I did create my own very simple and very cheap vacuum chamber and manual PVC pump,
which I successfully used on dozens of occasions. Later I upgraded to the Arbe Casting system
which does it all, working with both solid and perforated flasks for improved results.
Once the plaster has set and rested, it needs to be cooked in what’s commonly called a ‘Burnout
Oven.’ This uses a carefully controlled heating sequence taking several hours. The wax and resin
burn away cleanly, and the plaster is baked to prepare it for casting at very high temperatures,
so your kitchen oven just won’t do it. This means you WILL need a burnout oven. Now again, these can
be VERY expensive, though I am talking to various manufacturers to try and get cheaper options.
In the meantime I built my own electric furnace for just a few hundred pounds
and it’s much easier than you’d think. Yes, I employed a fancy hoist mechanism to raise
and lower it, but that drives up the cost and you might not need something this complex. You could
keep things much simpler and therefore cheaper. Once the burnout cycle is complete,
it’s time to melt some metal. You can’t use the Burnout Oven as that’s already busy,
plus a higher temperature is likely needed. So a second furnace is required.
Gas is very quick and I’ve already reviewed the Devil-Forge furnace
which does a fair job, but you can’t accurately control the end temperature.
For that reason I personally prefer electric furnaces, which work indoors,
are very quiet, reasonably quick and are very capably control the temperature.
This budget furnace I reviewed recently is still doing well so it’s worthwhile considering.
When it comes to the pour, again you’ll want to vacuum your flask.
Now trust me, I tried lots of ways to NOT use a vacuum and none of these achieved
suitable results. But when I finally came up with my homemade vacuum chamber and pump,
my results changed dramatically for the better. The purpose of the vacuum is simple. The resin
print has burned away leaving a print-shaped hole inside the plaster. Molten metal is poured in,
but this has trouble filling all the nooks and crannies. A vacuum system pulls on the
metal through the plaster, removing trapped air pockets and pulling the metal into every crevice.
When starting out, my homemade system will serve you well though, if possible, replace the plastic
pump with a proper vacuum pump, as manual pumping is a bit of a pain. Now my pump states that it
should NOT be used on anything hot. But I’ve it on dozens of occasions with a long hose,
all without incident - but do this at your own risk as these are expensive things to break.
However, of course, something like the Arbe System is a much better choice and
does the job faultlessly, though it will cost you that bit more.
Plunge the flask into a bucket of water a few
seconds after the red glow has gone from the visible metal.
Finally, it’s time to clean up your casting, cutting away the sprues and filing things smooth.
For this a simple jeweller’s saw works great and metal files help clean things up.
However, a multitool like a Dremel gives you cutting, sanding and polishing options.
A better choice would be a Foredom which has a strong, long-lasting motor to do the job better,
though these are expensive. Thankfully I recently reviewed the Arbe Pro-Flex system
which does exactly the same job for less than half the price.
I enjoy polishing this way as it gives me a feeling of control,
though I have made a vibrational tumbler which, though noisy, works fairly well. There’s also
the option of a barrel tumbler, which uses water and metal shot to planish the castings.
Before I move on, a lot of the aforementioned is covered separately and in more detail in other
videos, so I’ve put together a Video Playlist as well as list these video in the description,
to make life easier. I’ve also placed links to products for you guys,
but feel free shop around, especially if you’re in a different part of the world to me.
Lastly, don’t forget the safety equipment. I’ve never covered this in detail as it’s largely
a personal choice and common sense, but here’s my minimum recommendations.
A full face cover – not just goggles, as molten metal can splash.
A thick leather apron and sturdy boots, for the same reason.
Quality gloves to stop you burning yourself. And finally, a mask, especially if you
don’t work in a well-ventilated area, which you really should.
So in a nutshell, that’s investment casting. The technique can be applied to Resin, Wax
or PLA, but I personally love the ease and convenience of Resin printing.
It’s not the cheapest pastime, but it does allow you to make some fantastic things.
If you have any questions, as always feel free to drop me a line.
So that’s it for now guys. Take care and thanks for watching.