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Equipment Needed for Casting of Bronze


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Hi all:

 

In my on-going quest to fill my garage to the point of absurdity, I'm contemplating getting the equipment to do lost-wax cast bronze fittings.

 

Having long admired the work of Jake Powning, Anders Hogstrom and others who use this technique to produce blade fixtures, I'd love to learn how to do it.

 

From what I can gather from Jake's tutorial and other on-line sources, the two major peices of equipment necessary to do this are:

 

1: A kiln in which fire the molds.

 

2: A vacuum casting chamber in which to cast the bronze.

 

Also, I suppose, I would need to build a forge in which to melt the bronze (which I think I understand pretty well).

 

Here are the two items I'm looking at purchasing:

Vaccum Chamber

 

and

 

Electric Kiln

 

Any advice on if these are good choices, other types of equipmen/tools I'll need, books/videos on bronze casting, etc. would be appreciated.

 

Cheers,

 

Dave

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err.. if you buy a kiln.. ..evenheat has that smalley kiln that could work...and its cheep...... but does it go high enough?

http://www.evenheat-kiln.com/knifeovens/artisan688/artisan688.htm

 

if you think bout it... maybe i'd be worth it to get a long kiln.. then you could do bronze and heat up long swords.. ( myself i got that 40 inch biggy, as i ain't foolin around noooo more )

 

after seeing that sword you made.. go for it... that would have been off this planet with bronze- Jake-esque fittings...

 

 

Greg

 

forgot the link... jeez

http://www.evenheat-kiln.com/knifeovens/kf40/kf40.htm

Edited by Greg Thomas Obach
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I don't think you need super high temps to burn out the wax. The even heat should work for that. I am loooking into getting into casting as well :) I have several pounds of silicon bronze scraps that need recycled :)

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Hey Dave, here's a link to what I used Don Norris Steam Casting

 

It's a 'poor man's' method, but I liked it and it wasn't a big investment until I could figure out if casting was something I wanted to do more of. Jury's still out on that.

 

Dan

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if you think bout it... maybe i'd be worth it to get a long kiln.. then you could do bronze and heat up long swords.http://www.evenheat-kiln.com/knifeovens/kf40/kf40.htm

 

Greg,

 

That rocks! I think I'm going to have to get that long kiln! That would be awesome for heat treating and tempering swords. It would be nice to have even temps and reduced warping.

 

Thanks for the tip! They don't seem to sell them on that site, however. I'll look around for a vendor.

 

--Dave

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for lost wax casting ..

 

you need a means to melt the bronze - which im sure most of us can figure out.

 

you need investment ... which is a fancy way of saying plaster that can go to high temperatures without cracking or crumbling.

caution: investment is usually a high silicate compound and comes with huge amounts of warnings associated with it.

 

therefore - you also need the appropriate equipment to keep your lungs healthy for many years to come.

 

in order to 'burn out' the moisture and wax from the pots that you put your things/investment in you need a kiln.

depending on the size of the things you want to cast ... you need to make sure you have a kiln that is large enough to house the flasks/pots that you are going to use.

the kiln needs to be able to be fairly controllable, which isnt a problem anymore usually ... but just make sure that your kiln can be set to a temp and left with the understanding it will get to that temperature and stay there until you need to adjust the temperature again.

the investment that i use needs to be brought to about 1400*F at top temperature.

 

i have two kilns .. one big one and one small one ..

depending on how big of a production you want to do .. you dont really need much ... just take the measurements of the flasks that you intend to use and measure those against the inside chamber of the kiln ... and then figure out how many flasks you want to be pouring at a time... and there you go - you have your dream sized kiln.

 

and then you need a means to actually do the casting ..

there are two main ways used in my world ... one is vacuum casting and one is centrifugal casting.

ive got both and i use vacuum casting 99.9999999% of the time.

the vacuum setups are good because it allows you to use the vacuum chamber to take out all the bubbles from the investment when you pour it etc..

 

but its also most spendy if you are buying it.

 

i built mine ... so i cant personally speak from experience ... but the set of vacuum casting stuffs like what you have linked to are used all over the world and people have always raved about them ..

so i can unpersonally vouch for them.

 

thats about all i can think of ...

but i woke up about 3 minutes ago... so ill come back and check when ive found my brain and a cup of tea.

-_-

Edited by Dee
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Thanks Dee. That explains a lot.

 

I'm still a bit fuzzy on how you pour molten bronze into a vacuum . . . I mean, if there's a hole into which you pour the bronze, how can there be a vacuum on the other side? Air would rush in. . . .er, right?

 

I'm also confused on why the need for sprue holes if you cast in a vacuum. If the cast was filled with air, I'd understand why you'd need sprue holes through which the air could be displaced as the bronze fills the void. But if it's in a vacuum, there's nothing to displace, right?

 

I'm sure these sound like really dumb questions.

 

Since so many people use these devices to cast, I'm sure they work, so I guess understanding why they work isn't entirely necessary (heck, I don't understand how my microwave oven works, but I still use it to re-heat coffee!).

 

Thanks again.

 

--Dave

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ill try to explain ..

 

you start with the wax pattern of what you want cast.

whatever you carve into the wax will come out in the bronze ... so clean it up nice and shiny.

 

you place that pattern onto a sprue base .. which is a rubber base thing that will fit onto a vacuum pot/flask and basically is there to hold the wax in place while the investment sets.

but - it also keeps a pathway open so that you can pour bronze in later on

 

you fill the pot with investment, let it set and take off the sprue base ... this will leave you with a metal pot ... inside which is a hunk of plaster like substance (investment) and the wax pattern you have carved inside therein... held in place by the investment.

 

you put the pot into a kiln and you slowly burn out all the wax and all the moisture that is in the pot.

the wax melts and you are left with a void that is able to accept the molten bronze ...

 

the vacuum chamber/casting machine ... is a container that has an open top ...

putting a high temp gasket and the pot into this container will create a sealed container ... you then draw a vacuum onto this container ...

 

the vacuum isnt a total vacuum ... as in - the vacuum will draw in some air etc through the semi-pourous investment. (hence the reason for the holes in the pot... to allow the vacuum to be drawn through the investment)

this means that when you pour your molten bronze into the top of the pot while the vacuum is on ... the bronze is sucked into the void that is present within the investment and forms to the details as perfect as can be.

 

so ... its really just a means to get the bronze to form to the pattern that is present in the void.

you can just pour the bronze into the investment and not have the vacuum ... but you wont get as clear of a casting.

 

if you think of the centrifugal methods ... and think that they are basically pushing bronze into the void to make them take the shape that you have carved ..

then the vacuum method is just the same, except that its sucking the bronze into the void instead of pushing it in.

 

make sense?

 

no questions are stupid.

just hope i can explain it well enough via txt.

^_^

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$ 825 :o mmh ... it's a nice vacum machine, but if you want you can get your lost wax casting with a homemade machine...price around $ 20-30!

I have spent more than a year to learn this fascinating technique I made many mistakes but now I have excellent results. Unfortunately is impossible to buy all the equipment necessity because they are very expensive for me and so I had to engineer.

In this case, here is my machine vacuum, a section of pipe, very easy to make for us!

Simply connect to a compressor, can be used to debulizing investement (use a glass jar) and inserting the casting flask when you pour. These simple flask are handmade stainless steel, the commercial cost a lot.

As you can see it's not a nice vacum machine like that from $ 825 ... but does its job.

 

Look, this is one of my recent bronze cast, it is very complicated casting but the result (with my ugly vacum machine :P ) i think it is not different from that from $ 825!

 

I had a great experience in this field (learning from my mistakes) and I saw that the result does not depend on machines ...

 

I hope you understand my English, I have some problems in long speeches -_-

vacuum 640x480.jpg

Flask 640x480.jpg

Romancoin 640x480.jpg

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Mind that in principle, you need hardly anything to do lost-wax casting. This all depends on how reliable you want to make the process, and how much you're willing to spend. You can do perfect highly detailed lost wax castings using a charcoal fired pot furnace, home-made clay crucibles and gravity assisted pours in clay moulds. If you use a kiln to fire the moulds, you already take away much of the potential failures. A kiln can be as simple as a ceramic fiber lined chamber with a gas torch entering the bottom, and a thermocouple to check the temperature. Using gravity assisted casting does limit the openings through which the bronze will flow reliably (gravity needs to win from the surface tension of the bronze). This you can control up to some point by choosing the right alloy, temperature of the mould etc. Using clay moulds you can get details as fine as fingerprints. However, it depends highly on the clay you use. If you use lime-free clay, it works beautifully. Alternative to clay you can use castingsand, which needs no firing, but it limits to shapes without undercuts. You can get extreme detail in that as well, if you have a fine, high oil (sticky) variant. You can even make hollow castings using combination of casting sand and alternative medium such as clay for the cores.

 

Naturally though, if you are going to spend a lot of time on the waxes, and you want no failure then going full out on equipment like Jake uses would be worthwile. In that case it may also be worthwile making silicon-rubber moulds from the waxes, so you can make extra copies of the waxes so you can replace them if something goes wrong. This silicon-rubber is pretty expensive though, but it allows you to make many highly detailed copies of the waxes. It also allows you to make the moulds in different mediums if you prefer those over shaping waxes.

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In this case, here is my machine vacuum, a section of pipe, very easy to make for us!

Simply connect to a compressor, can be used to debulizing investement (use a glass jar) and inserting the casting flask when you pour. These simple flask are handmade stainless steel, the commercial cost a lot.

 

Can you explain this a bit more? My compressor doesn't have a "vacuum port"? How does your machine work? Please :lol:

 

Adriaan

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Hi Dave

 

after seeing Dee's tutorial on it .. started me thinking on electric oven.. i was alway hung up on getting salt but finally settled my mind on electric... honestly, salt is dangerous but with no decarb ( as i understand ) but electric has some decarb but no danger at all... like baking a cake.. .. jeez.. some decarb ain't bad as i alway like to leave them abit thicker so the swords don't warp.... and as for salt, sorry, i just don't see the need for something so dangerous in the shop for so little gain..

 

about the kiln.. i just got it bout a month ago.. so all i've been up to is a bunch o bowies ..no swords yet... its fun, you can stuff as many bowies in there as you can.. 6 -- O1 bowies just like that in one sitting.... and i didn't even break a sweat

- mine has the set pro controler... so i'm limited to 4 programs.. with 8 segments per program..... uhhhhh, so W1, O1, L6 champalloy, and crucible steel... so it fits my bill to a T

- only disappointing part... the kiln doesn't give off alot of heat... my darned shop is so cold here at -20 cel, i was hoping it'd give off some heat ... sorta sad in a way.. i could lay my hand ontop of the kiln after firing it and it was sorta hot but not too much..

 

i got mine from Mike Mossington in northbay... he was very cool about it.. got it shipped here on a transport on a skid.... it worry's me cause the IFB's are abit fragile and the kiln maybe in pieces by the time it got here...but the sealed it up with that expanding foam so it didn't jump around much at all A+

 

programing the controler... even for a knuckle dragger like me was a snap... ..

 

now i got some peace of mind over this heat treat stuff... no more hand balming a blade in a firey forge with pyrometer in one hand and tongs in the other..

 

i'm runnin free

 

maybe i'll even do some stainless.... hahahahaha... :unsure::ph34r:

 

 

by the by.. you can find decent vacuum pumps on ebay or local bargan hunter mag's.. that'll pull some decent Hg

- could even stabilize your own wood with it

 

 

take care

Greg

 

ps.. pm me if you have more kiln type questions ;)

 

 

 

 

 

Greg,

 

That rocks! I think I'm going to have to get that long kiln! That would be awesome for heat treating and tempering swords. It would be nice to have even temps and reduced warping.

 

Thanks for the tip! They don't seem to sell them on that site, however. I'll look around for a vendor.

 

--Dave

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Can you explain this a bit more? My compressor doesn't have a "vacuum port"? How does your machine work? Please :lol:

 

Adriaan

 

Adrian, all compressors have a "vacuum port" (it's near the USB port :P ), you only need a small change, look here, you can mount a gas tube with a bit of teflon here B)

-0.92 atm in few seconds.

Compressore 640x480.jpg

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Dave,

There is another option, of course. Look into sand casting. The only drawback here is that you can't reliably cast tang holes. A number of the jewelry supply companies sell a "Delft Clay" casting kit, and I found that to be a reasonable way to get into casting solid shapes.

 

So much is dependent on what you want to cast and how much metal you need to melt in order to do what you want to do. If all you want to do is simple guards (and are ok with having to mill out the slots for the tang), flat objects, small tsubas and menuki, then something like the Delft is just fine.

 

The amount of detail you can get on things is pretty impressive. I once cast a small face I made out of Sculpey, and the casting clearly showed my fingerprints on areas where I hadn't sanded them off the original.

 

You can scale up sand casting to large objects, too. Engine parts. Pulleys. Google "Backyard Metal Casting". It's a resource.

 

-J

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Dave,

There is another option, of course. Look into sand casting. The only drawback here is that you can't reliably cast tang holes.

You can, but you'd have to make a core out of a different material that's suitable for mould making.

 

A number of the jewelry supply companies sell a "Delft Clay" casting kit, and I found that to be a reasonable way to get into casting solid shapes.
These are usually quite expensive though. I buy the sand at 45 euro per 25 kilo, and use either cast iron frames for small castings, or wooden ones for larger ones. Wooden frames can be made in minutes.

 

So much is dependent on what you want to cast and how much metal you need to melt in order to do what you want to do. If all you want to do is simple guards (and are ok with having to mill out the slots for the tang), flat objects, small tsubas and menuki, then something like the Delft is just fine.

 

The amount of detail you can get on things is pretty impressive. I once cast a small face I made out of Sculpey, and the casting clearly showed my fingerprints on areas where I hadn't sanded them off the original.

Here are some fibulae I cast in sand:

http://1501bc.com/metalworking/08100002.jpg

Don't pay attention to the detail in the shape, that's still pretty coarse for what the sand can achieve. It actually copies all the little details as a result of the shaping of the model I pressed into the sand (model was carved in negative in soapstone and cast in tin to be pressed into the sand). So the actual details you can cast can be much finer. Once you have a model, making a mould generally takes about 10 minutes, and it's ready for casting. So you can melt your bronze, and during which prepare the mould and cast it when the metal is molten.

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