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rtropp

casting metal parts including cannon

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Brass and iron both require very high temperatures to be able to pore into a mold. That temperature is so high that you don't want to be creating it in your home, that alone prevents its use in most hobbyist levels, unless the hobby is casting those metals and the proper knowledge, location and tools are on site.

If you create the molds and can find a local foundry, you are in luck. Many colleges that have an art department teach casting in bronze, usually they will work with you, might need to take a class, check it out.

jud

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At the level most of us work in - white metal is the only real option for casting in metal - which is tin, with a couple of alloys for flow and hardness.  As mentioned brass is just too hot to do safely at home (900 - 1000°c) unless you invest seriously in equipment.   Iron 1200 - 1500°c is well beyond the hobbyist.

 

White metal melts around 260°c and casts just above 300, which is pushing the temp limit on RTV rubbers. 

 

Mold max 60 is a high temp tolerant silicone.

 

These guys sell metals, and their 5 Star is lead free.  (lead lowers the melting point, increases flow, and adds issues of toxicity and questionable longevity).  They also have some useful tutorials on the site.

 

http://shop.princeaugust.ie/

 

Colin

Edited by clloyd

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I was thinking about brass because I have a neighbor who has a clay kiln and I believe it gets to pretty high temperatures so I thought I might give it a try. He thinks it might be possible to set up a jig that will melt the metal above the mold and allow it to pour down via gravity.

 

Colin, the white metal looks a lot easier but I did not think you could get really detailed quality using white metal. I have looked at the links you provided and, maybe its me, I do not see really clean, defined edges on the castings.

Is that incorrect?

Richard

Edited by rtropp

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Bob is correct.

 

If you want to get into casting brass, you are going to have to become proficient at lost wax casting.  For small parts, the metal is most commonly melted with a torch in the crucible of the casting machine.  It is very different than casting low fusing metals.

 

At minimum you will need a burnout furnace, casting machine and torch.  Unfortunately your friends kiln won't be of any use.

 

So what you want to research is lost wax casting.  I've done a lot of gold casting, but I've always farmed out my brass parts.

 

There are methods for casting very detailed parts in white metal, but I am not familiar with the steps.  I thought I had heard it involved centrifugal casting into rubber molds.  These castings are from Paper Labs and keep in mind they are 1/350

 

1-1in-02.jpg

 

Paul

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Pewter or other formulas of white metal are best cast in vulcanized rubber molds on a centrifugal casting machine. This process will yield high quality, crisp detailed castings. Not to say you can't do it with gravity pouring, low temp metal into quality RTV silicone molds, but is a lot harder to get fine details. Brass is a different animal.

 

Do the parts have to be metal ? Well detailed castings can be made at home much easier with low viscosity casting resins in RTV silicone molds.

 

Once painted and installed, only the builder will know what the details are made from.

 

- Joe

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I was thinking about brass because I have a neighbor who has a clay kiln and I believe it gets to pretty high temperatures so I thought I might give it a try. He thinks it might be possible to set up a jig that will melt the metal above the mold and allow it to pour down via gravity.

Just my 2cents. I own a computer controlled kiln that will go to 2300 deg F - they run about $1700 not including $300 for the custom computer controller - see attached photo. You really can't use that for melting brass I don't think. For one thing, although I've never tried it, if you tried to put a flask with brass inside the kiln you might have to wait forever because the total continuous heat loss of the kiln will not allow the kiln to fire the flask up to POURING temperature, which must be considerably above the melting point, like 200 or 300 deg above melting temp. Even if it did melt it,  if the brass melts above the mold and dribbles in you haven't cleared off any dross at that point and it will go right into the pour with inclusions in the finished piece. But it will never get there I'm pretty sure. It just can't melt it.

 

Let me point out that there are some great books and resources on building furnaces to melt brass and bronze to name a few:

http://www.artfulbodgermetalcasting.com/7.html

I think this may be the best furnace:

“The Artful Bodger’s Iron Casting Waste Oil Furnace”.  Title says iron, but think silicon bronze

 

 

Then there's

"Li'l Bertha, A Compact Electric Resistance Shop Furnace" -David J. Gingery * see my note below concerning this book

"Handbook of Lost Wax or Investment Casting" - James E. Sopcak

both at http://www.budgetcastingsupply.com/Books.php    (I own most all the books located on that page.)

 

The there's

Building A Gas Fired Crucible Furnace  - David Gingery

and-

“The Complete Handbook of Sand Casting” by C.W. Ammenon   both on ebay or Amazon

 

 

I haven't had time to really get into casting but have accumulated some theoretical knowledge for backyard casting.

 

*about this book: I own a copy. But what you really need to read along with it is this website by Dan http://www.dansworkshop.com/2008/03/homebuilt-electric-melting-furnace-2/

post-10140-0-33531300-1392021294.jpg

Edited by JTownsend

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Hi Mark,

 

Yes, I've read the articles you mentioned....nothing wrong with them, and of course there are a number of ways one can go about creating molds and castings.....

 

I do think there are some areas that can can be improved upon however. Over the years of my experience with molding and casting I have learned a few tips and tricks, and I think that in the near future I will write up another guide showing some different methods and send that to the administrators for their review.

 

There are many different formulas out there for use in mold making, and a few options for casting resins as well. Setting a master or masters on a proper clay bed, and preforming the fill channel and even the vent channels ( as I like to do ) will also save on RTV mold material, reduce any cutting ( cutting the molds will decrease their usable life ) and presetting the dimples or aligning pins will also make a difference. There are also some alternatives for how the mold cavity is filled...direct pour ( from the top feed channel or indirect, by feeding the cavity from the bottom.....there is also the matter of clamping the mold shut - and doing so without creating distortion. Or, if necessary, creating a shell or "mother mold".

 

In the end, I just want to help other modelers out there to get the best results with the least amount of problems possible. I do not propose to be an expert, but having done production castings for quite a few cottage industry companies in the past, I have been down the trial and error road many times and I can possibly save some folks from wasting time and money and reducing the learning curve.

 

-Joe

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Would anyone be interested in a detailed tutorial on Resin Casting ? Both 1 pc and 2 pc mold making ? If there is enough interest I will pull some equipment out and put something together.

- Joe

I'd certainly be interested Joe. This is one area I have yet to explore.

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Joe,

 

Yes please - a tutorial would be very useful.

 

In the world of model railways resin casting has come on in leaps and bounds in the last few years from "dodgy chocolate block" to highly detailed results. It is now frequently used in high quality kits.

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Personally I prefer the bottom fill method to avoid bubbles and empty cavities.   Here are some pics with off-the-shelf resin/mold kit...there are plenty of techniques to learn and a tutorial would be welcome.  You can send it to me and I will post it in the database of articles.  The part you are looking at is only about 3/4" long if I remember correctly.

 

Chuck

 

 

casting 010.jpg

casting 013.jpg

casting 003.jpg

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Ok,

 

I will order some fresh materials and put something together. I will use some small ship parts of course !

 

In the photo from Chuck, you can see an example of 'bottom feed'....pour the resin into the fill port and it goes down, over and then comes up to fill the mold cavity....this allows air to escape, rather than pouring direct and trapping air in the process. It is an example of the best method, in my opinion ....you will use a bit more rubber when making a mold this way, but you have a much better chance for success. Anyhow, I will be happy to expand on the process and will submit a tutorial to Chuck in the very near future.

 

-Joe

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Thank you Joe, that will be a thing which I will surely follow with utmost interest! Meanwhile, thank you very much Chuch for your photos, they speak for themselves. As the saying puts it, a good photo worths more than a thousand words!

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Hi Bob,

 

I will be sending the tutorial to Chuck for review and approval before anything is posted, but will report back here when the go ahead is received.

 

Thanks,

 

Joe

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Resin, tin alloy, pewter, wood ...

There are certainly a lot of options open to the home hobbyist that can be done without costly equipment.

Chuck, unit I saw your photos of the resin cannon I had not realized they could looks that good and with such great detail.

 

I wonder, what actually are the differences in the look of the finished products, say of the same cannons but of different materials? Could you pick out the brass from the resin from the others without touching them?

 

Richard

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Joe,

 

I posted those for people like David so they can get an idea.  By all means feel free.  The more info, the better as there is no one right way for everyone.  Your way might be the perfect one for those who couldn't get the others to work for them.  And there's those who take a bit from one source, a bit from another, etc.  Once you're ready, let us know and we can get it added to the Article database.

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Colin, the white metal looks a lot easier but I did not think you could get really detailed quality using white metal. I have looked at the links you provided and, maybe its me, I do not see really clean, defined edges on the castings.

Is that incorrect?

Richard

 

 

If the finished master is made properly you will never know what it is made from by looking at the casting.

David B

 

Richard,

This is the answer to your earlier question.  The amount of detail you get is entirely dependant on the quality of the master.  You can capture huge amounts of detail in most of the materials available to the hobbyist.  Each type of material has it's pros and cons.  Resin produces great crisp casts with little fuss, but is intolerant of mistakes (the only thing to do with a miscast is bin it), and there is some waste of material.  Metal takes a bit more care with casting but miscasts and "sprue" can be remelted.  I've used both and like both for different things.

 

I've posted this elsewhere but it's relevant to your question - my cannon in whitemetal.  In brutal closeup and roughly to scale for the standard resolution for most LCD screens.

 

post-6015-0-87784700-1392129441_thumb.jpg

 

Colin

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Hi All,

 

Colin answered that pretty well. The quality of the master is very important......especially in resin casting, what you see is what you get.

 

You choose an appropriate resin to cast with and along with well made molds ( a big key here ), you get your castings.

 

Metal is a bit more involved..... Typically metal castings are done on centrifugal casting machines, using vulcanized rubber molds. The caster must have a good understanding of many factors that come into play.

 

White Metal is a generic term. There are many formulas to be had here, depending upon the mix. Tin, Antimony, and copper are the primary metals used in this mix, and the casting properties can be affected by the ratios of each metal used. Furthermore, the purity, the temperature, the spin speed, flow distance, part orientation and plate pressure of the mold clamps can all play a part. Most casters develop their own feel for it and manage to come to workable settings for the type of casting they do. It is part science, and part experience. Play with any of those variables and you can have any number of quality issues....mis-cast, porosity, drossy or dirty parts, brittle or crystalized looking parts, etc. Get them all right and you have clean, crisp, dense and well structured parts.

 

Trust me, there is a learning curve to production white metal casting !

 

As for the finished items and how do different materials compare, if the quality of the castings are equal - be they resin, metal or some other material, well painted and detailed parts will show no difference. For the hobby modeler who wishes to make castings, I would recommend RTV silicone molds and a low odor casting polyurethane resin.

 

- Joe

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