Thursday, October 16, 2008

Iron Furnace, Foundry Furnace and Induction Furnace Information

Casting

In Casting , the type of furnace you have at your foundry, or workshop determines a lot of the work you can or can not do. Since the beginning of time, people who enjoy casting have been making their own furnaces. The plans for home made furnaces are eagerly shared among the enthusiasts so finding blueprints and instructions should not be difficult. But before you rush off to find the blueprints you may want to take time to learn about the types of Metal Casting furnaces available to help determine which one will suit your needs. This is not saying that you should only have one furnace at any given time, but this way you will know what project will work best for which furnace.

Cupola

Cupola furnaces are among the most popular with backyard foundries. Many casters construct their own cupola which proves to be cost effective and highly efficient if done properly. Since cupola furnaces can achieve high melting temperatures they are primarily used for the melting of iron and bronze, though aluminum can also be melted when attention is paid to keeping the temperature low. The primary fuel source for cupola furnaces are coke using limestone for flux.

By not using a crucible, the Cupola furnace is able to melt the metal at a faster rate. While individual designs of these furnaces differ due to varying resources and design ideas, the basic component of a cupola furnace is the same. The cupola furnace must be elevated above the ground and installed with a drop bottom usually hinged, which will allow the excess metal, fuel source, and other waste to drop from the furnace. You will need at least two types of shafts, ladle shafts and air shafts and they both provide similar outlets for air and metal.  A slag tap hole can be placed on the furnace usually in the back, higher then the tap hole, which will allow the slag to flow out easily.

With most small home foundries, the cupola furnaces are preferred over that of other furnaces for its high melting rates and for how easily the construction of such a furnace can be.

Reverberatory

The Reverberatory Furnaces are commonly found in industrial plants but there have been quite a number of home grown foundries that have used this furnace type with much success. The basic idea of a Reverbeatory Furnace is to use the heat reflecting off a surface, usually brick, to heat the metal, which is aluminum in most cases. This helps because then the metal doesn't even come close to touching the flame or fuel. Its commonly known that the process is also used in Puddling Furnaces. The name Reverberatory and Puddling are often used interchangeably. By placing the metal in a shallow depression and then directing an intense flame over that depression and to the wall, the heat rebounds to melt the metal. Controlled the length of the path of the flame is something that most casters will do because then you can control the intensity of the heat.

There are many designs for the reverberatory furnace, all of which will include exhaust ports and the rear of the furnace must be able to withstand the intense heat and be able to bounce it back into the chamber.

Bronze, aluminum, tin, and many other ores can be melted in a reverberatory furnace all depending on the construction of the actual furnace and the heat of the flame. This type of furnace has been around since at least the Middle Ages and was used primarily for bronze work.

Electric Arc

Electric Arc furnaces are normally used in Industrial foundries. Most hobby casters do not use these furnaces due to cost, space issues, and a general inconvenience. There are two forms of the electric arc furnace, the direct and indirect.

The direct arc has three electrodes which are used to heat metal by way of the arc. This creates an incredible amount of heat and so water jackets and other cooling devices will be needed for operation.

An Indirect Arc is only using just one electrode and really thats only the thing that is different between the direct arc furnace.

Electric Induction Metal Casting

Electric Induction furnaces are becoming all the more popular with large industrial size foundries that enjoy the clean burning and efficiency of an electrical furnace. Copper coils surround the crucible with the metal inside which can reach extremely high temperature suitable for melting most metals.

Rotary

The Rotary style furnaces are hailed for their ease of use being fully or at the very least partially automatic. These furnaces tend to be harder to construct though there are resources and companies online that sell rotary furnace.

The different furnace types do affect the quality of the work being produced, so it is important to keep that in mind as you cast. With a little trial and error, you should find the perfect furnace to fit your needs so you can start building one of your very own.

 
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Wednesday, October 15, 2008

All About Brass Casting

Casting

Brass is a great metal to cast with as it can provide some really great looking results.  Many believe that brass, an alloy of zinc and copper, has been around since our prehistoric ancestors. You will find brass today is a lot of musical instruments including trumpets and of course the penny's in your pocket are made of brass.

The low melting point makes brass a really great material for metal casting since even the smaller home grown furnaces can be used. By adding and subtracting alloys from bronze one can successfully make hard or soft bronzes. Aluminum and tin are sometimes added to bronze to create a layer that is not corrosive and very durable. Of course, for the home foundry users, playing alchemist isn't really an option or necessary and scrap brass is perfectly acceptable in many cases. Locating scrap pieces of brass should be sufficient enough for whatever project you have in mind. Due to brass' gleam and yellow shine, many artists will use the alloy for sculptures, jewelry, and other decorative items. Other metal casters may choose to use brass for general hardware needs or vintage car restoration, and of course, whatever else they may choose.

Generally there are three casting methods that prove to be suitable for Metal Casting . Metal casters may choose to experiment with different methods and should not allow themselves to be limited.

Metal Casting casting is usually associated with bronze casting but can also be used for brass and for really any other metal. By using a wax model and covering it with a ceramic shell, artisans are able to inject the molten alloy which replaces the wax. The brass piece will be shown once you start to chip away at the shell. Lost wax casting is used when a high attention to detail is needed. Artists or metal casters looking to create decorative brass pieces or sculptures will find that the lost wax casting technique will meet their needs far better than other techniques and methods.

Die casting is yet another method used for Metal Casting . Die casting is normally used in commercial foundries since the initial start up cost is undesirable for the smaller home foundries. By using a reusable mold created from steel, the caster will be able to create scores of identical products. Die casting with brass should be used if the caster or artists is planning to make multiples of one product and can find a viable market for those pieces.

A very popular method for small foundries today is a type of casting that has been around the longest called Sand Casting. The brass is poured into sand molds and can create a unique look which may be preferred for the artisans. Sand casting tends to be the most economically sensible for small foundries and if the casting does not have to be incredibly attractive then this method is preferable for many.

Whichever casting method is used for casting the brass really depends on the individual. Many find that casting brass to be fun and easy since it does melt rather easily. What is nice about brass, is that its easier on the budget as the furnace required to melt the metal is a lot smaller and easier to have at a home. Many have even been able to melt brass in small ceramic pots using charcoal!

Some ideas of what to make with brass include candle holders, plumbing fixtures, and even musical instruments
 
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Bronze Metal and Bronze Casting Described

Metal Casting

Bronze Casting has been practiced for centuries. Many civilizations have used this alloy for weapons, sculptures, and general pieces of hardware. The popular way to cast bronze is the Lost Wax Casting process which was first used sometime in the 3000 BC near ancient Sumeria. The Lost Wax process is still used to this day and its modern equivalent Investment Casting is very popular with jewelry makers.

Bronze is the preferred alloy for metal working artists as it's relatively easy to work with and resistant to corrosion. The properties of bronze tend to be stronger than most other alloys, except of course for steel, and lends itself easily to the molding and casting process. Many small foundries like the kind that can be found in a backyard or workshop find that bronze is a great material to work with and with a melting point of 1,700 Fahrenheit or about 925 Celsius many homemade furnaces are able to melt down the bronze quickly and efficiently.

Many modern day artists create their own furnaces with the metal casting in mind. These metal casters employ the Lost Wax Casting method which proves to be the best when dealing with the alloy. The Lost Wax Casting is making an original of the sculpture from wax and then creating a mold using this original. Often times the original is lost during the mold making process so keep that in mind if you want to hang on to the original for whatever reason. Molten wax is poured into the mold which is chased or smoothed of imperfections. During this point, any other pieces are attached and small wax tubes are placed into the piece. These tubes will be how the molten bronze is going to travel into the piece replacing wax with the alloy.  When this is complete the artist will create a ceramic shell around the wax model. What really does the trick on helping to melt the wax is the shell which helps form the molten bronze which in turn melts the wax. When the molten bronze is poured the bronze takes place of the wax. Afterwards, the artist will crack the shell and reveal the bronze piece. If you are looking for a method that transfers every single detail from the wax onto the bronze, this method is going to give you more detail than any other.

Some artists really enjoy addint Patina to the sculpture but its really to each his own. The Patina is a chemical that when applied to bronze creates colors and makes the bronze take an aged look. The Patrina compounds used depends on the type of color desired. Ferric Nitrate will make the bronze take on a red or brown color while Sulphurated Potash will make black and Cupric Nitrate will create blue and green. Modern day artists choose to go with a very high polished bronze instead of using these compounds. This step depends solely on the artist’s taste and the look they are going for.

Metal Casting will remain a popular medium until another alloy is developed that exhibits properties that are easier to manage and are more resistant to corrosion. Casting the alloy is easily done so metal casters that want to experiment are encouraged to do so. Making anything from small figurines, large sculptures, and even cabinet handles can be accomplished with the use of bronze. The only limitations in Metal Casting are with the caster himself.
 
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Tuesday, October 14, 2008

Artistic Casting and Art Casting Information along with Metal Casting Basics

Metal Casting

Art Casting is an ancient method of creating statues and sculptures that has been in practice in Meso-America, China, and Ancient Egypt since 2000 BC. The Greeks practiced it, so did the Romans, and pretty much any civilization with a strong interest in art.

Bronze is an alloy of tin and copper that has been used to make weapons and sculptures since its discovery by man. Bronze is able to fill in the fine detail of molds making it very desirable to artists. When art casting, bronze is the alloy of choice since it is both beautiful and easy to work with. There are few examples of bronze statues left from antiquity since the alloy became scarce and many of the statues were melted down for weapons and other sculptures usually for new emperors or victors.

The Lost Wax Casting process is the preferred method used when art casting. This process was used in ancient times to create bronze items. Small foundries like the type found in backyards, personnel workshops, and garages are able to use the Lost Wax Casting process with a certain amount of professionalism. Commercial foundries and professional art companies use the Lost Wax Casting process as well to create custom items and monuments. The process remains, essentially, the same since the ancient craftsmen who first pioneered the method. Investment Casting is just the same as lost wax casting except its called a different name because its being used for commerical manufacturing or jewelry making.

Art Casting is one of the more enjoyable reasons to fire up the furnace and get into metal casting. While most think metal casting to be strictly limited to hobbyist and historical re-enactors, casting is a popular skill and craft used by a wide range of people for varying reasons. Artists see the need to have metal casting skills as it allows the artists to have direct control over the process instead of out sourcing it to a commercial foundry. Commercial Foundries have guys with lots of experience and so to hire their services you will pay the highest of prices. Metal Casting on your own is often times economical and just smart.

Plenty of time should be allocated to the Lost Was Casting process as well as plenty of attention to detail because although it is simple compare to other methods, if you don't have those two items, then you will be in trouble. The artists will start with an original piece sculpted from wax. The original can be made of other substances like clay or even metal but wax seems to be the easiest to work with. The original will be used to make the mold. If the piece to be cast is large, multiple molds will be needed. This is common in art casting and completely possible with the use of shims and keys that will allow placing the pieces together after the casting process easier. Most molds will be made out of latex or other materials to help transfer the fine detail into the mold cavity.

The original is often destroyed during the mold making process upon removal. Molten wax is poured into the mold until the desired thickness is achieved.  When dry, this wax copy is removed and chased which rids the piece of imperfections and is used to combine the pieces.  You will place paths for the molten metal on the wax copy.  You will also place a cup or funnel at the top of the copy. This process is called spruing and is done in wax.

A ceramic shell is placed around the copy. The shell isn't really ceramic but a sand and liquid silica combination.  You will repeat this step until the shell is thick enough for the piece. You will then heat the item which will melt the wax inside. The wax runs out of the shell through the paths placed during spruing. 

Then comes the part for the molten bronze. The bronze is poured into the top of the hollow shell. When cool you are going to remove the shell carefully to reveal the finished product. The bronze sculpture is chased, painted, and finished up however the artists choose.

Art casting can be done with any metal or alloy. If you are going to use the Lost Wax Casting process then you do not have to stick with bronze. In order to get that exact look sometimes you have to try a few other metals to see what works the best.

 
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Aluminum Foundry Information and Info on How to Aluminum Cast

Metal Casting

Aluminum is the most common alloy used in metal casting. There are a few causes as to why this would happen and the main ones are availability and quality. Many metal casters have access to a large amount of aluminum with soda and beer cans that they crush and melt down. Aluminum has several desirable properties for the metal caster no matter if they are a hobbyist, artist, or are casting needed parts for home repairs. Many who cast aluminum also love the alloy since it can be used in all of the varying casting processes giving it a wide range of possibilities. Aluminum is often used as a practice alloy for the first time metal caster or for casters who are trying out new methods and ideas.

Many of the small home furnaces that are found in most hobbyists’ foundries will be able to easily melt aluminum. It may even be possible to use charcoal though many just use propane since they have it on hand for other alloys. For your first run at casting, charcoal should be fine.

Soda Cans work out well for aluminum casting, but you need to have a pretty big supply depending on the size and shape of the object you want to cast. Make sure to crush the cans as much as possible before placing in the crucible or other area that will be used to melt the alloy.

Since any Metal Casting process can be used with aluminum the choice will rest with you. There are three casting methods out of the numerous methods available for aluminum that seems to be preferred by small time metal casters. These methods are sand casting, lost foam casting, and investment casting.

Remember, though, aluminum can be used with any metal casting process so do not be afraid to experiment.

Sand Casting

Sand casting aluminum is very common and is a popular way to break in a new furnace. What most casters do it use a bonding agend that they mix in so that a mold forms around the item to be cast. The item, or pattern, is removed very carefully revealing the mold. If there will be any empty spaces in the finished product then a core is added to the mold. The core can be made of sand and is placed so that the molten metal fills the area of the mold around it. So, say you're making a picture frame you will place a cone where the glass will go so the molten aluminum will not fill that area.

Many choose not to use sand casting since it does not allow for fine detail whereas other casting does, but it is inexpensive.

Lost Foam Casting

Lost foam casting which is sometimes called evaporative casting. The lost foam casting is a form of sand casting. Using old soda cans in conjunction with aluminum casting really makes the process even more affordable. A foam copy of what you want to cast is created and surrounded by a ceramic shell. Loose sand is where you will want to place the copy so that you can help to hold the shape during the pour. The molten aluminum is poured into a cup that in inserted into the copy. The foam vaporizes and the aluminum replaces it filling the area in the ceramic shell. Removing the shell will reveal the Metal Casting . This method is great for fine details but the copy is lost to the ages. Luckily, foam is not all that expensive.

Investment Casting

Investment casting is commonly used by jewelers as it allows precise castings with full detail. This form of casting has been around since ancient times under the name of lost wax casting. Investment casting involves creating a wax copy which is then covered in slurry creating a shell, much like the kind of shell in lost foam casting. The molten aluminum replaces the wax which melts out of the shell and can be collected for reuse. Artists and casters that need high precision parts favor this technique.

Given the number of options that aluminum presents to the caster finding the right casting method will involve some time. To help decide which Aluminum Casting process is best consider factors like quality and cost.

Many metal casters use aluminum far more then they use other alloys like brass, bronze, or iron.
 
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Monday, October 13, 2008

Cupola Casting Information

Metal Casting

A Cupola is a type of furnace that is very much alike to blast furnace. The Cupola furnace is refractory lined, stack of steel that is around 20 to 35 feet high. It rests on a base plate that is made of cast iron and has four legs. The casting that is obtained from the cupola furnace is known as a cupola casting.

Cupola Furnace: The Cupola Casting furnace is one of the oldest forms of furnace that have been used by the iron and metal foundries. Most of the industries are aware and have used the Cupola furnace as it is the curdest and simplest furnace in the industry. However, the cupola’s use is declining and the furnace is fast being extinct.

Merits of the Cupola Metal Casting Furnace: Though the electric or the blast furnace has started replacing the Cupola Furnace, it has some special benefits of its own. The Cupola furnace is very nice in the fact that its set up so it can remain always in action and working order. The furnace also offers a very high melting rate. The most important merit of the furnace is that it has relatively very low melting cost. The furnace has also permits a lot of ease of operation.

However, due to the invention and development of the electric furnace, the use of Cupola furnaces has substantially declined. The electric furnace melts a much larger amount of metal. The operation cost of the electric furnace is also very low. The electric furnace also emits a much smaller level of smoke heat and also pollutants.

Construction of the Cupola furnace: The Cupola furnace is constructed in a crude and simple manner. The Cupola Metal Casting furnace is a vertical structure like a steel shell. The steel is lined with refractory bricks from the inside. The furnace has an opening half way in the vertical shaft. The charge is introduced through the opening. The charge is divided into different layers. It contains the metal that is to be melted. The metal is mixed with coke, fuel, and lime stone flux. The fuel is burnt directly into the air and is introduced in to the furnace through the tuyeres which are positioned above the hearth. The hot gases that have been produced ascend and pre heat the charge.

The cupolas in majority of the cases have drop down doors. The bottoms can be dropped down to facilitate the cleaning and the repairs. At bottom in front of the furnace is a tap hole. The molten metal is removed from the tap hole. At the rear there is also another slag hole. On the top of the stag you will find that it is covered with a spark or what is also called a fume arrester.

Usually the cupola has a diameter of 405 to 2000 mm. It is operated on varying fuels for different metal ratios. The molten metal that can be produced in the copula of this size at a speed of 1 to 30 tones per hour.

Continuity of process: After the process of melting has ended, the charging is halted. However, the blast of hot air is always maintained till all the metal has been melted and has been taken out from the tap hole. When the air cools down, the doors at the bottom are opened and the residue that has been left behind is removed.           


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Saturday, October 11, 2008

Learn about Casting Patterns and the different types of Casting Patterns

Metal Casting

A casting pattern is basically a shaped form of either metal or wood where sand is packed around it in the mold. When this pattern is removed, the resulting cavity would be exactly the shape of the pattern object that was to be cast. The casting pattern should however be designed in order to be easily removed without any damage done to the mold. The pattern should be also be perfectly dimensioned and should be very durable for the intended use. The patterns that are used in sand casting can be made of plastic, metal, wood or any other material. The casting patterns are made to the right standards of construction this is basically because they can last for a reasonable time. The durability of the pattern would however depend according to the quality of grade in the casting pattern. If the pattern is made of right quality then they would be constantly providing dimensionally perfect casting patterns.

The process: The process of making Metal Casting is actually called as pattern making which is in fact a skilled trade which is related to the trades of die and tool making and mold making. However this also sometimes incorporates the elements of fine wood making. The makers of casting patterns basically learn their pattern making skills through trade schools and apprenticeships over a number of years of experience. The pattern maker is really the one who carries out the design but sometimes you will see an engineer who many help a few times.

Design: The Metal Casting incorporate proper allowances for the shrinkage and this process is called as contraction allowance. Their accurate values however depend on the alloys that are being used and the accurate sand casting methods that is used. There are a few alloys that have the overall linear shrinkage of nearly 2.5 percent as other alloys might actually experience 0 percent shrinkage or even a light positive shrinkage or it might also increase the size in the casting process. The amount of the shrinkage is also dependant on the sand casting process that is employed for instance chemical bonded sands, clay bonded sands or other bonding materials.

The casting patterns should also include proper allowance for the draft. This means that the sides would be tapered so that when it would be taken out from the sand it will not tend to drag out sand of place along with it. This process can be called a taper, but it is only preformed when the temperature ranges from one to three degrees. The foundry engineers or the pattern maker of the casting patterns actually decide where the gating systems, risers and the sprues are places in terms of casting patterns. In this pattern a hole is desired in the Metal Casting that uses a core which defines the location and volume of in the casting where the metal would not flow into. Chills are also used sometimes located on the casting patterns surface and these are then formed into sand molds. These casting patterns however continue to be a vital requirement for sand casting of metal.
 
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