Casting
Content
Lets get on with Day 1 of the Course: What Is Casting? Metal casting is an ancient technique that has a variety of applications and purposes. Civilizations from the dawn of time to present day have used metal working as a way of creating artistic, religious, and practical items. The process of metal casting involves melting metals at high temperatures and using molds to then shape the metal into new items. The furnaces used in metal casting helped pave the way for the Industrial Revolution, without which the course of history would be dramatically different. Metal casting is just one form of metal working that has seen a recent surge in popularity as resources are becoming more affordable and communities are springing up to share information, ideas, and projects. Metal casting requires specialized equipment, knowledge, and some creativity. While metal casting is used on an Industrial level as the process cuts cost and proves to be highly efficient, many individuals participate in metal casting as a hobby and in artistic endeavors. Many people are drawn to metal casting for one reason or another, although there seems to be two main motivations that stand out. The first motivation that brings hobbyists to practice metal casting is need; people may need to create items or parts for other ventures. Metal casting is a great way to build hard to find pieces for models, restoration projects, and even just small replacement parts needed for common household items. The second motivation for using metal casting is using it as a way to create sculptures or other artistic endeavors. Whatever the reason, small scale metal casting is attractive because that it can be done right at home, either in the backyard or workshop. Individuals working in metal casting are able to create home made tools and equipment like furnaces and molds. Metal casting is only limited by the individual’s desire, so for those with the time and the need, virtually anything is possible. The actual casting process in metal casting has several forms, the most popular being sand casting. Sand casting involves creating a mold from sand which can be created at home, and then pouring the liquid metal into the mold. Afterwards, the metal is allowed to air dry and the mold is removed. This type of casting proves to be the most economical, but other types of casting can provide fuller detail and higher quality results. Here is a link to a Web Page that covers this first email: http://www.metalcastingzone.com/casting-general/ Today we are going to talk about Die Casting. What about Die casting? Die casting is used by industrial foundries and manufacturers to create practically anything and everything, such as die cast cars. Many small foundries, like the one in your garage, backyard, of workshop may find that die casting is really just not economical. But who said that having fun and trying new things was ever economical? The process of Die Casting involves a simple concept. The molten metal is injected with high pressure into the mold or mold cavities. The mold used in die casting can have several small civilities of either the same pattern or different pattern. The name Die Casting comes from the molds which are called dies. These molds are reusable and are often made from steel but other alloys can be used as long as they can withstand high pressure. The reason dies must be created from metal and not from sand or other material is due to the high amount of pressure used to get
the molten metal into the mold. If sand molds were used in a Die casting procedure then the mold would crumble. There are plenty of advantages of using dies in a casting procedure which makes this method desirable for anyone wishing to create a high volume of similar castings. Die casting is perfect for anyone that needs to make a lot of the same thing without any quality or pattern deviation. This is especially helpful in certain industries where quantity and quality count. Many hobbyists may have no use for die casting on a practical basis but will often try at least one Die casting for the sake of trying. There are two types of machines used in the Die Cast procedure. These machines are essentially the same and are called the Hot-chamber and the Cold-chamber. The Hot-chamber machine melts the alloy and feeds it into a section of the machine referred to as the gooseneck. A piston then forces the alloy into the mold. A separate furnace is not needed but the draw back of this is that metals with higher melting points can not be used. The Cold-chamber is used for metals that can not be used by the Hot-chamber such as aluminum and copper. A separate furnace is needed to melt the alloy which is then poured into the injection cylinder and then shot into the mold. The advantages of using Die casting vary but the most noticeable advantages are the repeated quality, smooth casting surface, and the quick production of casts. While the initial cost of Die Casting exceeds several of the other casting procedures, those that need a high number of casts in the shortest amount of time possibly will benefit greatly from the investment. Die casting is commonly used to create commercial goods as it yields a high volume. The molds, or dies, used vary in life cycle depending upon the material used to create the die. The die can have one cavity or several cavities depending upon the need. Here is a link to a Web Page that covers this first email:
Here we are on day three, ready to learn about Lost Wax Casting. Lost Wax Casting is an ancient technique that has been used to create very complicated metal castings and involved pieces that would other wise be impossible either because of economic reasons or manufacturing reasons. Everyone from small jewelers to large industrial foundries can use Lost Wax Casting. This process is also called Investment Casting when it is used in commercial industries. While jewelry makers are the primary ones to use the Lost Wax Casting, many others use it to achieve a number aims and goals. Lost Wax Casting is the ideal and preferred method for artists who are interested in making items like sculptures or rings from a variety of alloys like bronze, steel, or copper. This process is quite involved but not all that complex as long as you have some kind of metal casting know-how. For anyone wanting to experiment with different casting methods Lost Wax Casting is a great option because it involves a few materials and methods that are not normally found in other methods like Sand Casting.
The most noticeable difference of Lost Wax Casting from other castings is exactly what’s in the name; the wax. To use Lost Wax Casting you do not necessarily have to be an artists but some skill in sculpting might be nice. You are going to start off by creating a sculpture from wax that will be the original. You will then create a mold of the original. The mold is usually created from plaster with latex lining to help preserve the details of the original. If this is your first attempt at Lost Wax Casting you may want to make an original without a lot of detail just to get the feel for the entire process and so you do not become discouraged if something does not work out. Remember metal casting is a skill that must be learned by research, trial, and error. Chances are that you will not be completely successful, the first time around. The original piece is usually lost after the construction of the mold. This is normal and if you do want to prevent this from happening you can create the original from material other then wax like a metal alloy. When the mold is ready you are then going to pour molten wax, you’re not ready for metal just yet, into the mold. The amount of wax needed for this step depends on the desired thickness. Once the copy is ready, you are going to remove it very carefully from the mold. You will remove any of the impurities from the copy. This is called chasing. You will then sprue the copy. Spruing is the act of carefully placing paths that will let the molten metal in and air out. Afterwards, a ceramic shell is created around the copy. The shell isn’t really ceramic but a combination of liquid silica and sand. Traditionally, and in some areas still, animal dung and dirt is used to create the shell. The choice of which shell material you want to use is up to you. The shell is hardened in the kiln and the wax melts out. If you want to reuse the wax then collect it during this step. Wax can be reused a number of times and if you are on a budget or are just trying out different designs and methods, collecting the wax is encouraged. Once the wax is gone and all that remains is the hollow shell you will want to run water through it to make sure there are no leaks. If there are then you will need to patch them before pouring the molten metal. You are going to want to reheat the shell before pouring the metal to avoid shattering the shell. The shell is still on the sprue tree so pouring the metal is an easy process. When the metal has hardened, then break the shell carefully and remove the cast. Afterwards, it is up to you to finish the piece to your liking and preference. The Lost Wax Casting process is an enjoyable experience but it does use a few tools that you might need to purchase before hand, like the wax and spruing tree. At the very least, you might want to try Lost Wax Casting once or twice to get a feel for it. This way you have another casting process at your disposal. Here is a link to a Web Page that covers this E-Course Email: http://www.metalcastingzone.com/lost-wax-casting/ Hello, We have an exciting topic today! It is called Casting Sand. Sand casting is the most ancient form of metal casting and has been around since at least Ancient Egypt. Many metal casters prefer using sand casting over many of the other forms of processes because it’s cheap and the sand used is readily available.
Many experienced metal casters will continue to use sand casting even though their abilities and resources allow them to use the other metal casting methods like Lost Wax Casting or Investment Casting. Sand casting involves less material and less effort than the other casting methods. Sand casting is a great way for new casters to get into the trade. In sand casting, the metal caster will create a mold by placing an original in the flask which is filled with sand. The original will be a pattern of what you want to cast. By ramming or vibrating the sand, the caster creates a mold of the original. The casting sand used needs to be able to retain the shape of the mold. Finding the right mixture of sand to water is crucial. Too much water can ruin the mold and possibly destroy it while too little water will create a poor casting. Green sand is a type of casting sand that many prefer since its ability to retain the shape of the mold is far better then normal sand. Green sand usually contains bentonite clay, sand, and water. After the sand is packed, the pattern or original is removed carefully. Molten metal is poured into the mold and allowed to cool. The metal caster will then break the mold and dig out the casting. While sand casting has its benefits the use of green sand can greatly increase the likelihood of a successful casting. Green sand is not really green the color refers to the damp nature of the sand. Green sand is created by adding water and bentonite to the sand. One of the benefits of using bentonite in green sand is that it makes the sand more permeable which allows more gas to escape. Metal casters can get the bentonite from a variety of sources like home improvement stores and even from household resources. Many have milled the type of cat litter that clumps since one of the ingredients is bentonite. Remember to work in a well ventilated room or to wear proper face gear when working with bentonite since it will irritate the lungs. There are several recipes online for green sand but the most common method is experimentation. What you are looking for when mixing the sand, water, and bentonite is a texture that is not wet but damp and will retain its shape when molded. The type of sand you use to make green sand depends on you and the availability of the sand. Many will use sand that they found out in the wilds of nature and some will buy bags of sand like playground sand. As you cast with green sand you will find out which works best with what metals. Green sand is growing in popularity as more casters are recognizing the properties of this method. If you have traditionally used regular sand casting, green sand casting will prove to be easier to work with and will produce better casts. The best part about green sand casting is that is does not cost a lot of green. Here is a link to a Web Page that covers this E-Course Email: http://www.metalcastingzone.com/casting-sand/ Today’s topic is about Crucibles. A very important part of metal casting. From the earliest attempts to make lead into gold and to the more modern use of making those empty soda cans into a replacement part for that model plane, crucibles have been an absolute necessity in metal casting. Crucibles are placed inside of the furnace where the metal is placed and then melted. The crucible then collects the melted alloy which will then be poured into the model. Since the crucible will be holding metals melted at extremely high temperatures the crucible will need to be created from very strong
material. The durability of the crucible will add a certain aspect of safety to the metal casting process. Using a crucible that is low in quality can result in shattering, which, let’s face it, is never ever a good thing. Any crucible at any given moment can shatter or fail which is why using appropriate safety gear at all times is so important. In order to handle the crucible which will be red hot you will need to wear boots, jeans, and gloves. The tools for lifting the crucible from the furnace and then the tool for tilting the crucible so that the molten metal will pour easily into the mold will vary crucible from crucible. Those that make their own crucible will be able to create them in an identical manner so the same tools can be used. The idea of these tools is to make sure that the crucible can be safely and securely lifted and poured. You will never want to directly touch a hot crucible, even with gloves. For those that either can not or will not make a home made crucible can buy a crucible and tools from any of the online stores. A common material for crucibles is graphite as it can withstand the molten metal. Many who cast metal will prefer using graphite crucibles as it can prevent impurities from being introduced into the gold or other precious metal being used. Another option is the Silicon Carbide crucible. Silicon Carbide is a great though expensive alternative to the graphite crucible. A crucible made from Silicon Carbide can handle rougher treatment then graphite so if you are not particularly gentle with your toys then this is a terrific option. Yet another option available to the home foundry is creating your very own crucible. Many don’t really recommend this since commercially created crucible tend to be more durable and will instill a bit more confidence in the casters. It is, however, possible to create a crucible as many of us will at one time or another. If you plan on creating your own crucible then keep this in mind. There are a few areas of home metal casting where you should not cut corners, these definitely include crucibles. The crucibles job is the transportation of incredibly hot molten metal which can easily exceed 1,000 degrees Fahrenheit and is really the only thing between you and this metal. When you plan on melting metals with extremely high melting points you will need crucibles made from material that will cost a little extra. Spend that money and do so gladly since it is just a small price to pay for your safety. Crucibles should only be used to melt one kind of metal. If you have always melted aluminum but decide to try melting brass then you will need a new crucible. This is done for safety reasons. Remember, a crucible is not meant to last forever. Always check your crucible before use to make sure there are not cracks or imperfections if there are then do not use that crucible. Crucibles come in a variety of sizes and can be made from a variety of materials. It all depends on the type of metal to be used and the size of the job. Never skimp on the price of this tool and always follow safety guidelines and use common sense when dealing with a hot crucible. Here is a link to a Web Page that provides more information about this Metal Casting topic: http://www.metalcastingzone.com/crucibles/ Today we learn about the different types of casting furnaces.
In Metal Casting, the type of furnace you have at your foundry, or workshop determines a lot of the work you can or can not do. Many metal casters enjoy making their own furnaces and have done so quite successfully. 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 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. The tap hole and shaft which will allow the molten metal to flow from the furnace and into the ladle and air shafts are also required. 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 way, the metal does not come into contact with the fuel or the flame. This 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. Many casters will adjust the length of the flame since a longer path will mean that the heat will be more intense. 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. The indirect arc just uses one electrode and works in much the same way as the direct arc furnace. Electric Induction 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. Here is a link to a Web Page that provides more information about this Metal Casting topic: Now that you have learned the basics of Metal Casting, you can begin to get a broader perspective of the entire Casting Process as a whole. Metal casting has endured through the ages since the time of Ancient Egypt, possibly longer. Since then small foundries have developed to meet the needs of the individual caster. There are several reasons that people choose to create their own home grown foundries. A top reason is the need to create parts and pieces that are no longer available on the market or that are just too expensive to purchase. Those who get into metal casting for this reason are usually interested in restoration projects, home improvement projects, or hobby building like model planes and trains. Artists are the other groups that see metal casting as a cheap and easy way to create sculptures from small to large. Jewelers even use metal casting to create complex pieces that would just otherwise be Impossible to create. Given the wide scope of metal casting there are several methods and techniques that have developed. For those new to metal casting or for those wanting to try some of these other methods may find it difficult to find information on your own. Luckily, there are several metal casting associations and groups that are more then willing to share information and exchange ideas, projects, and pictures of the goings on in the their home foundries. On the internet, metal casting associations and groups are either message boards full of casters where they can ask questions, post ideas, and pictures or are websites that are maintained by a set group of people offering general information and educational resources. Both of these types of websites are incredibly helpful to metal casters who can benefit from the educational purposes of some of the sites tempered with the real life applications and experiences of the message boards.
There will be more industrial foundry and metal casting information than sites directed at the small home foundries. Industrial metal casting sites can be wonderful sources of information so do not skip by these. Use both small metal casting sites and industrial sites to your advantage. One of the most popular message board type sites for information is the Casting Hobby Group found through Yahoo Groups. This casting group was developed and maintained by experienced metal casters and enjoys a high amount of activity. This is a great place to go to for quick information and ideas not to mention photos and even furnace building plans. The Casting Hobby Group can be found at http://groups.yahoo.com/group/castinghobby/ The Association of Backyard Metal Casters is located at http://www.abymc.com/. This online metal casting association has an extensive membership complete with informative articles, forums, and even live chat. Of course, pictures are posted on the site to give visitors ideas about what other furnaces and foundries look like. Don’t worry if you’re foundry isn’t pretty, there actually doesn’t seem to be very many of them that are. Now, The American Foundry Society is mainly for the industrial metal casters and companies but they also promote information and education to consumers. The information provided on the site is great for anyone wishing to follow advancements in metal casting technology. There is even an online store. http://www.afsinc.org/ is the online home for the American Foundry Society. For the most part metal casting associations and groups exist on the local level more than a unifying force on the web. What does exist on the web is a great source of information, ideas, and insight. It is a great idea to join any of the groups you can in order to share and find knowledge. Here is a link to a Web Page that provides more information about this Metal Casting topic: http://www.metalcastingzone.com/casting-associations/
the molten metal into the mold. If sand molds were used in a Die casting procedure then the mold would crumble. There are plenty of advantages of using dies in a casting procedure which makes this method desirable for anyone wishing to create a high volume of similar castings. Die casting is perfect for anyone that needs to make a lot of the same thing without any quality or pattern deviation. This is especially helpful in certain industries where quantity and quality count. Many hobbyists may have no use for die casting on a practical basis but will often try at least one Die casting for the sake of trying. There are two types of machines used in the Die Cast procedure. These machines are essentially the same and are called the Hot-chamber and the Cold-chamber. The Hot-chamber machine melts the alloy and feeds it into a section of the machine referred to as the gooseneck. A piston then forces the alloy into the mold. A separate furnace is not needed but the draw back of this is that metals with higher melting points can not be used. The Cold-chamber is used for metals that can not be used by the Hot-chamber such as aluminum and copper. A separate furnace is needed to melt the alloy which is then poured into the injection cylinder and then shot into the mold. The advantages of using Die casting vary but the most noticeable advantages are the repeated quality, smooth casting surface, and the quick production of casts. While the initial cost of Die Casting exceeds several of the other casting procedures, those that need a high number of casts in the shortest amount of time possibly will benefit greatly from the investment. Die casting is commonly used to create commercial goods as it yields a high volume. The molds, or dies, used vary in life cycle depending upon the material used to create the die. The die can have one cavity or several cavities depending upon the need. Here is a link to a Web Page that covers this first email:
Here we are on day three, ready to learn about Lost Wax Casting. Lost Wax Casting is an ancient technique that has been used to create very complicated metal castings and involved pieces that would other wise be impossible either because of economic reasons or manufacturing reasons. Everyone from small jewelers to large industrial foundries can use Lost Wax Casting. This process is also called Investment Casting when it is used in commercial industries. While jewelry makers are the primary ones to use the Lost Wax Casting, many others use it to achieve a number aims and goals. Lost Wax Casting is the ideal and preferred method for artists who are interested in making items like sculptures or rings from a variety of alloys like bronze, steel, or copper. This process is quite involved but not all that complex as long as you have some kind of metal casting know-how. For anyone wanting to experiment with different casting methods Lost Wax Casting is a great option because it involves a few materials and methods that are not normally found in other methods like Sand Casting.
The most noticeable difference of Lost Wax Casting from other castings is exactly what’s in the name; the wax. To use Lost Wax Casting you do not necessarily have to be an artists but some skill in sculpting might be nice. You are going to start off by creating a sculpture from wax that will be the original. You will then create a mold of the original. The mold is usually created from plaster with latex lining to help preserve the details of the original. If this is your first attempt at Lost Wax Casting you may want to make an original without a lot of detail just to get the feel for the entire process and so you do not become discouraged if something does not work out. Remember metal casting is a skill that must be learned by research, trial, and error. Chances are that you will not be completely successful, the first time around. The original piece is usually lost after the construction of the mold. This is normal and if you do want to prevent this from happening you can create the original from material other then wax like a metal alloy. When the mold is ready you are then going to pour molten wax, you’re not ready for metal just yet, into the mold. The amount of wax needed for this step depends on the desired thickness. Once the copy is ready, you are going to remove it very carefully from the mold. You will remove any of the impurities from the copy. This is called chasing. You will then sprue the copy. Spruing is the act of carefully placing paths that will let the molten metal in and air out. Afterwards, a ceramic shell is created around the copy. The shell isn’t really ceramic but a combination of liquid silica and sand. Traditionally, and in some areas still, animal dung and dirt is used to create the shell. The choice of which shell material you want to use is up to you. The shell is hardened in the kiln and the wax melts out. If you want to reuse the wax then collect it during this step. Wax can be reused a number of times and if you are on a budget or are just trying out different designs and methods, collecting the wax is encouraged. Once the wax is gone and all that remains is the hollow shell you will want to run water through it to make sure there are no leaks. If there are then you will need to patch them before pouring the molten metal. You are going to want to reheat the shell before pouring the metal to avoid shattering the shell. The shell is still on the sprue tree so pouring the metal is an easy process. When the metal has hardened, then break the shell carefully and remove the cast. Afterwards, it is up to you to finish the piece to your liking and preference. The Lost Wax Casting process is an enjoyable experience but it does use a few tools that you might need to purchase before hand, like the wax and spruing tree. At the very least, you might want to try Lost Wax Casting once or twice to get a feel for it. This way you have another casting process at your disposal. Here is a link to a Web Page that covers this E-Course Email: http://www.metalcastingzone.com/lost-wax-casting/ Hello, We have an exciting topic today! It is called Casting Sand. Sand casting is the most ancient form of metal casting and has been around since at least Ancient Egypt. Many metal casters prefer using sand casting over many of the other forms of processes because it’s cheap and the sand used is readily available.
Many experienced metal casters will continue to use sand casting even though their abilities and resources allow them to use the other metal casting methods like Lost Wax Casting or Investment Casting. Sand casting involves less material and less effort than the other casting methods. Sand casting is a great way for new casters to get into the trade. In sand casting, the metal caster will create a mold by placing an original in the flask which is filled with sand. The original will be a pattern of what you want to cast. By ramming or vibrating the sand, the caster creates a mold of the original. The casting sand used needs to be able to retain the shape of the mold. Finding the right mixture of sand to water is crucial. Too much water can ruin the mold and possibly destroy it while too little water will create a poor casting. Green sand is a type of casting sand that many prefer since its ability to retain the shape of the mold is far better then normal sand. Green sand usually contains bentonite clay, sand, and water. After the sand is packed, the pattern or original is removed carefully. Molten metal is poured into the mold and allowed to cool. The metal caster will then break the mold and dig out the casting. While sand casting has its benefits the use of green sand can greatly increase the likelihood of a successful casting. Green sand is not really green the color refers to the damp nature of the sand. Green sand is created by adding water and bentonite to the sand. One of the benefits of using bentonite in green sand is that it makes the sand more permeable which allows more gas to escape. Metal casters can get the bentonite from a variety of sources like home improvement stores and even from household resources. Many have milled the type of cat litter that clumps since one of the ingredients is bentonite. Remember to work in a well ventilated room or to wear proper face gear when working with bentonite since it will irritate the lungs. There are several recipes online for green sand but the most common method is experimentation. What you are looking for when mixing the sand, water, and bentonite is a texture that is not wet but damp and will retain its shape when molded. The type of sand you use to make green sand depends on you and the availability of the sand. Many will use sand that they found out in the wilds of nature and some will buy bags of sand like playground sand. As you cast with green sand you will find out which works best with what metals. Green sand is growing in popularity as more casters are recognizing the properties of this method. If you have traditionally used regular sand casting, green sand casting will prove to be easier to work with and will produce better casts. The best part about green sand casting is that is does not cost a lot of green. Here is a link to a Web Page that covers this E-Course Email: http://www.metalcastingzone.com/casting-sand/ Today’s topic is about Crucibles. A very important part of metal casting. From the earliest attempts to make lead into gold and to the more modern use of making those empty soda cans into a replacement part for that model plane, crucibles have been an absolute necessity in metal casting. Crucibles are placed inside of the furnace where the metal is placed and then melted. The crucible then collects the melted alloy which will then be poured into the model. Since the crucible will be holding metals melted at extremely high temperatures the crucible will need to be created from very strong
material. The durability of the crucible will add a certain aspect of safety to the metal casting process. Using a crucible that is low in quality can result in shattering, which, let’s face it, is never ever a good thing. Any crucible at any given moment can shatter or fail which is why using appropriate safety gear at all times is so important. In order to handle the crucible which will be red hot you will need to wear boots, jeans, and gloves. The tools for lifting the crucible from the furnace and then the tool for tilting the crucible so that the molten metal will pour easily into the mold will vary crucible from crucible. Those that make their own crucible will be able to create them in an identical manner so the same tools can be used. The idea of these tools is to make sure that the crucible can be safely and securely lifted and poured. You will never want to directly touch a hot crucible, even with gloves. For those that either can not or will not make a home made crucible can buy a crucible and tools from any of the online stores. A common material for crucibles is graphite as it can withstand the molten metal. Many who cast metal will prefer using graphite crucibles as it can prevent impurities from being introduced into the gold or other precious metal being used. Another option is the Silicon Carbide crucible. Silicon Carbide is a great though expensive alternative to the graphite crucible. A crucible made from Silicon Carbide can handle rougher treatment then graphite so if you are not particularly gentle with your toys then this is a terrific option. Yet another option available to the home foundry is creating your very own crucible. Many don’t really recommend this since commercially created crucible tend to be more durable and will instill a bit more confidence in the casters. It is, however, possible to create a crucible as many of us will at one time or another. If you plan on creating your own crucible then keep this in mind. There are a few areas of home metal casting where you should not cut corners, these definitely include crucibles. The crucibles job is the transportation of incredibly hot molten metal which can easily exceed 1,000 degrees Fahrenheit and is really the only thing between you and this metal. When you plan on melting metals with extremely high melting points you will need crucibles made from material that will cost a little extra. Spend that money and do so gladly since it is just a small price to pay for your safety. Crucibles should only be used to melt one kind of metal. If you have always melted aluminum but decide to try melting brass then you will need a new crucible. This is done for safety reasons. Remember, a crucible is not meant to last forever. Always check your crucible before use to make sure there are not cracks or imperfections if there are then do not use that crucible. Crucibles come in a variety of sizes and can be made from a variety of materials. It all depends on the type of metal to be used and the size of the job. Never skimp on the price of this tool and always follow safety guidelines and use common sense when dealing with a hot crucible. Here is a link to a Web Page that provides more information about this Metal Casting topic: http://www.metalcastingzone.com/crucibles/ Today we learn about the different types of casting furnaces.
In Metal Casting, the type of furnace you have at your foundry, or workshop determines a lot of the work you can or can not do. Many metal casters enjoy making their own furnaces and have done so quite successfully. 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 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. The tap hole and shaft which will allow the molten metal to flow from the furnace and into the ladle and air shafts are also required. 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 way, the metal does not come into contact with the fuel or the flame. This 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. Many casters will adjust the length of the flame since a longer path will mean that the heat will be more intense. 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. The indirect arc just uses one electrode and works in much the same way as the direct arc furnace. Electric Induction 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. Here is a link to a Web Page that provides more information about this Metal Casting topic: Now that you have learned the basics of Metal Casting, you can begin to get a broader perspective of the entire Casting Process as a whole. Metal casting has endured through the ages since the time of Ancient Egypt, possibly longer. Since then small foundries have developed to meet the needs of the individual caster. There are several reasons that people choose to create their own home grown foundries. A top reason is the need to create parts and pieces that are no longer available on the market or that are just too expensive to purchase. Those who get into metal casting for this reason are usually interested in restoration projects, home improvement projects, or hobby building like model planes and trains. Artists are the other groups that see metal casting as a cheap and easy way to create sculptures from small to large. Jewelers even use metal casting to create complex pieces that would just otherwise be Impossible to create. Given the wide scope of metal casting there are several methods and techniques that have developed. For those new to metal casting or for those wanting to try some of these other methods may find it difficult to find information on your own. Luckily, there are several metal casting associations and groups that are more then willing to share information and exchange ideas, projects, and pictures of the goings on in the their home foundries. On the internet, metal casting associations and groups are either message boards full of casters where they can ask questions, post ideas, and pictures or are websites that are maintained by a set group of people offering general information and educational resources. Both of these types of websites are incredibly helpful to metal casters who can benefit from the educational purposes of some of the sites tempered with the real life applications and experiences of the message boards.
There will be more industrial foundry and metal casting information than sites directed at the small home foundries. Industrial metal casting sites can be wonderful sources of information so do not skip by these. Use both small metal casting sites and industrial sites to your advantage. One of the most popular message board type sites for information is the Casting Hobby Group found through Yahoo Groups. This casting group was developed and maintained by experienced metal casters and enjoys a high amount of activity. This is a great place to go to for quick information and ideas not to mention photos and even furnace building plans. The Casting Hobby Group can be found at http://groups.yahoo.com/group/castinghobby/ The Association of Backyard Metal Casters is located at http://www.abymc.com/. This online metal casting association has an extensive membership complete with informative articles, forums, and even live chat. Of course, pictures are posted on the site to give visitors ideas about what other furnaces and foundries look like. Don’t worry if you’re foundry isn’t pretty, there actually doesn’t seem to be very many of them that are. Now, The American Foundry Society is mainly for the industrial metal casters and companies but they also promote information and education to consumers. The information provided on the site is great for anyone wishing to follow advancements in metal casting technology. There is even an online store. http://www.afsinc.org/ is the online home for the American Foundry Society. For the most part metal casting associations and groups exist on the local level more than a unifying force on the web. What does exist on the web is a great source of information, ideas, and insight. It is a great idea to join any of the groups you can in order to share and find knowledge. Here is a link to a Web Page that provides more information about this Metal Casting topic: http://www.metalcastingzone.com/casting-associations/
