Metal Casting Zone Info Blog

Kent Kelin asked:


Oxy-fuel cutting and oxy-fuel welding can be described as the processes of using oxygen and fuel gases to either cut or weld metals. There are some striking differences between these two processes. In the first process, a cutting torch is made use of for heating ferrous metal to a temperature of around 980 degree Celsius. An oxygen stream is being trained on a hot metal that combines with iron chemically which later flows from the kerfs, or cut in the form of slag of iron oxide. In the second process, a ‘welding torch’ is made use of for welding metals.

Torches that burn the inside fuel with air (atmosphere) cannot be termed as oxy-fuel torches. They stand out owing to the use of single tank. This is because oxy-fuel cutting/welding requires oxygen, fuel, and two tanks. It’s not possible to melt some of the metals with single-tank torches. Hence, these torches can be used for brazing and soldering, but not for welding. A metal-cutting torch is better known as hot blue spanner, blue wrench, hot wrench, smoke wrench, and gas-axe.

Types of Torches: The torch can be defined as the part held and manipulated by the welder to get the weld made. It possesses a valve and connection for oxygen and the same things for fuel gas, a handle to obtain the grip, an integrating chamber (angularly set) where there occurs a mixing of oxygen and fuel gas, with a tip where formation of flame takes place. The fuel gases used along with oxygen include propylene, propane, hydrogen gas, MAPP gas, Liquefied Petroleum Gas (LPG), and the most widely used is acetylene.

Injector Torch: It can be defined as an archetypal oxy-fuel torch, also known as an equal-pressure torch. It carries out the mixing of mere two gases. The injector torch operates in such a way that high pressure oxygen comes out of the tiny nozzle present in the torch head, and the fuel gas gets dragged towards it via the venturi effect.

Rose-bud Torch: The use of this torch is to carry out the heating of metals for straightening, bending, etc. It is generally used where a huge area requires heating. It produces a rose-bud shaped flame at the end, hence the name. This torch can carry out the function of heating small areas like rusted bolts and nuts as well. However, here, filler rod won’t be used with torch.

Cutting Torch: The head of the cutting torch is used for cutting metal. Its identification details are as follows: The inside of the torch consists of a combination of oxygen and acetylene. It helps in producing flame of a high temperature. It consists of 3 pipes going to a nozzle at 90 degree. It also contains an oxygen-blast trigger which blasts away the material during its cutting by the way of providing oxygen.

Welding Torch: The welding torch consists of either 1 or 2 pipes running towards the nozzle without oxygen-blast trigger. As the name suggests, it performs the function of welding.

Home Metal Casting

Brian Reuter asked:


Bulk metallic glass, a.k.a. amorphous metal, appears to have a very bright future. Being twice as strong as titanium, tougher and more elastic than ceramics, and having excellent wear and corrosion resistance makes them attractive for a variety of applications. It can even be cast in a mold to near net shapes.
Conventional Metals
In an ordinary metal the atoms of the metal arrange themselves into a repeating pattern of crystals or grains with different sizes and shapes upon cooling from the liquid state. Because metals typically do not solidify into single crystals, they have inherent weaknesses.
The boundaries between the grains are weak spots and under high enough stress and temperature the grains will slide past each other resulting in metal deformation. In addition, extra atoms are often present in grains causing planes of distortion called dislocations. Dislocations easily move through metal that is under stress, again causing deformation. Grain boundaries and dislocations greatly lower a metals strength compared to its theoretical maximum.
Casting of conventional metals also requires more manufacturing steps than bulk metallic glass. Conventional metals shrink significantly as they cool in the mold from liquid to solid form and often develop surface roughness. Secondary steps are usually required to get at the final product, such as grinding and polishing.
Bulk Metallic Glass
The structure of metallic glass is very different from that of conventional metals. Rather than arranging themselves into repeating patterns of grains, the atoms of metallic glasses are “frozen” in a random, disordered structure, similar to regular window glass. It even has a smooth surface like glass. So smooth, in fact, that paint does not adhere well to metallic glass. It is this amorphous structure, lacking in grain defects, that gives metallic glasses their strength, toughness, hardness, elasticity and corrosion and wear resistance.
First discovered by Pol Duwez in 1960 at Caltech, the technique to create metallic glasses required undercooling a molten metal uniformly and rapidly. Rapidly as in 1,000,000°C per second! The molten metal reaches its glass transition temperature without enough time or energy to crystallize, and instead solidifies as metallic glass. Because the material did not conduct heat well, only thin ribbons of metallic glass could be created because of the uniformity and speed of cooling that was required.
Around 1990 Akihisa Inoue and his team at Tohoku University in Japan discovered new alloys that could form thicker metallic glasses at cooling rates as low at 1°C to 100°C, as long as three conditions were met:
1) Use three or more elements in the alloy
2) The atomic size of the elements must differ from each other by at least 12 percent
3) Use elements that have a strong affinity for each other
Soon after, William Johnson and Atakan Peker at Caltech did the same. The lower cooling rates allowed for thicker materials to be created, up to four inches. These thicker materials are referred to as bulk metallic glass (BMG).
Currently available bulk metallic glasses are malleable at around 400°C, compared to over 1000°C for steel. This allows the material to be processed similarly to polymers, with high volume production via casting up to a thickness of four inches. The material has low shrinkage during solidification and can therefore be cast in near-net shapes with microscale precision. The smooth shiny surface eliminates secondary finishing processes. Scalpels made from bulk metallic glass come out of the mold sharp and ready to use.
Some Disadvantages
As with any material, BMG cannot be everything to every application. Its plastic like manufacturability also means that it cannot be used in high temperature applications, i.e., above 260°C, because it becomes soft and weakened. Pure bulk metallic glasses also exhibit cyclic fatigue from repeated stress. Because of their high elasticity and low plasticity, catastrophic failure occurs after only a small amount of plastic deformation.
BMG Composites
New developments in BMG composites are helping to reduce the limitations of the material. In a BMG composite the BMG is the matrix and a ductile crystalline-phase is the reinforcement material. The reinforcement can either be an added material, such as metal or ceramic fibers, or internally created by precipitating ductile dendrites within the BMG, yielding partial crystallinity. These composites combine the ductility, fracture toughness and plasticity of conventional metals with the high strength of pure BMG.
Applications
BMGs are being examined for or currently used in a wide variety of applications including:
– Industrial coatings for improved wear and corrosion resistance – As a replacement for depleted uranium in Kinetic Energy Penetrators for the military. – Casings for cell phones – Scalpels – Sporting goods such as bats and tennis racquets – Jewelry
The Defense Advanced Research Projects Agency (DARPA) also funding a three-year program called Structural Amorphous Metals (SAM). The aim of the program is to demonstrate the viability of BMG in structural applications. Specific applications being investigated include “corrosion-resistant, reduced magnetic mass hull materials; moderate temperature, lightweight alloys for aircraft and rocket propulsion; and wear-resistant machinery components for ground, marine, and air vehicles.”
U.S. Patent Situation
Upon examining several patents and class codes on amorphous metals it appears that the main U.S. patent classification codes for these materials are:
148/304 – Amorphous: Stock material which has no regular crystal structure but rather has a series of noncrystalline areas much like a glass.
148/403 – Amorphous, i.e., glassy: Stock material which has no regular crystal structure, but rather has a series of noncrystalline areas much like a glass.
148/561 – Passing through an amorphous state or treating or producing an amorphous metal or alloy: Process wherein a metal or metal alloy having no regular crystalline structure or periodicity (i.e., amorphous) in any amount is produced or treated by a process under the class definition or wherein a metal or metal alloy passes through a physical state having no regular crystalline structure or periodicity during the treatment of the metal or metal alloy.
Guideline examined patents assigned to these codes that were granted during the period from 1987 to 2003. We then compared the top patent holders for the above class codes in terms of number of patents published from 1987 to 2003.
Top BMG Patent Holders from ’87 to ’03
55 patents – YKK Corp.
43 patents – Honeywell
33 patents – Tsuyoshi Masumoto & Unitika Ltd.
26 patents – Akihisa Inoue
15 patents – Alps Electric Co.
14 patents – Koji Hashimoto
13 patents – California Institute of Technology
13 patents – Nippon Steel Corp.
11 patents – Hitachi Ltd.
11 patents – Kabushiki Kaisha Toshiba
One method Guideline uses to compare patent holders is by calculating an index referred to as Technology Influence. Technology Influence represents how often an assignee’s patents from the previous five years (in this case, 1998-2002) are referenced by patents published in the year of comparison (in this case 2003). A Technology Influence value of 1 represents the average. This shows how much a patent holder’s past technology developments are influencing current development. From this analysis Guideline determined that Caltech’s work has been most influential as their Technology Influence value is 5.06, whereas the next closest value is only 1.46, held by Alps Electric.
Applied Science is another calculation used to compare patent holders. This refers to the average number of non-patent references cited by a patent holder’s patents, such as scientific papers from journals, conference proceedings, etc. This gives an indication of which companies are working on the leading edge. Again, Caltech stands out as a clear leader with an Applied Science value of 7.3. This makes sense considering that Caltech is known to be one of the leaders in developing this technology. As mentioned earlier, metallic glass was first discovered at Caltech.
An analysis of patent assignees and inventors revealed that Akihisa Inoue has done extensive work and collaboration. He is listed as an inventor or co-inventor on a little over 60 patents with about 120 other Japanese researchers. All of this work was done with the following Japanese organizations, and this is only in regards to U.S. patents.
– Tsuyoshi Masumoto and Unitika, Limited – Teikoku Piston Ring Company Limited – Alps Electric Co., Ltd. – YKK Corporation – Honda Motor Co., Ltd. – Yamaha Corporation – Japan Science and Technology Corporation – Unitika Ltd. – Toyota Jidosha Kabushiki Kaisha – Research Development Corporation of Japan – Japan Metals & Chemicals Co., Ltd. – Sumitomo Rubber Industries, Ltd. – Mitsubishi Materials Corporation
Indeed, Inoue led a five year project sponsored by the Japanese government (Inoue Supercooled Liquid Glass Project), which reported the development of a less expensive copper alloy based BMG with a tensile strength over 2 Gpa. Currently Inoue is leading a five-year project sponsored by the Japanese New Energy and Industrial Technology Development Organization.
Although Inoue has done the most extensive work in terms of U.S. patenting on amorphous and glassy metal technology, the work being done by William Johnson’s group at Caltech appears to be having a larger impact on the overall body of work in U.S. patents over recent years.

Backyard Metal Casting

Kent Kelin asked:


DIY casting furnaces are nothing but Do It Yourself casting furnaces. One can make variety of furnaces. The procedure of some of them can be described as follows:

DIY Induction Furnace: Theoretically, only three things are required for implementing induction heating: High frequency Electrical Power Source, work coil for generating an alternating magnetic field, and a workpiece-electrically conducive. However, the practical approach is very complicated. For instance, the work coil and High Frequency source’ should have a matching network in between, to obtain better power transfer. Use of water cooling systems is very common in induction heaters of high power. This facilitates removal of waste heat from the matching circuit of the work coil and the coil itself. This process involves application of control electronics as well. Control Electronics, as the name suggests, controls the heating action’s intensity, thereby ensuring consistent results. It also provides protection against unpleasant operating conditions.

Usually, the incorporation of work coil takes place into a resonant tank circuit. There are innumerable advantages of this. The first advantage is that any one of the parameters, i.e. voltage or current is made sinusoidal. This causes fewer losses to inverter by the way of allowing it getting benefited from either zero-current-switching or zero-voltage-switching corresponding to the arrangement chosen. The visibility of sinusoidal waveform at work coil gives the proof of purity of signal. There also occurs less interference of radio frequency with the equipment in its vicinity. It’s up to the designer to choose one amongst several resonant schemes.

DIY Bronze Furnace: The making of DIY Bronze furnace involves taking silica bricks of 9 inches X 4 ½ inches X 2 ½ inches in the first place. After that, one is supposed to put a steel plate having dimensions 18 inches X 24 inches at the place where he intends building the furnace. In other words, the steel plate should be used as a base. The construction of furnace should start thereafter. It is advisable to keep the circumference of the furnace as 14 inches. A small hole of diameter 3 inches should be made at a height of 5.5 inches above the floor. Let the height of the cylindrical furnace be 11 ½ inches (including floor). This hole is to be used for inserting the burner.

The cutting of the burner port should be done in such a way that it acts as a perfect tangent to furnace. This should be done in order to make the flames whirl around crucible, thereby hitting it indirectly. The peculiarity of bronze casting is emission of toxic fumes. Therefore, it is always advised to perform the casting task in the area which has ample ventilation. Wearing of safety clothing is recommended. After the completion of furnace (including the cutting of hole to get the fitting of one’s biggest crucible enabled), it should be permitted to dry. At that time, trawling of water, vermiculite, and kaolin clay on the exterior is recommended. The immediate use should be strictly avoided, as it may develop cracks. After drying, let the furnace be heated slowly to reduce ‘kaolin paste’ cracking.

Back Yard Metal Casting

Kent Kelin asked:


There are various casting processes being implemented now days. The oldest amongst them is sand casting. Spin casting is also widely used. They can be described as follows:

Sand Casting: Sand casting involves formation of mold from a mixture of sand and to pour a casting liquid, most probably, a molten metal into mold. The metal is then allowed to solidify and the removal of mold, takes place. Sand molding consists of two types: green sand method and air set method. The first one consists of mixture of clay, moisture, silica, and many other additives. The second one consists of mixture of dry sand and other materials, not moist clay. They are mixed with the help of a quick curing adhesive. The collective use of these materials is called ‘air set’.

At times, there is temporary plug placed to pour the fluid which is to be molded. Air-set molds usually form molds consisting of two parts-the bottom and the top. The mixture of sand gets tamped down after its addition. It does not generate any by-product. After the solidification and cooling of metal, the mold gets usually destroyed. This is because its removal involves a lot of breaking and cracking. The casting accuracy depends a great deal on the sand and the process of molding used. Castings composed of green sand result into formation of rough texture on casting surface, and this characteristic makes them easily recognizable. Air-set molds produce smoother castings.

Many a times, the casting process results in losing of components of sand mixture. It is possible to reuse green sand by the way of adjusting the composition to get the lost additives and moisture replenished. The entire pattern itself is eligible to be reused for producing novel sand molds. The method of reuse can be continued for an indefinite period. In 1950, casting process got automated partially. They have been in great demand for developing production lines since then.

Spin Casting: Spin Casting is better known as Centrifugal Rubber Mold Casting (CRMC). It implies utilization of centrifugal force for producing castings out of rubber mold. As a customary practice, a mold having shape of a disc gets spun through its ‘central axis’ at a pre-decided speed. The material used for casting is usually thermoset plastic in the liquid form or a molten metal. It gets poured into the mold through the opening at its centre. Corresponding to the solidification of metal, or the setting of thermoset plastic, the spinning of the filled mold takes place.

Normally, organic rubber or vulcanized silicone is used as a mold-making substrate in spin casting. Vulcanization takes place in the middle of process of mold-making. After the successful completion of vulcanization process, venting and gating must be undergone by the mold. This implies carving of channels for ensuring proper material flow and air during the course of casting. A scalpel or knife is used to carry out the above two processes. The mold complexity is directly proportional to the time required in implementation of venting and gating.

Bronze Metal Casting

Kent Kelin asked:


DIY casting furnaces are nothing but Do It Yourself casting furnaces. One can make variety of furnaces. The procedure of some of them can be described as follows:

DIY Induction Furnace: Theoretically, only three things are required for implementing induction heating: High frequency Electrical Power Source, work coil for generating an alternating magnetic field, and a workpiece-electrically conducive. However, the practical approach is very complicated. For instance, the work coil and High Frequency source’ should have a matching network in between, to obtain better power transfer. Use of water cooling systems is very common in induction heaters of high power. This facilitates removal of waste heat from the matching circuit of the work coil and the coil itself. This process involves application of control electronics as well. Control Electronics, as the name suggests, controls the heating action’s intensity, thereby ensuring consistent results. It also provides protection against unpleasant operating conditions.

Usually, the incorporation of work coil takes place into a resonant tank circuit. There are innumerable advantages of this. The first advantage is that any one of the parameters, i.e. voltage or current is made sinusoidal. This causes fewer losses to inverter by the way of allowing it getting benefited from either zero-current-switching or zero-voltage-switching corresponding to the arrangement chosen. The visibility of sinusoidal waveform at work coil gives the proof of purity of signal. There also occurs less interference of radio frequency with the equipment in its vicinity. It’s up to the designer to choose one amongst several resonant schemes.

DIY Bronze Furnace: The making of DIY Bronze furnace involves taking silica bricks of 9 inches X 4 ½ inches X 2 ½ inches in the first place. After that, one is supposed to put a steel plate having dimensions 18 inches X 24 inches at the place where he intends building the furnace. In other words, the steel plate should be used as a base. The construction of furnace should start thereafter. It is advisable to keep the circumference of the furnace as 14 inches. A small hole of diameter 3 inches should be made at a height of 5.5 inches above the floor. Let the height of the cylindrical furnace be 11 ½ inches (including floor). This hole is to be used for inserting the burner.

The cutting of the burner port should be done in such a way that it acts as a perfect tangent to furnace. This should be done in order to make the flames whirl around crucible, thereby hitting it indirectly. The peculiarity of bronze casting is emission of toxic fumes. Therefore, it is always advised to perform the casting task in the area which has ample ventilation. Wearing of safety clothing is recommended. After the completion of furnace (including the cutting of hole to get the fitting of one’s biggest crucible enabled), it should be permitted to dry. At that time, trawling of water, vermiculite, and kaolin clay on the exterior is recommended. The immediate use should be strictly avoided, as it may develop cracks. After drying, let the furnace be heated slowly to reduce ‘kaolin paste’ cracking.

Metal Casting Zone

Kent Kelin asked:


Lost Foam Costing is a sub type of Investment Casting. This type of casting method uses foam pattern as the investment. This method benefits from the advantages of the foam properties helpful to make simple and cheap castings. These types of simple castings are impossible using the regular cope and drag method.

Casting process:

Foam Shaping: The original foam pattern of the Polystyrene is generally molded or carved.

Carving Polystyrene: The formed foam or polystyrene is then carved using traditional carving tools or the new-age hot-wire cutting tools. It can also be sanded easily.

Injecting Polystyrene in a Mold: Polystyrene contains pentane as a blowing agent and is commonly used for beads. The beads are pre-extended, stabilized and then blown into the mold to form pattern sections. A steam cycle forces the beads to expand fully, after this the fuse together and then it undergoes an in-mold cooling cycle. The final shape if very complex, then it is molded in sections. A cluster is formed by aging and gluing together the shaped foam sections.

Preparing Final Mold (Investment) for Casting: Gates and Raisers are generally attached to the pattern, they are also the part of the casting as this helps reduce the shrinkage. Pouring, dipping or spraying are the different methods used for coating the foam cluster with ceramic investment. The reason for this coating is that it forms a barrier and helps to prevent the molten metal to penetrate or cause sand erosion while pouring. Structural integrity of the casting is protected thanks to the coating. The cluster when dried is backed up with un-bonded sand and is placed in a flask. Proper and uniform compaction is then achieved by performing mold compaction using a vibrating table. After all this process and after proper compaction, the mold is ready to be poured.

Automatic pouring is the preferred method in Lost Foam Casting. This is the most critical process and also a bit difficult than the traditional foundry practice. As there are no parting lines or fins to remove the cleaning is easier and requires far more less time and operations in the Lost Foam Casting process.

Advantages of Lost Foam Casting: Due to its unique properties, foam is easy to carve glue and manipulate. It also provides accurate dimensions as Lost Foam Casting is more accurate and effective than sand casting. There are no fins or parting lines the finishing process is easy and less time consuming. The elimination of cores makes complex casting designs easy. Lost Foam Casting also allows us to control the wall thickness and thus no core prints are required thus eliminating shifts or fins and also saves the trouble of sand mixing and core defects. As there are no drafts multiple levels of casting is possible. Precise gate and riser replacements are achieved. Unconventional forms of casting that are difficult or impossible to achieve in traditional cope and drag method are easily achieved in Lost Foam Costing. Due to simpler process and easy finishing work, the process is very cost effective and lowers the overall price of the final product.

Foundry

Kent Kelin asked:


Die casting is the method used for forcing molten metal into mold cavities under high pressure. Die casting is very versatile and hence, is the widest used method for casting a metal. Die casting is same as permanent mold casting the only difference is that the metal is injected into the mould at very high pressure of 10-210 Mpa. This results in a more uniform part, usually good dimensional accuracy and also good surface finish.

The different metals and alloys that can be used in die casting are zinc, aluminum, copper, magnesium, tin and lead. Ferrous metals can also be used for die casting, die casting method is generally used for applications in which a large quantity is medium or small sized parts are required with detail, good dimension and fine surface finish.

There are namely two equipments used for die casting cold chamber and hot chamber process.

Cold Chamber process: In the cold chamber category of die casting, a cold chamber of each module is filled with molten metal. The time exposure provided for the molten metal to plunge the walls of the mold is less. This clod chamber process method is very useful for metals like aluminum, copper and metals that easily alloy with iron at high temperatures.

Hot Chamber process: In the hot chamber process method of die casting, the pressure that is connected to the die cavity is forever and permanently in molten metal. As the plunger moves towards the open position that is towards the non – pressurized area, the inlet port connected to the pressurizing cylinder is uncovered.

The die casting molds which are used in this method are expensive and take usually take long production time. These die casting modules are also called as “dies’

Advantages of Die Casting: The method of die casting gives excellent dimensional accuracy. The dimensional accuracy is as good as 0.1mm for the first 2.5cms and 0.005 for the first inch. Die casting also provides with smooth cast surfaces. Small and thin walls and can be made using the method of die casting walls as tiny as 0.75mm approximately can be casted. Inserts like thread insert, high strength bearing surfaces and heating elements can also be inserted using the Die Casting method. Die casting also helps in reducing or even completely eliminating the use of secondary machining operations. The use of Die Casting method also helps to reduce the production time and a huge number of articles can be produced in a very short time. Die casting method also helps to retain as well as increase the tensile strength of the metal. It offers tensile strength as high as 415 MPa that is 60ksi.

Disadvantages of Die Casting: The casting weight is very less hardly between 30 grams and 10 kgs. Also the size of the material that needs to be casted using the Die Casting method needs to small say around 600mm. the process of Die Casting requires high budget and can pile up high initial cost. Die Casting method makes the metal porous up to some extent. In the Die Casting method the thickest section needs to be less than 13mm or 0.5 inches.

Casting Furnace

Kent Kelin asked:


Die casting is the method used for forcing molten metal into mold cavities under high pressure. Die casting is very versatile and hence, is the widest used method for casting a metal. Die casting is same as permanent mold casting the only difference is that the metal is injected into the mould at very high pressure of 10-210 Mpa. This results in a more uniform part, usually good dimensional accuracy and also good surface finish.

The different metals and alloys that can be used in die casting are zinc, aluminum, copper, magnesium, tin and lead. Ferrous metals can also be used for die casting, die casting method is generally used for applications in which a large quantity is medium or small sized parts are required with detail, good dimension and fine surface finish.

There are namely two equipments used for die casting cold chamber and hot chamber process.

Cold Chamber process: In the cold chamber category of die casting, a cold chamber of each module is filled with molten metal. The time exposure provided for the molten metal to plunge the walls of the mold is less. This clod chamber process method is very useful for metals like aluminum, copper and metals that easily alloy with iron at high temperatures.

Hot Chamber process: In the hot chamber process method of die casting, the pressure that is connected to the die cavity is forever and permanently in molten metal. As the plunger moves towards the open position that is towards the non – pressurized area, the inlet port connected to the pressurizing cylinder is uncovered.

The die casting molds which are used in this method are expensive and take usually take long production time. These die casting modules are also called as “dies’

Advantages of Die Casting: The method of die casting gives excellent dimensional accuracy. The dimensional accuracy is as good as 0.1mm for the first 2.5cms and 0.005 for the first inch. Die casting also provides with smooth cast surfaces. Small and thin walls and can be made using the method of die casting walls as tiny as 0.75mm approximately can be casted. Inserts like thread insert, high strength bearing surfaces and heating elements can also be inserted using the Die Casting method. Die casting also helps in reducing or even completely eliminating the use of secondary machining operations. The use of Die Casting method also helps to reduce the production time and a huge number of articles can be produced in a very short time. Die casting method also helps to retain as well as increase the tensile strength of the metal. It offers tensile strength as high as 415 MPa that is 60ksi.

Disadvantages of Die Casting: The casting weight is very less hardly between 30 grams and 10 kgs. Also the size of the material that needs to be casted using the Die Casting method needs to small say around 600mm. the process of Die Casting requires high budget and can pile up high initial cost. Die Casting method makes the metal porous up to some extent. In the Die Casting method the thickest section needs to be less than 13mm or 0.5 inches.

Foundry

Kent Kelin asked:


Lost Wax Casting is known as Cire Perdue in French. It is a process in which an artist’s sculpture is used to cast bronze. The Lost Wax Casting method is also known as Investment Casting in the modern industrial world. This is a very ancient method used for casting small bronze sculptures, but today it is used to make many different artifacts and the process varies from foundry to foundry. Today this developed method of Lost Wax Casting is used to make articles like fine jewelery, show pieces, dental restoration, a few specific industrial parts and also some machine tools.

Process of Lost Wax Casting:

Rough Sculptor making: A creative artist makes an original sculptor or mold or an artwork by using raw material like wax, plaster of Paris or clay. A mixture of oil based clay and wax is preferred as these materials retain their softness.

Final Mold Making: A mold is then made as per the original sculptor. The mold is made up of two pieces and a key with shim is placed between the two pieces during construction so the mold can be put accurately back together. Molds are generally made using plaster or fiberglass or any other material that may be suitable. An inner mold of latex or vinyl or silicone is put pup preserve the details of the original art work. Generally, the original art work made of plaster mold cracks and breaks during the initial phase of deconstruction. Many a times, numerable molds are required to get the exact replica of the original art work.

Filling up the mold: Once the latex and plaster mold is complete and finished, molten wax is poured into the mold till it gets an even coating all around the mold. The thickness of the wax coating is around 1/8 inch. This process is then repeated until the desired thickness is achieved.

Removal of wax replica: The hollow wax replica of the original art work is then removed from the mold. The original mold can be used for making more wax replicas, but due to the wear and tear of the original mold the reuse of the mold is limited.

Softening: Each wax mold is then chased or softened using heated metal tools. The metal tools are rubbed around portions that show cracks or the joining line of the mold, where the pieces have come together. Separately molded wax pieces are then heated and attached. The finished mold is then dressed in order to hide any imperfections. The final piece then looks like a bronze sculpture.

Making paths for molten bronze: It is also known as “spuring”, in short the wax copy is then branched with treelike wax, so that the molten bronze reaches the right parts and also it helps the air to escape. The critical and careful spuring begins from the top of the wax copy. The top of the copy is attached to by wax cylinders to different points on the wax copy.

Slurry, burnout, testing, pouring, release, metal-chasing, and painting are the final steps in the process of Lost Wax Casting.

Hobby Metal Casting

Kent Kelin asked:


Brass casting, as the name suggests, involves the use of brass as the molten metal. Brass casting can be carried out by the way of sand casting only. Sand casting can be defined as a ‘cast part’ produced by formation of a mold from a mixture of sand and pouring the casting liquid (mostly molten metal) into mold. Then the air-cooling of the mold takes place. After the solidification of metal, the removal of mold takes place. The metal used here is brass. It is a known fact that brass is an alloy of copper and zinc. Hence, to be precise, the molten metal consists of two elements.

Sand molding consists of two types- ‘Green sand’ molding and ‘air set’ molding. The first one consists of a blend of moisture, clay, silica sand and other additives. The second one makes use of dry sand bonded to all the above materials except moist clay, by the way of using an adhesive, which is fast curing.

At times, there is a placing of a temporary plug (in the mold cavity) to enable the formation of a channel to pour the fluid which is to be molded. The molds of the second type, i.e. the air-set molds result in the formation of a 2-part mold. The two parts are bottom and top. The tamping-down of the sand mixture takes place as it gets added. Many a times, the final assembly of the mold is vibrated to get the sand compacted and get the unwanted voids filled. Then the molten alloy (brass) gets poured into mold. After the solidification and cooling of brass, the separation of casting from sand mold takes place. Normally, such molds are one-time usable.

Patterns: A designer or an engineer provides the design of the object to be produced. On the basis of this design, a pattern is built by an efficient pattern maker by the use of plastic, metal, or wood. Polystyrene can also be used. The casting brass would get contracted during solidification. Non-uniformity can also result out of this. Therefore, the size of the pattern should be a bit larger as compared to the final product. ‘Contraction Allowance’ is the name given to this difference. Brass enters the mold cavity through a runner system including sprue and other feeders.

Molding box: A molding box having multiple parts (also known as casting flask whose bottom and top halves are called drag and cope respectively) is constructed for receiving the pattern. There may be an addition of sand to nullify the defects introduced due to the pattern getting removed.

Chills: To have a proper control over metallurgical structure and solidification of brass, plates of brass, or any other metal can be placed in mold. A hard structure may get formed at these places. Chills can be used for promoting directional solidification as well.

Design Requirements: The thing in making and the pattern corresponding to it should be designed in such a way that every stage of process can get accommodated. One should be able to take away the pattern without causing any disturbance to molding sand.

Back Yard Metal Casting