Investment casting is a manufacturing process used to produce industrial parts using a wax model to create a mold that will be filled with molten metal. This type of casting is able to produce complex parts with fine details more effectively than die casting or other production methods.
Investment casting takes its name from the ceramic slurry that is used to form a shell around a wax pattern. A wax model is created and attached to a sprue. Several hundred waxes may be affixed to the same sprue forming an assembly called a tree. After the tree is dipped into the slurry multiple times it is sprinkled with coarse material such as sand. Once the investment is thick enough around the wax, it is inserted into an oven where temperatures can reach upwards of 1000°F. The wax melts and drips out while the investment maintains its size and shape. A metal is heated until molten and is poured into the hollow shell, traveling along the lines left by the sprue and filling the impressions left by the wax. When the metal is no longer glowing red hot, the shell is removed and the cast metal parts are cut off from the sprue. They may receive additional machining and finishing though they require less than other methods of casting.
Investment casting has been used to produce metal parts for thousands of years. Originally honeycomb was used to create the wax patterns. As materials and technologies have improved, the general process remains fairly simple and has not changed dramatically. It is a straightforward concept: form a mold around a wax pattern that will melt away, leaving a hardened shell that can be filled with molten metal. Today's manufacturers are aided by improved equipment that can produce identical results time after time. As the investment is mixed, fans and blowers remove the dust which contains silica, a potentially harmful dust that should not be inhaled. A vacuum is often used to remove air bubbles from the investment to ensure that all the patterns on the tree are encased in the ceramic slurry without pockets of air. Automated ovens and furnaces control the temperature for a precise burnout while other heating equipment can melt the alloys to the appropriate temperature. Extensive knowledge regarding the chemical formulas and molecular composition of the materials makes it possible for manufacturers to choose specific attributes for the part, such as durability, magnetism or weight load while avoiding negative characteristics. Science and engineering have helped make the traditional process of investment casting even more successful in the modern age.
The Advantages of Investment Casting
LOW COST TOOLING
Investment casting is known as a very cost efficient process as the molds and dies associated with investment casting are less expensive compared to those utilized in forging, die casting, or stamping. Molds used in investment casting actually create wax patterns which are designed to last indefinitely. Traditionally other processes the dies are frequently replaced which adds up costs very quickly.
ELIMINATION OF MACHINING
Another important benefit of investment casting is there is no need for machining. Most situations the materials used are extremely hard and machining those parts is expensive and requires a lot of time. With investment casting it is not only faster but much more affordable.
ELIMINATION OF FINISH OPERATIONS
Investment casting utilizes a smooth wax pattern and fine grained materials which provides a very uniform surface on every cast piece. Most types of investment castings are used with "as cast" surfaces and regardless of which alloy you use there is an expected micro-finish of 125. So whether the application requires an aesthetically smooth or functionally smooth surface, investment casting is unmatched.
MULTIPLE PARTS ASSEMBLIES
Assembling a number of different parts can actually somewhat expensive however a careful analysis of the parts can show that it is possible to incorporate multiple parts into a single investment casting. This will result in overall savings in machining and labor costs. Investment casting is an outstanding solution that many offer processes cannot match.
INTRICATE PARTS MADE EASY
Many companies are often confronted with the need for intricate components however due to the unique designs and internal surfaces many parts require expensive machining. These processes can greatly reduce the number of hours of labor involved with traditional machining and casting even offers an exact fit that meets the exact specifications of a particular component.
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compound consisting of either more than one metal or a metal and a nonmetal
- Casting that is not heat treated after being removed from the mold.
- The process whereby excess water and wax is removed from a molding.
- Forming and shaping a material substance, such as an industrial piece of equipment, by pouring liquid into a mold and allowing it to harden.
- The empty space within the mold into which the molten metal will be poured.
- The process of filling a permanent mold cavity with molten material while rotating the mold. Centrifugal casting is often used during the investment casting process to increase the amount of pressure exerted upon the metal in order to reproduce mold details, such as lettering and holes.
- The process by which an investment mold is created from a pattern in order to be cast. Ceramic molds consist of solid molds and ceramic shells.
- The method of creating a ceramic mold through the immersion of a pattern into a slurry of liquid and covering the coated pattern with sand. The pattern is usually immersed and coated nine to ten times before the shell is completed.
- The method of applying protective plastic to metal.
- Lines on the surface of a casting that are the by-product of the incomplete fusion of metal streams.
- The sharing of a common point or axis of two or more surfaces of shapes, such as cylinders, cones, spheres and hexagons.
- A form inserted into a mold to create internal mold features.
- A surplus of nonmetal substances within a casting.
- Pertaining to or containing iron.
- The method of reshaping metal through the application of heat and compression.
- The openings in the gating system that transfer the molten metal from the runners into the mold cavity.
- The structure that transfers the molten metal into the mold. Gating systems are designed to uniformly transfer the metal into the mold cavity to create an even mold.
- Small pieces of refractory materials, sand, slag or deoxidation products that have been trapped within the casting while it was solidifying.
- The injection of a molten substance, usually metal, under substantial pressure into a mold.
- An ancient process related to investment casting that consisted of creating and plastering a wax model, replacing the wax with molten metal and removing the plaster after the metal cooled.
- An incomplete casting.
- A hollow container from which liquid substances can be formed into solid shapes.
- A solid that has been converted into a liquid through the application of heat.
- Not pertaining to or containing iron. Examples of non-ferrous metals include aluminum- and copper-based substances.
- A casting model created by injecting metal dye with wax. When the wax solidifies, it forms the pattern, which is then molded and cast.
- A term that refers to the extent to which the pattern size must be increased to allow for metal shrinkage.
- The process in which a wax pattern is sprayed with plaster slurry to create a mold.
- The process of using metal, often iron, to create the mold. Permanent molds are cheaper than sand molds when a large quantity of parts is produced, as they can be used more than once.
- The part of the gating system that pushes the molten metal into a mold.
- An open space in a mold into which extra molten metal is trapped.
- Horizontal mechanisms connected to the sprue that transfer the molten metal from the sprue to the mold.
- The process of pouring molten metal into a natural or an artificial sand mold to form large parts, often made of iron.
- The process in which sand and plastic are poured over a hot metal pattern, whose heat causes the sand and plastic to mold to the pattern. The mold is removed from the metal, filled with molten metal and broken once the metal hardens, forming a cast.
- The contraction of metal during the cooling process.
- The degree to which a pattern is enlarged to allow for the contraction of the metal during the cooling process.
- The thick, insoluble liquid made of substances like plaster and silica from which a mold is created by repeatedly covering the patterned wax with the liquid.
- The method in which a wax pattern is placed within a steel container called a flask. The flask is then filled with a liquid plaster, which hardens into a mold of the pattern.
- Vertical mechanism connected to the pouring cup that transfers the molten metal to the runners.
- A term that refers to the deviation of the cast axis from the true axis.
- Small holes in the gating system through which air is pushed out of the mold as molten metal is poured into the mold.