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.
The investment casting process results in parts with excellent surface finishes because of the smooth impression left by the wax models. There are no seams or lines since the part is made whole, not in multiple pieces that must be joined; this also cuts down on wasted material. Investment casting products also fit the exact specifications of the original design. Investment casting is also called lost wax casting or, simply, wax casting. Many manufacturers depend on the investment casting process to produce dimensionally accurate precision investment casting parts. Though it is more expensive than other types of casting processes, it provides design flexibility with greater detail and a wide selection of metal alloys to use for materials. It also produces lightweight parts. Precision investment casting also saves money because it does not require welding, assembly or finishing work. The quality of precision investment casting is determined by the strength and tensile ductility of the casting. Similar to investment casting is centrifugal casting, a manufacturing process that produces cylindrical parts with thin walls. This technique is generally used for stock parts made in standard sizes that require additional machining or working; the parts are typically not end products themselves. Centrifugal casting produces high quality parts with uniform wall thicknesses because it has tight control over the material.
Investment casting is done with a wide variety of metals. Aluminum investment castings are among the most common, along with stainless steel and copper, though almost any castable metal may be used. Stainless steel castings are used frequently around hazardous substances or in sanitary environments because it is easy to clean and resists corrosion. Brass castings are used in many applications used industrially, commercially and domestically everyday. Copper investment castings are lightweight, strong and are widely used in many different capabilities such as pipe fittings, machine tools, mixing equipment, lock parts and jewelry. Investment castings can be found in the aerospace, automotive, chemical, defense, food processing, electrical, railroad, mechanical, marine, electronic, textile and engineering industries. When ordering steel investment castings, the type of steel that will be used to produce the part must be identified. By specifying the test methods for an order, the requirements of the material can be guaranteed. Because steel is stronger than cast iron, wrought iron and malleable iron, steel investment castings are typically used in the manufacturing of parts that must endure shocks, wear or heavy loads. Titanium castings are very strong and lightweight and are used for turbocharger components, industrial tools and instruments and other applications in the defense, aerospace, transportation, power generation, marine and medical industries.
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.
Brass investment casting - Rimer Enterprises, Inc.
Titanium investment castings - Ferralloy, Inc.
Titanium investment castings - Ferralloy, Inc.
Steel Casting - Ferralloy, Inc.
Investment castings - Rimer Inc.
Investment castings - Rimer Inc.
Investment casting can be put into the list of some of the oldest manufacturing processes, which we can take back to about 5,000 years or so. In this process, a molten metal is transferred into a mold, based on a thoroughly-designed concept. The mold is shaped according to the requirement of the industry or machinery, where the product will be used.
Because the pattern is invested or encircled in a ceramic pot, wherein the material toughens, it gets the name "investment casting." It is also called lost wax casting, because the wax is melted after the component is ready. Also, the mold gets destroyed in the process, hence "lost-wax" casting. Using this method, you can create even those machine parts that have a very detailed and complex design.
Investment casting has a host of benefits that help manufacturing houses keep their cost under control. In the following, we will discuss some of the biggest benefits of this industrial process over other techniques of part manufacturing.
Low Production Cost
Investment casting slashes down the labor cost that has a huge share in a business's final production cost. Other methods, like metal fabrication, consume an enormous amount of resources to give the final lot of goods. Investment casting, on the other hands, is a cost saver, it has less manpower requirement, plus, it does not take much time. Overall, it helps you save unnecessary expenses, allowing you to earn a substantial margin while keeping your price down.
Save Time and Wastage
If you are considering using machines to prepare machine parts, then there are chances that it will lead to a great deal of wastage. Wastage also adds to your production cost, and subsequently, your losses. Further, machining can be a prolonged process that might delay your final delivery schedule and cast an impact on your recognition. On the contrary, investment casting prevents the waste of material and time.
Way better and quicker than die casting
Die casting is another popular method that the industry follows for machining hard components. While it can be a cool play for large industry players, startups can have a nightmare because of its requirement of heavy and lasting tools and safety technology. Setting up steel tools and getting heavy metal tools is a very expensive affair for the beginners in the industry.
More reliable than any other technique
Investment casting, along with other similar techniques such as brass investment casting, aluminum investment casting, and forging, stands as one of the most reliable methods of creating machining parts. Engineers have strong control over the process throughout the process.
Products made through investment casting show a grander tolerance rate-to be approximate, a tolerance rate of ± .005".
Last but not the least, investment casting can be done via 9 wax patterns, and most of the time, patterns can be used again. It hence shows that investment casting procures the environment.
Investment casting is a very old industrial process-in fact, the oldest known. It is one of the most popular metal forming techniques, often is referred to as lost wax casting. Lost wax casting is a method in which a duplicate copy of a metal sculpture is made. The process of casting duplicate metal sculptures is also known as precision investment casting.
However, in industrial terms, the casting process is not about sculptures; it is solely about creating machine parts following the practices of wax sculpturing. Apart from wax, different varieties of wax, refractory materials, and alloys are used for creating articles. The reason why investment casting has been in practice for more than 5,000 years is its promise of accuracy. The sculptures, tools, and parts made through this process are undeniably accurate as their originals. This exactness is unattainable for the human hand. However, machines can produce exact items, but when it comes to creating miniature parts, this technique comes the finest.
Castings are created either from the original wax model or from wax replicas of an original pattern. The first method is called the direct method. The second one is the indirect method, in which it is not important for the model to be of wax. In the following descriptions, we discuss the various stages of investment casting.
Creating the master pattern. In the first stage, the engineers create a master pattern for the component that they have envisioned. Creating the master pattern itself is a tedious task, as it may take several hours and even days to come to a perfect pattern that exactly fits into their requirements. The master pattern is crafted on paper, based on the calculation of the artist or the engineer.
Creating the mold. Once you are done with the pattern, it is time to create a mold keeping the measurements as decided on the pattern. The mold is shaped from wax, clay, or plastic, depending upon the preferences of the artist or engineer, or the type of component. However, if an original component has been made from a metal such as steel, we can create its mold using the molten steel or metal. This mold will not only be strong, but also highly precise. Rubber and frozen mercury are also used as materials to prepare the mold.
Producing and assembling the pattern. The wax or the molten waxing material is poured into the mold, and is allowed to stay in it until an even and hard coating is accomplished. You can make numerous wax patterns, considering your requirements. You can also create a large cluster of patterns, depending on your production requirements.
Applying the investment materials. Investment is the industry term for a ceramic mold which is a thick result of multiple coating. This particular stage may take up to a few days.
Dewaxing. After the ceramic molds are ready, the most intricate stage occurs - dewaxing. For a wax mold, this stage could be a straightforward process. But, for the ones that have been created using the metal melt, you will need electric appliances and careful hand motions.
Investment casting and sand casting are two of the most followed techniques for producing precise metal parts. Both of these processes involve the use of liquefied metal.
In wax casting, a flowing wax is poured into 3D molds to create metallic components that are used in industrial machinery and other products. In the past, we have seen a sea of change in the practice, as it introduced a number of new technologies in the process. However, the prime purpose of the casting has remained the same.
In sand casting, a molten metal is used in place of wax, as in the wax or investment casting. Steel, bronze, brass, magnesium, iron, and other metals are commonly used in the process. And, the mold is composed by compressing the combination of sand and clay. In sand casting, molds are created in two parts or pieces. Both the halves are placed together, and filled with molten metal. Once the metal cools down, the mold is opened and the component is taken out after removing the sand and clay from it.
In both of the processes, multiple molds can be created to meet bulky production requirements. If we focus on the cost factor, investment casting will come out as an expensive technique, due to a number of traits such as preparation requirements.
The pointers below make an attempt to pinpoint some basic to technical differences between these two practices:
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.