businessIndustry Information
Investment Casting
Investment casting is a manufacturing process used to produce a wide range of lightweight industrial parts. Investment casting takes its name from the ceramic slurry that is used to form a ceramic shell around a wax pattern. Because it yields such precise and reliable results, this process is also sometimes known as precision casting. In addition, it is also called a “lost-wax process,” “lost wax casting,” or even just “wax casting.” This is because, after the wax cast part is ready, the remaining wax is melted down, or “lost.”
In non-industrial terms, lost wax casting and precision investment casting both refer to a method in which a duplicate copy of a metal sculpture is made. However, in industrial terms, the investment casting process is not about sculptures; it is solely about creating machine parts following the practices of wax cast sculpturing.
Many manufacturers depend on the investment casting process to produce dimensionally accurate precision cast parts. Investment casting is a diverse process that allows for the usage of all sorts of alloys and specifications. Investment castings can be found in the aerospace, automotive, chemical, defense, food processing, electrical, railroad, mechanical, marine, electronic, textile and engineering industries.
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Brass investment casting – Rimer Enterprises, Inc. |
Titanium investment castings – Ferralloy Inc. |
Titanium investment castings – Ferralloy Inc. |
Steel Casting – Ferralloy Inc. |
The History of Investment Casting
Investment casting is a very old industrial process. In fact, it’s the oldest known industrial process, and the earliest known description of investment casting was written around 1100 A.D. by a monk who wrote under the pseudonym Theophilus Presbyter. By 1100 A.D., though, it had already been around for a long time. In practice for over 5,000 years, the earliest examples of castings hail from the tombs of King Tut and the ancient civilizations of Harappa, Mesopotamia, Aztec and Mayan Mexico and the Benin civilization of Africa.
Originally, people used natural honeycomb or beeswax for the wax pattern, clay for the molds. They manually operated bellows as stoking furnaces. In contrast, today, people make the wax pattern using a variety of pure and synthetic waxes, and they make molds using a variety refractory material types and alloys. Instead of handheld bellows, they use a cast foundry.
Investment casting entered the modern era in the late 1800s. At that time, dentists were beginning to use it to make crowns and fillings. The investment casting process was ushered into the industrial world during World War II, when it was used with alloys and other materials in precision net shape and near-net shape manufacturing.
Today, investment casting is a staple of industrial manufacturing.
Design
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 temporary mold or permanent mold, based on the measurements from 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 or alloy steel, you can create its mold using that molten metal alloy. 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. Per your requirements, you can make numerous wax patterns, and you can also create a large cluster of patterns.
Applying the Investment Materials: Investment is the industry term for a ceramic mold, which is a thick result of multiple coating. During this stage, you create the ceramic mold by coating, stuccoing and hardening a wax pattern cluster over and over again until you reach the thickness you want. This particular stage may take up to a few days.
Dewaxing: After the ceramic mold or molds are ready, the most intricate stage, dewaxing, occurs. For a wax mold, this stage may 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.
Features
Investment casting 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.
The creation of investment cast parts starts with the wax model, which, after it is created, is attached to a channel called 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. Manufacturers heat a metal until it melts. Then they pour the molten metal into the hollow shell, where it travels along the lines left by the sprue and fills the impressions left by the wax. When the molten metal is no longer glowing red hot, manufacturers remove the shell and cut the investment cast metal parts off from the sprue. After this, the now solid parts may receive additional machining and finishing. However, they do they require less than other methods of casting.
As manufacturers mix the investment, fans and blowers remove the dust which contains silica, a potentially harmful dust that should not be inhaled. They often use vacuums to remove air bubbles from the investment to ensure that all the patterns on the tree are encased in the ceramic slurry free of air pockets. 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 investment cast 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.
Investment cast parts and investment cast products are unique because their success has spanned thousands of years. Investment casting stands the test of time. In addition, investment cast parts are less expensive to make and less taxing on the environment.
Types
There are many different types of investment cast parts, each produced through a similar cast process. Some investment cast parts are named after the material related processes used to make them. These include aluminum investment casting, brass investment casting, copper investment casting, ferrous and non-ferrous investment casting, carbon steel investment casting, stainless steel investment casting and titanium investment casting. Each of these processes is used to create parts made from those respective materials (aluminum investment casting creates aluminum investment cast parts; non-ferrous casting is used to make metal cast parts from a non-ferrous alloy, etc.)
Each investment casting type offers something different. For example, brass castings are quite attractive. For this reason, brass investment cast parts are used in many applications domestically, commercially and industrially every day.
Meanwhile, copper investment castings are lightweight and strong. As such, these investment cast products have diverse applications, including pipe fittings, machine tools, mixing equipment, lock parts and jewelry.
Because steel is stronger than cast iron, wrought iron, and malleable iron, steel investment cast products are typically used in the manufacturing of parts that must endure shocks, wear or heavy loads. Also, stainless steel castings are used frequently around hazardous substances or in sanitary environments because stainless steel is easy to clean and resists corrosion.
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.
Another type of investment cast product, centrifugal castings, which are made by the process of the same name, centrifugal casting, have particularly thin walls. They are mostly used as cylinders or stock parts.
Advantages of Investment Casting
Choosing to make investment cast parts has a host of advantages. These include its low production costs, efficiency, lack of waste, reliability and environmental friendliness. In addition, investment cast parts have superior tolerances, excellent surface finishes, no seams and no lines. Also, the investment process allows manufacturers to create complex parts with extra fine details that match the exact specifications of the original design.
Low Production Costs: Investment casting has lower production costs than many comparable methods, such as metal fabrication. Requiring less manpower, it slashes capital-consuming labor costs. It also requires the use of fewer resources, and it takes less time. Precision investment casting also saves money because it does not require welding, assembly or finishing work. All of these factors add up to lower production costs that allow you to earn a substantial margin.
Low Wastage and Fewer Time Delays: Investment cast parts are much better than machined parts for a number of reasons. For example, if you are considering using machines to prepare your 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. Furthermore, machining processes can easily become prolonged and delay on-time delivery. On the contrary, investment casting prevents the waste of material and time.
High Reliability: 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.
Environment Procurement: Last but not the least, investment casting offers great environment procurement. In other words, investment casting takes and uses resources in a way that is sustainable for the environment. For example, manufacturers can make most investment cast parts using just 9 wax patterns, most of which can be used time and time again.
Complexity, Details, and Quality: Investment casting is effective at producing lightweight, complex and detailed parts that other methods cannot. It allows for a greater design flexibility and metal alloy selection, as well as a superior surface finish. In addition, because the part is made as one whole piece, investment cast parts have no joints or flash lines. This means investment cast parts are more durable and less susceptible to breakage than other products.
Accessories
Today's manufacturers are aided by improved equipment that can produce identical investment cast parts again and again. These include 3D printers, mold frames, molding rubber, easy ring, measuring cylinders and bowls, crucible, tongs and more.
Proper Care for Investment Castings
How to care for your investment cast product depends entirely upon what it is. So, while we can certainly offer generic recommendations, such as to store your investment cast parts in a dry place, and do not use your investment cast parts in ways that exceed their weight limit, we cannot offer much specific advice. For that reason, in that regard, it’s best to discuss care for your individual investment cast part with your manufacturer.
Standards
The standards to which you’ll want your manufacturer to adhere when making your investment cast parts depend upon your application, industry, and region. For example, if you’ve requested a part for a military application, you’ll want it to meet Mil-Specs. Likewise, your investment cast part may need to meet FDA, ADA, OSHA, EPA or any other host of standards. Make sure you know what those are by discussing your industry and your specs with your supplier. For the best and most reliable investment cast parts, you’ll also want your manufacturer to follow the manufacturing standards of ISO (International Standards Organization).
Things to Consider
Investment casting is a great method that has been proven to work well over thousands of years. If you’re not sure if it’s right for you, though, ask yourself the following questions:
-Does your part require great precision or detail?
If yes, consider investment casting!
-Do you need to create parts with close dimensional accuracy?
If yes, consider investment casting!
-Are you looking for a machining alternative with high quality and low tooling costs?
If yes, consider investment casting!
-What is your application’s weight requirement?
Please note that investment casting can only work with applications up to around 695 pounds.
If your intended application exceeds this limit, do not fear! Consider its cousin, sand casting, which can be used to create castings weighing up to 2204.62 pounds, or 1000 kilograms. In sand casting, manufacturers use a molten metal in place of wax, along with a mold composed by compressing a combination of sand and clay. These molds are created in two parts or pieces. To perform casting, manufacturers put both the halves together and fill them with molten metal. Once the metal cools down, they open the mold, take the new part out and remove the sand and clay from it.
Once you’ve made the decision to go with investment casting, consider design factors like required flexibility, desired surface finish, required tensile strength, required weight, production volume, etc.
The last thing to consider is your manufacturer. There are many talented manufacturers out there, so how do you choose? We recommend that you look for the manufacturer who is dedicated to you and the outcome of your investment (pun intended!) in them. In addition, look for a manufacturer that adheres to the standards of non-destructive testing (NDT). When manufacturers use NDT, they are able to “look into” a part and check it for discontinuities and other imperfections, without rendering the part unusable. Find the one for you by reaching out to and discussing your specifications with one or more of those excellent companies we have listed above.
Investment Castings Types
- Aluminum investment casting is the process that produces industrial parts through the metallic
replication of wax models. Molten aluminum is used to create parts that
have a very smooth surface finish, high dimensional accuracy and acute
detail without flash or parting lines. Aluminum and aluminum alloys are
among the most commonly used metals for investment casting.
- Brass investment casting is the manufacturing process that creates parts through the metallic
replication of wax models. Investment casting using molten brass
results in a final product that is very smooth and detailed without
flash or parting lines. This technique creates parts that are precise
and lightweight.
- Centrifugal casting is a manufacturing process that is used to produce parts with thin
walls. This technique is generally used for cylinders or for stock
parts in standard sizes that are not finalized products.
- Copper investment casting is the process where parts are manufactured through the metallic
replication of wax models. The process of investment casting uses
liquid copper to manufacture parts that have a very fine, smooth finish
and are intricately detailed.
- are cast out of metals that contain iron, including
300- and 400-series stainless steels, carbon and alloy steels and cobalt
and tool steels.
- is the method through which industrial parts are produced through the metallic replication of wax models.
- Investment casting products are parts produced through the metallic replication of wax models. The
parts may be made of almost any castable metal including carbon, stainless steel,
aluminum, copper, titanium and brass. Because the parts are made from a
wax model made to the exact specifications of the intended design,
there is a high degree of dimensional accuracy.
- consisted of creating and plastering a wax model, replacing the wax with molten metal and removing the plaster after the metal cooled.
- are formed from metals that do not contain iron, including
aluminum and copper-based alloys.
- refers to the highly precise and reliable method of metal casting also
known as investment casting. Investment casting is used to produce
complex metal parts in an assortment of sizes, shapes, and weights.
Many manufacturers depend on the investment casting process to produce
accurate dimensional, precision investment casting parts.
- Stainless steel investment casting is the process through which parts are manufactured by the metallic
replication of wax models. Parts created by investment casting have
very fine finishes that require little additional machining. There are
no flash or parting lines because the part is made as one whole piece
from molten stainless steel. High levels of accuracy and precision are
attainable; investment casting can produce parts that are too complex
for other methods.
- are a type of ferrous investment casting in which casts are made out of
stainless and carbon alloy steels. During steel investment casting,
free-flowing liquid steel is shaped through the use of molds. Steel
investment casting produces small, complex, or hard-to-machine shapes,
eliminating the need for assembly, welding, and other finishing work.
- is the manufacturing process that produces parts through the metallic
replication of wax models. The resulting titanium parts have a very
smooth finish that requires little finishing after the process.
Investment casting is effective at producing complex and detailed parts
that other methods cannot. There are no joints or flash lines because
the part is made as one whole piece.
- Wax casting is a process that uses a wax pattern to create metal parts.
Due to the smooth surface of the wax pattern that is used to create a
ceramic mold, the resulting parts have a very fine finish that requires
little machining. Wax casting is effective at producing complex and
detailed parts that other manufacturing methods cannot.
Investment Casting Terms
– A
compound consisting of either more than one metal or a metal and a nonmetal
blended together.
–
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.
More Investment Castings Information
Investment Casting Informational Video