With an increase in industrial demands and applications, there has been a parallel increase in the demand for complex and high-quality products.
Fortunately, there are different types of casting processes that can manufacture complex and precise products for various applications and user needs.
In order to select the right method of casting for your manufacturing requirements, it is beneficial to realize the advantages and disadvantages of these methods.
This article provides a brief overview of various types of casting processes and their pros and cons.
Different Types Of Casting Process
There are different types of casting processes, and each process has its own advantages and disadvantages as per the user requirement.
#1. Sand Casting.
Sand casting, also known as sand molded casting, is a metal casting process characterized by using sand known as casting sand as the mold material.
The term “sand casting” can also refer to an object produced via the sand-casting process.
Sand castings are produced in specialized factories called foundries. In 2003, over 60% of all metal castings were produced via sand casting.
nThe sand-casting process has evolved significantly since the beginning. But the process of how to sand cast has not strayed.
The cast molding process is basic, create a cavity in the shape of the part you want and pour molten metal into it.
For sand casting beginners, the process is referred to as sand casting because the mold that contains the cavity, into which metal is poured, is made of compressed or compacted sand.
The sand does contain other materials that encourage it to hold shape.
Sand casting is the most versatile and arguably most widely used metal casting method, after centuries of development.
Design requirements, piece and tooling cost, quantity needed, and even feasibility to manufacture dictate which metalworking processes are most suitable.
Product manufactured using sand casting employ techniques that produce shaped parts of nearly any design, including very large parts and those with internal passageways.
There may be more optimal casting or metalworking processes for any specific product based on:
- Needed tolerances
- Design intricacy
- Volume
- Tooling availability
- Lead time
It is likely that a casting in the needed configuration could be made using the sand-casting process. Learn more about how to sand cast and the cast molding process below.
#2. Die Casting (Metal Die Casting).
Die casting is a metal casting process that involves feeding molten nonferrous alloys into dies under high pressure and at high speed to rapidly create molded products. The main materials used in die casting are alloys of aluminum, magnesium and zinc.
Die casting is a manufacturing process that allows the production of metal parts with a high degree of precision.
In this casting process, molten metal is injected into a mould, where it cools and hardens to create the desired shape.
The method can be used to create various metal parts, from gears and engine blocks to door handles and electrical components.
Die casting is prized for its ability to produce parts with a smooth surface finish and precise dimensions.
In addition, this process is relatively fast and cost-effective, making it an attractive option for many applications.
#3. Investment Casting.
Investment casting is a manufacturing process in which a liquid material is poured into a ceramic mold, which contains a hollow cavity of the desired shape, and then allowed to solidify.
The solidified part is the casting, which is broken away from the ceramic mold to complete the process.
Investment casting is a precision casting process used to create complex and intricate metal parts with high dimensional accuracy and fine surface finishes.
This casting method is ideally suited to producing relatively high-quality components with intricate details, delicate features, and tight tolerances.
Investment casting is commonly used in industries such as: aerospace, automotive, jewelry, and medical devices, in which high precision and intricate designs are essential.
It also produces castings with very tight tolerances and high dimensional accuracy. Investment castings typically have smooth and fine surface finishes.
Investment casting can be used with a variety of materials, including various metals and alloys.
It can also produce parts with complex shapes, internal cavities, and thin walls that are challenging for other casting methods.
#4. Gravity Die Casting.
Gravity casting is among the oldest known processes for fabricating metals and metal alloys.
It involves the pouring of molten metal from a crucible into a mold under only the force of gravity, without the use of pressurized gases, vacuums, or centrifugal force.
Small-scale molds used for this form of casting have most commonly been made of sand, tufa stone, and cuttlebone as well as charcoal and plaster as these materials are generally easy to shape (unlike iron or steel), do not break down when suddenly exposed to high temperatures (unlike glass, wood, or plastic), do not deform easily (unlike silicone) and are widely available.
#5. Continuous Casting.
Continuous casting, also called strand casting, is the process whereby molten metal is solidified into a “semifinished” billet, bloom, or slab for subsequent rolling in the finishing mills.
Continuous casting is a manufacturing process that allows metals and metal alloys to be shaped then solidified without interruption.
Metal is poured into a mold and rapidly chilled to ensure a uniform grain structure within the metal.
Most often, these shapes are tubes and solids, but can also include squares, rectangles, and other irregular shapes as requested.
This method improves quality and is more cost-efficient than other options, such as sand casting.
#6. Shell Molding.
Shell molding, also known as shell-mold casting, is an expendable mold casting process that uses resin covered sand to form the mold.
As compared to sand casting, this process has better dimensional accuracy, a higher productivity rate, and lower labour requirements.
It is used for small to medium parts that require high precision. Shell molding was developed as a manufacturing process during the mid-20th century in Germany.
It was invented by German engineer Johannes Croning. Shell mold casting is a metal casting process similar to sand casting, in that molten metal is poured into an expendable mold.
However, in shell mold casting, the mold is a thin-walled shell created from applying a sand-resin mixture around a pattern.
The pattern, a metal piece in the shape of the desired part, is reused to form multiple shell molds.
A reusable pattern allows for higher production rates, while the disposable molds enable complex geometries to be cast.
Shell mold casting requires the use of a metal pattern, oven, sand-resin mixture, dump box, and molten metal.
Shell mold casting allows the use of both ferrous and non-ferrous metals, most commonly using cast iron, carbon steel, alloy steel, stainless steel, aluminium alloys, and copper alloys.
Typical parts are small-to-medium in size and require high accuracy, such as gear housings, cylinder heads, connecting rods, and lever arms.
#7. Lost-Foam Casting.
Lost-foam casting (LFC) is a type of evaporative-pattern casting process that is similar to investment casting except foam is used for the pattern instead of wax.
This process takes advantage of the low boiling point of polymer foams to simplify the investment casting process by removing the need to melt the wax out of the mold.
Lost foam casting is a type of evaporative pattern casting. This method is quite similar to investment casting which uses wax instead of foam in the pattern making process.
The foam pattern was first used in metalworking in 1958. Although this mold casting technique is not as popular as other methods such as sand mold casting or permanent casting, it maintains outstanding advantages, especially in casting complicated and precise molds.
Unlike traditional methods which include the pattern withdrawn process before casting and require skillfulness in the pattern removal step, with respect to the lost foam method, the pattern is evaporated when the molten metal is poured into helping to reduce these considerations.
#8. High Pressure Die Casting.
High-pressure die casting is a process wherein molten metal is forced, under pressure, into a sealed mould cavity.
It is held in place by a powerful compressive power (true die installed in hydraulics machine) until the metal solidifies.
Following solidification, the die is released, opened and the metal is released.
Following removal, the mould cavity is resealed for the next cycle.
Molten metal injection into the mould cavity occurs in a fraction of a second (usually under 100 ms).
One time die cavity is filled, extremely high pressure is applied (often over 1000 bar) into a molten metal true injection plunger. This phase is called intensification.
This pressure compresses out any gases trapped in the metal (during extremely fast and turbulent cavity filling) and feeds more metal into the mould to partially compensate for the shrinkage in the metal whilst it is solidifying.
#9. Centrifugal Casting.
Centrifugal casting is a process that delivers components of high material soundness.
As a result, it is the technology of choice for applications like jet engine compressor cases, hydro wear rings, many military products, and other high-reliability applications.
It has also proven to be a cost-effective means of providing complex shapes with reduced machining requirements and lower manufacturing costs as compared to forgings and fabrications.
The centrifugal casting process steps begin with molten metal being poured into a preheated, spinning die.
The die may be oriented either on a vertical or horizontal axis depending on the configuration of the desired part.
By spinning a mold while the molten metal is poured into it, centrifugal force acts to distribute the molten metal in the mold at pressures approaching 100 times the force of gravity.
The combination of this applied pressure and the engineering mechanics of controlled solidification and secondary refining produces components of superior quality.
As the die begins to fill, the more dense molten metal is forced to the wall of the spinning die.
Directional solidification of sound metal progresses from the O.D. towards the bore, while the less dense material, including impurities, “floats” to the I.D.
Once the casting has solidified, the part is removed from the die and residual impurities in the I.D. are machined away, resulting in a defect-free structure without cavities or gas pockets.
#10. Permanent Mold Casting.
Permanent mold casting (PMC) is the process of transferring molten metal to a metal mold by the gravity assistance and ensuring that the metal solidifies in this mold.
Permanent molding casting is a casting process that uses strong durable reusable molds to produce parts and components using molten metals.
The molds for permanent mold casting are made from steel or cast iron and are able to endure repetitive use to produce thousands of dimensionally accurate parts and components.
Typically, aluminum, copper, and magnesium are melted and poured into permanent molds but the process can be used for any type of metal that can be melted to a molten state.
The popularity of permanent mold casting is due to the tight tolerances, surface finishes, and exceptional mechanical properties produced by the process.
These characteristics are the result of pouring molten metal into a reusable mold, which is unlike sand casting and lost wax casting that have molds that are not reusable and are expendable.
The surface of the permanent metal mold chills the metal being cast during solidification, which produces a finer grain structure and reduces porosity in the cast component.
#11. Vacuum Casting.
Casting is a manufacturing process in which a liquid material is poured into a mould and allowed to solidify.
Vacuum casting involves using a vacuum to remove air from the mould, which helps ensure that the object takes on the desired shape.
This process is often used for casting plastics and rubber parts. Vacuum casting is often used for prototype projects or small-scale production runs, as it can be faster and less expensive than other methods, such as injection moulding.
The main advantage of vacuum casting is that it allows for high accuracy and repeatability, making it an ideal choice for applications where precise dimensions are critical.
It also allows for more intricate designs to be cast. However, vacuum casting is not suitable for all applications. For example, it cannot be used to cast materials that are sensitive to heat or pressure.
#12. Low-Pressure Casting.
Low-pressure die casting is a method of production that uses pressure – rather than gravity – to fill molds with molten metal such as aluminum and magnesium.
In this process, the holding furnace is located below the cast and the liquid metal is forced upwards through a riser tube and into the cavity.
The pressure is applied constantly, sometimes in increasing increments, to fill the mold and hold the metal in place within the die until it solidifies.
Once the cast has solidified, the pressure is released and any residual liquid in the tube or cavity flows back into the holding furnace for “recycling.” When cooled, the cast is simply removed.
#13. Squeeze Die Casting.
Squeeze casting, also called liquid forging, is a hybrid metal forming process that combines permanent mold casting with die forging in a single step in which a specific amount of molten metal alloy is poured into a preheated and lubricated die and subsequently forged and solidified under pressure.
Squeeze casting is a casting method that combines die casting and forging.
It starts with low-pressure casting, followed by the application of very high pressure as the material cools, producing a high-quality casting.
This is often carried out using a hydraulic press as part of the casting apparatus.
Squeeze casting was originally created to make stronger metal parts for use in the construction and defense industries.
The metal parts created by this process are more resistant to wear and heat and have historically been very expensive to produce.
The market for these parts has grown to include the agricultural and automotive industries.
#14. Plaster Casting.
Plaster mold casting also referred to as rubber plaster molding (RPM) is a method of pouring liquid metal into plaster molds which will produce aluminum or zinc castings.
Plaster Mold Casting works much like other castings processes where a heated liquid material is poured into a mold that contains a hollow cavity of the desired shape. This is then allowed to solidify. The solidified part is known as a casting.
Once it has molded and cooled the cast is broken out of the mold to complete the process.
#15. Lost-Wax Casting.
Lost-wax casting also called investment casting, precision casting, or cire perdue is the process by which a duplicate sculpture (often a metal, such as silver, gold, brass, or bronze) is cast from an original sculpture. Intricate works can be achieved by this method.
lost-wax process, method of metal casting in which a molten metal is poured into a mold that has been created by means of a wax model.
Once the mold is made, the wax model is melted and drained away. A hollow core can be effected by the introduction of a heat-proof core that prevents the molten metal from totally filling the mold.
Common on every continent except Australia, the lost-wax method dates from the 3rd millennium bc and has sustained few changes since then.
To cast a clay model in bronze, a mold is made from the model, and the inside of this negative mold is brushed with melted wax to the desired thickness of the final bronze.
After removal of the mold, the resultant wax shell is filled with a heat-resistant mixture.
Wax tubes, which provide ducts for pouring bronze during casting and vents for the noxious gases produced in the process, are fitted to the outside of the wax shell, which may be modeled or adjusted by the artist.
Metal pins are hammered through the shell into the core to secure it. Next, the prepared wax shell is completely covered in layers of heat-resistant plaster, and the whole is inverted and placed in an oven.
During heating, the plaster dries and the wax runs out through the ducts created by the wax tubes.
The plaster mold is then packed in sand, and molten bronze is poured through the ducts, filling the space left by the wax.
When cool, the outer plaster and core are removed, and the bronze may receive finishing touches.
#16. Rapid Casting.
Rapid casting is an integration of investment casting with rapid prototyping/3D printing. In this technique disposable patterns that are used for forming molds are created by any 3D printing technique, including fused deposition modeling and stereolithography.
Rapid casting is about creating molds for casting using 3D printed sand.
Instead of the traditional metal patterns, a digital file is directly translated into a sand mold via 3D printing. At MakerVerse, our team of experts can design the mold for you based on your part.
During the 3D printing process, binder jetting creates complex geometries layer by layer. After the sand mold is printed, molten metal is poured into it. Once cooled and solidified, you have your cast part. The sand mold can be broken away.
#17. Expendable Mold Casting.
Expendable mold casting refers to the molds that are used for the molten metal during the pour to create the part.
Once the metal hardens, the mold is broken apart as it cannot be used to make another part right after.
Expendable mold casting refers to any manufacturing technique where the molds become expendable instead of reused.
So, the lost-wax process, sand casting, and investment casting falls into the expendable mold casting category.
For processes that retain the mold so that it may be reused again and again, these techniques fall into the non-expandable mold casting category.
Centrifugal casting, die casting, continuous casting and permanent molding are all non-expendable casting processes.
#18. Non-Expendable Mold Casting.
Mold casting processes are classified as either expendable or non-expendable, depending on whether or not the mold can be reused.
With expendable casting, the mold can’t be reused. With non-expendable casting, the mold can be reused.
Non-expendable mold casting, as you may have guessed, refers to any casting process in which the mold is or can be reused.
Some molds are stronger and better suited to withstand the hot temperatures of molten metal than others.
If a mold is made of a metal, for instance, conventional wisdom should lead you to believe that it’s stronger than a mold made of foam.
Foam molds are commonly used in the expendable casting process lost-foam casting. With lost foam casting, molten metal causes the foam to melt and evaporate.
As a result, foam molds can’t be reused. Molds made of metal, on the other hand, can be reused multiple times.