14 Different Types of Casting Processes

Casting is a basic manufacturing procedure that entails molding molten material into the desired shape inside of a mold. There are different types of casting processes, including: sand casting, die casting, and investment casting. Each method offers various solutions for various industries while boasting its own advantages and disadvantages. For example, sand casting involves creating a mold out of sand, while die casting involves using metal molds for high-volume production. Investment casting is known for its intricate designs, which combine wax patterns with ceramic molds.

Listed below are 14 different casting techniques, their definitions, importance, and brief discussions on how they work. 

1. Sand Casting

The versatile metal forming technique of sand casting uses non-reusable sand molds to produce intricate metal castings. It's an essential method for creating metal parts in various sizes, ranging from ounces to tons. This technique is indispensable in many different industries because it excels at shaping alloys with high melting temperatures, such as: steel, nickel, and titanium. Inexpensive and recyclable materials are combined to make up molding sand with exceptional heat resistance. Silica is the preferred casting sand, though chemically bonded systems and green sand are also used. The effectiveness of the mold in maintaining its shape and producing high-quality castings depends on key characteristics like strength, permeability, and flowability. To learn more, see our guide on Sand Casting Manufacturing.

2. Die Casting (Metal Die Casting)

Die casting is a precision-focused manufacturing process that involves melting a metal with low melting point and injecting it into a long-life die-casting mold. These steel molds, which are created using cutting-edge techniques like CNC machining, guarantee high levels of accuracy, precision, and repeatability when creating metal components. The process has a long history that dates back to the 19th century. It has developed into two separate procedures: hot chamber and cold chamber die casting. Based on their different melting points, each process can handle a variety of materials, including: aluminum in cold chamber casting and alloys of zinc, tin, lead, and magnesium in hot chamber casting. Die casting finds extensive use in industries ranging from consumer and automotive products to aerospace components, making it an indispensable part of modern manufacturing. To learn more, see our guide on What is Die Casting Used For.

3. Investment Casting

Investment casting, a meticulous method, crafts ceramic molds around wax patterns, in order to serve as encasements for molten metal. Multiple wax patterns can be melted onto a gate system, and then a layered casing is created by submerging the pattern(s) in slurry and sand. After the wax is removed, molten metals like stainless steel or aluminum are poured in to create intricately detailed copies. Investment casting efficiently creates complex parts that are difficult for other processes to produce; the advantages include: undercuts, fine detail, and smooth finishes. Investment casting has developed from its ancient roots to modern applications to become an essential technique used in a variety of industries, preserving fine craftsmanship and enabling effective large-scale manufacturing. To learn more, see our guide on What is Investment Casting.

4. Gravity Die Casting

The time-tested metal casting method known as gravity die casting uses gravity to introduce molten metal into a mold's cavity. This approach, which has roots in antiquity, offers simplicity and economics. Manufacturers coat the cavity, melt the metal, pour it in, and then wait for the metal to solidify. The process uses automatic or manual machines. Positive mechanical characteristics, lower costs, and improved finishing are all advantages. The drawback of gravity die casting, however, is the length of time required to make intricate parts. Despite technological advancements, this seemingly crude method is still effective for smaller parts, finding use in a variety of applications including: kitchenware, lighting, and automobiles. Alternatives like aluminum die casting and sand casting are preferable for complex, high-volume production.

5. Continuous Casting

Continuous casting creates uniform, fine-grained, solid shapes with superior physical properties by quickly cooling molten metal inside a vertical or horizontal mold. This technique minimizes contaminants while maximizing yield because it uses gravity to ensure a steady flow. Although various configurations like squares and hexagons can be made, tubes and solids are the most typical shapes. When the metal has cooled after entering the mold and reached the desired length, it is continuously extracted. Continuous casting excels at producing high-density, pressure-resistant products for applications requiring precision and structural integrity. While continuous casting provides benefits like effective stock utilization and dimensional consistency, mold costs and suitability for particular alloys and quantities should be taken into account.

6. Shell Molding

A thin mold is made around a heated metal pattern as part of the precision casting process known as shell molding. Dry silica sand combined with a thermosetting resin forms a shell—that is about 6 mm thick—around the pattern. This shell is then dried, stripped, and joined to form a cavity for pouring molten metal. For the mass production of thin-walled castings, shell molding is the best option because it offers dimensional accuracy and a superior surface finish. Despite being more expensive than green-sand molding, it produces metallic patterns with high-quality results that guarantee intricate details and reliable results.

7. Lost-Foam Casting

In lost-foam casting, molten metal is poured into a foam mold (that evaporates during the pour) which is encased in sand. The mold is made of carved, machined, or injection-molded polystyrene foam. The waste gas can escape into the sand because the ceramic refractory coating is made permeable to a degree. The lost-foam casting process allows for complex shapes and thin walls at a lower cost and with less lead time and machining requirements than many other casting methods. Complex CAD designs and constrained part sizes, however, present difficulties. This process is used by a variety of industries, including: the arts, defense, and automotive, to produce a wide range of parts, including circuit boards, sculptures, and automobile components.

8. Pressure Die Casting

Modern metal processing methods like high-pressure die casting involve quickly and rapidly filling a mold with molten metal to create castings. It boasts strong mechanical properties, minimal machining, high production efficiency, and excellent surface finish. Key process parameters include: time, temperature, speed, and pressure. Filling capacity and specific pressure have an impact on compactness. Mold temperature has an impact on cooling speed and surface quality. The manufacturing of toys, appliance parts, and automotive housings are just a few examples that make use of pressure die casting.

9. Centrifugal Casting

The centrifugal casting method, also referred to as roto casting, is used to create thin-walled cylinders from materials like metal, glass, and concrete. It produces a fine-grained casting with rotational symmetry by rapidly rotating a permanent mold while pouring molten material. Instead of producing custom-shaped parts, the centrifugal casting method is often employed to produce standardized stock materials for further machining. It was created in 1852 by Alfred Krupp and is used to make things like pipes, flywheels, and cylinder liners.

10. Permanent Mold Casting

Permanent mold casting is a method of casting metal that produces accurate, high-quality castings using reusable molds made of materials like steel or iron. It is widely used in sectors like automotive and aerospace that demand complex shapes, large volumes, and superior mechanical properties. Cost-effectiveness, fine-grained structures, smooth finishes, and intricate designs are some of its advantages. Initial costs, a lack of material compatibility, and problems with heat transfer are obstacles. Innovations include CAD, hybrid processes, and 3D printing for making molds. Applications benefit from improved durability, accuracy, and customization in the automotive, aerospace, and medical industries. To learn more, see our guide on Permanent Mold Casting.

11. Vacuum Casting

Vacuum casting, also known as polyurethane casting or urethane casting, uses silicone molds to produce rubber and plastic components in a vacuum. This adaptable method creates bubble-free castings with smooth surfaces by mimicking injection molding. Rapid prototyping and low-volume production of complex parts benefit the most from its use. Numerous resin options are available for vacuum casting, which also has uses in the automotive, aerospace, and product design verification industries. Vacuum casting has advantages in terms of flexibility and cost-effectiveness, but it's important to take mold wear and shrinkage rate into account. The ability to produce intricate features and additive manufacturing are examples of innovations.

12. Low-Pressure Casting

Low-pressure die casting (LPDC) is a metal casting process in which molten metal is poured into a die-cast mold at low pressure, typically 20 to 100 kPa. This method continuously fills the die cavity to account for volume shrinkage during solidification, maintaining high accuracy. The castings are pure due to LPDC producing little slag and less oxidation. LPDC is particularly adept at creating intricate geometries with sharp contours and smooth surfaces. It has limitations in the production of thin-walled parts and slower cycle times, despite its benefits in accuracy and formability. Automotive parts like cylinder heads, blocks, and wheels, as well as everyday kitchen appliances like pressure cookers, are just a few examples of the many applications in which LPDC can be used. To learn more, see our guide on Low-Pressure Casting.

13. Squeeze Die Casting

Squeeze die casting, a combination of casting and forging processes, uses high pressure to solidify molten metals between hydraulic press plates. It produces nearly net-shaped casting that is almost pore-free and highly dense. The two primary types, direct and indirect, each have unique advantages. Indirect casting is similar to high-pressure die casting, whereas direct casting involves pouring metal into the die and pressing it under pressure. The process results in improved mechanical properties, shorter production cycles, and better metallic properties. Material selection varies, with aluminum, magnesium, and copper as common choices. Squeeze casting finds applications in automotive parts, aircraft components, and more. 

14. Plaster Casting

Plaster casting, also known as plaster mold casting, creates molds using a gypsum mixture and additives. A rubber or metal pattern coated with anti-adhesives serves as the mold's basis. The mold is created by pouring, setting, and removing the pattern from the plaster. The plaster is removed after the metal has cooled after being poured into the mold. It allows for intricate parts and provides precise shapes with little scrap. Plaster molds produce smooth surfaces, are disposable, and work best with non-ferrous metals. Applications include: prototypes, short-run aluminum/zinc production, gears, valves, ornaments, and lock components.

What Is Casting?

Casting is a manufacturing process that involves pouring a liquid substance into a mold with a hollow cavity that has the desired shape. The material then goes through solidification, creating a solid object that fits the shape of the mold. Numerous industries use this technique to create intricate and adaptable parts, from sculpture to automotive parts. To learn more, see our guide on Casting.

How Does Casting Work?

A series of steps are involved in casting. First, a mold that closely resembles the intended product is made, typically out of metal, sand, or ceramic. Then, a liquid substance, such as molten metal, is poured into the mold's cavity. The substance takes on the shape of the mold as it cools and solidifies. When the cast object has fully solidified, the mold is removed to reveal it. 

How Is Casting Used in Manufacturing?

Casting is a common manufacturing technique used to produce a wide variety of intricate parts and goods. Manufacturers can produce intricate geometries and precise designs by using molds to shape liquid materials like molten metal. This process is necessary for creating items with a range of dimensions, shapes, and complexity for a variety of markets, including: the jewelry, automotive, and aerospace industries.

What Industry Uses Casting?

Numerous industries, including automotive, aerospace, building, jewelry, and consumer goods, use casting extensively. For engine components, casting is crucial in the automotive industry. Casting is a key component of aerospace for complicated aircraft parts. It is used in the construction sector to adorn buildings. Casting is a technique used by jewelry designers to create intricate ornaments, and consumer goods include a variety of cast items like tools and appliances.

How To Choose a Type of Casting Process?

Considerations for selecting an appropriate casting process include: material, complexity, quantity, and desired properties. Investment casting works well for complex designs, while die casting is best for mass-producing metal parts. For larger components, sand casting is more affordable, whereas precision casting offers tighter tolerances. Centrifugal casting works best for cylindrical objects, while gravity casting is appropriate for simpler shapes. To make an educated decision, assess the requirements of your project.

What Is the Most Popular Type of Casting?

One of the most well-liked and widely employed casting techniques in manufacturing is sand casting. All industries prefer it because of its flexibility, efficiency, and capacity to create complex shapes. The adaptability of sand casting in terms of material choices and mold design, as well as its suitability for both small- and large-scale production, contribute to its widespread use in industries like automotive and aerospace.

What Are the Materials Used in Casting?

Materials used in casting include:

1. Metals: Such as iron, aluminum, copper, and zinc.
2. Alloys: Combining metals to enhance properties, like bronze and brass.
3. Ceramics: Like porcelain and clay for pottery.
4. Plastics: Including thermoplastics and thermosetting plastics.
5. Composite materials: Mixing fibers and resins for specialized applications.
6. Rubber: For creating flexible parts.
7. Glass: Used for artistic and functional objects.
8. Concrete: Common in architectural and decorative casting.

Is Metal Used in Casting?

Yes, casting does often incorporate metal. Metal is cast by pouring molten metal into a mold to create different shapes and objects. It is one of the most commonly employed casting materials because of its adaptability, toughness, and variety of uses in sectors like: construction, aerospace, and automotive. To learn more, see our guide on Metalloid Uses.

Is Polyethylene Used in Casting?

Yes, polyethylene is used in casting, and more specifically, polyethylene cast films are used. These films are made using a cast extrusion method, in which plastic resins, such as polyethylene, are melted and created into thin films by being extruded through a slit die. These films find use in a variety of industries, including: packaging, agriculture, and construction. To learn more, see our guide on PE Plastic.

What Differentiates Casting From Injection Molding?

Injection molding involves pushing melted material (most commonly plastic) into a mold under high pressure, as opposed to casting, which broadly involves pouring molten material into a mold and waiting for it to solidify. A wider variety of materials, including metals, and larger, more complex shapes are suitable for casting. For smaller parts, injection molding offers high precision and is an affordable option for mass production. Both approaches have specific benefits, and in some manufacturing processes, they can work well together. To learn more, see our guide on the Process of Molding.

Summary

This article presented the different types of casting, explained each of them, and discussed how each of them work. To learn more about the types of casting, contact a Xometry representative.

Xometry provides a wide range of manufacturing capabilities, including casting and other value-added services for all of your prototyping and production needs. Visit our website to learn more or to request a free, no-obligation quote.

Disclaimer

The content appearing on this webpage is for informational purposes only. Xometry makes no representation or warranty of any kind, be it expressed or implied, as to the accuracy, completeness, or validity of the information. Any performance parameters, geometric tolerances, specific design features, quality and types of materials, or processes should not be inferred to represent what will be delivered by third-party suppliers or manufacturers through Xometry’s network. Buyers seeking quotes for parts are responsible for defining the specific requirements for those parts. Please refer to our terms and conditions for more information.

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.

Overview of Casting Process

The casting process is a manufacturing method that produces desired-shape metal parts by pouring molten metal into a mold and solidifying and cooling it to the room temperature. It’s capable of producing complex and intricate parts, irrespective of their sizes.

Casting can produce isotropic metal parts in bulk quantities, as a result, making it suitable for mass production. Furthermore, to meet specific user requirements, there are different types of casting that differ by the material and mold used.

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 Process

Sand casting is a versatile casting process that can be used to cast any metal alloy, ferrous or non-ferrous. It is widely used for mass production in industrial units, such as automotive metal casting parts, like engine blocks, cylinder heads, crankshafts, etc.

The process uses a mold that’s made of silica-based materials, such as naturally-bonded or synthetic sand form the smooth mold surface. The mold surface has 2 parts, cope (the upper half) and drag (the lower half). Molten metal is poured into the pattern using a pouring cup and left to solidify to take the final shape. Finally, trimming off extra metal is done for the finishing of the final metal casting product.   

Sand casting has its advantages and disadvantages.

2. Gravity Die Casting

Gravity die casting, also typically known as permanent mold casting, uses reusable molds made of metal, like steel, graphite etc. to fabricate metal and metal alloys. This type of metal casting can manufacture various parts like gears, gear housing, pipe fittings, wheels, engine pistons, etc.

In this process, the direct pouring of molten metal into the mold cavity takes place under the effect of gravity. For better coverage, the die can be tilted to control the filling. The molten metal is then allowed to cool and solidifies within the mold to form products. As a result, this process makes casting of materials like lead, zinc, aluminum, and magnesium alloys, certain bronzes, and cast iron more common.

This casting process works on the bottom-up approach to fill the mold, in contrast, to other pressure casting processes. Although, the process has a higher casting rate than sand casting. But, it is relatively higher in cost due to expensive metal molds. Check its advantages and disadvantages below.

3. Pressure Die Casting

There are two types of pressure die casting depending on the pressure. Namely, the low-pressure die casting and the high-pressure die casting. High pressure die casting is more popular for mass production of complex geometries that require high precision. Whereas, for large and simple parts production, low-pressure die casting is a preferable casting process.

In this type of metal casting, non-ferrous metals and alloys such as zinc, tin, copper and aluminum are injected into a reusable mold coated with a lubricant at high pressure. Thus, high pressure is maintained throughout the rapid injection process to avoid metal hardening. Finally, after completion of the process, extraction of casting and finishing takes place to remove any excess material.

Pressure die casting differs from gravity die casting in the process of filling up the mold. Where pressure die casting uses high-pressure injection of molten metal into the metal mold. The molten metal is then solidified rapidly to produce the required product.

Its advantages and disadvantages are summarized below.

More: Choose A Righ Process Between Die Casting vs Sand Casting for Your Applications.

4. Investment Casting

Investment casting, also known as lost-wax casting, is a process that invests wax pattern with refractory material and a binding agent to shape a disposable ceramic mold, and then molten metal is poured into the mold to make metal castings. Investment casting is an expensive and labor-intensive process and can be used for mass production or in complex castings to produce metal casting products ranging from gears, bicycle trunks, moto discs, and spare parts in blasting machines.

Below summarizes its advantages and disadvantages.

5. Plaster Casting

The plaster casting process is similar to sand casting, except that the mold is made of a mixture called ‘Plaster of Paris’.  Due to the low thermal conductivity and heat capacity of plaster, it cools the metal more slowly as compared to sand, which helps in attaining high accuracy, especially for thin cross-section parts. However, it is not suitable for high-temperature ferrous materials.

Particularly, small castings of 30 grams, as well as large castings of 45 kilograms, can be manufactured through the plaster mold casting process. For example, the image below shows a cast component of a section thickness of 1 mm made by this process.

Learn more about its advantages and disadvantages.

6. Centrifugal Casting

Centrifugal casting, also known as roto casting, is a process for industrially manufacturing cylindrical parts with centrifugal forces. This type of metal casting uses a preheated spinning die in which the molten metal is poured. The centrifugal forces help to distribute the molten metal within the die at high pressure.

Three variations of centrifugal casting exist; true centrifugal casting process, semi centrifugal casting process, and vertical centrifugal casting process. Semi centrifugal casting, unlike true centrifugal casting, has the mold completely filled using a sprue. However, in true centrifugal casting, molten metal sticks to the sides due to continuous rotation. On the contrary, vertical centrifugal casting, as the name suggests, uses directional molding following the same process as true centrifugal casting.

Typically, centrifugal casting produces rotational shapes like cylinders. In particular, parts like bush bearings, clutch plates, piston rings, and cylinder liners, etc. Also, the pouring of metal in the center of the mold helps in reducing defects such as blow holes, shrinkage, and gas pockets. However, it is not suitable for all kinds of metal alloys.

7. Lost-Foam Casting

Lost-foam casting method is similar to investment casting with the difference that it uses foam for the pattern instead of wax. Once the pattern is formed, coating with a refractory ceramic takes place by dipping, coating, spraying, or brushing. Then, the molten metal is poured into the mold to form the desired product.

This technique can be used for various materials like alloy steel, carbon steel, alloy cast iron, ferrous alloy, etc. In particular, products like pump housing, fire hydrants, valves, and fittings are made through the lost-foam casting process.

Lost foam casting possesses numerous advantages which include high precision and high accuracy production. However, there are a few limitations of this process that makes it unsuitable for low-volume applications.

8. Vacuum Casting

Vacuum casting, as the name suggests, is the type of casting where production occurs under vacuum pressure of 100 bar or less to exhaust gas from the mold cavity. In this process, molten metal is poured into the mold cavity inside a vacuum chamber in order to eliminate bubbles and air pockets. The vacuum evacuation of the die cavity reduces the entrapment of gases within the cavity during the metal injection process. Finally, the metal is cured in a heating chamber and removed from the mold.

The vacuum die casting process is popular in various industries including automobiles, aerospace, electronics, marine, telecommunication, etc. As a result, some components fabricated by this manufacturing process include structural chassis components and automotive body parts.

9. Squeezing Casting

Liquid forging or squeeze casting is a hybrid metal forming process that merges permanent mold casting and die forging in a single step. In this process, a specific amount of molten metal alloy is injected into a die, and pressure is applied to shape it. Then, the metal part is heated over melting temperature and extracted from the die.

Particularly, squeezing die casting is a potential casting process for safety-critical parts in automotive systems. For example, space frame joints, aluminum front steering knuckles, chassis frames, brackets, or nodes.

This type of metal casting combines the benefits of casting and forging processes. For example, the high pressure applied during solidification helps prevent shrinkage and porosities. However, due to specific tooling requirements, it is not as popular as other casting processes for mass production.

10. Continuous Casting

As the name suggests, it allows consistent mass production of metal profiles with a constant cross-section. This type of casting is popular in the production of steel bars. Also, the vertical cast creates semi-continuous casting like billets, ingots, bars, etc.

In this process, molten metal is poured at a calculated rate in a water-cooled, open-ended mold that allows a surface of solid metal to form on the liquid metal in the center. Metal solidification, thus, happens from the outside in. After this process finishes, strands of metal can be continuously extracted from the mold. Predetermined lengths of products can be cut off by mechanical shears or traveling oxyacetylene torches.

Generally, the products created using continuous casting are homogeneous, consistent, and dense. However, it also limits its use to such applications. Some other advantages and disadvantages are:

11. Shell Molding

Shell molding is an expendable mold casting process. It is similar to the sand casting process except for that the hardened shell of sand forms the mold cavity instead of a flask of sand. The sand used is finer than that utilized in sand casting and it is mixed with a resin so that it can be heat treated and hardened into the shell around the pattern.

Shell molding makes industrial products, for example, gearbox housing, connecting rod, small-size boats, truck hoods, cylindrical heads, camshafts, valve bodies, etc.

The casting products possess a good surface finish and dimensional accuracy. However, the limitation of this kind of casting includes the size and weight limitation of the parts. Some other advantages and disadvantages are:

Basic Steps of Different Casting Production

Mostly, casting processes follow some basic steps like pattern making, mold making, selection and pouring of metal alloys and finally, finishing of the casted part.

• Pattern making

To create a pattern, it is important to determine the shape of the mold. For this, the materials used are wax, sand, plastic or even wood.

• Mold making

Following on, there is a requirement to create different types of molds for casting. Single-use mold can be made out of sand, plaster, or ceramic shell. Each of them has a different production method. Also, patterns made from foam or wax are burnt in a kiln.

• Choose metal alloys

Metal castings are produced from ferrous or non-ferrous alloys. Alloys are a chemical mixture of elements with mechanical properties which are best for the final cast applications. Where, ferrous alloys include steel, malleable iron and gray iron. While non-ferrous metals include aluminum alloys, bronze and copper.

• Melt and pour the alloy

After the selection of the metal alloys, the next step is the pouring of metal into the mold. The process involves placing a solid metal over a crucible and heating it with an open flame or inside the furnace until it melts. For small casting, pouring the molten metal directly from the crucible is possible. However, larger castings may require the transferring of metal into a larger ladle before pouring into the mold.

• Finishing

After solidification, the casting product is removed and metal surface finishing is done on it. Furthermore, the process of finishing can include the removal of excess material by scrubbing or machining for larger waste material.

Outsource Your Casting Needs to RapidDirect

It is important to choose the right type of casting process and expertise for your products. At RapidDirect, we provide you access to a team of professional engineers with a vast experience in different casting services, like die casting services, vacuum casting, etc. The expertise of our working team puts us in a better place to advise you and answer any queries that you may have.

We provide rapid online quotes for your parts on uploading a design file to our online quotation platform. You can rest assured that we provide the best at competitive market pricing.