Types of Casting: Advantages, Limitations, Uses, & Tips

Types of casting

The types of casting are sand, investment, die-casting, permanent mold, centrifugal, vacuum, plaster, low-pressure, squeeze die, high-pressure die, lost-foam, shell molding, continuous, and gravity die casting. These metal casting processes use a mold cavity to shape molten metal into the desired parts. Manufacturers and buyers considering types of casting are faced with questions concerning part complexity, material type, process cost, and surface finish. 

You don’t want to choose the wrong method because that would mean weak parts, rejected parts, and lost revenue. With about 14 types of casting actively in the market, a decision has to be made carefully, preferably with the help of an expert. 

Usually, sand casting is for cost-effective prototypes, investment casting for complex geometries, and die casting for high-volume, precise parts. Miss these fundamentals, and you are looking at scrap or tooling replacements. 

 

What is Metal Casting?

Metal casting is a manufacturing process that entails pouring molten metal into a mold cavity to produce parts. The mold bears the reverse shape of the desired part. The mold material should be refractory, so sand is a popular option. 

After the molten metal has filled the cavity, cooled, and solidified, it is removed from the mold. Some finishing processes are often necessary before the part can be ready for use. Casting is a popular industrial process because it is economical, versatile, suitable for isotropic parts, and ideal for complex shapes. 

 

The Types of Casting Discussed

The types of casting covered below are: Sand casting, investment casting, die casting, permanent mold casting, centrifugal casting, vacuum casting, plaster casting, low-pressure casting, squeeze casting, high-pressure die casting, lost-foam casting, shell casting, continuous casting, and gravity die casting.

As outlined below, each of these processes should be matched with your material, volume, and tolerance requirements. 

Sand Casting

Sand casting is a versatile and economical casting method that entails producing a sand mold and pouring molten metal into the mold to produce parts. 

Sand casting

Other materials used alongside sand in this process are additives and binders. Sand casting is widely used in the automotive and construction industries. 

Advantages	Limitations
Short lead times Metal compatibility  Cost-effective for small production runs Sand molds can be reused Can produce sizeable, complex parts	Lower dimensional accuracy  Difficulty producing fine details  Relatively rough surface finish

Investment Casting

Investment casting, also called lost wax casting, is an ancient type of casting that uses a wax model. The model is covered in a ceramic layer that forms a mold. The wax is melted out, leaving a mold that can be filled with molten metal. This casting method is based on standard air and pressure conditions.  

Materials for lost-wax casting include copper and copper alloys, aluminum and aluminum alloys, steel, and precious metals such as gold and silver. [1]

Advantages	Limitations
Relatively high dimensional accuracy Design flexibility  Minimized material loss Cost-effective for small and medium runs	Relatively expensive to produce wax patterns and ceramic moulds Complex and time-consuming process Not recommended for large parts

Die Casting (Metal Die Casting)

Metal die casting entails pouring or injecting molten metal into a metal die to produce parts. It is mostly done for nonferrous metals such as aluminum casting, Magnesium Casting, and zinc casting. Applications of metal die casting include appliance heat sinks, automotive engine blocks, aerospace fittings, and laptops. 

The two categories of metal die casting are hot chamber die casting and cold chamber die casting, the difference being where the metal is melted. For hot chamber die casting, the metal is melted in a furnace within the casting equipment. 

Pressure in casting can reach 1,200 bar. However, this depends on the die design complexity and the locking force. 

Advantages of die casting	Limitations of die casting
Easy to make complex shapes Perfect for mass production Merges seamlessly with modern supporting technologies – CAD/CAM software, 3D printing Excellent surface finish	High initial investment  Size and weight limitations

Permanent Mold Casting

Permanent mold casting method comprises a pair of metallic molds. It is a gravity-fed process, meaning that gravitational force alone is used to pour molten metal into the mold. Common mold metals are steel, cast iron, and refractory alloys. CNC machining is typically used to produce the cavities in the molds. The mold surface is covered with hard refractory material, for example, clay. A lubricant such as silica is also used. 

Advantages	Limitations
Can be automated – high throughput rates Tight tolerance  Excellent surface finish	Only for simpler shapes Costly mold

Centrifugal casting

Centrifugal casting

Centrifugal casting entails a permanent mold rotated along its axis at 300 to 3000 rpm.[2] Molten material is poured as the mold rotates. Due to centrifugal forces, the molten material concentrates on the outer walls of the mold. Since most impurities are lighter than the metal, they are closer to the inner diameter where they can be machined away.  

Advantages	Limitations
Parts with fine grain microstructure Large cylindrical parts	Limited shapes Relatively expensive

Vacuum Casting

Vacuum casting, also referred to as counter-gravity casting, is similar to investment casting, but the mold filling mechanism is different. For vacuum casting, a vacuum pump is used to suck the material upwards into the mold. 

Vacuum cast part

Advantages	Limitations
Can create hollow castings  Can produce thin-walled parts  Fast  Complex parts	Low volume

Plaster-Mold Casting

The mold for this technique contains plaster of Paris (CaSO4), silica flour, and talc. This type of casting creates a perfect pairing with nonferrous metals such as aluminum, magnesium, zinc, and copper. 

Advantages	Limitations
Excellent surface finish and dimensional accuracy Relatively weak at temperatures above 1200°C Complex shapes	Low production rate Only nonferrous metals

Squeeze die casting

Squeeze casting is a mix of forging and casting. Molten metal is put in a pre-heated die, then a ram steadily applies pressure on the molten metal head. This pressurization is important for a balanced flow of the metal. It minimizes microshrinkage porosity. Controlled cooling further ensures a fine microstructure. [3]

Advantages	Limitations
Very low porosity  Forged-grade strength  Suitable for thick aluminum sections	High tooling and press costs Precise process control

Low-Pressure Die Casting

The low-pressure die casting machine is vertically aligned. It comprises a moving and fixed machine plate. With the holding furnace below the fixed plate, a pressure of up to 1 bar is applied to the furnace, pushing the molten metal. 

Advantages	Limitations
High strength values Can produce complex geometries – sand cores applicable High dimensional accuracy Process suited to automation	Slower casting cycles

Lost-Foam (Expendable-Pattern) Casting

Lost-foam casting

This casting process uses a polystyrene pattern. Since this material is 95% air, it evaporates when molten metal is poured on it. [2] The pattern is produced by molding. Examples made through lost-foam casting include engine shafts and blocks. 

Advantages of Lost-foam casting	Limitations of Lost-foam casting
Cost effective  Complex geometries Good surface finish	Low-strength castings Typically more expensive

Shell-Mold Casting

Shell casting comprises a silica sand and resin shell molded around a hot metal pattern. Molten metal is poured into the resulting mold cavity. 

Shell mold casting

While the process is comparable to sand casting and relatively more expensive, it produces parts with smoother surface finishes and more accurate dimensions. 

Advantages of Shell casting	Limitations of Shell casting
Smooth surface finish Larger volumes Less labor than sand casting	Relatively expensive

Continuous casting

Continuous casting is used to produce continuous strands of metal. The main component in the setup is a water-cooled mold, which helps draw a billet or bloom. The majority of the semi-finished aluminum and steel stock available worldwide is made by continuous casting. 

Advantages	Limitations
Minimal material waste Uniform grain structure	Simple cross sections Not suitable for complex geometries

 

What is the Most Popular Type of Casting?

Sand casting is the most used type of casting globally. Manufacturers prefer this type of casting because it is economical, versatile, and capable of producing complex components. It applies to both ferrous and nonferrous metals across a wide range of sizes.  Aerospace and automotive are among the most common industries for sand casting. In the automotive space, for instance,  gray iron castings, cast in sand molds, are specified. [5] Typical applications of gray iron for automotive castings include exhaust manifolds, diesel engine blocks, clutch plates, and transmission cases.  

 

How To Choose a Type of Casting Process

The four variables to consider when choosing a metal casting process are material type, quantity/volume, desired properties, and part complexity. 

• Material Type: Different materials require unique casting methods. 
• Quantity/Volume: Some casting types are designed for low volumes, while others are for high volumes. 
• Desired Properties: These include mechanical properties and surface finish. Some types of castings yield better mechanical properties or smoother finishes than others. 
• Complexity of parts: Intricate parts may require casting methods with matching capabilities. For instance, investment casting is typically specified for complex designs, whereas sand casting is suited for simpler designs.

Investment casting complex part

Consider the following table as a guide to choosing the ideal type of casting. 

Type of casting	Production scale	Material types
Sand casting	Low to Medium	Aluminum, bronze, iron
Investment casting	Low to Medium	Stainless steel and alloys
Die casting	Medium to High	Aluminum, magnesium, zinc
Permanent mold casting	Medium	Aluminum, copper
Centrifugal casting	Medium to high	Iron, steel, alloys
Vacuum casting	Low to medium	Aluminum, precision alloys
Plaster-mold casting	Low	Aluminum, copper, zinc
Squeeze die casting	Medium to high	Aluminum, magnesium
Low-pressure die casting	Medium	Aluminum, magnesium
High-pressure die casting	High	Aluminum, magnesium, zinc
Lost-foam casting	Medium to High	Aluminum, steel
Shell-mold casting	Medium	Aluminum, iron, steel
Continuous casting	High	Aluminum, copper, steel
Gravity die casting	Medium	Aluminum, copper, zinc

Note: These are general guidelines. Actual Production scales and Material types can vary based on wall thickness, tolerance, and part geometry

What do you make of these casting options? Share your part specs with our engineers for a prompt recommendation of which casting process to use. 

 

What Materials Are Used in Casting?

Metals dominate the materials used in casting, but the process is not limited to them. Here is the list of materials used in casting. 

1. Metals: Metals are the primary casting materials. Both ferrous and nonferrous metals can be cast, but the method used depends on the metal. 
2. Ceramics:  These are used for heat-resistant and refractory components. 
3. Rubbers: Rubber, usually urethane rubber, is used for flexible tooling or prototypes.   
4. Plastics: Plastics are cast for low-volume or prototype parts 
5. Composite Materials: These are ideal for lightweight structural parts
6. Glass: Cast glass parts typically serve optical and artistic purposes
7. Alloys:  Metal alloys suit applications where specific properties – thermal, corrosion resistance, strength – are required.

Industries that Use Casting

The most common industries using cast products are automotive, aerospace, consumer goods, jewelry, and building, with products ranging from transmission housings in automotive to architectural fittings in the building industry. 

The table below summarizes application examples. 

Industry	Examples of Cast Parts
Automotive	Suspension parts, transmission housings, engine blocks
Aerospace	Landing gear components, turbine blades
Consumer goods	Appliance housings, fittings
Jewelry	Intricate designs using investment casting
Building	Architectural fittings, structural hardware

 

Designing a Part for Manufacturability (DFM) in Metal Casting

Designing for Manufacturability (DFM) in metal casting means pursuing uniform wall thicknesses, generous radii, draft angles, and parting lines. These factors ensure the part not only solidifies evenly but also ejects smoothly from the mold. 

• Uniform Wall Thickness – Designers should apply uniform wall thickness to ensure balanced cooling and shrinkage, which prevents part defects. 
• Generous Radii – This prevents stress concentration at the sharp corners of the part 
• Draft Angles –  Well-designed draft angles allow clean release of the part from the mold
• Parting Line – This feature should be placed strategically because it affects the mold complexity and flash formation. 

Parting line

Different Heat Treatment Methods for Metal Casting

Annealing, normalizing, and tempering/quenching are the main heat treatment methods for metal cast parts. The post-solidification processes are used to enhance the mechanical properties of the material. 

• Annealing – This is a material softening method that relieves internal stresses
• Normalizing – This method helps attain uniform mechanical properties through grain refinement 
• Quenching – This is the rapid cooling of the cast part using air, water, or oil. The process enhances the part’s strength and hardens the microstructure. 
• Tempering – Tempering is the subsequent controlled reheating of the quenched part below the critical temperature. The heat treatment process reduces brittleness but retains most of the hardness. 

 

The Future of Casting

Casting technologies are leaning towards shortening the development cycles and reducing scrap rates. Computational fluid dynamics models will increasingly be used to predict part defects. [4] 3D printed cores and molds are increasing the prototyping speed. Simulation software is also being used to detect defects early in the design process – before tooling. 

The industries are increasingly using hybrid casting processes and lighter alloys to make lighter, stronger parts. Whatever the future of casting holds, the main types of casting and other fundamentals discussed above still hold.

Summing Up 

Getting reliable products from casting comes down to matching volume, part complexity, desired properties, and material to the type of casting engineered for the job. Die casting is used for high-volume precision, sand casting for economical versatility, and investment casting for complex details. Specialized casting methods such as vacuum casting fill niche performance requirements. 

Since no single type of casting fits every part, the versatility of casting in manufacturing is unmatched. There are DFM principles to incorporate, including proper draft angles, adequate radii, and uniform wall thickness. Don’t forget about post-process heat treatment.  

For your transition from design to production, upload your part design today for a DFM review and instant quote. If there are any casting issues, the engineers will flag them before tooling to save you costs. 

 

FAQ

How does the type of casting affect costs?

Costs vary with the types of casting. Some options may be cheaper, but require more rework than more expensive options. 

Why is the knowledge of material type crucial in casting?

Knowledge of material type makes sense because it determines the matching of material properties to the application. For instance, aluminum and steel have distinct properties, and this affects the application’s suitability. 

What is the role of production volume in selecting a casting method?

The production volume determines the economic sense of a casting method. The relationship between per-unit cost and upfront tooling cost differs from one method to another. For low volume, investment casting and sand casting are preferred. Centrifugal casting and permanent mold casting are the best fits for medium volume. In high volume, die casting is the dominant method. 

Resources 

[1]https://aristo-cast.com/wp-content/uploads/2020/09/ICI_Metal_Standards_Spec_Manual.pdf

[2]https://www.uobabylon.edu.iq/eprints/publication_1_1951_6172.pdf

[3]https://www.sciencedirect.com/topics/engineering/squeeze-casting 

[4]https://doi.org/10.20944/preprints202405.1297.v1

[5]https://store.astm.org/a0159-83r24.html