What are metal castings? Types, processes, applications and how to choose a supplier

Published - 11th Jul 2025

Metal castings are integral components in a wide range of demanding industries – from structural brackets in aircraft to corrosion-resistant housings for offshore energy systems. As demand for precision-engineered parts grows across sectors like defence, aerospace, marine and renewables, understanding the advantages of metal castings and selecting the right casting supplier has never been more important.

This guide explains what metal castings are, the main casting methods available, how the process works from start to finish, typical applications, and what to look for in a supplier. Whether you’re an engineer, sourcing manager or procurement lead, you’ll find practical insights to help you make the right technical and commercial decisions.

What are metal castings?

Metal casting is a manufacturing process in which molten metal is poured into a mould to form a specific shape as it solidifies. It enables the production of complex, high-performance parts that might otherwise be difficult or uneconomical to machine from solid metal.

What are the benefits of metal castings?

Casting offers numerous benefits that make metal castings preferred components across a wide range of industries, including performance automotive, EV, aerospace, defence and medical. Here are the key advantages:

Cost-effectiveness

• Metal casting is generally less expensive than other manufacturing processes like forging or fabrication, especially for large production runs. The initial mould or ‘pattern’ can be reused multiple times, reducing per-unit costs and enabling economies of scale.
• It requires fewer resources and less energy compared to processes like forging, where significant pressure and energy are needed to shape metal.

Complexity and design flexibility

• Casting allows for the creation of highly complex shapes, internal cavities, and intricate details that would be difficult or impossible to achieve with other methods. This is because molten metal can flow into every part of the mould, including tight corners and undercuts.
• Engineers can design parts with varying thicknesses, hollow sections, and unique geometries, providing significant design freedom.

Material versatility

• A wide variety of metals and alloys can be cast, including iron, steel, aluminium, copper, zinc and more. This allows manufacturers to select the optimal material for specific applications and desired properties.

Product quality and strength

• Metal castings exhibit high strength, excellent fatigue properties, and good dimensional stability. The process can produce parts with thin walls and high compressive strength without compromising structural integrity.
• Controlled cooling and heat treatment can enhance the grain structure, resulting in improved toughness, wear resistance, and corrosion resistance.

Reduced waste and material efficiency

• Casting minimises material waste by enabling near-net-shape production, reducing the need for extensive machining or post-processing. Excess material from the casting process (such as sprues and runners) can often be recycled and reused.
• This makes casting a more sustainable and environmentally friendly option compared to fabrication or machining, which often generate more waste.

Speed and efficiency

• Metal casting enables rapid manufacturing, especially for small batches or prototypes. Once the mould is prepared, parts can be produced quickly and in large quantities.
• The process simplifies production by reducing the number of components and assembly steps, leading to faster turnaround times and lower labour costs.

Improved surface finish and tighter tolerances

• Casting can achieve smoother surface finishes and tighter dimensional tolerances than some other manufacturing methods, as molten metal fills the mould evenly and solidifies uniformly.
• This reduces the need for additional finishing processes and improves the overall quality of the final product.

These benefits make casting particularly attractive for applications that demand a balance of mechanical performance, dimensional control and affordability.

Where are metal castings used?

Metal castings are used in demanding sectors where quality, reliability and performance are non-negotiable. For example, metal cast components can be found in:

• Aerospace and aviation – components such as housings, brackets and end plates that must meet tight dimensional tolerances and withstand extreme operating environments.
• Defence and security – castings for surveillance, munitions and vehicle systems that require robustness, traceability and UK-based production.
• Marine – corrosion-resistant castings for pumps, housings and deck equipment used in both commercial and military vessels.
• Medical – precision components for diagnostic equipment, imaging systems and surgical tools, where hygiene, repeatability and certification are critical.
• Energy and renewables –parts for wind turbines, energy storage systems, and oil and gas infrastructure, often in demanding physical environments.
• Electric vehicles and automotive – Casting lightweight structural parts, brackets and enclosures that support energy efficiency and system integration.
• Industrial and safety-critical systems – Supplying components for plant equipment, sensors, control housings and structural elements that require long life and dimensional stability.

This extensive demand for metal castings is expected to increase rapidly – projected to reach a valuation of USD 225.7 billion by 2032, growing at a compound annual growth rate (CAGR) of 5.3% from 2024 to 2032 according to SNS Insider.

Why precision matters in metal castings

In modern engineering accuracy is non-negotiable. A precisely cast component can mean the difference between a system that functions flawlessly and one that requires costly downstream correction. This is particularly true in sectors such as aerospace, defence and medical where safety, performance and compliance are paramount.

Precision casting reduces:

• rework and scrap due to dimensional inconsistencies
• assembly issues caused by poor fit or warping
• machining time and cost through near-net shape accuracy

Precision casting improves:

• part interchangeability and modularity across systems
• product lifespan and reliability in critical applications
• regulatory and quality compliance with full documentation.

What are the main types of metal casting?

Metal casting encompasses a variety of techniques used to shape molten metal into components of varying complexity, precision and scale. Each method offers distinct advantages depending on the material, part geometry, volume, and performance requirements. Understanding these differences is therefore crucial when selecting the most appropriate process for a given application.

Sand casting

One of the oldest and most versatile casting processes, sand casting involves packing sand around a reusable pattern to form a mould. Molten metal is poured into this mould, and the sand is removed once the metal has solidified.

This method is highly adaptable, making it suitable for producing large components, complex geometries, and short to medium production runs. Sand casting is widely used across aerospace, marine, defence and energy sectors due to its design flexibility and cost-effectiveness.

Gravity die casting

Also known as permanent mould casting, gravity die casting produces metal castings using reusable metal moulds. Molten metal is poured into the mould under gravity rather than pressure. The result is a denser, more dimensionally consistent product with a smoother surface finish compared to sand casting.

Gravity die casting is ideal for medium to high volume production of simpler components where tighter tolerances and surface quality are important, such as in the automotive or electronics industries.

Investment casting

Sometimes referred to as ‘lost wax casting’, this process begins with a wax pattern coated in ceramic to form a shell. The wax is melted away and replaced with molten metal.

Investment casting delivers exceptional accuracy and surface finish, and is well suited to intricate parts with fine details – common in aerospace, medical, and instrumentation applications. It generally incurs greater costs and process time than other forms of metal casting, making it most appropriate for high-value or highly complex parts.

Pressure die casting

In pressure die casting, the liquid alloy is forced under high pressure into a steel tool. The alloy solidifies rapidly and takes the form of the tool along with the finish of the tool. The pressure die casting process has the advantage of excellent process repeatability.

How to choose the right metal castings process?

Your metal manufacturing partner should have the experience and expertise to advise you on the optimal casting method based on the component’s geometry, functional requirements, volumes and intended application.

UK castings manufacturer Haworth Castings specialises in sand casting and gravity die casting across a range of materials including aluminium, steels and copper. These methods offer an excellent balance of quality, efficiency and affordability, particularly for applications requiring high precision and performance in medium to low volumes. Here is a more detailed explanation of the process for each.

The precision sand casting process

Precision should be embedded at every stage of the sand casting journey. In a metal castings company where your sand castings process is built on decades of expertise, advanced simulation tools and strict quality control protocols, you achieve consistently high-quality results through the key stages in sand casting:

1. Design for manufacture (DfM)

Castings engineers work closely with customers from the concept stage to ensure the part is optimised for casting. This includes detailed analysis using 3D CAD models and solidification simulation software to evaluate metal flow, cooling rates, and shrinkage tendencies. This early collaboration helps eliminate downstream issues, improving castability and reducing costs.

2. Pattern making

Precision patterns are critical to dimensional accuracy. Your team will work closely with the metal casting company pattern makers to ensure the pattern allows for the optimal placement of runners and risers and various other elements. The pattern maker also manufactures patterns for the cores needed to create any cavities.

The pattern will be machined from high quality resin, its size carefully calculated to allow for shrinkage factors tailored to the metal alloy which is to be cast.

3. Mould creation

Using high-quality sand, sand casting experts prepare robust moulds that replicate the pattern details exactly. An expert sand casting company will ensure that the sand system is continuously monitored for moisture content, grain size, and compaction to ensure consistency.

Core assemblies are added at this stage for internal cavities, as well as the runners and risers needed to ensure that molten metal will flow evenly and at the correct speed throughout the sand mould.

4. Metal melting and pouring

The next step is for the skilled foundry team to melt the specified alloys in dedicated furnaces. Melt quality is verified through temperature control, degassing, and spectrographic analysis. The pour of molten metal is carefully controlled to avoid turbulence and minimise oxide formation.

5. Cooling and shakeout

Controlled cooling is a critical part of expert sand casting. As with all types of metal castings, the sand casting must be allowed to solidify at the optimal rate to deliver the desired mechanical properties.

After sufficient cooling, the sand mould is broken away in a shakeout process, and the casting is removed.

6. Fettling and inspection

Gates, risers and excess material are removed through sawing and grinding. The surface is cleaned via shot blasting. Each casting is then visually inspected for defects before progressing.

7. Machining and finishing

Components that require tighter tolerances can be machined to precision. If you choose the right sand casting company, they will be able to provide this service in-house for you, to avoid delay and added logistical issues. Expert sand casting companies can offer CNC machining as well as precision finishing services such as anodising, painting and impregnation to enhance durability and appearance.

8. Testing and quality assurance

All metal castings undergo dimensional inspection using tools such as Coordinate Measuring Machines (CMMs) and functional testing including pressure or leak testing depending on the specification. For critical components, metal castings manufacturers offer radiographic (X-ray), ultrasonic or dye penetrant inspection with full traceability.

This comprehensive, end-to-end metal casting process ensures that each sand casting meets the highest standards of dimensional accuracy, mechanical performance, and surface integrity.

The precision gravity die casting process

Metal castings manufactured using the gravity die castings process generally provide excellent dimensional consistency, enhanced mechanical properties, and smoother surface finishes than other metal forming methods.

The process for gravity die castings has many similarities to sand casting, and demands expert understanding of metallurgy alongside practical expertise. Here are the main steps in gravity die casting:

1. Tool design and manufacture

As with other metal castings, the gravity die casting process begins with the design and machining of moulds – this time usually in durable steel. These moulds are engineered for long life with consistent replication, and include features such as cores, runners and cooling channels to optimise metal flow and solidification.

2. Mould preparation

Before each casting cycle, the die is pre-heated and coated with a specialist release agent. This ensures proper filling, aids ejection, and helps extend tool life.

3. Metal melting and pouring

As with sand casting, the melting processes must be carefully controlled. An expert die casting foundry will perform degassing and chemical composition checks to ensure molten alloys meet specification. The molten metal is then poured directly into the die under gravity.

4. Controlled solidification

The metal solidifies quickly within the metallic mould, producing a dense, fine-grained structure with minimal porosity. Cooling may be enhanced through water-cooled tooling where required.

5. Casting removal and trimming

Once solidified, the metal casting is extracted and any excess material (such as runners and flash) is trimmed or machined away. Castings are then cleaned and surface treated as necessary.

6. Finishing and inspection

Gravity die castings benefit from reduced machining requirements, but customers may still require CNC finishing to meet specification. Each component undergoes rigorous inspection to ensure conformity to dimensional and structural standards.

Gravity die casting provides an excellent solution for repeatable, high-quality parts where improved surface finish and tighter dimensional control are priorities. This process is particularly well suited to parts for defence, energy, transport and instrumentation sectors.

When to choose sand casting vs gravity die casting

The best metal castings companies will have experts to help you determine the best process for your part based on your specific requirements, including geometry, tolerance, production scale, and cost targets. To help decision-makers quickly compare the strengths of each method, here’s a summary of the key factors:

How to choose a metal castings supplier

When sourcing cast components, your supplier must be more than just a foundry — they must be a technical partner. Look for:

• Proven expertise in metal casting
• Help with Design for Manufacture (DfM)
• Advice on optimal metal casting process for your needs
• In-house CNC machining and post-processing
• Ability to handle complex and safety-critical components
• UKAS-approved testing and ISO 9001 certification
• Membership of JOSCAR for defence sector compliance
• Full design, manufacture and supply chain management

The Cast Metals Foundation is the leading trade association for the UK casting industry, promoting best practice, innovation, and collaboration. The site offers resources, news, training, and a directory of foundries and suppliers.

Metal Casting in the UK

According to Casting for the Future there are around 400 foundries in the UK. They are located in all parts of the country. UK foundries produce precision engineered components worth around £2.2B annually, using all metals and alloys and a wide range of casting processes.

Whilst Haworth Castings specialises in casting aluminium, it also works in a wide range of alloys suited to specific applications. For example, the company has significant experience in producing sand castings from alloy steel, carbon steel, cast iron, stainless steel, copper and magnesium, in addition to its core aluminium castings expertise.

Why choose Haworth Castings?

With over 70 years of experience, Haworth Castings has earned its reputation as a trusted partner to global manufacturers. The company’s core strengths include all the technical capabilities listed above – plus customers benefit from Haworth Castings’ strong relationship with our sister UK-based manufacturing operations, and global sourcing options.

UK-based manufacturing operations

Haworth Castings is part of the Expromet Technologies Group – a family of advanced manufacturing businesses with complementary specialisms. Through this connection, we can offer our customers a broader range of metal forming and finishing solutions, including investment casting, sand casting, gravity die casting, pressure die casting, CNC machining and fabrication.

Our sister companies include:

• Investacast: experts in investment casting and pressure die casting, with operations in the UK and global sourcing partners
• Metaltech Precision: specialists in high-precision CNC machining for complex, critical components

Global sourcing options

Haworth Castings can provide access to a trusted network of global foundry and machining partners located across Europe and Asia. This network is carefully managed and audited through Expromet Technologies Group, ensuring quality, traceability, and delivery standards are never compromised. Our global sourcing capability allows us to:

• Support high-volume production where cost and lead time are key drivers
• Offer flexibility through dual sourcing or hybrid UK/overseas production models
• Align to procurement strategies in sectors where overseas supply is appropriate

Working as part of the group allows Haworth Castings to collaborate across sites and capabilities, offering customers an integrated solution that supports development, production, and delivery – whether parts are made in the UK or globally to recommend the most suitable process, location and facility for each project.

This global reach, paired with our in-house capabilities and group network, enables us to tailor production strategies to meet technical requirements, commercial goals and delivery schedules.

Learn more or request a quote

Choosing the right metal casting method and castings manufacturing partner is critical to your project’s success. Whether you need high-precision prototypes, medium-volume production, or a reliable long-term supplier, Haworth Castings is here to help.

We combine the flexibility of sand casting with the consistency of gravity die casting, supported by in-house machining, global sourcing, and the extended capabilities of Expromet Technologies Group.

If you are looking for a trusted manufacturing partner, Haworth Castings is here to help. Contact us today to discuss your next project and discover how our precision casting solutions can meet your exacting requirements.

FAQs: Metal castings

1. What are metal castings?
   Metal castings are components made by pouring molten metal into a mould, where it solidifies into a specific shape. This process allows for complex, high-performance parts used across sectors such as aerospace, defence and energy.
2. What are the main types of metal casting?
   The four main types of metal casting are sand casting, gravity die casting, investment casting and pressure die casting. Each method suits different part geometries, production volumes and tolerances.
3. What are the benefits of using metal castings?
   Metal castings offer cost-efficiency, design flexibility, high strength, material variety, reduced waste, and fast production times — making them ideal for critical applications.
4. When should I choose sand casting over gravity die casting?
   Choose sand casting for complex or low-volume parts that require high flexibility. Opt for gravity die casting for simpler shapes, better surface finishes and higher-volume production.
5. Which industries use metal castings?
   Metal castings are essential in aerospace, defence, marine, medical, automotive, renewable energy and industrial equipment sectors.
6. How do I choose the right metal casting process for my part?
   The best process depends on part complexity, material, volume, tolerances and cost. A specialist like Haworth Castings can advise on the optimal method for your needs.
7. What makes a high-quality metal casting supplier?
   Look for a supplier with proven expertise, in-house machining, UKAS-accredited testing, ISO 9001 certification, and membership of compliance bodies like JOSCAR.
8. Why is precision important in metal casting?
   Precision reduces scrap, machining costs and fitment issues, while improving product reliability, safety and compliance in critical systems.
9. Can metal castings be customised for specific applications?
   Yes. Metal casting allows for bespoke designs with complex features, tailored alloys, and specific finishing processes like anodising, painting or impregnation.
10. Does Haworth Castings offer global sourcing?
    Yes. As part of Expromet Technologies Group, Haworth Castings combines UK manufacturing with a trusted global network to meet technical, cost and delivery needs.