Frequently Asked Questions (FAQs)

General Die Casting FAQs

What is die casting?

Die casting is a manufacturing process that uses high pressure to inject liquid metal into a reusable steel die. Rapid cooling solidifies the metal into a final shape.  

What materials are used for creating die cast parts?

The die casting process can create parts with alloys of the following elements (listed from most common to least):
  • Aluminum – Lightweight, high dimensional stability, good corrosion resistance and mechanical properties, high thermal and electrical conductivity, strength at elevated temperatures
  • Zinc – Easy to cast, high ductility, high impact strength, easily plated
  • Magnesium – Easy to machine, excellent strength-to-weight ratio
  • Copper – High hardness and corrosion resistance, high mechanical properties, excellent wear resistance and dimensional stability
  • Lead / Tin – High density, good dimensional control, special forms of corrosion resistance

More details about die casting alloys can be found on the webpage.

What is the history of die casting?

The earliest example of a die casting by pressure injection (as opposed to gravity pressure) occurred in the mid-1800s. A patent was awarded to Sturges in 1849 for the first manually operated machine for casting printing type. This process was limited to printer’s type for the next 20 years, but development of other shapes began to increase toward the end of the century. By 1892, commercial applications included parts for phonographs and cash registers, and mass production of many types of parts began in the early 1900s.

The first die casting alloys were various compositions of tin and lead, but their use declined with the introduction of zinc and aluminum alloys in 1914. Magnesium and copper alloys quickly followed, and by the 1930s, many of the modern alloys still in use today became available.

The die casting process has evolved from the original low-pressure injection method to techniques including high-pressure casting (at forces exceeding 4500 pounds per square inch or 31 megapascals), squeeze casting, and semi-solid die casting. These modern processes are capable of producing high integrity, near net-shape castings with excellent surface finishes.

What are the advantages of high pressure die casting?

  • High Speed Production – Die casting provides complex shapes within closer tolerances than many other mass production processes. Little or no machining is required and hundreds of thousands of identical castings can be produced before additional tooling is required.
  • Dimensional Accuracy and Stability – Die casting produces parts that are dimensionally stable and durable, while maintaining close tolerances. Castings are also heat resistant.
  • Strength and Weight – The die casting process is suited for thin wall parts, which reduce the weight, while maintaining strength. Also, die casting can incorporate multiple components into one casting, eliminating the need for joining or fasteners. This means that the strength is that of the alloy rather than the joining process.
  • Multiple Finishing Techniques – Die cast parts can be produced with a smooth or textured surface, and they are easily plated or finished with minimum or surface preparation.
  • Simplified Assembly – Die castings provide integral fastening elements, such as bosses and studs. Holes can be cored and made to tap drill sizes, or external threads can be cast.

What markets are supported by the die casting industry?

Die castings are used in every industry. Some of the industries that use large numbers of die castings are:

  • Automotive
  • Builder's Hardware
  • Telecommunications
  • Power & Hand Tools

What are some examples of die castings?

Examples of die castings can be found on the Casting Award Winners page of this website.

What does the size of the die casting machine mean?

Die casting machine sizes are given in tons (or metric tonnes). This refers to the clamping force, holding the dies halves together, when the machine is closed. So a 900 ton die casting machine would have 900 tons of force holding the die halves together when metal is injected.

What is the future of die casting?

  • Quality – An area that has already seen significant advances with the high integrity die casting processes (high vacuum, squeeze, and semi-solid). Research continues on how to improve quality even further in both conventional and high integrity processes. Identifying internal defects and heat treating die castings to improve mechanical properties of the casting.
  • Adaptability – Die casting research and development are looking at how to reduce change over times between one product and the next on a die casting machine.
  • Die Design and Construction – New die materials, as well as advancements in additive manufacturing is changing die design and construction. These changes can improve the die casting process and quality of the castings, as well as increase the life of the die.

How do I find more information about research and development in the die casting industry?

  • NADCA Members can access the NADCA Technical Archives to read papers from the industry.
  • NADCA Members can also attend NADCA Die Material Committee and Research and Development Committee meetings to hear about current research.
  • Research from the industry is presented at the annual NADCA Technical Congress. Information about the next Technical Congress can be found on the Congress and Exposition  webpage.

How do I find a die caster who can produce my part?

Die casters can be found using the Die Casting Companies Directory.

How does die casting impact the environment?

As with any manufacturing process there is an impact on the environment. Melting metal and running machines require significant amounts of energy and wastewater needs to be properly treated. Die casting limits the overall impact on the environment by using a significant amount of recycled materials (which is less energy intensive to produce) and producing thin walled, light weight components (which reduce the fuel consumption on cars and trucks).

Die castings are recyclable components with engineering advantages not available in other metalforming processes. The major cost and performance benefits of parts consolidation possible with plastic components can be carried forward in die casting designs with additional advantages.

Over 95% of the aluminum die castings produced in North America are made of post-consumer recycled aluminum. Since the production of recycled aluminum alloy requires approximately 5% as much energy as primary aluminum production, there is a dramatic conservation of nonrenewable energy resources.

Die Casting Process FAQs

What is the die casting process?

The basis for the die casting process is using high pressures to inject liquid metal into a reusable steel die. There are some variations to the process, such as: hot chamber die casting, cold chamber die casting, structural (or high integrity) die casting.

What is hot chamber die casting?

Hot chamber refers to the relative temperature of the injection mechanism. In the hot chamber process the injection mechanism is submerged in liquid metal inside the melting furnace. Because the metal does not need to be transferred to the injection mechanism production rates can be higher. The hot chamber process is limited to metals with lower melting temperatures or don’t react with steel, such as: zinc, lead, tin, and some magnesium alloys.

What is cold chamber die casting?

Cold chamber refers to the relative temperature of the injection mechanism. In the cold chamber process metal is melted in an external furnace and transported to the injection mechanism when the machine is ready to make a casting. Because the metal needs to be transferred to the injection mechanism production rates are typically lower than the hot chamber process. Aluminum, copper, some magnesium, and high aluminum content zinc alloys are produced using the cold chamber die casting process.

What is structural or high integrity die casting?

Structural die castings (sometimes referred to as high integrity die casting) are variations of the die casting process used to produce castings for specific applications (typically requiring minimized gas porosity in the casting). These include:

  • High Vacuum Die Casting - The die is sealed and a vacuum is used to remove gas from the die cavity (< 50 mbar) while the metal is injected, reducing the amount of gas that can be trapped in the casting. Parts produced with high vacuum have higher mechanical properties and can be heat treated. The high vacuum process should not be confused with vacuum assist, which uses vacuum to help with the filling of a trouble area in the die.
  • Squeeze Die Casting - Liquid metal is injected at slower speeds to eliminate turbulence. High pressure is used to “squeeze” the metal into die, creating high quality castings that can be heat treated.
  • Semi-Solid Die Casting (or Semi-Solid Molding) - A semi-solid (between the melting temperature and the solidification temperature) billet is injected into the die. The metal’s semi-solid state reduces the amount of gas that is picked up during injection, creating dense, heat treatable castings.

Die Design/Construction FAQs

What are good design practices for die cast parts?

  • Wall Thickness – Die castings benefit from a uniform wall thickness.
  • Draft – Sufficient draft is required to extract the casting from the die.
  • Fillets – All edges and corners should have a fillet/radius.

Additional information on design considerations can be found on the website.

How is the die designed?

The following are some of the considerations taken into account during die design.

  • Metal Flow – Metal needs to flow into all areas of the die, without trapping gas
  • Venting – As metal flows into the die it pushes the air in front of it. The air needs a way to escape out of the die.
  • Cooling Lines – Cooling lines are required to remove the heat from the steel die. The location of these cooling lines is important to ensure thermal balance across the die.
  • Ejection – Ejector pins are needed to push the casting out of the die. They need to be positioned to smoothly push the entire casting without twisting.

Modern die cast engineers utilize a combination of calculations, fluid flow simulation, and finite element analysis to ensure the die is properly designed to make quality die castings.

How is the die constructed?

The die is made from alloy tool steels in at least two sections – the stationary (or cover) die half and ejector die half. Modern dies may also have moveable slides, cores or other sections to produce holes, threads, and other desired shapes in the casting. The stationary die half has a hole to allow metal to enter the die and fill the cavity. The ejector half usually contains the runners (passageways) and gates (inlets) that route molten metal to the cavity. Dies also include locking pins to secure the two halves, ejector pins to help remove cast parts, and water or oil channels for cooling the die.