This article contains information regarding die casting and its use.
Here is what you will learn:
Die casting is a metal casting technique that utilizes high pressure to force molten metal into a mold. This process generates metal components with precise dimensions and a superior surface finish. Known for its ability to create intricate details, it is particularly useful for large-scale production. Typically, die castings are produced using non-ferrous metals such as zinc, copper, aluminum, magnesium, lead, pewter, and tin.
There are two main techniques in the die casting process: hot and cold chamber. The chosen method depends greatly upon the type of metal and the characteristics of the part. Cold chamber die casting is suited for metals with high melting points like aluminum alloys, brass, or copper. Conversely, hot chamber die casting is used for metals that remain stable when heated, such as zinc, lead, and magnesium alloys.
The die casting procedure is both efficient and cost-effective, allowing for a variety of shapes and products. The finished parts are sturdy and can be designed to be aesthetically pleasing, offering designers numerous benefits and advantages.
Die casting's rapid process enables the creation of complex shapes with precise tolerances, eliminating the necessity for further processing. It does not require additional tooling or shaping. The final components are heat resistant with impressive tensile strength.
Depending on the specific feature and its scale, tolerances of +/- .002" are achievable for aluminum, with tolerances of +/- .0005" in zinc.
Die casting and forging are two different metal forming processes with significant differences.
In die casting, molten metal is injected into a mold cavity under high pressure, resulting in detailed and complex shapes with high dimensional precision. This method is perfect for producing intricate, thin-walled components with a smooth finish, making it ideal for industries like automotive and consumer electronics.
Forging, on the other hand, involves shaping metal by applying compressive forces through pressing or hammering at high temperatures. This technique enhances the material's grain structure and strength, yielding strong parts often used in heavy machinery, aerospace, and construction equipment. While die casting is favored for its accuracy and complexity, forging offers unmatched strength and integrity.
Choosing the right metal for die casting is a crucial factor that directly impacts the performance, durability, and cost-effectiveness of the final product. The type of metal alloy selected depends on factors such as application requirements, weight considerations, corrosion resistance, and desired mechanical properties. For example, aluminum die casting is widely employed for automotive and truck parts thanks to its excellent strength-to-weight ratio, lightweight characteristics, and natural corrosion resistance. In contrast, medical instruments and surgical tools often utilize stainless steel for its biocompatibility, hygienic properties, and exceptional resistance to corrosion and oxidation.
Metals and alloys selected for die casting must retain their favorable mechanical, thermal, and chemical properties before, during, and after the manufacturing process. The primary metals and casting alloys used in commercial die casting processes include:
Each of these metals offers unique properties, making them suitable for different industrial, commercial, or consumer applications. Learn more about the specific benefits and limitations of the most popular die casting metals below.
Zinc is a highly adaptable and often underutilized die casting alloy, recognized for its superior balance of strength, ductility, and finishing options. Because zinc is 2.3 times heavier than aluminum, it is frequently chosen for small, intricate die-cast parts or medium-volume production where superior surface finish and thin-wall castability are essential. Zinc die casting provides high dimensional accuracy and the ability to produce complex geometries, making it a go-to material for the electronics, automotive, and hardware industries.
Zinc alloys, particularly ZAMAK variants, possess high ductility, remarkable impact strength, and are easily plated, lending themselves to decorative as well as functional applications. Tight tolerances and excellent repeatability can be achieved in high-volume manufacturing, while zinc’s natural lubricity and strong bearing properties can eliminate the need for bushings or additional wear inserts—adding value and reducing assembly complexity in components such as gears, housings, and connectors. Additionally, the low melting temperature of zinc drastically minimizes die wear, which translates to longer tool life and lower replacement costs, making zinc alloys extremely cost-effective for large production runs.
The outstanding fluidity of zinc alloys enables manufacturers to cast fine details, frictionless moving parts, and thin-walled components (down to 0.025 inches/0.65 mm). This provides significant advantages in miniaturized consumer electronics, medical device housings, and intricate lock or fastening systems. The reduced thermal shock due to lower casting temperatures further preserves die integrity, lowering maintenance intervals and improving productivity for die cast manufacturers.
Zinc’s relatively low melting point (approximately 419°C/786°F), while beneficial for extended die life, makes it less suitable for cast components destined for high-temperature environments, such as under-the-hood automotive engine parts or industrial ovens and furnaces. In situations where superior corrosion resistance is paramount—such as marine hardware or aggressive chemical processing applications—zinc may require post-casting processing or the application of coatings for protection. Surface integrity can also suffer if the casting process is not tightly controlled, occasionally resulting in porosity or surface defects.
Aluminum die casting is the industry standard for high-volume production components where lightweight, superior strength, corrosion resistance, and outstanding thermal conductivity are required. Aluminum alloys such as A380 and ADC12 are especially valued for their ability to form complex part shapes with thin walls, making them optimal for the automotive, aerospace, and electronics sectors. This leads to significant weight savings—crucial for applications where improving energy efficiency and reducing emissions (such as electric vehicle parts, transmission housings, or consumer electronics enclosures) is key.
Aluminum alloys offer a high strength-to-weight ratio, ensuring die castings can withstand demanding loads while minimizing overall component mass. Their excellent thermal and electrical conductivity make aluminum castings ideal for heat sinks, LED housings, chassis, and battery enclosures in power management and telecommunications. Furthermore, aluminum’s natural oxide film provides a layer of corrosion resistance, extending service life for both indoor and outdoor die cast components. The alloy’s malleability and machinability also deliver cost and time advantages in downstream processes.
Despite its many benefits, aluminum presents some manufacturing challenges. The relatively high shrinkage rate during solidification can cause dimensional variation, necessitating secondary machining or close process control to achieve tight tolerances in complex or multi-cavity molds. On the material side, certain aluminum alloys can be more brittle than zinc or magnesium, which could increase the risk of cracking or fracturing in applications with frequent impact or heavy mechanical loads. Aluminum can also be more prone to porosity if the die casting process does not adequately address gas entrapment or the use of optimal die temperatures and venting.
Brass is prized in the die casting industry for its robust corrosion resistance, electrical conductivity, and pleasing gold-like appearance, making it a popular choice for decorative hardware, plumbing fittings, and electrical connectors. The alloy’s resistance to rust and tarnishing makes brass ideal for exterior or high-humidity environments where longevity and reliability are critical, such as marine components, valves, and architectural fixtures.
Beyond corrosion protection, brass’s high thermal conductivity is advantageous for manufacturing components requiring rapid heat transfer or dissipation, found frequently in HVAC systems, electrical contacts, and specialty lighting applications. Brass die castings also offer impressive strength and wear resistance, enabling use in lock bodies, mechanical gears, and other high-cycle parts that require both durability and dimensional precision.
Brass die casting presents unique process challenges. The melting and casting of brass necessitate rigorous temperature control and close monitoring, which can be labor-intensive and increase operational complexity. Improper management of alloys and casting lubricants can result in casting defects such as scaling or burning. Regular issues like porosity (microscopic holes within the metal) and die adhesion demand the expertise of experienced foundry professionals to mitigate. Additionally, because brass has a lower melting point than some other alloys, its use may be limited in high-temperature or high-stress environments, where deformation or material fatigue could compromise part performance over time.
For applications with even more demanding properties—such as ultra-high thermal conductivity or special mechanical attributes—alternatives like bronze or specialized steel alloys may be evaluated by engineers and product designers.
When selecting the best die casting metal or alloy for your next project, it’s essential to consider not only the functional requirements of the part (such as strength, durability, thermal performance, and corrosion resistance) but also cost, production volume, secondary machining needs, and design complexity. Consulting with reputable die casting manufacturers and material experts ensures the optimal balance of performance and manufacturability for your product application.
TThe most common types of die casting are hot and cold chamber die casting. In hot chamber die casting, metals are heated directly in the casting machine, whereas in cold chamber die casting, metal is preheated in a furnace and then transferred to the casting machine as molten metal. Both processes yield complex shapes with tight tolerances, offering heat resistance and high tensile strength with minimal requirements for additional tooling and shaping.
Hot chamber die casting uses alloys with a low melting temperature. Dies have two sections – movable and fixed. The fixed half is the covered die and is mounted on a stationary platen aligned with the gooseneck that connects to the chamber for inserting the molten metal. The movable die is the ejector die.
Molten metal is held in an open holding pot that is connected to the combustion area or furnace from which the molten metal enters the holding pot. With the plunger, that drives the molten metal up the gooseneck into the mold, in the up position the molten metal flows into the shot chamber. Once the metal is present, the plunger moves down forcing the molten metal up the gooseneck into the die.
The two halves of the mold are forced together under great pressure to close the mold. The plunger remains down until the molten metal in the die cools. After solidification, an ejection system pushes the casting out from the two die halves.
Cold chamber refers to the temperature of the chamber when the molten metal is introduced. With hot chamber casting, the chamber is filled with molten metal prior to beginning the casting process. In the cold chamber process, the chamber is at room temperature before the molten metal is poured.
High melting temperature metal alloys are used for cold chambered die casting. The molten metal is heated in a separate furnace and ladled or poured through a pouring hole into the shot chamber that encloses a ram for pushing the molten metal into the die. The parts of the die are the same with movable and fixed sections. The cold chambered method forces the molten metal in vertically.
As the ram moves vertically toward the die, the molten metal is forced forward at pressures between 2000 psi or 2 ksi to 20,000 psi or 20 ksi. The pressure is held by the ram until the molten metal cools and solidifies to be ejected.
The basic steps for high pressure die casting are listed below. They vary depending on the chosen process of a manufacturer. (from https://www.thediecasting.com/the-die-casting-process-step-by-step/)
Step one – Preparation of the Die: To prepare the die for casting, it is sprayed with a lubricant or releasing agent. Lubricants allow for clean part release by placing a film over the part. To make application easy, the lubricating agent is mixed with water that evaporates when sprayed on the heated steel die.
Step two – Clamping the Die: The halves of the die are clamped together under high pressure. The amount of force is determined by the machine.
Step three – Cooling: Cooling time depends on the type of metal and the temperature at which it will solidify. The geometry and wall thickness of the part are also factors.
Step four – Ejection: The halves of the mold are separated, and an ejection mechanism forces the part out of the die. The amount of force for removal has to be carefully monitored.
Step five – Trimming: Flashing (a thin portion of metal around the edge of a casting) is removed, known as deflashing, which is excess material such as metal that may have seeped between the die halves or runners.
(from www.kineticdiecasting.com)
Die casting design geometry determines how parts fill and cool as well as how their geometry affects stress, grain, and porosity. The grain structure and level of stress are determined by the type of metal.
The examples in the above diagram are a sampling of the types of geometric features produced by die casting.
Drafting is a draft angle that varies depending on the type of wall and surface, the depth of the surface, and the selected metal. A mathematical formula determines the angle.
Fillet radii makes a part stronger by redirecting stress concentration at sharp interior corners by distributing it over the broader volume of the fillet to lessen weak points. It prevents cracking during straightening.
The parting line is where the two halves of the die meet, defining the inside and outside surfaces, as well as determining which side of the die serves as the cover and which side serves as the ejector.
Bosses are mounting points, stand offs, and are designed to maintain uniform wall thicknesses to eliminate after casting machining.
Ribs facilitate the complete filling of the die casting with molten metal. They create pathways for the molten metal and streamline the ejection process, thereby enhancing efficiency and speed.
Holes and windows necessitate the highest degree of drafting because they connect directly with the die surface, potentially impeding ejection and obstructing the flow of molten metal.
Holes can be seen in this die cast plunger lock from Window Repair Parts.
There are several variations of die casting, each offering unique characteristics and advantages. These variations are selected based on factors such as material choice, part geometry, production volume, and quality standards. Manufacturers meticulously evaluate these factors to determine the most suitable die casting method for a particular application.
The variations described below have been developed to address flaws, errors, deformities, and other challenges encountered in die casting operations.
Prior to injecting or pouring the molten metal, the die cavity is filled with oxygen. When the hot metal enters the cavity, the oxygen chemically combines with it to prevent gas bubbles eliminating trapped gas pores. In the diagram below, note the opening for active gas in this cold forging process.
Acurad is an anagram for accurate, reliable, and dense. It combines stable fill and directional solidification to create fast cycle times. It includes thermal analysis, flow and fill modeling, heat treatable castings, and indirect squeezing. Double pistons increase the pressure when the shot is partially solidified.
Molten metal is poured directly into a permanent die, completely filling it, which minimizes turbulence, oxidation, and foaming. The die can be vertical, horizontal, or tilted, resulting in parts with high quality, strength, and mechanical characteristics, as well as stiffness.
Investment or lost wax casting, is labor intensive process involving shaping of the mold from a wax prototype dipped in liquid ceramic. When the ceramic hardens, the wax is melted away. Molten metal is poured into the ceramic cavity. After solidification, the ceramic mold is broken away and the metal casting removed.
The die is enclosed within an airtight housing. Pressure is applied to the die cavity, drawing in molten metal which solidifies before being ejected.
Semi-solid metal, in a semi-solid or slurry state, is agitated, poured, and directed into a shot sleeve to be forcefully injected into the mold cavity under pressure. This process results in parts with excellent surface finishes, tight dimensional tolerances, and a favorable microstructure.
Low Pressure the chamber with the molten metal is below the die, as can be seen in the diagram. It is pushed up through an intake port into the die chamber. The pressure is maintained until the molten metal solidifies.
Die castings are crafted from steel alloys and consist of two sections: the fixed or cover half and the ejector or removable half. A sprue hole, typically round and tapered, serves as the entry point for molten metal into the die cavity. The ejector half features a runner or passage, along with a gate or inlet, to direct the molten metal into the die cavity. The two halves are secured together using ejector pins.
The die has an opening for a coolant or lubricant, which helps in releasing the part from and keeping the temperature even. Lubricant improves the finish and prevents the part from sticking to the die cavity. The most common form of lubricant is water mixed with oil.
A die can last through several thousand parts, which depends on the amount of stress it endure, maintains, and cared. Die casting dies are expensive and can add to the cost of the final part.
Several types of dies have been developed and continue to evolve due to the dynamic nature of die casting technology. New dies are regularly introduced to enhance capabilities and efficiency.
Below is a description of a few of the common ones.
This process produces a single unit and is compatible with machines designed for one die, considering factors like shot height, locking force, and die size. It is particularly beneficial for low-volume production runs, center gating (the entry point for molten metal), and intricate parts with multidirectional features.
Multiple cavity dies are designed to produce multiple identical parts in a single casting operation.
Combination dies, a type of multiple cavity die, produce different parts that fit together instead of casting identical parts. The diagram illustrates examples of the parts that can be produced from a single die casting.
Unit dies can be inserted into larger dies where the larger die remains fixed, allowing flexibility to create various components with the unit die. However, there are constraints related to the size and weight of the unit die, determining its feasibility for insertion.
Die casting is the quickest and most economical of production processes. Hundreds of thousands of parts can be produced from one mold producing dimensionally accurate and precision parts. Listed below are the advantages and disadvantages of die casting.
Dimensional accuracy typically ranges within 0.1 mm for the first 2.5 cm and 0.02 mm for each additional centimeter.
Surface finishes of 1 – 25 μm. (from website https://firstratemold.com/advantages-and-disadvantages-of-die-casting/).
The production rate depends on cavitation, which refers to the number of cavities in a mold. A single mold can achieve between 200 to 300 shots per hour. For smaller parts, this rate can increase to the thousands per hour.
Reproduces any design down to the finest details with thin walls and structures.
Threaded inserts, bearings, and addons can be easily included.
Parts have tensile strengths of 60,000 psi or a 415 MPa.
Hydraulic and pneumatic equipment are commonly used for efficiency and lower cost.
Produces complex parts with extremely close tolerances.
Every mold has to be individually precision manufactured, which requires hours of crafting, shaping, and forming.
Furnaces have to burn into the 1000‘s of degrees consuming costly energy that produces pollutants that have to be air filter controlled.
Molding and shaping equipment is precision designed to withstand the stress of the heating process.
Only metals with high fluidity can be used, which influences the types of parts to be produced.
The process requires careful monitoring and management, particularly during the cooling phase.
Dies are made of hardened steel and cannot be adjusted or changed. They are very expensive and costly.
Porosity, shrinkage, and metal pouring are common defects.
Requires very long lead times.
Aluminum casting is a method used to produce high-tolerance, high-quality parts by injecting molten aluminum into a meticulously designed and precision-engineered die, mold, or form. This efficient process enables the production of complex, intricate, and detailed parts that precisely match the specifications of the original design.
Zinc die casting is a process in which molten zinc is injected into a steel die cavity that matches the shape, size, and dimensions of the part or component being manufactured. The resulting cast zinc product exhibits...
The casting process is an ancient art that dates back several thousand years to the beginning of written history. Archaeological finds document the use of casting over 6000 years ago, around 3000 BC or BCE...
Investment casting is a metalworking process that involves creating a ceramic shell over a wax pattern to produce parts with exceptionally uniform and smooth surfaces. The wax pattern is typically created using an aluminum die. The final products of investment casting are free from parting lines, mold half marks, or other deformities.
An iron casting is a durable product made by combining iron with carbon. It can be easily cast into a mold and generally contains a higher proportion of carbon than steel, typically ranging from 2 to 4.3 percent.
Lost wax casting, also known as precision casting, is a process that uses a wax pattern to form a ceramic mold for creating intricate part or product designs. This method is renowned for its accuracy in reproducing parts with precise tolerances over the years.
Permanent mold casting is a process that utilizes robust, reusable molds to manufacture parts and components from molten metals. These molds are typically constructed from steel or...
Sand casting is a manufacturing process where liquid metal is poured into a sand mold, which holds a hollow cavity of the desired shape until it solidifies.
Aluminum forging is a method used to process aluminum alloys, employing pressure and heat to create high-strength, durable products. This process involves pressing, pounding, and...
Cold forging is a metal shaping & manufacturing process in which bar stock is inserted into a die and squeezed into a second closed die. The process, completed is at room temperature or below the...
Copper and brass forging involves shaping copper and brass to create complex and intricate forms. The forging process meticulously controls the temperature at which copper and brass are worked, ensuring precise results and...
Forging is a metalworking process that involves manipulating, shaping, deforming, and compressing metal to achieve a desired form, configuration, or appearance as specified in a metal processing design or diagram...
In this article, essential terms associated with both open and closed die forging are discussed, emphasizing the importance of comprehending their definitions. Forging, a manufacturing process involving pressing, hammering, or shaping metal...
Rolled ring forging is a metalworking technique wherein a thick, solid, round metal piece is punched to form a hole, creating a donut shape. Subsequently, the donut shape is squeezed and pressured to transform it into a thin ring...
Forging steel is a manufacturing process that shapes steel through localized compressive forces, such as hammering, pressing, and rolling. This method is extensively employed to produce high-quality steel products...
The ancient craft of forging can be categorized into two main types – hot and cold forging. Hot forging has a long history spanning centuries, whereas cold forging emerged during the 19th century industrial revolution. Despite their distinct origins,...