The contents of this article is everything you need to know about zinc die casting and its use.
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Zinc die casting is a manufacturing technique where molten zinc is forced into a steel mold designed to produce components of specific shapes and dimensions. The resulting zinc castings inherit the full range of zinc's mechanical properties, including its durability and visual characteristics. Zinc alloys are preferred in this process due to their flexibility, resistance to impact, and low melting temperature, making them highly suitable for casting applications.
Zinc casting is carried out at lower temperatures because of zinc's relatively low melting point. Before starting the casting process, the dies are thoroughly cleaned and treated with lubrication. Various zinc alloys are utilized, such as different zamak alloys, zinc-aluminum, and zinc-copper, with zamak 3 being the most popular choice due to its consistent dimensional stability and robust physical and mechanical characteristics.
Among the metals commonly used in casting, zinc is known for its ease of casting and its abundance on Earth. It is a brittle metal with a silvery-white appearance and a slight blue hue, which tarnishes when exposed to air. Zinc die-casting alloys typically consist of 78% zinc, combined with varying amounts of lead, tin, copper, aluminum, and magnesium to enhance the desired casting properties and mechanical performance.
Zinc provides engineers with unique design opportunities that are difficult to achieve with other metal alloys. Its strength allows for the creation of thin-walled designs while minimizing material consumption. Additionally, zinc's excellent bearing and wear characteristics make it perfect for producing bushings or components with detailed and complex shapes.
Die casting methods generally involve injecting molten metal into a mold under high pressure to ensure complete coverage of the mold’s contours. In zinc die casting, the mold, or die, is shaped in reverse to the final component. This process uses zinc alloys, which consist of zinc combined with other metals. Zinc is selected for its adaptability and superior casting qualities.
During the injection stroke, the plunger provides the driving force behind sending the molten zinc through the gooseneck and into the nozzle. At the beginning of a casting cycle, it retracts and pulls molten zinc into its cylinder. The shot cylinder is powered by a CNC machining that provides the power for the plunger’s downward stroke. As the plunger moves downward, it cuts off the flow of molten zinc into the cylinder and gooseneck.
The pressure generated by the downward movement of the plunger ranges from 700 psi to 5000 psi (5 MPa to 35 MPa). The plunger maintains this pressure on the die for sufficient time to allow the part or component to solidify. During the filling of the die cavity, instantaneous pressures can significantly exceed these values due to the momentum (mass x velocity) of the molten metal.
In hot chamber zinc die casting, the main components include the furnace, gooseneck, nozzle, and the plunger or piston, which transfers the molten zinc to the die. The stationary part of the die is fixed onto a large plate, which is connected to the hot chamber die casting apparatus.
The furnace is built into the hot chamber die casting machine. It burns fuel that melts the zinc and has an intake port that is attached to the gooseneck passage and is below the shot cylinder that contains the plunger. When the plunger is raised, molten zinc is allowed to flow through the intake port into the gooseneck.
The gooseneck is a distinctive component in hot chamber die casting, serving as the conduit between the injection system and the feed line that directs molten zinc into the die. It is submerged in the molten zinc pool and constructed from highly durable materials to withstand the extreme temperatures of the zinc. Connected to a cylinder housing the plunger, the gooseneck helps push the molten zinc through to the nozzle and into the die. Due to the demanding conditions, goosenecks are closely monitored for signs of wear and tear.
The nozzle facilitates the smooth transfer of molten zinc into the die cavities. At the end of the casting cycle, it also enables the excess molten material to return to the furnace for reuse.
During the injection stroke, the plunger provides the driving force behind sending the molten zinc through the gooseneck and into the nozzle. At the beginning of a casting cycle, it retracks and pulls molten zinc into its cylinder. The shot cylinder is powered by a hydraulic motor that provides the power for the plunger’s downward stroke. As the plunger moves downward, it cuts off the flow of molten zinc into the cylinder and gooseneck.
The pressure generated by the plunger's downward motion ranges from 700 psi to 5000 psi (5 MPa to 35 MPa). This pressure is maintained on the die for a sufficient duration to ensure that the part or component fully solidifies.
The stationary half of the die is secured to the cover platen, while the movable or ejection half is firmly pressed against it. The ejection half features pins that help to eject the solidified part from the die. When the die halves open, these ejection pins push the finished component out of the mold.
The full cycle of hot chamber zinc die casting encompasses hot chamber filling, injection, high-pressure application, and cooling. This process is designed to be efficient and cost-effective, enabling rapid production.
The main distinction between hot chamber and cold chamber zinc die casting lies in the temperature of the chamber where the molten metal is introduced. In cold chamber die casting, molten zinc is first poured into a cold shot chamber, from which it is then injected under pressure into the sealed movable and fixed halves of the die.
The die used in cold chamber die casting is constructed from the same materials as those employed in hot chamber die casting. The fixed part of the die is attached to the shot chamber, where the molten zinc is introduced. Other features of the mold are similar to those in hot chamber die casting. Before the casting process begins, the mold is coated with a lubricant to facilitate the removal of the cast part. A motor applies pressure to press the movable portion of the die firmly against the fixed portion, ensuring a secure fit.
In cold chamber zinc die casting, the heating furnace is independent of the casting mechanism. Zinc is heated in a separate furnace, then transferred to the shot chamber of the cold chamber die casting machine using a ladle. The molten zinc is poured into the shot chamber for the casting process.
The shot chamber is a long cylindrical container where molten zinc is poured through a pour hole, which has a diameter approximately 70% of the shot chamber's inner diameter. This pour end is the hottest part of the cold chamber system and is equipped with a temperature control device. Unlike the vertical plunger cylinder used in hot chamber die casting, the shot chamber in cold chamber die casting is oriented horizontally. The piston or ram is located at one end, with the opposite end attached to the fixed half of the die. The pour hole, positioned at the end nearest to the plunger, is where the molten zinc is introduced into the chamber.
To facilitate processing, the shot chamber is preheated to over 400°F (204°C). This preheating step reduces start-up scrap and improves production efficiency. By heating the shot chamber beforehand, better control is achieved during the cold chamber die casting process.
The plunger's operation must be smooth and linear along the length of the shot chamber, with a gap between the plunger and the chamber wall not exceeding 0.004 inch (0.102 mm). The walls of the shot chamber are designed with uniform thickness to prevent hot spots and uneven expansion. The effectiveness of cold chamber die casting relies on the even application of pressure by the plunger throughout the process.
Cold chamber die casting starts with a precise quantity of molten zinc, which is ladled from the furnace. This measured amount is sufficient for a single casting shot.
Cold chamber zinc die casting can yield parts with greater density and improved mechanical properties. The process's higher pressure enables the creation of components with thinner walls, intricate details, and complex features.
Zinc die casting machines are produced by manufacturers in Asia and Europe, with China and India being leading suppliers. Prominent brands include Techmire and Frech, both of which have distributors in the United States and Canada. Techmire is particularly recognized for its multi-slide die casting machines, which feature a distinctive and advanced die casting process.
The Urpe CC25 is a hot chamber die casting machine tailored for non-ferrous metal applications. It features an electric furnace with a 240 kg capacity, capable of reaching temperatures up to 750°C. The machine offers a casting force of 42 kN and a plunger stroke of 85 mm. The Urpe CC25 supports manual, semi-automatic, and automatic operation modes, with user-friendly controls conveniently positioned on the machine.
The ZL60 is a versatile zinc die casting machine designed to accommodate a wide range of applications.
The ZL60 features a modular design, enabling customization to meet specific production requirements. It is equipped with a robust hydraulic system that provides high clamping forces and accurate injection. The machine includes an intuitive interface for straightforward operation and monitoring. Additionally, it incorporates energy-saving technologies and optimized cooling channels to enhance overall efficiency.
The HMT1600 is a heavy-duty zinc die casting machine known for its durability and strength. It employs advanced control technology to ensure precise and consistent casting outcomes. With its large platen size and high clamping force, it is well-suited for managing complex molds. The machine features a multi-stage injection system for improved shot control and includes safety features and an ergonomic design for enhanced operator comfort.
The ZDC-2000 is a compact and efficient zinc die casting machine optimized for high-speed production and reduced cycle times. It utilizes advanced hot chamber technology for accurate metal injection and facilitates rapid tooling changes with minimal maintenance. Additionally, the ZDC-2000 features a user-friendly control system equipped with sophisticated diagnostics and troubleshooting functions.
The ZP 8 is a high-performance zinc die casting machine designed for large-scale production. It boasts a modular construction that allows for flexible customization. The machine uses energy-efficient servo technology for precise control and includes an integrated spraying system for die lubrication and cooling. Additionally, the ZP 8 is equipped with a comprehensive monitoring system to optimize the casting process and detect faults.
Keep in mind that the availability and features of specific models may change over time. For the latest information on models that best meet your needs, it is recommended to contact the manufacturers or their authorized distributors.
Zinc alloys employed in zinc die casting include varying percentages of other metals like aluminum, magnesium, copper, iron, and tin. These additions modify and improve the properties of zinc. The selection of a specific alloy depends on the required characteristics and performance of the finished part, as each alloy offers distinct attributes. Die casting manufacturers typically provide a range of zinc alloys with detailed descriptions. The choice of alloy is guided by the specific application of the cast part.
Zinc alloys encompass a broad spectrum of metals, ranging from those used in soldering and coating to those specifically designed for die casting. The composition and types of metals used in these alloys vary based on the proportion and type of alloying elements. Zinc alloys are categorized by their composition, processing techniques, performance characteristics, and intended applications.
Zinc alloys offer a high melting point, excellent corrosion resistance, a strong strength-to-weight ratio, affordability, and non-magnetic properties. They surpass carbon steel in shear strength, making them well-suited for structural support and load-bearing applications, such as in medical equipment and computers.
Zamak 2, also known as Kirksite, is the most robust and hardest alloy in the Zamak series due to its high copper content of 3%. Zamak alloys are zinc-aluminum alloys with an aluminum content of 4%. The name "Zamak" originates from Germany, where it stands for zinc, aluminum, magnesium, and Kupfer (the German term for copper). Zamak 2 offers excellent castability and creep resistance, with a melting point ranging from 2615°F to 2635°F (1435°C to 1446°C) and a Brinell hardness of 100.
Zamak 3 is the most commonly used alloy in zinc die casting, favored for its excellent castability and long-term dimensional stability. It can be easily plated, coated, and treated with chromate. Like other Zamak alloys, Zamak 3 contains aluminum, copper, magnesium, lead, cadmium, and tin in varying amounts. It has a Brinell hardness of 82, with a tensile strength of 283 MPa and a yield strength of 221 MPa. The popularity of Zamak 3 in die casting is attributed to its outstanding strength and ductility.
Zamak 5, the most widely used zinc alloy in Europe, features a higher copper content compared to Zamak 3, which reduces its ductility and makes it less flexible and more challenging to bend or shape after casting. The increased copper content—by an additional 1%—enhances its corrosion resistance, hardness, and strength. Zamak 5 is suitable for plating, polishing, finishing, and machining, with a melting point ranging from 380°C to 386°C (717°F to 727°F). Its remarkable strength makes Zamak 5 a popular choice globally for producing wheel balancing weights, automotive engine components, and die-cast toys.
ZA 8 stands out from other Zamak alloys due to its higher aluminum content, approximately 8.4%. It is unique among zinc alloys for its suitability for hot die casting, owing to its superior tensile strength, hardness, and creep resistance. In addition to its aluminum content, ZA 8 includes small amounts of magnesium and copper, contributing to its status as the lowest density zinc die casting alloy.
ACuZinc5 features a copper content ranging from 5% to 6% and an aluminum content between 2.8% and 3.3%. This alloy has a significantly higher copper content compared to Zamak 3, Zamak 5, and ZA 8, while its aluminum content is comparatively lower. ACuZinc5 exhibits enhanced tensile strength and creep resistance, with a Brinell hardness rating of 118. The elevated copper levels also provide ACuZinc5 with superior wear resistance, comparable to that of bronze and aluminum alloys.
EZAC is a specialized zinc alloy that combines zinc, copper, and aluminum to offer exceptional strength, hardness, and long-term creep resistance. Creep refers to the gradual deformation of die-cast components under stress and high temperatures over time. Zinc's inherent resistance to creep is one of the key reasons for its widespread use in die casting applications.
EZAC was developed to address the need for a zinc alloy with enhanced mechanical properties, particularly in terms of creep resistance. Following extensive research and development, engineers introduced EZAC to tackle issues related to creep. This alloy maintains its dimensional stability even at temperatures up to 212°F (100°C), making it an ideal choice for hot chamber zinc die casting.
ZA-12, typically used in gravity casting, is also suited for cold chamber die casting when higher strength and durability are needed. It offers tensile strength ranging from 276 MPa to 317 MPa and a yield strength of 214 MPa. ZA-12's robustness makes it ideal for components with thin walls. Like other substantial zinc alloys, ZA-12 is known for its excellent strength, hardness, creep resistance, and dimensional stability. The '12' in ZA-12 denotes its 12% aluminum content, consistent with the naming convention of the ZA series of alloys.
GDSL is an ultra-thin zinc alloy with higher levels of copper and aluminum. It is based on the zamak alloys and offers exceptional castability. Known as the ultra-thin casting alloy, GDSL boasts fluidity characteristics similar to high fluidity alloys, allowing for casting parts with wall thicknesses as thin as 0.3 mm (0.012 inch). Often referred to as "superloy," GDSL provides superior strength, elongation, and creep resistance. It also requires less injection pressure and plunger speed for hot chamber casting.
Zinc is highly effective for creating components with detailed and intricate designs, especially those requiring thin walls and superior electrical performance. Its casting properties make it suitable for applications where precise detail and tight dimensional tolerances are crucial. As the fourth most widely used metal globally, following iron, aluminum, and copper, zinc die casting is extensively employed in manufacturing parts for various construction and industrial applications. Its most notable application is in the automotive industry, where die casting technology was first developed.
Hot chamber zinc die casting is an efficient and high-output manufacturing technique, particularly favored in the automotive industry. This method is known for its ability to quickly produce high-quality components with precise tolerances while being cost-effective and resource-efficient. In automotive manufacturing, zinc die casting is often preferred over aluminum due to its lower production costs and longer tool lifespan.
Components for vehicles made through die casting include:
The choice of zinc die casting for medical devices is driven by the need to meet stringent clinical requirements, reduce human error, and enhance patient safety. These instruments must be biocompatible, easy to clean, and resistant to antimicrobial agents, maintaining their functionality even after frequent sanitation.
Zinc's exceptional hardness, self-lubricating qualities, dimensional stability, and high modulus make it an excellent choice for precision medical instruments. The increasing need for advanced medical devices also drives the incorporation of intricate details and fine adjustments, which zinc die casting can efficiently accommodate.
Today's medical instruments often contain delicate electronics for measuring and recording patient information. To prevent electromagnetic and radio frequency interference, which can disrupt readings, zinc’s shielding capabilities are utilized to safeguard these devices and maintain their accuracy.
The use of zinc alloys for the manufacturing of locks is due to its castability, ability to create complex shapes, thin walls, and exceptionally smooth surfaces. The price of materials for casting locks is low, which makes their selling price lower than other metals. Zinc locks can be produced in a wide variety of shapes to fit the needs of diverse and unique applications.
Zinc die castings are utilized to shield against electromagnetic interference and to help absorb vibrations, crucial for protecting electronic components. Its versatility in casting allows zinc to be molded into various shapes, making it adaptable to diverse electrical applications.
Zinc die cast heat sinks are preferred over aluminum ones due to their capacity to form complex and detailed shapes. Zinc heat sinks can integrate fins directly into the frame, housing, or enclosure, reducing thermal resistance. They also offer dimensional stability and effective shielding against EMI and RFI. Despite being heavier than aluminum alternatives, zinc heat sinks are valued for their high-quality finish and cost-effectiveness.
Zinc's versatility allows it to be customized and engineered to suit a wide range of design requirements. Before opting for zinc die casting for a custom project, it's crucial to evaluate key factors to ensure success. One of the primary considerations is selecting the appropriate zinc alloy that meets the application's specific needs. Consulting with experts in zinc die casting can help determine the best alloy for the job.
Choosing the right zinc alloy involves selecting an appropriate die casting method that aligns with the alloy's properties. Some alloys are better suited for hot chamber die casting, while others are ideal for cold chamber die casting. Key factors in this decision include the alloy's density, which is affected by copper content, and the overall cost of the process. Typically, zinc die casting is efficient, cost-effective, and optimizes resource use, making it a time-saving option.
Zinc is a versatile, robust, and corrosion-resistant metal alloy known for its malleability. It can be easily molded to suit various applications. Its durability and resistance to creep over time make it an excellent choice for a diverse range of projects.
Zinc die casting offers an economical solution for producing robust and durable components. This method yields parts that are strong, resilient, and precise, all while remaining cost-effective. The mechanical properties of zinc die castings can equal or surpass those of other casting metals such as aluminum, magnesium, bronze, and cast iron.
In die casting, the most significant cost is tooling for the creation of dies. The process of tooling takes hours of machining, preparation, and craftsmanship to produce dies with exactly the right shape, tolerances, and dimensional accuracy. Zinc die casting dies last ten times longer than aluminum dies and five times longer than magnesium dies due to zinc’s low melting temperature.
The expense of aluminum dies is influenced by the use of high-quality, costly H13 tool steel, which is required due to aluminum's higher thermal properties. This premium steel is essential for handling the heat involved in aluminum die casting. In contrast, zinc dies are produced using P20 steel, which is more affordable than H13 steel, thereby reducing the initial cost of manufacturing zinc dies.
Zinc dies offer exceptional durability, leading to reduced repair needs, minimized downtime, and increased production capacity over their lifespan. A single zinc die casting die can produce over one million components throughout its service life, significantly lowering the cost per part.
Maintaining durability and rigidity is essential in die casting, particularly for medical equipment and instruments. Zinc die casting offers components with an optimal strength-to-weight ratio, enhancing their robustness, resilience, longevity, and rigidity.
Zinc alloys that can be cast achieve tolerances as tight as ± 0.001 inch (0.0254 mm) for smaller components. This high level of precision often negates the need for additional machining. Furthermore, the accuracy of zinc die casting enables the creation of designs with thin yet strong walls. It is feasible to manufacture parts with wall thicknesses as small as 0.006 inch (0.15 mm), resulting in more compact, lightweight, and cost-effective components.
In addition to its precise tolerances, zinc die casting enables the production of multicavity components with intricate designs and shapes, maintaining consistency across all units. These parts exhibit resistance to heat and wear, and retain their dimensional stability over time, without experiencing creep.
Zinc die cast alloys are known for their superior impact strength and remarkable ductility, which is beneficial for machining after casting. These alloys exhibit greater impact resistance than aluminum and magnesium die castings, even in extremely low temperatures. Moreover, zinc alloys offer excellent corrosion resistance, high rigidity, and exceptional toughness in their mechanical properties.
Zinc die castings are effective conductors of heat and electricity, making them suitable for applications like heat sinks that require efficient heat dissipation. Their capacity for thin-walled designs allows for various fin and cooling pin configurations, enhancing thermal management. Additionally, the electrical conductivity of zinc die castings provides effective shielding against EMI, RFI, and ESD.
A key advantage of zinc die castings is their capability to create highly complex and detailed shapes while maintaining excellent load-bearing strength. This makes them particularly well-suited for manufacturing components like bushings.
Zinc die casting initially gained attention due to its excellent surface finish. The smooth and visually appealing finish of zinc die castings makes them perfect for applications where both functionality and aesthetics are important. Moreover, the casting process itself yields a high-quality surface with minimal need for additional machining.
Zinc die casting boasts a cycle rate that is 150% to 200% faster than aluminum, thanks to zinc's lower melting point. The hot chamber die casting method integrates melting and injection into a single process, enhancing efficiency and accelerating production. Additionally, the rapid solidification of zinc castings shortens cycle times, boosting productivity and significantly lowering casting costs.
Using a combination or unit die allows for the casting of an entire assembly in a single cycle, leading to significant cost savings, reduced labor expenses, and enhanced efficiency. This approach enables the production and assembly of a full set of individual parts in just one casting cycle.
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