Small, large, delicate, thin, fast – zinc die casting is the answer

The die-casting mold closes, and then, under high pressure, liquid melt is poured in, defining the entire technological-metallurgical design of the component. All of this happens within 10 to 20 milliseconds, barely perceptible to the human eye – after all, a single blink of an eye takes a proud 100 milliseconds. Broadly simplified, this describes the most crucial step of the zinc die-casting process.

The sequence of the zinc die-casting process has fundamentally remained unchanged since the method became known in the early 20th century. Notably: nothing fundamental. However, like any process, zinc die-casting has proven over the past decades how much potential for performance enhancement and innovation lies within. Zinc die-casting meets various requirements. Performance and records aside: simply bigger, faster, further – in the spirit of the Olympic idea – are not the deciding criteria in zinc die-casting.

"When looking at requirements for today's zinc die-casting products, fast production and the realization of large components play a role. In addition, parts that are thin-walled, small, and delicate, often with high functional integration, stand out visually and are still quickly, efficiently, and of high quality. All these requirements have changed the zinc die-casting process – and can be achieved with it. Modern die-casting machines and innovative process techniques are available for this purpose," explains Dr. Norbert Erhard, former CEO of Oskar Frech GmbH & Co. KG, whose business activities range from the production of hot chamber and cold chamber die-casting machines to tool technology and automation of die-casting cells.

Strict standards in zinc die-casting

From tooling to manufacturing, strict standards are applied in zinc die-casting. Human, tool, material, machine, and process: these five criteria form the success team for powerful and innovative zinc die-casting. For zinc die-casting parts to be perfectly integrated into their respective application areas, strict standards apply from tooling to production. The material used, shrinkage of the cast part, design of the mold, process stability. Many parameters are considered to ensure the final result is correct, and no subsequent processing is required.

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60 to 70 percent of a component's quality is created in the tool. Intelligent component design ensures that demanding geometries can be cast with maximum precision and highest quality. Specialists in engineering and design are in demand here – the human being is at the center of the entire process.

Dr. Frank Kirkorowicz, CEO of Adolf Föhl GmbH + Co KG

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Alloys for thin-walled designs

Speaking of "material": alloys ZL 0400, ZL 0410, and ZL 0430 have established themselves in practice. They are based on fine zinc with a purity of 99.995 percent zinc. Aluminum, copper, and magnesium are further components that significantly influence the alloy's property profile. Copper improves tensile strength and hardness, magnesium prevents intercrystalline corrosion, and aluminum favors zinc's processability as well as its most important properties, such as tensile strength, elongation at break, and impact bend strength.

"The fact that predominantly only three alloys are used in zinc die-casting is very comfortable," says Kirkorowicz, "however, optimized alloys make more applications possible – especially when thinking about the electronics sector, where components must be much thinner."

This is where so-called High-Fluidity alloys come into play, which were specifically developed for thin-wall casting and have the same good mechanical, electrical, and thermal conductivity properties as classic alloys, but are up to 40 percent more flowable.

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While in the 1990s, wall thicknesses of 1.5 mm were state-of-the-art, today a thickness of 0.5 mm is standard due to process optimizations. Yet, development continues, so 0.3 mm or even 0.2 mm are already technologically feasible.

Dr. Norbert Erhard, former CEO of Oskar Frech GmbH & Co. KG

Further development opportunities: Additive Manufacturing

Efficiency and innovation in machine and process technology are other central topics when it comes to performance enhancement in zinc die-casting. Mold filling and solidification simulations create a series-like preliminary stage from an idea even before tooling. This provides an assessment of how the cast product will behave – various variables such as temperature and air levels are taken into account.

3D printing with fine zinc powder is increasingly being used for prototyping. In the area of small quantities, the transition from rapid prototyping to additive manufacturing has already been made. The latter shows its strengths where a high degree of design freedom, function optimization, and integration with extremely light and stable complex structures is required.

Modern machines for accurate repeatability

And the die-casting machine itself? Kirkorowicz: "Today's die-casting machines are easier and more precise to operate, ensuring accurate repeatability of processes. Control, monitoring, and visualization of the die-casting machines have developed enormously – for example, through sensors in the tool that guarantee contour-based manufacturing. Milestones are the near-gateless/ gateless casting and real-time control, which enable targeted braking with minimal mold filling time. The fact that machines can readjust themselves using algorithms is still a glimpse into the future, but this will be possible in the foreseeable future."

Erhard adds: "Die-casting machines today must do more than just cast. It's also important, for instance, to minimize resources. By avoiding runners, savings can be made in two ways: on the one hand, less material is consumed, and on the other hand, the required energy is reduced, which protects the environment."

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Larger, smaller, more delicate, thinner, produced faster

Zinc die casting scores points in all these disciplines – and, in a metaphorical sense, can climb podium places. Both now and in the future. The list of existing and potentially future areas of application is long. A single glance at the automotive industry shows: Although the proportion of zinc die-cast products in cars has slightly decreased in Europe, this is almost offset by a doubling of the number of components made from zinc die casting.

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The electronics sector is also a rapidly growing market – regardless of whether you think of smart solutions for one's own home or electric cars. Nowadays, every compact car has more control units and communication interfaces than luxury vehicles did ten years ago. Additionally, the concept of the "Smart Home" is becoming increasingly important – this is where zinc die casting is gaining general significance.

An assessment that Kirkorowicz shares: "In the areas of e-mobility and Smart Home, safety and connectivity are paramount. Individual parts are becoming smaller and more precise. Zinc die casting can score here – especially when, as in these areas, large quantities are involved – and it is increasingly becoming the production method of choice." The natural element of zinc, with its recycling potential and low energy requirement in the melting process, is a perfect basis for these future developments and requirements.

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