Special Requirements for Die Casting

In recent years, the scope of magnetic clamping plates as fast and reliable clamping devices for molds has broadened beyond plastic and rubber processing to include sheet metal forming and the die casting industry. Hilma-ROEMHELD, based in Hilchenbach in the Siegerland region of Germany, has been a global leader in hydraulic and magnetic clamping devices and has been pioneering the introduction of magnetic clamping technology to the die casting industry since 2003.

One significant advantage of these clamping devices is their ability to quickly position and clamp molds of all sizes and shapes, including non-standard ones, without requiring mold standardization. They are versatile, suitable for a variety of applications, and can withstand ambient temperatures up to 240°C, or 465°F. Moreover, existing systems can typically be retrofitted with ease, depending on the application. The operation of these devices is straightforward, allowing clamping even in hard-to-reach areas, which enhances work safety. Additionally, the low-distortion and highly precise clamping reduces mold wear and increases process safety, making magnetic clamping technology ideal for producing components with narrow dimensional tolerances.

An Alternative to Hydraulic Clamping

In 2006, the design engineers at Oskar Frech sought an alternative to hydraulic quick-clamping systems and mechanical clamps for hot chamber die casting, aiming to facilitate simple, fast, and flexible mould changes. This search was driven by requests from two zinc casting industry clients who needed clamping equipment that allowed frequent mould changes in small series without the need for reworking the tools. After testing various magnetic clamping technologies, the team led by design manager Jürgen Kurz chose the clamping devices from Hilma-ROEMHELD GmbH.

Hilma-ROEMHELD is a leading expert in mold clamping and effective mold change in mechanical engineering, forming technology, and the plastics and rubber industry. The company develops, produces, and distributes individual clamping systems and standard fixtures for production on a global scale, with magnetic clamping technology playing a crucial role. As part of the ROEMHELD Group, Hilma is supported by sales and service companies in 39 countries across all continents.

Advantages and Adaptations of Hilma's Magnetic Clamping Technology in Die Casting

In addition to the benefits, the design engineers saw Hilma's magnetic clamping technology as advantageous due to its intrinsic safety, user-friendly operation, and easy integration into their die casting machines. A key benefit was the significant reduction in setup times, with savings of up to 40 minutes per operation compared to traditional clamping claws.

However, material limitations had to be considered: the processing of aluminum and magnesium involves very high temperatures around 650°C or 1200°F, which would damage the magnetic plates over time, making the technology unsuitable for these metals. In contrast, zinc die casting operates at processing temperatures around 420°C or 790°F, with the molds being heated only to 180 °C, allowing the use of magnetic clamping technology. Consistent and even temperature distribution over the entire mold is critical, as fluctuations of more than ten degrees can impair the quality of the cast product. The elimination of clamping slots contributes to this constant temperature distribution, adding another advantage to the use of magnetic plates.

To adapt the system to the specific production conditions in die casting, various modifications were made to the control system. In hot chamber die casting, with closure forces between fifty and eighty tons and mold weights up to 400 kilograms or 880 pounds, very high ejection forces for the cast product could occur when opening the molds. Without changes to the control software, using magnetic clamping technology could lead to operating errors and malfunctions. There was a risk that the mold could shift during the uncontrolled ejection of cast products, triggering error messages and causing machine downtime. However, by limiting the ejection forces through the control system, this risk was effectively reduced without significant effort.

Successful Integration and Future Prospects of Hilma's Magnetic Clamping Technology in Zinc Die Casting

Following the integration of Hilma technology into the zinc hot chamber die casting machines of the "DAW-F" series, Oskar Frech delivered three machines to customers in various European countries in 2007. Since then, these machines have operated continuously and without issues, as reported by design manager Jürgen Kurz, who notes the satisfaction of their customers. The evaluation phase is set to continue until the end of 2009, after which the chief designer and his team will review the accumulated experiences. Kurz envisions future applications for magnetic clamping technology in die casting, particularly for zinc casting customers who frequently change molds in small batches. For these users, the reduced set-up times and increased productivity result in significant cost savings.