Lowering the Pressure on Diecasting Development

May 16, 2021
A new research foundry adopts a series of flexible melting and forming capabilities that suggest a new range of possibilities for low-pressure diecasting.

Diecasting has earned considerable attention from industrial designers in recent years, regarding finished products and consequently production systems. This is mainly the outgrowth of those designers’ efforts to develop lighter versions of standard products, in automotive manufacturing most obviously. Those efforts led to the development of structural castings and drivetrain parts designed in aluminum alloys, for volume production. High-pressure diecasting is adopted to manufacture parts that might otherwise be produced by sand casting or investment casting, often to be followed by extensive finish machining and assembly. HPDC makes it possible to produce highly detailed but lighter engine and drivetrain components, lighter structural parts, and possibly to eliminate some post-production steps.

The next turn in this tale involves systems for producing those parts, and the recent emergence of super-sized machines to produce lightweight diecastings of expanded dimensions.

And both of these ongoing trends will leave some asking: What else can diecastings do? Germany’s Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM) opened a new research operation in Wolfsburg, Germany, to address that question, but there the focus is on low-pressure diecasting.

Low-pressure diecasting accounts for a much smaller proportion of all diecasting operations than HPDC. Typically, it is applied for alloys with low melting points (e.g., aluminum alloys) and parts weighing up to 150 kg (about 325 lbs.) The advantages of LPDC are that it can form very high-strength parts with complex geometries and excellent dimensional accuracy. Solid castings with thick walls are typical applications, such as light-alloy automotive wheels, but also some chassis and drivetrain components and housings.

IFAM’s LPDC foundry is intended to host applied research projects, with conventional melting and casting capabilities for aluminum but also higher-temperature melting, for example for copper alloys. This multi-functionality is possible thanks to both direct and indirect induction melting and a “crucible quick-change system.” It can melt standard metals (aluminum, copper, brass, bronze, magnesium, or steel) as well as non-metallics, like salt mixtures.

Currently, salts are a medium being studied for “lost core” processes using HPDC to develop hollow castings, like engine and battery housings. IFAM suggests its new foundry could be a center for researching salt cores in low-pressure diecasting.

The new foundry’s furnace is a 110-liter, 130-kW vessel for melting at up to 1,650 °C, with casting pressure up to 1.0 bar. The 1,310 × 1,290 mm2 lower mounting surface can accommodate molds weighing up to 3,500 kg. The upper mounting surface of 1,200 × 1,200 mm2 allows a maximum clamping force of 60 metric tons.

A vertically movable furnace chamber allows free accessibility of the melting crucible -- for quick alloy changes. In addition to the flexible processing of different melts, the plant can work with conventional steel molds, as well as sand or semi-molds.

Fraunhofer IFAM also has invested in a Kurtz AL 16-12 LPDC system, to be commissioned later this year.

The new plant concept was developed in collaboration with TEGISA Giessereianlagen und Industrieöfen GmbH, based on a prototype in operation at Fraunhofer IFAM in Bremen since 2015.

Examples of research to be taken up by IFAM include composite casting for integrating metallic structures and profiles (aluminum or steel) directly into a casting; combining low-pressure diecasting with non-metallic primary or forming processes (e.g., sheet metal forming or plastic injection molding); or producing cast rotors for electric drives – generally a product of high-pressure diecasting.

The capabilities adopted by IFAM indicate a new range of growth possibilities for LPDC.