The aluminum die-casting foundry
Halls K10 and K11, located in the southern part of the area, accommodate the aluminum die-casting foundry and the mechanical processing of the components. Audi, the leading automotive brand in the field of lightweight construction, has adopted a new approach here: The facility’s own foundry once again extends the boundaries of what is technically feasible; it takes on the role of innovation leader and thus pushes technical progress forwards. New alloys and high-end manufacturing methods allow the production of components with lower material thicknesses which are at the same time extremely light, strong and precise.
In its layout, the foundry follows the principles of the Audi Production System (APS), which focuses on efficient and ergonomic working routines. For example, the large die-casting cells are mainly set into the floor. Thorough cleanliness is a matter of honor for Audi – something which is not always taken for granted in the foundry industry.
The first processing stage in Hall K10 is to smelt the aluminum blocks that have previously been delivered. Pick-and-place machines transport the approximately 60-centimeter-long bars into two gas-fired furnaces operating day and night with a highly energy-efficient bath-smelting process. One furnace is designed for naturally hard aluminum alloys, the other for hardened aluminum alloys; each of them can smelt 2.5 tons of material in one hour.
When the alloys are fluid at a temperature of about 700 degrees Celsius, lift trucks transport the molten mass in closed, insulated crucibles to the fully automated die-cast cells. The first two of these large pieces of equipment was set up in the fall of 2013 with another three to follow. Several holding furnaces in the cells keep the molten metal at a constant temperature.
The actual casting process takes about 80 to 120 seconds. The two halves of the heatable tool, sprayed with an emulsion of water and separating agent by a robot, are evacuated and closed with a pressure of 4,400 tons. The required amount of molten aluminum first flows into the filling chamber. From there, the hydraulically operated die-casting piston shoots it into the steel molds with a speed of 25 meters per second. The piston maintains a static pressure of approximately 200 bar until the aluminum is completely solid.
After the so-called “shot,” a robot retrieves the component, which now has a temperature of about 300 degrees Celsius, out of the mold and lays it in a lifting station, which lowers it into a tank of water for further cooling. From there, it is taken to the stamping press, which is integrated into the die-casting cell. Excess metal is removed here and then smelted once again for optimal recycling. The components are then marked with their part numbers at a marking station and checked with measuring instruments using x-rays and spectral analysis.
In the adjacent Hall K11, the aluminum components are affixed to ultramodern processing machines. In this stage of processing, the parts are drilled and milled with the utmost precision. The fitting of threaded inserts in various sizes enhances the strength of the threads. Subsequently, all components pass through a tank in which they are washed, cleaned and conversion coated. At the end of the manufacturing process, so-called blind-rivet nuts are inserted in the thin-wall components for assembly at a later stage.
The production of structural components in Münchsmünster has been designed for a daily capacity of 2,500 units. Some of the structural body castings for the Audi models with longitudinally mounted engines are produced here. At present, these are the long connecting elements between the sills and the rear longitudinal chassis beams, the so-called overhead carrier for the pedal holder, and the supports for the front suspension struts. All components are substantially lighter than conventional welded parts made of steel plate; with the strut supports, weight savings of about 30 percent are achieved.