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There are many reasons that automakers add metalcasting capacity, but all of these generally amount to two necessities: the producers require more casting volume and better casting quality to meet changing demand. Each of these is on display among the many projects recently completed or still in progress for automotive foundries.
Automakers were among the hardest hit by the global recession of 2008, and their casting operations were not spared in the downsizing that followed. But since the start of the economic recovery, automakers have been investing generously in new plants, new equipment, and new capabilities.
For example, Teksid Group added production of compacted graphite iron cylinder heads at its foundry in Monclova, Mexico, putting it in position to supply CGI parts just as that lightweight alternative takes a new prominence in gas engine programs. Teksid is understood to be adding CGI at its Brazilian foundry, too.
In the North American auto industry, General Motors included its foundries in Saginaw, MI, Defiance, OH, and Bedford, IN, in the series of capital programs that eventually totaled more than $2 billion, to install production capabilities for its more fuel-efficient Ecotec engines. GM is also expanding its powertrain operations Mexico, including new melting and pouring capacity.
Chrysler Group LLC initiated a $374-million program last spring at the Kokomo, IN, aluminum diecasting operation and the adjacent powertrain plants. Another $162 million was targeted to buy and retool a third transmission plant in Tipton, Ind.
Transmissions were the point of Honda’s $50-million expansion of aluminum melting and high-pressure diecasting capacity at Russells Point, OH. It initiated a third transmission assembly line nearby, and the new casting capacity will supply that program.
The domestic metalcasting industry also has seen some considerable capital investment by automotive Tier suppliers: Magna International acquired an idle plant in Holland, MI, and remodeled it to produce high-pressure diecastings at a reported cost over $160 million.
But, among the world’s automakers the boldest investment recently was made by Audi AG, which took the ‘clean slate’ approach to addressing new demand. The luxury automaker has been increasing its global footprint in pace with its rising output, but operations at its main assembly plant in Ingolstadt, Germany, were not optimal for the production capacity that Audi intended. Thus, in 2012 the plan was put forward to build a new production center for diecast aluminum structural parts and hot-and cold-formed steel panels, at a greenfield site.
New Competency Centers
The new plant in Münchsmünster is approximately 30 km east of the Ingolstadt plant, and the automaker describes it as an element of its overall expansion program: it adds capacity for critical products, and it reduces the pressure for productivity on the main plant. Further, it allows Audi to establish new competency centers for automotive suspension parts. It sees the new plant as a foundation for its lightweight design objectives, but also indicated the plant’s “new production methods extend the boundaries of what is technically feasible.”
The start-up for the 3 million-square-feet plant, carefully estimated to have cost a “low three-digit million” figure, took place in late 2013, and operating capacity will be increased in stages toward full capacity by 2016. By then, it will occupy about 800 workers.
The foundry represents just part of the overall operation at Münchsmünster. Aluminum melting is done in two Ecomelt multi-chamber gas-fired furnaces, designed by Hertwich Engineering to process scrap from various sources (including ingots as well as painted or foil-coated scrap, beverage cans, automotive trimmings, chips, etc.) The furnaces perform the necessary pyrolysis and combustion of VOCs that are needed for such charge materials. An electromagnetic pump circulates molten metal between the furnace chambers.
The furnaces preheat the scrap to optimize melting cycles and conserve thermal energy, and while overall energy consumption is low thanks to effective automation, the level of metal loss is significantly reduced and metal quality is enhanced. Together, Audi’s two melting furnaces are rated to produce 100 metric tons of liquid metal per day.
Hertwich Engineering also supplied the new foundry with a multi-container charging system, crucibles, melting tanks, and a crucible charging and treatment station.
Audi claims the new foundry’s layout upholds the Audi Production System, a management program that emphasizes efficiency and ergonomic working routines. For example, the large diecasting cells are installed below the main floor level to reduce lifting and bending requirements, and to help maintain overall cleanliness in the plant.
The first process step is remelting aluminum ingots. Pick-and-place robotics transport 24-in. bars to the furnaces, operating round the clock. One furnace is designed to handle naturally hard aluminum alloys, the other for hardened aluminum alloys, but both are able to remelt 2.5 metric tons/hour of the alloyed charge material.
At about 700°C, when the alloys are fluid, lift trucks transport the molten metal in sealed, insulated crucibles to the automated diecasting cells. Two cells were installed at the plant’s start-up last fall; three more will be in place by the time the plant is completed. A series of holding furnaces keep the molten metal at a constant temperature as it waits to be cast into shape.
Automated Diecasting Cells
The pouring process is fast, 80-120 seconds to complete mold filling, according to Audi. The two halves of the heated tool are robotically sprayed with an emulsion of water and a separating agent, then closed with a pressure of 4,400 metric tons. The required volume of molten aluminum flows into the filling chamber, at which time the hydraulic piston injects it into the steel molds at a rate of 25 meters/second. The piston maintains static pressure of approximately 200 bar until the aluminum is fully solidified.
After the “shot,” a robot retrieves the 300°C component from the mold and lays it in a lifting station. The casting is lowered it into a cooling water tank, from which it will be collected and transported to a trim press integrated with the diecasting cell.
Excess metal is trimmed from the casting, and it is returned to the melting area for recycling.
Finished castings are marked with part numbers and inspected by X-ray and spectral analysis.
In an adjacent production hall, aluminum components are processed further. Each part is automatically milled and drilled with precision, and threaded inserts of various sizes are fitted to the castings. At this point, all components pass through a tank for cleaning and conversion coating. In the final stage of manufacturing, “blind-rivet nuts” are inserted in the thin-wall components for assembly at a later stage.
Audi designed the Münchsmünster foundry to produce aluminum structural nodes for vehicles with longitudinally mounted engines, at a rate of 2,500 per day. 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 the components are substantially lighter than conventional welded parts made of steel plate, Audi emphasized, achieving weight savings of about 30%.