Audi Toolmaking occupies a leading position among the international competition, an achievement confirmed not least by multiple overall victories in the renowned competition “Excellence in Production”. The department also has a key position within the company: It covers the entire process of sheet-metal production, making it an indispensable contributor to the precision of Audi car bodies. With realization of the “smart factory”, Audi Toolmaking is developing intelligent tools and currently testing a 3D printer for printing metal.
Precision to within one hundredth of a millimeter: the intelligent tools
Were it not for the uncompromising precision in toolmaking and in the press shop, it would be impossible to convey Audi’s striking design characteristics, with their crisp edges and tight radii. The aluminum engine compartment lids of the models in the Audi A3 and TT families, for example, have outer shells with two sharp contours. These “swoosh lines,” as they’re called by people at the company, are created by means of an innovative Audi Toolmaking technology: intelligent tools. These tools are further improving the contours’ precision, which is already in the hundredth of a millimeter range.
Like any mechanical process, the forming of the sheet-metal blanks and aluminum blanks in the press can be influenced by certain variable factors. In some instances, the material composition of the blanks or their lubrication is not entirely uniform,for example. That effects how the sheet metal is drawn in on the flange (on the edge), which in turn is needed for the metal to be drawn over the form. If that happens too slowly compared to the specified sample, the tension is too high. In this case, slight cracks could form. But if, on the other hand, the sheet metal is drawn in too rapidly, the strength of the component could suffer.
Intelligent tools are the answer to this challenge. Four lasers are installed in the tool for the engine compartment lids of the Audi A3 and Audi TT; they measure the drawing in of the flange and then send their data to a computer. In the event of deviations from the target value, the tool regulates the clamping forces of the four drawing aids that precisely clamp the sheet metal in the flange area, each with about 30 metric tons of force, by means of an electric actuator, a type of motor.
The intelligent tools are a development that sums up the Audi philosophy in a nutshell. They reduce the number of rejections, save on material and therefore support sustainable production. The tools also enable stable processes of reliable, consistently high quality and continue to raise the bar in terms of what is physically feasible. Aluminum, a relatively brittle material, is giving the brand an opportunity to really display the depth of its expertise – the new Audi TT is the aluminum car with the tightest radii in the world.
Development in the field of intelligent tools got started six years ago, at the initiative of Prof. Dr.-Ing. Hubert Waltl, who today is Board Member for Production. Today, Audi is using a total of 12 such tools at the Ingolstadt, Neckarsulm, Bratislava and Győr sites. Looking to the future, the brand’s experts are already giving lots of thought to new solutions in the areas of sensor systems and actuator technology. In a further step, the tools could communicate with the presses, for example, to adjust the forces or their distribution as necessary.
Small series as a goal: screws from the printer
In many places 3D printers, which manufacture objects from plastic powder, have already been in use for several years. A new development, though, is the 3D printer that Audi installed at Toolmaking in October 2014. The printer uses a laser melting process to produce metal components whose complex geometries – as seen in cooling ducts, for example – make it hardly possible (if at all) to manufacture them with conventional processes.
The material for the laser melting process is metal powder with a grain size ranging from 15 to 40 thousandths of a millimeter – about half the thickness of a human hair. All materials that can be welded are suitable – tool steel as well as metals like aluminum and titanium. The printer fills in the powder in layers, and a CAD-controlled laser then melts and fuses it to produce the shape of the desired component. Whether nozzles, hinges or metal panels – with edge lengths of up to 240 millimeters (9.4 in) and a height of up to 200 millimeters (7.9 in), practically all forms and objects can be made. The printed components are as strong as conventionally manufactured components.
The large-scale 3D metal printer that Toolmaking is using at Audi’s Ingolstadt site is a pilot plant. The process – which encompasses programming, refitting and preparation of the printer – is still very time-consuming. Audi’s medium-term plan calls for reducing the time required, to make the printer a viable choice for production of small series components.
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