The next step: 3D printing with metal powder
3D printers that create objects out of powdered plastic are already firmly established. The next stage of evolution is 3D metal printers. Audi has already installed some of them in its Metal 3D Printing Center for production applications. They use the laser melting process to produce steel and aluminum parts out of metal powder. This process is applied today in series of tools. In the coming years, vehicle components for small production series could also be produced in this way.
In principle, all materials that can be welded are suitable for 3D printing – tool steel as well as aluminum or titanium. The process starts with metal powder with a grain size of 15 to 40 thousandths of a millimeter, similar to the thickness of a human hair. The printer deposits the powder in thin layers and the laser melts it in accordance with the CAD data, thus creating the contours of the part being produced. By means of 3D printing, also known as selective laser melting (SLM), objects can be produced with free, highly complex geometries that would be very difficult or impossible to produce with other methods.
Audi creates valuable synergies in the newly established Metal 3D Printing Center, which is located at the Audi Toolmaking division in Ingolstadt. Specialists from Toolmaking collaborate closely with experts from the Casting Technical Center of Production Planning. In cooperation with the Technical Development division, they use their three metal printers to produce steel and aluminum parts for testing in engines and suspension.
Before the Metal 3D Printing Center was founded, the tasks were distributed more specifically. The steel printers in Toolmaking primarily produced individual parts for press tools, such as cutting inserts and blades, as well as components with integrated cooling coils and networks. They improve cooling performance in large tools, which then accelerates casting or forming processes for example.
With the 3D metal printers in the Casting Technical Center, the main aim was to get to know the material “printed aluminum” and its production technology better. Various automobile parts were produced, such as space‑frame components that integrate fluid containers, and including the first suspension components.
The analysis and bench tests that Audi has carried out so far confirm the potential: Printed aluminum components have better specifications than parts made as structural castings. Their tensile strength of 400 million pascal is twice as high, and they have additional advantages in terms of weight. The situation with printed steel parts is similar; they achieve a tensile strength of more than one billion pascal.
A particularly impressive result of 3D metal printing is exhibited in the foyer of the Toolmaking building at the Audi plant in Ingolstadt: a model of the legendary Auto‑Union Type C racing car at half of its original size. Its chassis and external panels are printed out of aluminum and the instruments out of tool steel. Audi intends to go a long way with the new technology – as far as the moon in fact, with the self‑driving reconnaissance vehicle rover Audi lunar quattro, which is 85 percent printed aluminum. In the context of the Google Lunar XPRIZE, the Berlin engineering group “Part‑Time Scientists” plans to send the rover to the moon by rocket with Audi’s support by the end of 2017.
Today, 3D printing is still very expensive, limited in size and above all slow. The biggest of the three printers at Audi’s Metal 3D Printing Center can print objects up to 400 millimeters long; the two smaller ones manage lengths up to 290 or 280 millimeters. It takes about a day to produce a metal pipe weighing about one kilogram – plus the time required for programming and preparing the printer, as well as for subsequent work on the printed object, which is printed onto a support structure.
Audi believes that series application of the process will become possible when metal printing technology makes a great leap forward. And when that happens, the Audi brand will be at the forefront.
Fast assistance from specialists: the remote maintenance portal
Technical equipment in a production plant at Audi is planned, installed and controlled with the utmost precision. Nonetheless, due to its extreme complexity, it can never be completely free of malfunctions. In such a situation, the Equipment and Device Construction department of Audi’s Toolmaking division comes into action. With its remote maintenance portal, it serves as a central support facility and thus ensures uniform standards at all Audi plants all over the world. The remote maintenance portal started in 2008 and is available around the clock.
Audi Toolmaking’s remote maintenance portal supports body‑shop equipment at five locations. It also offers access to eight other technical areas – for example in Toolmaking and Technical Development in Ingolstadt, in Logistics in the Goods Transport Center in Ingolstadt, in the Paint Shop at the Neckarsulm plant, in Technical Development in Wolfsburg and in CFRP Production at Lamborghini. As well as a total of 13 current projects, there are 17 new requests. In the year 2015, there were approximately 1,600 deployments of the remote maintenance experts, where by about 1,500 hours were booked on equipment worldwide.
If an equipment operator – for example in Bratislava or at the youngest Audi plant in San José Chiapa, Mexico – recognizes a malfunction that cannot be resolved with local resources, support can be requested from the remote maintenance portal. The server identifies the external specialists whose technology is required and passes on the request for assistance. The employees then log on to the protected Audi production network via a secure connection and access the equipment – always in the restricted area for which they are authorized.
In this way, the external support employees can access the control monitor of the affected unit on their own display and can actively intervene, if desired by the local operator. They can install updates and backups or can reprogram the entire control system via closed virtual private networks (“tunnel services”). Video support in the new so‑called conference center is even more innovative: This is where pilot projects run, by which cameras, tablets and data glasses provide support with the transfer of images and plans.
As well as the typical rectification of a malfunction, the remote maintenance portal offers other possibilities: Some service providers use it to monitor a ramp‑up on their equipment. The advantages of remote maintenance are especially apparent in commissioning phases, which are constantly becoming faster: A lot of time, money and CO2, are saved because fewer journeys are necessary. Other areas of application include the qualification of components and staff – this is where the remote maintenance portal won the company’s internal “Audi Education Award” and the “Education Award” of the Volkswagen Group Academy in 2016.
Audi is already planning the next steps, with the goal of recognizing how equipment is changing and thus carrying out preventive maintenance. For example, if the welding gun of a car‑body robot is nearing its wear limits, the quality of the welding points decreases and each weld takes longer to carry out. Preventive remote maintenance – or remote monitoring – can avoid both problems. Also in this context, Audi plans to create a new standard with its remote maintenance portal.
The utmost precision in a tight process window: smart analytics in the press shop
Sophisticated design, systematic lightweight construction and intelligent functions – in the production of sheet‑metal parts, Audi’s press shops have to meet extremely high requirements. In order to fulfill rising quality standards in the future, the brand is applying the latest measuring technologies and developing a holistic data-collection system – in this way, the press shops are becoming part of the smart factory.
In the competence center for plant equipment and forming technology, which comprises the press shops and toolmaking, approximately 750,000 parts are produced at the four Audi press shops worldwide. The production of every car starts in the press shop, involving immense forces and highly complex functions.
A good example of this is Press Line 14 in the Ingolstadt North Press Shop. The large‑scale suction press there is 75 meters long and forms three‑dimensional parts out of flat sheet metal with up to 15 strokes and more than 7,300 tons closing force. For example, a side‑panel frame in the area of the door cutouts has a depth of about 30 centimeters. With its sharp edges, complex geometries, constant radii and a surface precision allowing tolerances of only a few hundreds of millimeters, it is typical of Audi’s high quality.
The process windows in which the press shops work are very small – and they will get even smaller in the future. This is why Audi has equipped its press shops with sophisticated measuring technologies.
The first measuring station is installed on the strip‑cutting machine, where the flat pieces of sheet metal are cut out of coils. The coils consist of rolled-up sheet metal with lengths of two to three kilometers and weighing 25 to 30 tons. They are never completely homogeneous, because the supplier’s manufacturing process is subject to fluctuations; various thicknesses, stretching or inclusions can affect the material’s tensile strength.
In the eddy‑current test on the strip‑cutting machine, a sensor scans the cutouts; its magnetic field penetrates the surface. The current is affected if any structural differences exist, and this is then registered by a receiver coil.
The next step on the strip‑cutting machine is that the layer of lubricant is automatically registered. This affects the material’s behavior when being formed. The third level of control is the so-called optical tear recognition by cameras. The cameras are designed to be extremely robust and are installed in different places – for example, in the waste chute of the first forming stage or on the parts bin of the sixth stage, which is not required for many sheet‑metal parts and therefore remains empty. In other cases, the cameras are in the so‑called feeder, a system of conveyors and suction arms that transports the parts to the next stage. The cameras monitor all of the forming processes in which the sheet metal is deep-drawn – from door inner sections to side-panel frames to the spare‑wheel well. These are the areas that are susceptible to tears. If the cameras recognize a defect, there is an audible warning signal. At the end of the line, the defective part is then illuminated so that the employees can immediately recognize and extract it.
In addition to optical tear recognition, Audi uses acoustic resonance analysis in some presses. Here, the sheet metal is struck by clappers; the frequency pattern that is produced is then compared with the norm pattern.
The intelligent tools that Audi now applies in its press shops all over the world have their own integrated monitoring and control units: Lasers monitor the so‑called flange feed during deep drawing and generate a large amount of data. When the computer recognizes deviations from the specified values, it modifies the clamping force in the tool with the help of active integrated components.
Intelligent tool technology is an important step towards full connectivity, which Audi aims to achieve in its competence center for plant equipment and forming technology. In line with the “smart analytics” motto, the specialists are working on collating all data on sheet‑metal parts, tools and presses in a central “data lake.” In the first stage, the focus is on the findings from the optical tear recognition and the intelligent tools. The goal is to create full documentation for each sheet‑metal part – whether tunnel reinforcement or roof panel – including all key parameters. The complete information collected in this way will then be passed on with the part to the next stage of production, the body shop.
Already today, Audi’s presses automatically mark the parts being produced with a stamp. In the future, the company intends to oblige its steel and aluminum suppliers to take more responsibility for quality control; after all, they have detailed knowledge of their coils’ production data. For example, if codes were printed onto the coils, the work of the presses could be more exactly optimized for the parameters of the sheet metal. Apart from that, there are many other possibilities for optimal parameter setting – from the pressures of the displacement cylinders to additional spray lubrication.
In the competence center for plant equipment and forming technology, many projects come together whose data flows into a shared “data lake” for holistic data analysis. All the projects have one objective: even more stable processes and even higher precision.
Lighter, stiffer, more precise: the new tool generation
Presses are amongst the heaviest machines in the production process at Audi – they weigh up to 45 tons. The engineers who develop them are now applying new lightweight‑construction methods: The design of the cast‑iron housing now follows bionic principles, and some components are made of aluminum and plastics. This reduces the overall weight by up to 20 percent and the energy requirement by about ten percent.
“The right material in the right amount in the right place.” This principle has applied for Audi cars for many years, and especially for the car bodies. It has made the brand with the Four Rings into the world’s lightweight‑construction pioneer. For example, the body of the new Audi R8 high‑performance sports car is made of carbon‑fiber‑reinforced polymer (CFRP) and aluminum; the so‑called Audi Space Frame (ASF) forms a lattice that is stiffened by sheet‑metal parts. These are examples of the perfect interplay between geometrical and functional lightweight construction with the right materials.
With a conventional press tool, however, the load‑bearing structure is always designed conservatively. There are massive horizontal and vertical struts between the lower and upper panels of the base, which cross at right angles. Their design is adapted as well as possible to the special loads acting on the tool in the press. The vertical ribs provide stiffening where the strongest forces are acting. With the deep drawing process, the first stage of forming, those forces can be up to 20,000 kilo newtons (more than 2,000 tons).
Audi started developing its new generation of tools five years ago. In the first step, the engineers replaced the right‑angled struts in the base of the large‑scale tools, which are up to five meters long and 2.5 meters wide, with arc‑shaped structures. In the second step, they designed free shapes reminiscent of natural geometries such as are found in leaves or skeletons. Some of the struts are twisted, others change their profile several times over their lengths. As a result, the new tools are on average about ten percent stiffer than conventional tools.
Extremely high requirements apply for the design of the press tools, which takes place with similar instruments and methods as the car‑body development. The topology must be selected so that it guarantees stiffness in the right areas without adversely affecting adjacent areas. The load‑bearing structure must interact with the installed components as precisely as with the press. This is helped by the reduced weight. A lighter tool reduces the mass dynamics, so that momentum and vibrations decrease and precision increases. Just hundredths of a millimeter are crucial for the quality of a sheet‑metal part.
The new lightweight‑construction principle also applies for the installed components in the tools, which give the sheet metal blanks their complex shapes. Slides, levers and extensions that control the vertical forces of the press are now increasingly made of not steel, but of aluminum or a composite material. Such a slide arm now weighs just 550 instead of 900 kilograms; it runs smoothly and saves a lot of energy.
With tool components that have large, repetitive reciprocating movements, reducing their mass through the use of lightweight materials is especially effective. The advantage with tools for door inner panels for example is up to 2.5 tons. In addition, components made with metal printers are increasingly being used in tools, such as structure‑optimized cutters with integrated functions. These components could hardly be produced by any other method – another example of functional lightweight construction.
Audi applied the first tools of the new generation in 2013; since then, they have gradually been developed further. Today, they are used in almost all of Audi’s press shops – in Ingolstadt, Neckarsulm, Győr, Bratislava and San José Chiapa. In the Audi A4 family, they are applied in the production of doors, roofs, side panels and hoods.
On average, the new tool generation is 20 percent lighter than the conventional predecessors, and in some cases 40 percent lighter. With no detrimental effects on quality, this allows the number of strokes in the press, which is between nine and 18 per minute, to be increased by one to two. The bottom line is that about ten percent less energy is required – for the press process and for the transport between tool changes. Audi’s specialists estimate that CO2 emissions can be reduced by an average of at least ten percent with each new tool, assuming a lifetime of seven years.
An additional factor is that the new tools wear out more slowly and are run in faster thanks to their improved precision. About two years passed between the first designs and the handover of the press tools to the press shop. Uncompromising quality continues to have top priority at Audi.
Checking car bodies against a data model: virtual assembly technology
Narrow, parallel panel gaps, highly precise surfaces and exact seams – every Audi demonstrates the brand’s high level of quality. Long before the start of production, the components of an Audi car body come together for the first time – as data sets on the computer at Toolmaking in Ingolstadt.
Audi’s Toolmaking division is responsible for the precision of sheet‑metal parts. As a strategic system supplier of production equipment, it covers the complete chain of those parts’ manufacturing process, starting with the CAD data from the Technical Development division. Accordingly, it has a broad base in the field of measuring and analysis technology, with state-of-the-art optical measuring equipment at the sites in Ingolstadt, Neckarsulm, Barcelona, Győr, Bratislava, San José Chiapa, Changchun and Foshan.
With this 3D scanning technology, the employees can examine all major components – the body shell, doors, hood and trunk lid, exterior panels and other fitted parts – from almost any angle. Within one to two seconds, up to 16 million measuring points are recorded; the high‑resolution point cloud exactly describes the component’s surface. Thanks to this precise data with diverse applications, optical measuring technology is more flexible than the tactile method with regard to the possibilities of virtual assembly.
With the virtual assembly technology in Ingolstadt, the specialists put together the component data sets that they receive from the plants into a complete virtual car body on the computer. A data set has a size of up to 120 gigabytes. Audi’s reference point system (RPS) serves as a working basis; assembly on the computer rules out manual gap errors. In the evaluation – comparing actual values with target values – the software shows a clear picture. Zones marked green are exactly as specified, in the blue areas the surface is minimally below the data model and in the red areas it is slightly above.
Audi sets very high standards. The brand’s precision is reflected in the dimensional accuracy of the sheet-metal parts, with tolerances of just a few tenths of a millimeter. One example is the zero gap between roof and side panel, which doesn’t need a cover strip. Another example is the exactly parallel lines of the gaps.
When the customer has got into the car, this precision and the exact dimensions of the door seals have a major impact on the closing of the doors and on acoustics when driving. A typical hot spot on any car body is the intersection of the A‑pillar, front fender, door and hood, where all lines have to be very exact. With some Audi models, such as the new Audi A5, car bodies with different side panels have identical doors. Their exact interplay in terms of contours, flushness and gap width requires a high degree of expertise.
The recording of car-body data begins in the development process of a car with the first prototypes, more than two years before the start of production, and often leads to tool adjustments to optimize the production processes. Two years ago, Audi Toolmaking introduced virtual assembly technology for all plants. This quickly became established, also because it takes place much faster than manual inspections on the physical object. And when components and car bodies have to be assessed at various production sites, the experts in Ingolstadt also save numerous flights – so virtual assembly technology significantly reduces CO2‑emissions as well.