Insights into Practice A Visit to Audi's 3D Printing Center
Audi is going to implement a successful in-house additive production. In the medium term, this process could lead not only to the construction of prototypes but also to the provision of spare parts in line with demand - at the expense of die casting?
Buy a 3D printer, feed in CAD data, start the printing process — the optimized component is finished. Many users have already realized that it is not that simple. But Martin Bock reveals how much work really goes into successful additive production (AM). He is project manager of Audi's 3D Metal Printing Center in Ingolstadt and has been working with his team at this center for two years to raise 3D printing to Audi standards. The entire VW Group, to which Audi belongs, owns more than 120 plants worldwide for additive production with metal and plastic. Three 3D metal printers, an M 400 and an M 290 from EOS and a 280 HL from SLM Solutions are used in Ingolstadt. They all work with powder bed-based SLM technology (selective laser melting). This process was chosen because the technology was the most advanced. Especially the EOS 400 M is used even in medium-sized companies for rapid prototyping and tooling.
The center is located in the internal toolmaking department. When the decision to invest in metallic 3D printing was made almost three years ago, the company needed suitable premises in which all process-relevant steps could be accommodated. Thus, the three machines stand in a room that still offers space for future purchases. The car maker himself has introduced small automation approaches: on the large EOS machine, the construction panel is removed by a ceiling crane and Audi has retrofitted a powder feed system for the SLM system. Next to the machine room are the material store and the finishing room with its own chamber for aluminum components. The three engineers and two applicators sit in a front office. Another applicator from the small machine park is on hand for hot phases with many orders. Ingolstadt needs two of them, as they also use two different machine manufacturers. In order to bring the quality of the printed components to a high level and to keep it there, the applicators must know their machines very well.
What you Need? A Lot of Experience
Even before the printing process starts, a lot of experience is required. Apart from an AM-compliant design, it is also important to design a component in such a way that distortions and component tear-off are less likely to occur, that the support structures are well positioned and that the objects are correctly placed on the construction panel. Although manufacturers — both machine manufacturers and software houses — offer supporting programs, the Audi team has always had to contribute their own experience. According to Bock, there is no software that provides clear programming specifications; it depends on the know-how of the application engineers, on their ability to react to process fluctuations that might occur. "This is exactly where we need specially trained employees," Bock says, "people who have been trained in the use of software and who have gathered experience in the use of the machines.”
Meanwhile, very few errors occur in the 3D printing center. A fact Bock can be proud of. However, this is also owed to several years of work and experienced people — and some disappointments, too. But now the company is well equipped. "Our machines are good, and we have successfully developed process technology in recent years. Simply because we have gained experience and implemented technology, damages rarely occur." This refers to experience in the additive process, with the machine, with the material used, and experience in the design of parts.
Exchange of Experiences Results in a Better Process
The know-how gathered in Ingolstadt is not kept a secret: A considerable part of Bock's tasks is the exchange within the VW Group. Together with colleagues working with other AM machines, for example, specifications for machines and for the software development are defined. They are looking for "software that balances the safety of the construction process, the accuracy of the component and how quickly support structures can be removed — and which also meets the high requirements of the automotive industry". Bock has not yet come across a solution that meets all of these requirements. But the company passes the high demands of his industry on to system and software manufacturers. In this way, users outside the Group also benefit from this strategy.
Another task manufacturers have to fulfil is construction process monitoring. "It is not enough to take pictures per shift to ensure good surveillance. We demand a further development based on artificial intelligence". Bock explains what he means by this: "During the construction process, we expect a machine for additive production to automatically evaluate the images per shift and provide feedback as well as input for the process cycle and change parameters or cancel the construction job if necessary. The latter is useful, for example, if cavities have formed in a particular area.”
Post-Processing also Requires Initiative
Even though the printing process is not yet monitored to the full satisfaction of the manufacturer, it still runs automatically, without human intervention, even during the weekends. On Mondays the work continues: The construction panel is taken out, the printed objects are removed from it, the components are freed from their support structures and post-processing begins. The company offers milling, turning, eroding and heat treatment. Even if heat treatment seems to be an inconspicuous process, a lot of developments are needed for additive production. "Developing safe process parameters for the two metals we use, i.e. AlSi10Mg and 1.2709, took quite some time," emphasizes Bock. New heat treatment processes were required, since laser melting causes changes in the microstructure, which in turn can result in defects. However, the purpose of heat treatment is to compress the microstructure and expand the properties of the component. This creates a new business field for manufacturers who use conventional processes. But they are lagging behind the development in additive manufacturing. "There is a lack of experience and knowledge of how the printed components behave," Bock assumes. "Just because of the volumes. We've printed 4,000 parts in two years."
Audi invests a lot of their own manpower in the further development of the additive process chain. In addition to the automation approaches on the machines and the further development of heat treatment, this also includes the mixing of powder with a flow aid. This is to make the installation space of the 3D printer easier to clean and also speed up powder feeding. Small details that taken together are to save a lot of time in future industrial production.
What Does Audi Manufacture Additively?
One of their successes so far is the prototype of a steering box. The request came from the pre-series center. They wanted to add the metallic component instead of using die casting as usual. "We have reduced the delivery times from seven to one week and reduced the production costs for this component by a factor of 10," Bock emphasizes the advantages of their process. Prototyping is the classic application for 3D printing, as far as "classic" is the right term to use. A new thing is that due to the progress made in material and process development in recent years some of the additively manufactured components can also be used as spare parts. Audi is also already using this process to manufacture components for exhibition models, pre-production vehicles and in motorsport. One reason for this is that the SLM process can is very fast.
Related Content: Interview with Dr. Ulrich Widmann, Head of Functional Design at Audi: "Bionics, functional integration and hybrid structures are becoming increasingly important in the lightweight construction of the future.”
Spare parts production is an important topic at the 3D Metal Printing Center. The parts are mainly made of AlSi10Mg aluminum. "Last year we printed the water connection piece of the W12 engine," says Bock. Other departments can now order it. "This means that the water connection has successfully undergone all quality control runs at Audi. We are very proud of that!" The team is in close contact with colleagues in After Sales of the Audi Tradition segment and, following this success, identifies further components that are suitable for 3D printing. In a few years the warehousemen could call Bock to order the spare parts requested by an authorized workshop directly for one or two items. Because "if the tool costs and thus also the start-up costs for a tool are eliminated, no one has to buy 100 parts anymore," says Bock.
One third of the incoming orders concerns equipment such as close-to-contour cooled mold inserts or bionically optimized elements for plant and fixture construction. The advantages Bock offers colleagues in this area include the reduction of cycle times for die casting tools or hot forming when die inserts are printed, as well as weight savings offered by bionically optimized components. An element for plant fixture construction previously weighed 12 kg. Thanks to bionic production, the company was able to reduce the weight by a third using 3D printing. "In this way, lighter and faster robots are available. It even improved the quality of the welding process," Bock points out the advantages.
Occasionally, the carmaker is asked when the first Audi will come out of the 3D printer. This will certainly take some time, is the answer. Among other things, the printers still lack the size of the installation space and the right material. And of course, a car consists of a mix of materials, which is also not feasible with additive production at present.
This article was first published by MaschinenMarkt