Cleanliness and gloss forever – Oleophobation and UV paint
Oleophobation
AUDI AG
Helmut Donaubauer, Materials Engineering Interior/Equipment
Stains and discoloration caused by water or dirt in the passenger compartment – that just doesn’t go with an Audi, not even after years of operation by the customer. A Quality Assurance team for interior A- and B-pillar liners therefore developed a coating that repels liquids and provides for easy cleaning.
After the textiles are manufactured, a coating is applied to the fabric intended for the liner. This coating is a type of impregnation that repels liquids such as water or oil similar to the lotus effect. This surface masking stands up to UV radiation and is also resistant to all the other various environmental influences that act on the vehicle interior, which vary depending on the regional conditions prevailing in the sales markets throughout the world. The textile decor elements are placed in molds and back-injected with plastic to produce the finished pillar liners.
The fact that water or coffee beads and can be removed without leaving residues behind is not the only advantage of the coating: Unlike untreated fabric covers, it is also easy to clean. Testing has shown that even heavy soiling such as soot can be removed nearly completely even from light-colored parts.
High gloss and UV paints
AUDI AG
Ronald Schiweck, Head of Materials Engineering Interior/Equipment
Every Audi interior makes a shining impression thanks to its numerous high-gloss control elements – from light switches to the fascia in the doors and the cockpit to the air conditioning system. An increasing number of high-gloss components are being used – a current trend in car making that has also left its mark on Audi.
Even before the classic grand piano, high-quality instruments, furniture and other objects with a high-grade surface in high-gloss black have fascinated the observer. Unfortunately, these decorative items are often not as robust in use as Audi quality standards demand, such as with respect to scratch resistance. Audi therefore insisted that high-gloss components for automotive interior applications must be classified according to the loads that they can withstand. The first step here was to analyze the loads placed on the high-gloss surfaces in daily use by the customers according to comprehensive criteria: see and touch; decorative or functional surface; location within the direct reach of the occupants; low or high frequency of actuation.
The “Guidelines for the Load-based Classification of High-Gloss Components” cover all of these parameters and depending on how high the loading on the part is, specify a maximum permissible change in gloss following the scratch-resistance test.
In the future, Audi will apply a high-gloss finish with a UV-curing topcoat to all high-load control elements. This can also reduce inadvertent damage caused by objects such as rings, keys or mobile phones.
During the conventional painting process, a special topcoat system is applied to the respective part, and the surface is subsequently exposed to UV light. This results in an extreme increase in hardness due to the reaction of certain components in the paint. Curing is extremely fast, eliminating the need for an additional energy-intensive drying line.
Cerapaint® – the perfect protection for aluminum
AUDI AG
Waltraud Betz, Materials Engineering Corrosion Protection
Audi offers its customers a special option – the high-gloss package – for many of its models. This package includes body trim elements such as the window capping trim or the lower door trim made of aluminum. As the first and only car maker in the premium segment, Audi coats these premium parts with the high-end protective coating Cerapaint to keep them shining over the life of the car.
The current standard in the automobile industry is the Eloxal process, a technique in which the aluminum base material is oxidized with oxygen. This is done by applying a direct current and by means of electrolytic anodization – a process in which the workpiece acts as an electrode and accepts electrons, driving an oxidizing reaction. The oxide layer thus produced has column and honeycomb-shaped pores that seem to grow out of the surface of the component. Anodic oxidation requires a final densifying step: The open, porous oxide layer is closed by embedding water in the amorphous oxide. The disadvantage of this is that certain chemicals, such as insect removers or highly alkaline prewash agents in car washes, attack this layer and can cause irreparable damage and corrosion.
The Cerapaint process does not suffer from this weakness. The aluminum is first anodized and then densified in a special process. A thin layer of silicatic gel is then sprayed onto this layer. It is only one to two thousandths of a millimeter thick, but it is characterized by a dense, closed surface, high hardness and excellent chemical resistance.
The protective coating is resistant to acids and bases and thus all types of road salt, repels dirt and is easy to clean. The Cerapaint process can be applied to all versions of the trim elements in colors ranging from the natural color in high-gloss to black.
The scent detectives – the Audi Nose Team
AUDI AG
Heiko Lüßmann-Geiger, Material and Corrosion Engineering Total Vehicle
Audi customers want to experience their cars with all of their senses as a place where they can feel comfortable. Audi applies stringent criteria in this area and here too is a pioneer in the industry. The Audi Nose Team, assigned to Quality Assurance in the lead up to the start of production, combats offensive aromas on board the vehicles.
The smell inside a car is of fundamental importance, although it is generally perceived subliminally. People can differentiate between thousands of aromas and keep them in memory. Smells generate positive or negative associations; they inspire sympathy or antipathy. Unpleasant smells trigger – consciously or subconsciously – defense reactions and can have far-reaching consequences. If a vehicle interior smells unpleasant, the customers may also evaluate the other properties of the car less highly.
The Audi “Nose Team” was formed in 1985; seven years later, the process it developed had become the standard in the German automobile industry. The six-member core team, supported by three outer “bench players,” decides whether materials are suitable from an olfactory perspective for use in the car. Materials that don’t clear this high hurdle are stricken from the procurement list.
The work in the Nose Team is a special assignment; normally the professional sniffers work in the Quality Assurance materials laboratory. They were chosen for the smell team by virtue of their particular sensitive noses, which they have to take good care of: Smoking is prohibited, a cold stops team members from working and team members must not give off any scents of their own during testing – whether perfume, shower gel, after shave or maybe even garlic.
The members of the Nose Team meet daily in the Ingolstadt plant’s Quality Center. The employees cut small pieces out of the components to be tested – from the cockpit to wood inlays to the leather upholstery for the seats. These specimens are then placed in a standard canning jar equipped with an odorless gasket. An oven heats the sealed jar to 80 degrees Celsius for two hours.
Now it is time for the evaluation: Each tester in turn lifts the cover slightly, sniffs briefly at the contents of the jar, reseals it and quickly passes it to his or her colleague. Each team member writes down their grade in secret. After five or six tests, the noses need a one to two hour break before they are again capable of exact evaluations.
The German school grading system is used for scoring the results. Materials given a grade of one (“odorless”) to three (“strong inherent smell, but not yet offensive) pass the test. Materials with the grades four (“offensive”) to six (“unbearable”) fail. Plastic parts that give off unpleasant odors, leather that smells of fish oil or floor mats with an air of onion about them don’t stand a chance at Audi.
The Nose Team analyzes roughly 500 different components from the passenger compartment for each model. It also examines complete components such as dashboards to test the interaction of various materials. They are brought up to temperature in a large custom heat chamber of stainless steel. During the test, the testers stick their heads through a hole in the chamber and assess the smell.
The last step is the evaluation of the entire complete vehicle. This is done by heating the interior in a climate chamber with large heat lamps. When a car sits in the blistering sunshine, the interior can easily reach temperatures of up to 80 degrees Celsius. The members of the Nose Team evaluate the overall impression and also attempt to identify components with dominant smells.
Nose Team members also use highly advanced technical methods in addition to subjective evaluation. All air samples are analyzed in a gas chromatograph, frequently in combination with mass spectroscopy. These enables the Audi specialists to precisely analyze the chemical composition of the substances emitted and unequivocally identify all volatile organic compounds, which enables offensive materials to be precisely identified and eliminated.
The result of this elaborate series of tests is the subtle olfactory impression exuded by every Audi. Internally it is designated as “neutral.” Each part contributes to this neutral smell with the authentic smell corresponding to the respective materials. Audi uses no artificial scents in its cars, in part because there is no one aroma that appeals equally to all customers. The fully scentless car is also not the objective – that is as unappealing as a sound-dead vehicle.
The Audi Nose Team is not only involved in the development of new models, it also checks that the olfactory quality of production vehicles remains at a consistently high level. Individual cars are randomly pulled from Production and sniffed over in the test chamber.
The INKA Test – time-lapse torture
AUDI AG
Werner Piller, Materials Engineering Corrosion Protection
A fog of saltwater solutions sprayed onto the sheet metal panel through countless nozzles. Test drives on gravel roads. A hydropulser in a minus 35 degree Celsius climatic chamber that twists the body. Audi tortures its test vehicles mercilessly. The INKA test (Ingolstadt Corrosion and Aging Test) simulates all the rigors of a 12-year service life in only 19 weeks.
The INKA test is performed at the Audi proving grounds near Ingolstadt. Not only are there various selective test tracks there, but also a large building with eight special test rigs. Weaknesses that would only occur after two or three years of normal wear manifest after just a few weeks on the test rig.
Each test is conducted in five phases. In the first phase, the car placed in a climatic chamber at 35 degrees Celsius and enshrouded in salt fog. It is then subjected to damp heat – up to 50 degrees Celsius at a maximum of 100 percent humidity. In the third phase the temperature is reduced to 42 degrees Celsius, but an artificial sun with an output of 1,000 watts per square meter beats down from the ceiling. This simulates the UV exposure of an African summer. The extreme irradiation heats the body to as much as 90 degrees Celsius. Colors in the interior must not fade and the materials must not become brittle.
Phase four simulates winter conditions at the polar circle. A hydropulser with four activation points – one for each wheel – shakes the car at a temperature of minus 35 degrees Celsius to depict the twisting of the body and the loads on the suspension components and engine mounts when driving on poor roads. This also reveals any trim elements that squeak or rub. In between – in phase five – test drivers do repeated runs totaling 12,000 kilometers over specially prepared routes featuring difficult profiles, pools of saltwater and mud, and gravel tracks where stones constantly rattle off the sheet metal.
At the end of the tests, specialists dismantle the entire car and body down to their individual parts and search for weak spots using sophisticated test equipment. Is there corrosion on an edge somewhere? Did a weld seam weaken? How did the scratches intentionally made in the paint during the test develop? Did adhesives in the body begin to deform? And how did the engine, the transmission, the electrical system and especially the many plugged connections and also the suspension hold up to the torture? The specialists devote particular attention to those areas in which different materials are combined or are joined using innovative techniques.
Although the INKA test has long enjoyed the status of a benchmark within the industry, Audi is not content to rest on its laurels and is continuously refining the test method based on its many years of experience. This enables Audi to achieve optimal design-based corrosion protection in the early stages of development of every car.
Design and safety – alloy wheels
AUDI AG
Andreas Wild, Materials Engineering Corrosion Protection
The alloy wheels from Audi are surely the most eye-catching parts of the vehicle that are of major importance in terms of both design and safety. Accordingly, Quality Assurance devotes a great deal of attention to them. The Materials Engineering specialists track the wheels from development through to their use by the customer.
To satisfy Audi’s stringent requirements, an alloy wheel must complete a demanding testing program comprising a series of material, surface and strength tests and inspections. The wheels are examined for casting defects, anomalies and cracks in the X-ray check. The roll motion test simulates travel through curves with extreme lateral forces. In the recreation of driving over the curb at high speed, the rim flanges must withstand hard impacts without fracturing. Audi wheels can endure such impacts because they are cured by means of a special process that simultaneously enhances strength and strain.
With respect to surfaces, Audi has set the bar higher than any other car maker. Competing products, which periodically run through the test program, repeatedly fail various criteria. The corrosion test, in which acid and temperature intensify the conditions, lasts for over 240 hours. Of equal duration is the paint adhesion test, which is performed at nearly 100 percent humidity. A stone-chip resistance test and tests to determine chemical resistance, weatherability and light stability round out the program.
Aluminum wheels from Audi have complex surfaces, regardless of whether the wheel is cast, forged or rolled. The corrosion protection coating system, comprising a primer, basecoat and clearcoat, is common to all versions. The wheels are tested for tightness prior to coating – Audi does not accept use of the coating as a sealant.
If requested by the customer, Audi also supplies custom wheels – in standard silver and high gloss, with polish and clearcoat or with diamond-cut design surfaces and contrasting paint for a two-color effect. Custom surfaces – with chromed plastic wheel cover or galvanically chromed – are also available. Audi achieves uncompromised quality in the demanding chrome plating process, whereas many competitors have problems here with corrosion and thus diminished visual appeal.
One new development is the Durabright technology, which makes the surface so dirt-repellent that cleaning requires nothing more than soap and water. Audi plans to begin using a special chrome surface in the near future that is characterized by a subtle flat finish (“iridium look”) and simultaneously demonstrates the high level of quality demanded by Audi.
Service life testing – durability
AUDI AG
Reiner Steppan, Head of Materials Engineering Suspension/
Corrosion Protection
At Audi, durability means the guaranteed service life of all vehicle components in the customer’s possession – from the seal strip to the crankshaft, from the wheels to the links in the suspension. Ensuring durability is one of the classic tasks of Quality Assurance.
The work of the quality assurance specialists extends to many different levels, and includes random checks of components used in series production, various concept experiments, the determination of the service life of components and the analysis and recreation of damage. When a defect does occur in practice, Quality Assurance analyzes the environment and background with great precision and recreates the events that led to the damage. It often turns out that the customer was overly ambitious with his car – driving over a traffic island at excessive speed is too much for even the most robust wheel suspension – but the investigation of these extreme cases also provides valuable lessons for continuous improvement.
Durability tests are performed on test rigs that enable the function and behavior of components to be precisely determined. Whether a control arm behaves suspiciously under certain loads or overload situations – such as driving too fast over a curb – can be determined relatively quickly, for example. Road testing takes much longer. The Audi quality assurance specialists often investigate very specific issues, down to the question of whether cleaning procedures for aluminum components or country-specific types of road salt have an effect on service life.
The range of test rigs comprises twelve individual hydropulse cylinders, a three-axis axle test rig and a series of specialized systems for testing such things as joints, crankshafts, rubber-metal bearings and wheels. Audi has codeveloped proprietary test rigs for assessing the wear and function of the ball joints used in the company’s complex multi-link axles.
High-tech measurements – the Audi laboratory
AUDI AG
Martin Poese, Head of Materials Engineering Assemblies/Transmissions
How strong and how durable is a material? What is the distribution of chemical elements in the materials? When does sheet metal start to corrode when sprayed for weeks on end with a concentrated saltwater solution? How do the reinforcing zones of a pivot bearing have to be designed so that the component is as light as possible yet absolutely reliable over a long service life? All of these questions are investigated and answered by Materials Engineering Ingolstadt, a department within Audi Quality Assurance.
The lab is the materials engineering competence center for the entire company and is closely networked with the laboratories at other Audi sites. Established in 1971, it currently employees roughly 70 people. The lab is responsible for all materials engineering matters, from development to use in production vehicles, and is also largely responsible for the corrosion protection of the complete vehicle.
The lab monitors many technical components throughout the entire development process and beyond. As a skilled partner, the lab supports the colleagues in Technical Development, Planning and Production in numerous areas, such as materials consulting and development, damage analysis and the testing/inspection of components. Before a new engine block that was hand-built at great expense is subjected to rigorous, time-consuming and costly testing on the engine test rig, the lab’s specialists preemptively conduct a detailed analysis of the quality of the casting.
The high-tech equipment in the Ingolstadt lab has a replacement value of over 30 million euros. Whether gas analysis using high-performance liquid chromatography, x-ray diffractometry to measure internal stresses in components or inductively coupled plasma for trace analysis of heavy metals – Materials Engineering has the ideal measuring equipment in practically every case.
From aluminum to high-strength steels, from engine to suspension to body – metallic materials are naturally the focus of the lab’s work. However, the Audi specialists also work with rubber and plastics, textiles and leather as well as glass and ceramic. A highly specialized team analyzes the smell of the materials fitted in the interior – gas chromatography devices and mass spectrometers used for measuring are complemented by people with an exceptionally highly trained sense of smell, as there is nothing better than the subjective opinion of the expert. The uncompromising approach to quality at Audi extends to the smallest possible component with the focus always on the ultimate deciding factor – people.
Computer tomography – Technology from the world of medicine
