Surfaces and Tests Diversity and safety
Every FUCHSFELGE wheel is forged, machined and finally painted using state-of-the-art production technology and great craftsmanship. After a thorough inspection and final check, the wheels are delivered to the customer, ideally prepared withstand the rigors of everyday use for many years, even decades if necessary.
Surface Diversity
Wheels are not only functional components of a car, but also an expression of style and aesthetics. The forging process not only gives the wheels inner strength, but also a unique identity. High strength, a striking design and visible lightness are the results of this elaborate process. But there are still a few steps to go before the wheel is mounted on the vehicle.
OTTO FUCHS has developed various techniques to give each wheel its individual character. These techniques take into account not only the technical requirements, but also the aesthetic effect. Because a wheel should not only shine through its invisible inner values, but also through its outer appearance. Each wheel is carefully designed to perfectly match the vehicle on which it will later be mounted. This results in unique wheel designs that meet the demands for quality, functionality and beauty.
3-LAYER-SILVER
The three-layer coating is the standard paintwork for most light alloy wheels. In addition to the distinctive look, very good corrosion protection is ensured by their polyester base coat, the colouring liquid paint and protective acrylic clear-paint.
POLISHED-TURNED AND DEBURR POLISHED
Forged wheels are ideal for this surface finish due to their fine grain structure and smooth surfaces. The following example illustrates one of the options: The pictured 18-inch wheel for the VW Golf GTI was painted black in the first step and then gloss turned. The paint disappears on the spokes and the rim flange and the silver aluminium reappears. Now the edges are trimmed by polishing and finally clear finished.
BICOLOR
This surface version might even be the most typical within the OTTO FUCHS portfolio, but it is marked by the fact that the vent windows in the wheel are painted in colour and thus are in perfect harmony with the silver polished spoke tops. In this process, the wheel is initially primed, then completely painted with the desired colour and finally sealed with a clear acrylic-paint. Now the surfaces that are to later shine metallic are turned and then polished to a high gloss. Finally, a two-layer clear coat is applied consisting of a polyester primer and acrylic clear coat.
Vibratory finishing
This surface variation is the fast seller in some international markets, for example, in the US. Americans love chrome and the look of the smooth polished wheels is very similar to chrome with its gloss. The fine grain structure can bring out the fine »gloss potential« of the wrought alloy. Although the wheel looks almost like a chrome wheel, it avoids the disadvantages of electroplating: the extra weight from the thin layer of chromium. In the vibratory finishing process, the entire wheel surface is polished and then clear finished. Here a degree of gloss and a surface structure is achieved with forged wheels that is not possible with cast wheels.
ANODISED
By anodising the surface, the wheel gets a very special character of genteel elegance. Anodizing only works with forged wheels. The wheel is sent through a variety of cleaning, pickling and rinsing baths before ending up in a sulphuric acid bath where current is passed through the wheel. The uppermost layer of the aluminium is oxidised here, thus converted into aluminium oxide. This results in a very hard and chemically stable layer. This anodic coating is not only corrosion resistant, but it also provides a good adhesion base the matte black paint. The locations on the wheel that are not to be black are covered with a stencil beforehand. A clear coat sealer is no longer necessary.
BICOLOR, ANODISED
Some surface versions can also be combined. One example of this is the two-tone anodised surface. Here the wheel is provided with a three-layer coating prior to anodising, then turned in the visible area and then polished. The following anodising bath is dyed with the desired colour. Only the areas turned beforehand, that is to say the bare aluminium, are conductive and therefore the anodizing process only takes place there. This gives the wheel a really unique look. For the ultimate finish, the wheel is coated with clear finish powder to ensure the UV stability of the coloured anodised layer.
Tests for a long (car) life
Wheels are essential components for the safety of a vehicle. That is why we at OTTO FUCHS subject them to particularly thorough inspections and comprehensive tests. This process begins with chemical material tests and ends with demanding endurance runs on testing machines.
Why this effort? Because we want to meet not only the legal requirements and the specifications of the vehicle manufacturers, but above all our own high quality standards. After all, wheels are no ordinary parts like glove compartment interior lighting or trunk carpets. They contribute significantly to stability, vehicle control and safety.
Our forged wheels undergo a rigorous testing process before they go into series production. We rely on careful testing to ensure that every wheel meets the highest standards. Because the safety of our customers is our top priority.
Bending circulation test
The circumferential bending test simulates cornering with different loads. For this purpose, a wheel without tires is clamped onto a test stand and loaded with a rotating bending moment via the contact surface. The maximum permissible bending moment is of course known because it has been calculated beforehand. This bending moment is generated by the vertical normal force acting on the wheel, a value defined by the vehicle manufacturer. In addition to the normal force, there is also the horizontal lateral force that occurs when driving through a bend. Such real maximum bending moments are between 2,500 and 10,000 Nm, depending on the size and weight of the car. Depending on the vehicle manufacturer's requirements, the tests can now be carried out with 75 and 100 percent of the maximum bending moment, for example, to prove the fatigue strength of the wheel.
Material / Tensile Test
In the tensile test, performed in-house in the OTTO FUCHS laboratory, the material properties of the alloy used are tested. The material samples of a forged Fuchsfelge and a cast rip-off serve as an example. Both tensile specimens are clamped into the corresponding test device and pulled apart mechanically. The sample of the forged Fuchsfelge first deforms before fracture occurs. The sample from the cast copy does not deform on the other hand, but breaks abruptly, even before the sample of the forged wheel deforms at all. The reason for the material response is the much lower ductility of the cast material.
ZWARP Test
The so-called biaxial wheel test, or ZWARP for short, is complex and extremely informative. At OTTO FUCHS, testing is carried out on a realistic outer drum. The ZWARP makes it possible to simulate very specific routes and road conditions, for example the Nürburgring Nordschleife or a corrugated metal track that kills material.
The so-called European cycle defines such different routes. The large picture shows a ZWARP test stand. To make sure it doesn't become too easy for the wheel, it is given some preliminary damage on the long journey by simulating a rough kerb crossing on the inner rim flange. However, this plastic deformation may only amount to a few millimeters. Now the wheel and tire are mounted and swivelled onto the drum. Let's go. During the test procedure, the wheel is loaded with different radial and axial forces. The forces applied naturally depend on the type of wheel and the vehicle on which it is to be used later. The wheel of a heavy SUV must of course be able to withstand more than that of an electric car such as the BMW i3. The contact forces can be up to 35 kN.
Now a little patience is required, because the wheel to be tested has a somewhat longer journey ahead of it, 15,000 kilometers to be precise. This distance corresponds to a car's life in fast motion, as it represents a real load of 300,000 kilometers. The test not only simulates a complete life, it also runs extremely precisely according to the vehicle manufacturer's specifications, where every radial and axial force is specified in detail. Needless to say, a wheel has to survive this distance without any further damage or cracks before the production process actually starts.
Ultimately, the vehicle manufacturer determines what the wheel should look like after the test. If, for example, a wheel for AMG survives the 15,000 kilometers without any damage, it is possible that the weight will be tweaked even further to make the wheel even lighter. In this way, a wheel can be pushed to its limits.
This is exactly what some vehicle manufacturers want. If a wheel survives this ZWARP test without damage, OTTO FUCHS' experience shows that it will last considerably longer than the vehicle, and certainly considerably longer than 300,000 kilometers.
CASS Test
In the salt spray test, also known among experts as the CASS test (copper accelerated salt spray test), a complete wheel whose paintwork has been damaged down to the base metal with scratch marks and grid cuts is permanently sprayed with an aggressive copper-salt solution for 240 hours. If the paintwork blossoms in these areas, there is something wrong with the surface protection.
Polished and bright-finished wheels have to endure even more. In the Filiform test (as in the CASS test), wheel segments damaged in this way are tested in a climate chamber at 60 degrees Celsius and 82 percent humidity for 28 days. It is only a matter of time before the paint is infiltrated in the form of threads (i.e. filiform). The maximum length of these threads is specified by the vehicle manufacturer. The test is designed to ensure that this length is not exceeded. Only then is approval given.
Filiform Test
In this corrosion test, the wheel's paint is also pre-damaged or scratched and the wheel is exposed to 60 degrees Celsius and 82 percent humidity in a climate chamber over a period of 28 days. Filiform corrosion is characterized by a thread-like (filiform) infiltration of the paint.
Stone Chipping Test
This test simulates possible stone chips caused by grit or small stones. A special test device is filled with a defined mass of steel shot. This steel shot is then fired at the respective painted wheel segment under high air pressure. It is checked whether and how the stone chips lead to unacceptable flaking of the paint.