Electroplated plastic controls are inexpensive, lightweight and easy to manufacture. They allow a high degree of design freedom and are therefore often used in the cockpit of vehicles.
Manufacturers swear by plastic for bezels, buttons and switches in modern vehicles because the material is lighter than metal and the manufacturing and processing costs are comparatively low. In order to meet the requirements for good haptics, scratch resistance and an elegant design, the plastic components are galvanized to give them a metallic surface. However, the industry is facing new challenges that make it necessary to adapt the electroplating processes. Among other things, the demands on the design and functionality of these control elements are increasing. For example, many of them have to be provided with symbols, some of which are multi-colored, and must be clearly visible at night, i.e. have a day-night design. Kunststofftechnik Bernt GmbH solves these challenges with an adapted process chain in which several lasers play a special role. Laser technology allows a high degree of flexibility in design, and symbols, fonts and structures can be implemented very sharply and cleanly to generate a high-quality appearance.
Multi-coloured symbols that are backlit, finely structured surfaces and high-quality gloss with a convincing feel: these are just some of the requirements that car manufacturers want to meet today for a customizable interior ambience. For electroplating companies that process and finish the necessary parts before final assembly, this increasingly means further developing and adapting their own processes in order to meet increasing quality requirements. Precision and attention to detail in production should be noticeable and visible in the vehicle. This makes it all the more important that the contrast of the surfaces and symbols does not run, or that they appear unclean or are unevenly backlit in the night design. However, this requires new, sophisticated processes that go beyond normal printing methods or the simple production of components using multi-component technology.
With multi-component technology, it is possible to allow the transparent component to pass through to the A-visible surface and thus create backlit symbols or structures. However, there are considerable limits to the level of detail and fineness of the structures with this technology. With conventional printing technologies, a covering varnish is usually printed onto the surface of the component using tampoprinting in order to keep the illuminated structures free of the metal layer. However, these methods have the disadvantage that the edges of the translucent structures look washed out and imprecise. Laser technologies are an alternative. Although they require a higher initial investment, the running costs can be limited as the otherwise necessary production and provision of new or different tools can be dispensed with. Laser marking allows several different variants with different symbols to be produced on the basis of one component. Theoretically, this technology also allows the personalization of components.
However, an injection-molded part cannot simply be coated with the desired metal look and then processed directly with a laser. The applied finish is simply too thick and treating the entire metal layer would melt the underlying plastic. This is why Kunststofftechnik Bernt GmbH uses a process in which the component is removed from the system after pre-treatment and processed with a laser before the actual electroplating. The pre-treatment layer (electroless nickel) is a very thin layer that can still be easily processed with the laser without introducing too much heat into the plastic component. Very fine geometries and symbols can be defined and worked out thanks to the fast and punctual processing. The high precision ensures good reproducibility, so that automation is practical and possible for large quantities.
Hidden Line: More flexibility in day-night design
However, there are further challenges: nowadays, many components must have a closed surface in day design and be translucent in night design. This is achieved with many fine structures, for example rectangles with an edge length of less than 0.5 mm. The production of such structures requires laser systems with maximum precision and very fast scan heads. Kunststofftechnik Bernt has several such precision lasers at its disposal.
In principle, this method is suitable for all components that need to be illuminated in a day-night design. The precision with which the laser can structure can be demonstrated by enlarging a typical component: if, for example, the elongated area of a decorative panel is to be equipped with fine diamonds measuring 200 × 200 μm, each 50 μm apart, the laser can be moved very close to the edge surface without risking inaccuracies. The high repeat accuracy means that around 40,000 squares can be produced precisely and reproducibly in just a few minutes for this component.
3K technology: multi-colored day-night design
As Kunststofftechnik Bernt GmbH has its own injection molding systems, raw parts can also be produced from three components on site. In addition to 2K components, these can also be easily structured and processed with a laser. An additional component is useful, for example, to prevent creaking noises and to enable active steering wheel lighting. Active steering wheel illumination means that individual symbols are illuminated separately from the others. This requires light-tight seals that prevent extraneous light from illuminating the other symbols. In both cases, an intermediate layer is required that serves either as a noise buffer or as a light shield. The lowest layer under the symbols is formed by light guide components made of transparent polycarbonate (PC), which scatter the light and direct it to the surface. Black PC is inserted as the middle layer, which acts as a light barrier or light labyrinth. It separates the illuminated areas from the non-illuminated areas. The third component is a plastic (e.g. ABS/PC), which can then be electroplated. A fully automatic camera control system checks the illumination and symbol position during the injection molding, laser and final quality control process stages.
Illuminated Brush: Brushed surfaces with surface light effect
In addition to an extended day/night design, brushed surfaces on trims and other components are increasingly being requested by car manufacturers in order to achieve an elegant, aluminum-like look. Kunststofftechnik Bernt has developed the Textured Plating technology for this purpose. This involves producing injection molded parts with a tool in which the visible side (often the nozzle side of the tool) is structured by laser processing in such a way that the resulting molded part has a brushed structure. However, if such a component is electroplated conventionally, the copper layer in particular causes a certain leveling of the structure. This is entirely intentional in the case of normal components, as it conceals slight surface defects and, for example, bonding skins, i.e. they become less visible. Brushed components, however, tend to look artificial and not really brushed. In a coating process specially developed by Kunststofftechnik Bernt for this application, this leveling is reduced to a minimum, resulting in components that only an expert can distinguish from components that have actually been brushed.
With Illuminated Brush, lighting can now also be combined with this technology. For Kunststofftechnik Bernt, the use of lasers on the component has the decisive advantage that the brush structure can also be illuminated by removing the electroless nickel layer in the direction of the brush structure. The process can be applied to the entire component as well as to partial areas.
Litho-Graphics: hardening symbols and graphics with a laser
With the litho-graphics method, a UV-curing covering lacquer is applied to the area of the symbols. This can be carried out using various methods. In addition to a spray application, such as painting, printing with Tampoprint has proven its worthAfurther development of the tried and tested laser process from Kunststofftechnik Bernt should pursue two main objectives. Firstly, to offer a process at a lower cost and secondly, to increase flexibility in terms of design and coloring. At the same time, accuracy and edge definition should be at a similar level as far as possible. This was achieved with the development of the Litho-Graphics® process. With this method, a UV-curing cover varnish is applied in the area of the symbolism. This can be carried out using various methods. In addition to a spray application, such as varnishing, printing with tampoprint has proven itself. In terms of accuracy and edge definition, this process is nowhere near the level of laser technology. However, this is not even necessary, as the UV varnish is only cured with a UV laser exactly where the symbolism is required. Excess, uncured varnish is then cleaned off. On the cost side, the fact that the components can now be electroplated in a single process and do not have to be discharged from the electroplating system after pre-treatment has a positive effect. This is due to the fact that the process described above can be carried out directly on the injection molded part. At the same time, with Litho-Graphics® it is also the laser that ensures the flexibility, accuracy and edge definition of the process. In the course of development, the possibility of multicolored symbols has also been added. In the printing process, up to four different colors can be applied in a single step. In addition to the classic motifs such as the window regulator symbol, typical multi-colored identification symbols such as the manufacturer's brand symbols or flags that can be illuminated are now also available.REACh: Chromium (III) as a possible alternative to chromium (VI)
Since September 2017, chromium (VI) can only be used under very strict conditions and for a limited time. Current plans assume authorization until at least 2024. Kunststofftechnik Bernt is already working intensively on alternatives. Since September 2019, all of the technologies described above, as well as conventional components, have been available with a chrome (III) coating. The first components are already in series production.
Conclusion
Increasing demands on design and stricter requirements imposed by legislators with regard to the choice of materials should ideally be met in electroplating by adapting the individual process steps and integrating new technologies, even if these may initially mean a higher investment. The example of laser technology clearly shows that the resulting greater flexibility in processing can have a positive effect on running costs and the final quality of the product. In addition, the combination of already optimized processes also makes it possible to achieve enhanced functionality with high design and material quality. For example, 3K technology, brushed surfaces and alternating transillumination can be combined well.
Kunststofftechnik Bernt GmbH
Kunststofftechnik Bernt supplies high-quality plastic parts. The company has extensive expertise at all stages of the value chain, from parts development and tool design to mold making, plastic injection molding and surface finishing in its own plastic electroplating facility. The range of services extends from technical functional parts to surface finishing; it often includes the production of complete assemblies. New technologies and process applications such as lasers and automation components are also used. Customers include companies from the automotive, household appliance and sanitary sectors. The Kaufbeuren-based company employs around 300 people.
