Solutions to Boost Quality, Efficiency and Flexibility in Automotive Finishing

Continuously changing customer requirements and rising quality demands, increasingly rapid model transitions compared to the past, growing use of lightweight technology, and the progressive digitalisation and networking of production processes can be a source of concern for the automotive and supplier industries. Companies operating in the field of industrial coating technology are working continuously and innovatively across all areas to effectively meet the requirements arising from these trends. Giving metal sheet an attractive appearance and the best protective properties: these are the classic tasks of the automotive paint industry. But conditions have changed significantly over time. For example, individualised products are now being demanded in batch-size proportions. Body panels and components are now being made from material combinations that reduce vehicle weight and consequently fuel consumption. Vehicle-sharing applications, electric vehicles and autonomous vehicles require new tasks and requirements for coating technology, as well as digitalisation of production processes and networking. Increasing first-run yield and plant availability, as well as enhancing material and energy efficiency, play an important role in applying these tasks in the global market. For this reason, companies in the paint and coating technology sector are working to improve existing solutions throughout the production chain and to develop additional solutions.

Customised Pre-treatment

In multi-component products, particularly the combined use of carbon-fibre-reinforced plastics (CFRP) with metallic components, presents a problem that has not yet been completely overcome. On one hand, many intermediate steps that still need to be worked through with sanding and putty are necessary to create a Class A surface. On the other hand, it is important to avoid electrochemical corrosion in CFRP components, especially at edges and corners, which can occur when exposed carbon fibres come into contact with metallic components. Among other problems are various ongoing projects aimed at developing a process that will provide adequate edge sealing. During pre-treatment, heat-sensitive lightweight materials such as plastics and composites can be problematic when subjected to high baking temperatures of 180–200°C after cathodic deposition coating. Paint manufacturers are currently working on solutions that significantly reduce baking temperatures. However, it must be ensured that other processing steps, such as hardening of adhesives and sealants and baking of thermosetting alloys, can be reliably carried out at these lower temperatures. Cathodic deposition coating quality control, still currently applied through detailed and destructive methods, can be reduced or even completely replaced through simulation using correct simulations. Likewise, in pre-treatment of plastic and carbon-fibre components, conventionally applied high-pressure washing and drying systems are increasingly being replaced by alternative technologies such as carbon dioxide snow cleaning, plasma cleaning or steam cleaning. The reason behind these changes is significant cost, space and energy savings, as well as the easy integration and controllability of these alternatives in networked production.

High-efficiency Painting Processes

Primer-free painting is not a new topic but remains highly current. In this integrated concept system, a water-based paint system takes over the function of the primer. The appearance, colour and quality achievable with primer-free processing can, depending on the finish, sometimes represent a more efficient alternative to the traditional method of applying primer, paint and clear coat as wet-on-wet without intermediate drying. A rail-free body panel conveyor that allows transport speed to be adjusted according to the processing stage saves energy and increases painting flexibility. Carbon dioxide snow blasting cleaning, which is increasingly gaining ground in the coating of plastic parts, makes it possible to achieve significant cost, space and energy savings.

To further increase the paint application efficiency of atomisers, various optimisation options are available such as adjustable spray jet width, air delivery units and interchangeable cups.

When it comes to appearance, new trends in this area are also moving towards multicoloured and individualised paints. The goal here is to paint without masking or with masking reduced to a minimum. Thanks to a new technology, it is now possible to apply coatings to aircraft side engines using droplets without overspray. Another method is to use a spray film that is precisely applied with robotic assistance and can be removed at any time. On one hand, a new conveyor system that transports vehicle body panels to the paint station without rails can reduce energy costs because rails no longer need to be heated and cooled. On the other hand, painting flexibility also increases because speed can be adjusted depending on the process stage. This means both cycle times and efficiency can be designed flexibly and optimised. For vehicle interiors and body moulds, decorative and functional parts such as direct interior trim are typically produced through plastic injection moulding. The surfaces of these components must meet very individual expectations regarding their properties and resistance, both in terms of appearance and quality. Efficient ceramic coating methods with improved solutions can be applied here. Two paint components are added to the main mould or rear injection during processing. When a third element, colour, is added, mixing heads enable their direct application to the part and colour change is as easy as in spray painting. This makes it possible to produce coated components in a single step. In conventional spray painting of vehicle interior plastic parts, single-layer systems reduce the number of process steps, which saves time and material while also increasing production volume. Additionally, newly developed paint systems are available to protect delicate wood decorations. These provide significant time savings in both conventional manual spray application and automatic spray painting applied at room temperature, providing a significant increase in efficiency.

Improved Efficiency and Application Technology

The primary objective of application is to enable processes that prevent or significantly reduce overspray. To achieve this, companies use different optimisation potential such as adjusting spray jet width through changing air direction units and cups. These atomisers used for water-based paints can be used for painting different plastic parts and at junction points in vehicle interiors and exteriors due to their flexibility. Furthermore, their small and compact size provides easy access even to geometrically difficult areas. These new atomisers also feature powerful high-voltage technology and low-contamination properties, which reduce the energy spent on cleaning. A new VOC-free washing technology in paint application system cleaning enables rapid colour and coating system changes and further increases the flexibility and efficiency of the painting process. In overspray separation, there is a clear trend towards dry separation systems. This means cabin air can largely remain in internal circulation. In addition, it eliminates the need for air dehumidification required in wet washing systems, saving energy. New drying concepts with rotatable blowers integrated into the drying tunnel with heating capability not only provide significant savings in energy, space and facility costs, but also ensure proper baking of different body types and areas.

Innovative Drying Technologies

There are new dryers that provide significant savings in both energy and space requirements in body panel painting. For example, there is now an oven with resistors and fans integrated into the side walls of the drying tunnel. This new product not only becomes smaller and saves space, but also reduces current losses. Thanks to its rotatable blowers, heat and air flow can be adapted optimally to different body panel types and areas. As a result, for example in electric vehicles, the thicker material in threshold areas can be guaranteed to be heated in a balanced and appropriate manner with lower material thickness underlayers. Another feature of the new dryer is that it can operate load-aware, which can provide a significant reduction in operating costs. Coating inspection of painted body panels, previously carried out visually by workers, causes fatigue and is considered a source of error. Now there are new solutions such as tunnels in which the body panel is illuminated homogeneously and glare-free thanks to energy-efficient LEDs, which make it possible to both reduce error rates and increase ergonomic working conditions for workers. Furthermore, inspection data is automatically recorded and can be transferred to production control. In a self-programming booth, the trajectory of the droplets can be pre-calculated through multi-physics simulation of spray painting; the example shows a Volvo V60 body panel. Thanks to a new polyurethane-based paint system, 78 percent time savings can be achieved in complete installation of open-pore wood decorative coatings compared to conventional systems.

Paint Shop 4.0 and Machine Learning

A powerful Manufacturing Execution System (MES) that monitors and controls production is now of key importance. Data collected by sensors in various sections of the paint shop can now be directly integrated into the system, making operations more efficient. Moreover, when necessary information about the condition of the facility, processes and products is analysed and linked, systems can be made intelligent and self-regulating through knowledge-based algorithms. Suitable solutions already exist for various areas such as air management of paint dryers and preventive maintenance. Self-programming booths for coating products in batch size 1 are no longer just a concept. This system, developed in a research project, performs automatic painting in five steps: The object to be painted is first scanned in three dimensions and a fluid dynamics simulation is created based on the scan data. At this stage, the trajectory of paint particles is determined and the optimal amounts of paint and air for the desired layer thickness are established. Based on this data, the system creates the best possible robot path for the painting process in the third stage. The fourth step is the painting process itself, followed in the fifth stage by quality control using Tetrahertz technology.

PaintExpo – International Industrial Paint Technology Trade Fair

PaintExpo, which covers the entire process chain in paint technology, presents comprehensive and detailed information about the latest developments. Wet, powder and coil coating, immersion and UV systems, paints for all types of applications, application systems and spray guns, automation and conveyor technology, separation, pre-treatment, drying and curing, environmental protection, compressed air, air flow and waste air cleaning, water treatment, recycling and waste management technologies, consumables, measurement and testing equipment, quality assurance, paint removal, masking, contract painting, packaging, marking, various services, from technical literature to training and research – PaintExpo, the international industrial paint technology trade fair addressing all sectors of the industry, attracts participation from all major leading companies in the sector. Due to its comprehensive range of prestigious products and services, direct comparison of various systems and applications at a single location is possible, and access to all types of detailed information is provided. PaintExpo will take place on 17–20 April 2018 at the Karlsruhe Exhibition Centre (Germany). www.paintexpo.com Doris Schulz Journalist Author Schulz. Presse. Text.