Attractive appearance and optimal body protection – these have always been the foremost expectations of an automotive paint shop. But requirements on the paint shop have changed
radically: Demand for personalized vehicles and the need for green production processes are raising the bar. To satisfy these new expectations, manufacturers must devise efficient and economical processes.
Important aspects of this include process stability from the outset, maximum plant availability, and efficient use of materials and energy. Automakers and suppliers are addressing these aspects at all stages of the paint shop process chain, striving to improve existing solutions and develop new approaches.
New shop concept
To address market demand for greater vehicle diversity and environmentally responsible production, auto manufacturing is shifting toward the so-called “digital paint shop” concept. This is based on three interlinked approaches: Digital consistency from vehicle design to production, utilization of industrial robots for spot-on automation and reliance on digital factory twins.
1. Digital consistency: To create end-to-end connections between design and production, the user can leverage the geometry features defined in the engineering phase to develop a paperless, flexible and speedy exchange of information along the paint shop value chain. This speeds up production planning for new models and variants, and it permits early integration with the paint shop production lines. An accelerated exchange of information also provides information feedback from production planning back to engineering, enabling early design corrections and thereby avoiding costly changes further downstream.
2. Industrial robots for spot-on automation: Automation in the automotive paint shop has undergone major changes in recent years. The more or less rigid automation lines with their application machines and manual support workflows have been replaced by highly flexible industrial robot setups. The use of robots permits rapid reprogramming and flexible reaction to new model series and derivatives.
3. Digital factory twins: A digital factory twin is a realistic computerized replica of a real-world production facility. To deliver a maximally realistic reproduction, the twin must be able to model not just the mechanical setup, but also the electrical components such as control devices and electrical connections as well as the individual process steps and the final process result. For the application of a top coat, the user has to model not only the movements of the industrial robots, but also the paint application, per se, including simulation of the respective coat thickness.
Users who are serious about implementing a digital paint shop need high-performance simulation software. It must provide a scalable data model that is able to process the geometry information generated by engineering, support the individual process steps and process simulations, and apply the simulation layout to the entire project sequence.
Admittedly, these are steep demands. But they are precisely what the 3-D simulation suite FastSuite E2 software from Cenit AG is designed to do: Create a digital factory twin as an accurate replica of a real-world plant facility. The simulation has the same structure and behaves in exactly the same way as the real plant. What the users see on their monitors is not an emulation, but rather a full-fledged simulation based on the plant components and the behavioral model.
Let’s look at the process of seam sealing to see how the principle of digital coherence combines with the digital factory twin to deliver major benefits. Specifically, let’s examine a digital twin
that is already proving its usefulness at an automotive plant in southern Germany.
Seam sealing protects a car body from moisture and corrosion. Special PVC materials are used to coat the welding seams. This sealing process is executed mainly by robots that apply the sealing substance to the car body from above and below. In complex vehicle geometries, 150 m of seal may need to be treated in this way. And it all has to be implemented by way of robot programs.
Robot simulation and programming systems typically focus on machine capabilities rather than looking at product characteristics, which imposes certain limitations. But the so-called CAD-to-path approach opens up new and innovative solutions for robot simulation and offline programming because it is based on a methodology that permits contour-based robot programming.
CAD-to-path centers on the concept of process geometries with associative links to product features; these may be point-, contour-, or surface-related. This permits active linkages between product properties and the offline robot program, which in turn opens the door to semi-automated robot programming and automatic updating.
Typically, contour lines are mapped as a succession of individual points that enable robot approaches via point-to-point and linear movements and are programmed via a teach-in process. In contrast, the CAD-to-path method contained in FastSuite E2 views the contour as a continuous line and relies on circular movements for robot approaches.
On this basis, the orientation of the contour line can be interpolated and manipulated as a whole: Via a search, the relevant contours are simply recorded from car body geometry or imported directly from engineering as a geometry feature. Depending on requirements, approaches to the contours can be linear or circular with suitable offsets added as required. This generates harmonious movements that deliver the required surface quality – and it also ensures minimum material consumption.
The next steps are aggregating the seam sealing programs for the individual robots within the respective stations, simulation of the entire process sequence and, finally, virtual commissioning of the facility.
So, what exactly are the benefits of contour-based seam sealing? For one, the standardized CAD-to-path approach boosts efficiency. The use of process technologies and methodologies (recipes) and the reuse of expert know-how permits standardized offline programming and thereby shortens time-to-market cycles. It also accelerates program generation because less time is needed for model setup, and the various seam segments can be programmed more efficiently. Compared to other robot offline programming systems, CAD-to-path can reduce programming effort by about one-third.
But is the digital paint shop just a vision? Not at all. It’s already in productive use. Not just for the seam sealing applications presented here, but also for injection of sound absorber mats and foams, cavity protection and vehicle body painting. And with the right software support, users can achieve considerable process optimization benefits, as well.
Automation driven by industrial robotics thus increases the demand for intelligent and efficient programming systems. If and when these are based on a consistent digital backbone, they can bring genuine progress.