More Precision in Body-In-White Production Fully Automated Defect Detection on Raw Car Bodies

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The robot-based SurfaceControl inspection system from Micro-Epsilon for fully automated surface inspection detects dents, bumps, and pimples on raw car bodies. The system provides quantitative geometric features for rework, quality evaluation, and process optimization and impresses with high area coverage—even in edge areas.

In body-in-white production, the foundation for stable paint quality is established. If surface or geometry defects go unnoticed, they often lead to costly rework, additional audit loops, or scrap later on. Since many issues originate in early process steps, late detection involves significant analysis efforts. The quality lever, therefore, lies in standardized inline inspection that works reliably, independent of subjective factors. With the Surfacecontrol Automotive inspection system, Micro-Epsilon addresses precisely this need: the complete system—comprising sensors, robotics, computer, software, and interface package—is custom-configured and enables highly precise, reproducible detection and localization of various surface defects. The number of sensors and robotics can be flexibly scaled to meet different cycle times and throughput requirements.

Stripe Light Projection Provides True 3D Data

Raw car bodies predominantly reflect light diffusely. Therefore, Surfacecontrol Automotive uses 3D sensors that capture the surface geometry through fringe projection. From the measurement data, a 3D point cloud is generated, making local shape deviations visible—not just as a purely optical impression, but based on measurable 3D characteristics. The system detects shape defects with high precision and reproducibility and evaluates them objectively.

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3D Features Instead of Subjective Assessment

A key feature of the measurement system is the true 3D reconstruction of defects. Each defect is assigned geometric attributes—such as diameter, area, and height. Classification is performed considering adjustable tolerances. The data is stored in an XML file and can be integrated into existing quality assurance systems. The results can also be forwarded to customer-specific interfaces. This allows the inspection system to provide a quantitative description of deviations with reliable metrics. It supports consistent assessment of defect severity and lays the foundation for targeted rework and process optimization. Typical types of defects that occur in body-in-white inspection include, among others:

• Bumps, dents, notches
• Pimples, waviness, pressure marks, sink marks
• Cracks, run-off edges, necking, and sink-in areas

Furthermore, the raw car bodies can be inspected for various testing characteristics such as shape or distortion.

Fast Project Planning and CAD-Based Simulation

For process-reliable operations, planning the measurement positions is crucial. Surfacecontrol Automotive supports modern simulation methods based on the CAD model of the raw car body. Fields of view, measurement distances, and potential shadowing can be analyzed during the planning phase; sensor positions and movement sequences are virtually optimized without the need for physical prototypes.

This reduces setup effort and increases planning reliability: Critical areas are identified early, testing strategies are realistically evaluated, and integration into existing production lines is significantly simplified. Additionally, the system can be adapted more quickly to new models and variants, which is a clear advantage in production facilities with high model diversity.

Surface Coverage as a Success Factor

For an inline inspection to truly replace manual visual checks, it must also cover areas that are the most challenging to inspect in practice: right up to the edge, on design lines, and in severely curved areas such as door handle recesses. Surfacecontrol Automotive achieves an outstanding surface coverage of at least 97% of the outer surface, reliably capturing even recessed areas. This high coverage is not only a quality feature but also has a direct impact on production: defect-free inspected raw car bodies can be passed directly to the painting process without manual visual inspection. At the same time, rework becomes more manageable, as defects are precisely localized and described in their characteristics.

Reproducible Inspection Process

In series production, not every deviation is automatically a defect. Component-specific tolerances—including those on movable parts such as flaps, doors, or hoods—are common and must be accounted for in the inspection process. Surfacecontrol Automotive uses a learning method with AI-based algorithms for this purpose: from datasets of defect-free reference parts, a Digital Master is created that defines the "good condition." Based on this, relevant local shape defects are detected while permissible deviations are tolerated.

The result is a reproducible inspection process that can be quickly adapted in parameter settings to customer standards, model changes, or plant specifics. Especially during the launch of new car bodies or model variants, this quick adaptability is a crucial component for stabilizing inline inspection operations and standardizing quality standards across the entire corporation.

Powerful Software Tools

In addition to the metrology hardware, the inspection system includes a powerful software platform with tools for data analysis. Key components are the generation of a Digital Master from datasets of defect-free reference parts, as well as additional analysis tools such as the Digital Sanding Block and the Digital Light Tunnel for individual part analysis. For line assessments, measurement and classification results are provided in various views—from the 3D view of the car body to plant-specific visualizations such as butterfly images or coverage analyses. Integrated auditing features support transparent approval and traceability of evaluations.

Robust Against Position and Alignment Tolerances

Series production involves variability: a raw car body does not always arrive at the inspection cell in an identical position. Therefore, Surfacecontrol Automotive features an integrated 6D offset correction to automatically compensate for positional and orientation deviations. Geometric features are captured, the spatial position is calculated, and the sensor paths are adjusted accordingly. The result is fast, precise, and repeatable measurements without manual recalibration. The 6D offset correction enhances process reliability by ensuring the inspection strategy remains stable despite tolerances, maintaining high coverage even in everyday production.

Scalability and Global Rollout

Surfacecontrol Automotive is customized for clients but designed for transferability in operation. Quick adjustment options in the error detection parameter settings make it easier to transfer to other plants and new models. Additionally, error classification can be specifically optimized by using AI-based algorithms. This allows established inspection processes and validated quality standards to be rolled out across the entire corporation without starting anew each time. Combined with standardized result delivery—such as in XML format—a foundation is created for cross-site quality comparisons and a unified language in defect assessment.

Comprehensive Concept from Body-In-White to Painting

For many OEM projects, it's not just the measurement technology that matters but the overall solution. Micro-Epsilon offers project planning as a general contractor: from robot setup and planning to integration into existing controls, implementation of data and software interfaces, as well as service and maintenance packages.

An additional benefit arises from the integrated tool and software landscape: Surfacecontrol Automotive uses the same software platform as Reflectcontrol Automotive for painted car bodies. Combining both systems enables the implementation of a consistent inspection concept from body-in-white to painting. The results can be overlaid to maintain consistent quality assessments throughout the entire production process and enable upstream analyses. An initial OEM project with a leading automaker has already been successfully implemented—since then, the entire factory's production has been inspected using the system.

Conclusion: Surface Inspection Provides Quantitative Defect Data

Surfacecontrol Automotive enables fully automated, objective surface inspection in body-in-white production, delivering quantitative defect data instead of subjective visual assessments. Extensive surface coverage, including edge areas and design lines, 6D offset correction, and CAD-based simulation ensure a reliable and fast inline inspection process. Powerful analysis tools and transferable parameter settings support standardized inspection processes and targeted rework. Combined with Reflectcontrol Automotive, a seamless inspection from body-in-white to painting is achieved.