Surface Inspection of Polymer Parts Using Shape-from-Shading Technology

Challenge

In modern manufacturing, ensuring flawless surface quality on painted polymer parts is essential for both visual appearance and functional performance. After the painting process, polymer parts must be carefully inspected for extremely fine surface defects, including paint spots, scratches, inclusions, lint, lacquer runners, and other raised or recessed imperfections. Traditional inspection methods often struggle to detect subtle defects, particularly on glossy or reflective surfaces, and may lack consistency across varying gloss levels. Additionally, manual inspection processes can be time-consuming and prone to human error, making it difficult to maintain high throughput in production environments.

Solution

To overcome these challenges, a Shape-from-Shading system was introduced for automated surface inspection. The system captures eight images of each part using eight different illumination directions, allowing for comprehensive surface analysis. These images are processed using Shape-from-Shading algorithms to generate a detailed height map of the surface, which reveals even the smallest deviations. The evaluation and defect detection are performed using senswork’s VisionCommander® image processing software ensuring accurate inspection results.

Results

The implemented system enables highly reliable detection of raised or recessed defects, such as paint spots, scratches, lacquer runners, and inclusions, ensuring even the smallest imperfections are identified. Its ability to perform consistently across surfaces with varying gloss levels significantly improves inspection reliability compared to conventional methods. The non-contact measurement approach also eliminates any risk of damaging the surface during inspection. This ensures only defect-free parts proceed to the next stage of production while maintaining efficiency for high-volume manufacturing. As a result, quality control is enhanced. By combining Shape-from-Shading technology with senswork’s VisionCommander®, the manufacturer achieved reliable and fully automated surface inspection of painted polymer parts.

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About senswork

senswork is an expert in complete solutions for industrial image processing, automatic inspection, and deep learning (AI). Their automation and quality assurance solutions are used daily in numerous industries, such as the automotive industry, mechanical engineering, and medical technology. From their headquarters in Burghausen and all their global locations, they serve renowned customers from industry and research. They offer everything from a single source, from the initial concept to the integration of the finished solution.

For more information about senswork, please visit: www.senswork.us