Abstract
Automotive coating systems are designed to protect vehicle bodies from corrosion and enhance their aesthetic value. The number, size and orientation of small metallic flakes in the base coat of the paint has a significant effect on the appearance of automotive bodies. It is important for quality assurance (QA) to be able to measure the properties of these small flakes, which are approximately 10μm in radius, yet current QA techniques are limited to measuring layer thickness. We design and develop a time-domain (TD) full-field (FF) optical coherence tomography (OCT) system to scan automotive panels volumetrically, non-destructively and without contact. We develop and integrate a segmentation method to automatically distinguish flakes and allow measurement of their properties. We test our integrated system on nine sections of five panels and demonstrate that this integrated approach can characterise small flakes in automotive coating systems in 3D, calculating the number, size and orientation accurately and consistently. This has the potential to significantly impact QA testing in the automotive industry.
Highlights
The purpose of applying paint coating to automotive bodies is corrosion protection and aesthetic enhancement [1, 2]
5 paint samples were scanned with our FF-optical coherence tomography (OCT) system in 9 different regions
The top two layers, clear coat and base coat, were focused in order to analyse the characteristics of the metallic flakes in the base coat
Summary
The purpose of applying paint coating to automotive bodies is corrosion protection and aesthetic enhancement [1, 2]. The industrial paint process requires spray-painting with significant manual craftsmanship or automated computer-controlled spray guns Important parameters, such as spraying pistol type, spraying speed, spraying pattern, nozzle size, air pressure and distance between pistol and object, have key effects on controlling flake orientation. The small flakes, which are approximately 10μm in radius, are dispersed in the base coat and give the metallic sparkle effect of the paint system The alignment of these flakes has a critical effect on achieving the desired appearance from all angles. The measurement of these parameters is significant to achieving a desired appearance Resolving these flakes and calculating their size and orientation requires three-dimensional (3D) data with sufficiently high spatial (axial and lateral) resolution to assure that each flake can be clearly resolved and distinguished from the others
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