Automotive Coating Hiding Thickness Measurement
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Solution Overview
Problem
Current methods for determining the hiding power of coating compositions, such as automotive paints, are prone to errors due to visual subjectivity and are not adaptive to different colors and finishes, particularly those with metallic flakes, leading to inaccurate measurements of hiding thickness.
Innovation Solution
A method and apparatus that apply a monotonic layer of coating over a test pattern, sequentially illuminate and measure target areas, and use photosensitive devices to calculate ΔRGB values, classify hiding data, and fit equations to determine the hiding thickness, providing a more accurate and adaptive measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If visual observation method is used to determine hiding power, then the process is simple and quick, but the measurement precision is low due to visual subjectivity and lighting variations
Solution Approach 1:
The patent replaces the visual observation method with an automated optical measurement system using a colorimeter or spectrophotometer to objectively measure color differences (ΔE, ΔRGB, or ΔL*a*b*) between test pattern areas, eliminating human visual subjectivity and lighting variations while maintaining measurement speed
Solution Approach 2:
The patent introduces an intermediary computational model that correlates color difference measurements with hiding thickness through fitted equations (e.g., ΔE = a·exp(−b·t) + c), serving as a bridge between the optical measurement and the actual hiding thickness determination
2Ease of operation
If a single predetermined color difference value is used to represent hiding, then the method is simple to operate, but the adaptability is poor for different colors and finishes
Solution Approach 1:
The patent implements a dynamic threshold selection mechanism where the hiding threshold is not a fixed predetermined value but is adaptively determined based on the specific coating composition, color, and finish being measured, allowing the system to optimize performance for each unique application
Solution Approach 2:
The patent changes the measurement parameters (color difference metrics such as ΔE, ΔRGB, or ΔL*a*b*) and threshold values based on the specific coating properties being measured, enabling accurate hiding determination across different color families and finish types including metallic flakes
3Measurement precision
If film thickness measurement by gage is performed, then the hiding thickness can be determined, but the measurement precision is reduced due to sensitivity to usage technique and additional error sources
Solution Approach 1:
The patent replaces mechanical film thickness gages with an optical measurement system that determines hiding thickness through color difference analysis, eliminating the sensitivity to gage usage technique and reducing additional error sources while maintaining the ability to determine hiding thickness
4Reliability
If color and film thickness measurements are performed on prepared hiding panels, then hiding data can be obtained, but the reliability is reduced due to random errors from air bubbles, smudges, and scratches
Solution Approach 1:
The patent implements a feedback mechanism where the measured color differences are compared against a computational model, and the system iteratively refines the hiding thickness determination by minimizing the difference between measured and predicted values, thereby compensating for random errors from panel defects
Solution Approach 2:
The patent prepares hiding panels with specific test patterns (such as black and white stripes or checkerboards) beforehand with controlled properties to minimize the impact of random errors from air bubbles, smudges, and scratches during measurement
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces errors and provides accurate determination of hiding thickness for various colors and finishes, including those with metallic flakes, by using a systematic and adaptive method to classify and fit data, resulting in precise coating application thickness.
Implementation Method 1
The light source illuminates target areas P1 to Pn of the monotonic coating 24... the photosensitive device 8 sequentially receives reflections of the light portion 30 and the dark portion 32
Data Source
AI summary
The present invention is directed to an apparatus and a method that characterizes the hiding of coating compositions, such as automotive OEM and refinishes paints. The method is directed to sequentially storing in a computing device hiding data obtained by measuring the color difference (ΔRGB) in reflections of light and dark portions of target areas of a monotonic coating resulting from a coating composition applied over hiding test panel and by measuring coating thicknesses of the monotonic coating that correspond to the target areas, classifying the type of the hiding data, selecting fitting equations applicable to the classified hiding data, fitting the selected equation to match the classified hiding data and locating a hiding thickness on the monotonic coating that corresponds to the threshold value of the color difference at that location to determine the hiding thickness of the coating composition.