Non-Contact Paint Layer Thickness Measurement Using Deflectometry
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Solution Overview
Problem
Current paint layer thickness measurement techniques, such as ultrasonic and magnetic sensing, are contact-based and inefficient, leading to high reworking rates and increased production costs in automobile manufacturing, with existing non-contact THz radiation methods not fully optimizing the painting process.
Innovation Solution
A sensor system utilizing a robot arm with a Terahertz radiation emitter and receiver, combined with a deflectometry system and control unit, allows for non-contact measurement of paint layer parameters like thickness, type, and defects, enabling precise and rapid quality control before the paint dries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contact-based ultrasonic or magnetic sensing is used for paint layer thickness measurement, then measurement can be performed, but the measurement process is inefficient and requires physical contact with the paint surface
Solution Approach 1:
The patent replaces contact-based mechanical measurement systems (ultrasonic and magnetic sensors requiring physical contact) with a non-contact optical measurement system using a camera and deflectometry. The camera captures light reflections from the paint surface, and the deflectometry system calculates thickness and curvature from these optical patterns without touching the surface, thereby eliminating the operational constraints of contact-based methods.
2Measurement precision
If quality control is performed after the furnace using prior art techniques, then paint layer thickness can be determined, but the production time is increased and reworking rates remain high
Solution Approach 1:
The patent implements preliminary quality control measurement immediately after paint application, before the painting process is complete and before the furnace step. By measuring paint layer thickness and detecting defects at this early stage using non-contact optical methods, the system enables immediate feedback and correction, preventing defective parts from proceeding through the entire production process including the energy-intensive furnace step, thereby reducing both time and resource waste.
3Ease of operation
If non-contact THz radiation methods are used for paint film characterization, then contactless measurement is achieved, but the measurement system complexity and cost increase
Solution Approach 1:
The patent replaces expensive, complex THz radiation equipment with a relatively simple and inexpensive digital camera system. The camera captures standard visible light reflections, and through deflectometry algorithms, extracts paint layer thickness and surface curvature information. This substitution dramatically reduces equipment cost and complexity while maintaining non-contact measurement capability and achieving comparable or superior measurement accuracy for paint characterization.
4Reliability
If around 28% of automobile bodies undergo reworking due to quality control failures, then quality standards are maintained, but manufacturing costs and production complexity increase significantly
Solution Approach 1:
The patent implements a real-time feedback system where the camera continuously captures paint surface images during and immediately after application. The deflectometry system processes these images to calculate paint layer thickness and detect defects, providing immediate feedback to operators and the painting system. This enables real-time adjustments to painting parameters, preventing defective parts from being produced rather than detected later, thereby reducing reworking rates and improving overall manufacturing efficiency.
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 solution enables accurate and timely quality control of paint layers, reducing reworking and production time, and optimizing the painting process by allowing early detection and correction of defects, thereby decreasing manufacturing costs and increasing efficiency.
Implementation Method 1
a radiation emitter and a radiation receiver, which work in the Terahertz range, for measuring the parameter of the at least one paint layer
Implementation Method 2
a sensor arrangement comprising a deflectometry system including a camera for sensing an orientation and a distance of the measuring device with respect to a surface of the object
Data Source
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Figure 5
AI summary
A sensor system (1) for measuring a parameter of at least one paint layer provided on a surface of an object (2) is provided. It comprises a robot arm (40), a measuring device (42) mounted to the robot arm (40), comprising: a radiation emitter (10) and a radiation receiver (20), which preferably work in the Terahertz range, a sensor arrangement (25) for sensing an orientation and optionally a distance of the measuring device (42) with respect to a surface of the object (2) when the measuring device is positioned in a predefined pose, a control unit (30) configured for controlling the robot arm (40), and for controlling the operation of the measuring device (42), wherein the control unit (30) is configured to control a movement of the robot arm (42) with the measuring device (40) about the object (2), for carrying out a measurement of a parameter of the at least one paint layer at at least one predefined measuring location on the surface of the object (2), by taking into account positioning data of the robot arm (40) and measurement data from the sensor arrangement (25) and optionally from the radiation receiver (20), so that prior to carrying out a measurement: a distance between the measuring device (42) and the surface of the object (2) is adjusted to be in a predefined distance range, and a vector of the measuring direction of the measuring device (42) is adjusted to be normal with respect to the surface of the object (2) within an angular tolerance range from -5° to 5°. Further, a respective method is provided, and a coating facility including such a sensor system.