Thermographic Surface Layer Inspection for Solvent Evaporation Defects

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Solution Overview

Problem

Existing methods for inspecting surface layers of coating materials on components are limited, unreliable, or costly, and cannot effectively detect defects such as air inclusions and contaminants.

Innovation Solution

A testing method using a thermographic camera to measure temperature changes caused by solvent evaporation from coating materials, allowing for the determination of layer parameters like width, thickness, and solvent content, and detection of defects by analyzing temperature profiles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional inspection methods (gloss level monitoring, UV camera monitoring) are used, then surface layer inspection is possible, but the methods are unreliable or require extensive project-specific trials and have strong dependence on ambient conditions

Engineering Contradiction:
Improvereliability of surface layer inspectionVSAvoidcomplexity of inspection system
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces optical inspection methods (gloss monitoring, UV camera) with a thermal measurement method using infrared thermography. The temperature change of the surface layer is measured to detect coating application, eliminating dependence on ambient light and coating material properties. This substitution provides more reliable inspection without requiring complex project-specific trials.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the inspection parameter from optical properties (gloss level, UV fluorescence) to thermal properties (temperature change). By measuring the temperature change of the surface layer caused by solvent evaporation, the method achieves reliable inspection that is independent of ambient light conditions, coating material composition, and surface properties.

Inventive Principle:
Principle #35Parameter changes

2Measurement precision

If UV camera monitoring with fluorescent material is used, then surface layer detection is possible in darkened area, but the coating material cost increases significantly and paint booth must be completely darkened

Engineering Contradiction:
Improvedetection capability of surface layerVSAvoidcost of coating material
Core Design Contradiction:
Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent extracts the detection principle from the coating material itself by measuring the temperature change caused by solvent evaporation. Instead of adding fluorescent materials to the coating (which increases cost), the method detects the natural thermal effect of the coating's solvent evaporation, eliminating the need for expensive fluorescent additives.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent converts the harmful effect of solvent evaporation (cooling effect) into a beneficial detection signal. The temperature change caused by solvent evaporation, which was previously just a physical phenomenon, is now used as the basis for reliable surface layer detection without requiring additional fluorescent materials.

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If thermographic method is used to measure evaporative cooling, then coated surface areas can be distinguished from uncoated areas, but the method requires precise temperature measurement capabilities

Engineering Contradiction:
Improveability to distinguish coated from uncoated areasVSAvoidtemperature measurement precision
Core Design Contradiction:
ReliabilityVSMeasurement precision

Solution Approach 1:

The patent uses an intermediary substance (solvent) that causes a measurable temperature change when applied to the surface. The solvent evaporation creates a thermal signal that mediates between the coating application and the detection system, enabling reliable distinction of coated areas without requiring extremely precise temperature measurements.

Inventive Principle:
Principle #24Intermediary (Mediator)

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

Provides accurate and reliable inspection of surface layers, enabling detection of defects and ensuring the coating material is within the optimal temperature range for subsequent processes, thus improving the quality and efficiency of bonding operations.

Implementation Method 1

solvent-based coating materials (e.g., primers, cleaning agents, activators, etc.) cause local cooling after application to the component surface, due to the evaporating solvent

Methodology Applied
Scientific EffectEvaporation: Evaporation

Implementation Method 2

the evaporative cooling of a coating is measured in order to distinguish coated surface areas from uncoated surface areas

Methodology Applied
Scientific EffectEvaporative cooling: Evaporative Cooler

Data Source

PatentEP4372308B1Test method and test device for testing a surface layer
Publication Date: 2026.03.18 DUERR SYST AG
  • EP4372308B1 patent drawingFigure 1
  • EP4372308B1 patent drawingFigure 2
  • EP4372308B1 patent drawingFigure 3

AI summary

The invention relates to a testing method and a testing device for testing a surface layer made of a coating material, in particular a solvent-based pretreatment material, a primer, an adhesive, a sealant, or an insulating material, on a component (1), in particular on a motor vehicle body component (1), wherein the surface layer causes a temperature change after its application to the component (1), in particular by evaporation of solvent from the surface layer. The invention provides that the temperature change caused by the surface layer is measured, in particular by means of a thermographic camera (10), in order to test the surface layer.