DE102025100487A1 describes a method and a device for measuring the composition of dynamic paint droplets. The aim is the monitoring of coating processes in spray painting. The patent application was filed by ai-quanton GmbH together with the Duale Hochschule Sachsen in Dresden.
The Challenge
The quality of a painted surface depends strongly on the composition of the paint. Color shade, waviness and other surface properties must match, even when parts are painted in different plants or lines. During atomization, the paint breaks up into many moving droplets. Pigments and metallic flakes are distributed inside them. Static droplets can be analyzed with spectroscopy or microscopy. For moving droplets in a spray, no such method was known.
Semi-Transparent or Non-Transparent?
A paint droplet passes a shaped light beam. Part of the light is reflected at its surface, and part is refracted through the droplet. Inside the droplet, the light is absorbed and scattered by the suspended particles. The more pigments and flakes a droplet contains, and the larger the droplet, the weaker the refracted light becomes.
Two detectors record the scattered light. The order of the signal peaks shows which light dominates. If the refracted light dominates, the droplet is semi-transparent. If the reflected light dominates, the droplet is non-transparent.
From Counting to Composition
The relative number of semi-transparent droplets in a statistically relevant ensemble describes the composition of the paint droplets. It reflects the particle concentration and the size of the suspended particles. In addition, the largest possible mean size of the semi-transparent droplets can be determined. Both values correlate and can be used to check each other.
The signal processing is simple: only the maxima of the scattered light signals must be detected. This enables compact and cost-effective instruments. Optionally, a machine learning model can classify the droplets from the signal shape of a single detector.
Applications
The method supports the monitoring and optimization of spray painting, for example in automotive painting with rotary atomizers. It helps to detect changes in paint properties and irregularities in droplet formation at an early stage. At ai-quanton, the principle is used in SprayQuantAI® SQA2, which distinguishes transparent and non-transparent droplets with two detector channels.
Published application (title page): DE102025100487A1 (PDF) · DEPATISnet
