J. Eur. Opt. Society-Rapid Publ. 2026, 22, 41 Ó The Author( s), published by EDP Sciences, 2026 https:// doi. org / 10.1051 / jeos / 2026033 Available online at: https:// jeos. edpsciences. org
EOSAM 2025 Guest editors: Omar El Gawhary, Stefan Witte, Ignacio Moreno
Journal of the European Optical Society-Rapid Publications
SHORT COMMUNICATION
Verifying optical simulations for infrared curing of powder coatings
Monika Kroneberger 1, H,*
, Eva Stanik 2, 3, H, and Thorsten Doehring 2 1 digitX GbR, Östlicher Dammweg 36, D-83052 Bruckmühl, Germany 2 Technische Hochschule Aschaffenburg, D-63743 Aschaffenburg, Germany 3 NETZ Technologietransferzentrum für nachhaltige Energien, D-63755 Alzenau, Germany
Received 29 December 2025 / Accepted 26 March 2026
Abstract. In line with the energy transition, it is desirable to replace fossil fuels in the curing process of industrial powder coatings. Infrared heating is the considered method here. Near Infra Red-emitter arrangement in the reflective heating chamber, their geometry and the dwell time of the components are crucial for a successful and efficient process. Process optimization has to consider the optical parameter variation of the powder coating during the procedure. Measurements in the NAPUBEST(“ Nachhaltige Pulverbeschichtungs- Technologie”: sustainable powder coating technology) prototype are compared with optical simulations of the setup to get the simulation parameters in agreement with reality and to provide a foundation for the layout of industrial processes.
Keywords: IR-curing, Optical simulation, Powder coating, Sustainable energy transition, Infrared heating.
Introduction
The recent energy crisis revealed the dependence of many manufacturing companies on fossil fuels. Industrial processes need to be transformed into sustainable alternatives. For powder coatings, which traditionally rely on gas or oil heating systems, short wave infrared radiation e. g. from infrared heating emitters can deliver the required process heat. It is an approved method for flat steel strip surfaces in the steel industry [ 1 ]. The strong dependence of the IR absorption on the geometry of the irradiated parts as well as on the colour and sort of the coating powder [ 2, 3 ] has to be considered before the deployment of this innovative heating. The aim of the NAPUBEST project( German abbreviation for“ Nachhaltige Pulverbeschichtungs-Technologie” which means“ Sustainable Powder Coating Technology”) is to get a better understanding of these correlations. In our laboratory, we created a prototype of an octagonal IR oven for test measurements. The high reflectivity of silver-coated reflector sheets facilitates the concentration of infrared radiation inside the oven. On the other hand, the absorption of powder-coated samples in different paint colours has an impact on the heating efficiency. The arrangement of the Near Infra Red( NIR)-emitters in the reflective heating chamber, the geometry and the dwell time of the components are therefore crucial for a
* Corresponding author: monika. kroneberger @ digitx. de H These authors contributed equally to this work. successful and efficient process. Process optimisation has to consider various optical and mechanical parameters for different coatings and components. Some of the parameters are also subject to change during the curing procedure.
The objective of this investigation is the verification of a simple simulation model with simplified optical parameters that can be easily adapted and used during production.
Simulation model and heating tests
The NAPUBEST heating chamber is made of Alanod Miro Silver sidewalls and a Heraeus Noblelight M220x511 NIR / SWIR heating module with 4 fast short wave emitters( 1.5 kW, 1.4 lm peak wavelength each) [ 4 ]. The high reflectivity of the Alanod sheets guarantees a homogeneous radiance inside the chamber( except in front of the infrared emitters). For the optical simulations, the program FRED from Photon Engineering was used. The geometry of the heating chamber was exactly reproduced in the simulation model. The heating module was represented by the aluminum backside of the emitter-mount, the fused silica glass cover and the 4 emitter tubes. The filaments of the emitters were simulated as an emitting tube.
Since the heating chamber has no facility( yet) to hang the samples into the middle of the chamber they were placed onto the bottom sheet. The same position was used in the simulation( see Fig. 1). Free hanging as in conventional gas ovens will be beneficial since the light will reach
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