Thickness determination of wet coatings using self-calibration method

Weber, Stefan; Klier, Jens; Ellrich, Frank; Paustian, Stephan; Güttler, Nico; Tiedje, Oliver; Jonuscheit, Joachim; Freymann, Georg von

doi:10.1109/irmmw-thz.2017.8067107

Cited by 4 publications

(5 citation statements)

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“…For thin layers with optical thicknesses of d opt < 150 μm, the pulses from the front and back interface are not temporally separable anymore. However, in order to determine the thicknesses of thin, single, as well as multilayer samples, a transfer-matrix model-based algorithm can be used to extract the thickness information from the measured waveform [5,13]. In [14], an optimized transfer-matrix model, Rouard-based approach, is described for thickness determination of up to four layers on different substrates.…”

Section: Figmentioning

confidence: 99%

Influence of System Performance on Layer Thickness Determination Using Terahertz Time-Domain Spectroscopy

Weber

Liebelt

Klier

et al. 2020

J Infrared Milli Terahz Waves

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The quality of coatings in industrial applications and scientific research with thicknesses in the micrometer range is an important criterion for quality management. Therefore, thickness determination devices are of high interest. Terahertz time-domain spectroscopy systems have demonstrated the capability to address thickness determination of dielectric single-and multilayer coatings on different substrates. However, due to the large range of different samples, there are different performance requirements to ensure a high-quality determination result. In this paper, we investigate the influence of system parameters-bandwidth and dynamic range-on thickness determination performance for a single-layer coating on metal substrates with thicknesses from 0.5 to 100 pm, based on measurements and numerical calculations within dynamic ranges from 10 to 90 dB and bandwidths from 1.5 to 10 THz.

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Section: Figmentioning

confidence: 99%

Influence of System Performance on Layer Thickness Determination Using Terahertz Time-Domain Spectroscopy

Weber

Liebelt

Klier

et al. 2020

J Infrared Milli Terahz Waves

Self Cite

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“…A sensor detects the reflecting parts and the film thickness of the individual layers is calculated with known material parameters. For a detailed description and comparison to conventional film thickness measurement methods like magnetiv-inductive the reader is referred to Pfeiffer et al [5] and Weber et al [6,7].…”

Section: Modules 2 and 3: Path Generation And Paintingmentioning

confidence: 99%

A self-programming painting cell "Equation missing" SelfPaint"Equation missing" : Simulation-based path generation with automized quality control for painting in small lot sizes

et al. 2021

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The increasing diversity of products and variants requires a flexible and fast path generation in robot-based painting processes. In the state of the art, path generation in the painting industry is a time consuming and cost-intensive iteration process in which the generated paths are evaluated and optimized via painting trials. In this paper, we present a novel concept for a self-programming painting cell, which is based on the key technologies 3D-scanning, multi-physics painting simulations, and a contactless film thickness measurement using terahertz technology. The core element of this cyber-physical painting system is a unique combination of numerical painting simulations with a gradientbased multi-objective optimization method, to virtually compute painting paths that produce a homogeneous thickness on the painted object. In order to drastically reduce the time and computationally intensive numerical fluid dynamic simulations, a step-by-step coupling of an offline and online simulation was implemented. In a final step, a collision free robot motion without singularities is generated automatically from the computed painting path. The concept was validated under pilot plant conditions by the painting of a fender using an electrostatically assisted high-speed rotary bell atomizer. The paint film thickness, measured with terahertz technology was used as the target and validation criterion, as it shows a strong correlation to other quality values. The results show that the achieved film thickness was within the process specification, although deviations between simulated and measured film thicknesses were found in the edge zones of the workpiece.

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“…Modern algorithms enable the evaluation of multilayer measurements within less than a millisecond on standard CPUs. This evaluation principle is not only applicable to extract the layer thickness, but also to determine the unknown optical constants and the layer thicknesses at the same time [33,34]. Figure 10 shows the evolution of these constants (or variables in this case) during a run of the Fig.…”

Section: Submillimeter Layer Characterizationmentioning

confidence: 99%

“…As the alcohol-based solvents are showing considerably different optical properties in comparison with the strongly absorbing bulk water, these two classes behave differently in the terahertz frequency range. Even though the absorption of bulk water is very high in the terahertz frequency range (about 250 cm −1 at 1 THz), the measurement of water-based paint is possible in general, as the layer thickness of wet paint is often less than a millimeter [33,34,48,49]. Figure 13 shows a measurement of wet paintings on a metallic substrate directly after the application of the paint and after curing in comparison with a tactile measurement with an inductive sensor.…”

Section: Wet Paintmentioning

confidence: 99%

Terahertz Quality Inspection for Automotive and Aviation Industries

Ellrich

Bauer

Schreiner

et al. 2019

J Infrared Milli Terahz Waves

131

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Nondestructive quality inspection with terahertz waves has become an emerging technology, especially in the automotive and aviation industries. Depending on the specific application, different terahertz systems-either fully electronic or based on optical laser pulses-cover the terahertz frequency region from 0.1 THz up to nearly 10 THz and provide high-speed volume inspections on the one hand and high-resolution thickness determination on the other hand. In this paper, we present different industrial applications, which we have addressed with our terahertz systems within the last couple of years. First, we show three-dimensional imaging of glass fiber-reinforced composites and foam structures, and demonstrate thickness determination of multilayer plastic tube walls. Then, we present the characterization of known and unknown multilayer systems down to some microns and the possibility of measuring the thickness of wet paints. The challenges of system reliability in industrial environments, e.g., under the impact of vibrations, and effective solutions are discussed. This paper gives an overview of state-of-the-art terahertz technology for industrial quality inspection. The presented principles are not limited to the automotive and aviation industries but can also be adapted to many other industrial fields.

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Thickness determination of wet coatings using self-calibration method

Cited by 4 publications

References 1 publication

Influence of System Performance on Layer Thickness Determination Using Terahertz Time-Domain Spectroscopy

Influence of System Performance on Layer Thickness Determination Using Terahertz Time-Domain Spectroscopy

A self-programming painting cell "Equation missing" SelfPaint"Equation missing" : Simulation-based path generation with automized quality control for painting in small lot sizes

Terahertz Quality Inspection for Automotive and Aviation Industries

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