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According to the current state of the art, wear conditions of forging dies are assessed visually in the dismantled state, as there is no measuring procedure available for inline wear measurement of hot forging dies. This paper introduces a handling concept for automated loading and in-situ tool inspection for a hot forging process. Based on an industrial robot and quickchange systems, the process integration of hightemperature grippers and an endoscopic 3D-measurement sensor for the in-situ inspection of hot forging dies is carried out. By adapting the measuring method of fringe projection to an endoscopic design, the measuring system can be navigated into the difficult-to-access geometry of the die and take high-precision 3D-measurements inside. The ambient air heated by the forming process creates an inhomogeneous refractive index field around the measuring system and the hot die, so that the straight beam path required for optical measuring systems cannot be ensured. This can lead to strong deviations in the reconstructed point clouds and the functional geometries derived from them. By means of a compressed air actuator, the measuring system can be protected from the hot tool and dirt as well as the effect of inhomogeneous refractive index can be reduced. With this approach the in-situ wear measurement at highly stressed regions using the example of the mandrel radius and the flash radius will be demonstrated. These functional elements are of particular relevance, as the thermalstress is high and large material flow takes place. For the wear measurement, the functional elements of the tool are examined in detail by fitting geometrical features into the reconstructed point clouds and determining the deviations from a reference geometry. In addition, the measurement data is validated with the aid of a commercially available state-of-the-art measurement system.

SARS-CoV-2 papain-like protease (PLpro) covers multiple functions. Beside the cysteine-protease activity, PLpro has the additional and vital function of removing ubiquitin and ISG15 (Interferon-stimulated gene 15) from host-cell proteins to aid coronaviruses in evading the host’s innate immune responses. We established a high-throughput X-ray screening to identify inhibitors by elucidating the native PLpro structure refined to 1.42 Å and performing co-crystallization utilizing a diverse library of selected natural compounds. We identified three phenolic compounds as potential inhibitors. Crystal structures of PLpro inhibitor complexes, obtained to resolutions between 1.7-1.9 Å, show that all three compounds bind at the ISG15/Ub-S2 allosteric binding site, preventing the essential ISG15-PLpro molecular interactions. All compounds demonstrate clear inhibition in a deISGylation assay, two exhibit distinct antiviral activity and one inhibited a cytopathic effect in a non-cytotoxic concentration range. These results highlight the druggability of the rarely explored ISG15/Ub-S2 PLpro allosteric binding site to identify new and effective antiviral compounds. Importantly, in the context of increasing PLpro mutations in the evolving new variants of SARS-CoV-2, the natural compounds we identified may also reinstate the antiviral immune response processes of the host that are down-regulated in COVID-19 infections.

For the automated optical inspection of manufactured components with complex geometries or highly reflective surfaces, a suitable selection of measurement poses and the associated planning of the measurement trajectory is crucial. This is especially important for active triangulation measurement methods like fringe projection. Due to complex measurement object geometries or poor alignment of the measuring system the influence of multiple reflections can potentially lead to incorrect or incomplete 3-D reconstruction of the specimen surface. This paper introduces a simulative GPU-based inverse ray tracing approach to identify low-reflection measurement poses for active optical measurement systems. Starting from the virtual camera origin, rays are emitted from each camera pixel and the reflection at the measurement objects surface is calculated using the Torrence- Sparrow BRDF. With an additional approach based on Whitted raytracing, the influence of multiple reflections and the reflection depth on the rendered camera image is taken into account. By calculating the summed reflection depth of each rendered measurement sequence, a height map of the reflection frequency distribution is created. By sampling a predefined surface point on the path of a limited sphere, the comparability of possible measurement poses is achieved. Thus, local minima can be identified and the poses with the lowest reflection influence can be selected to perform a suitable trajectory planning. This a priori knowledge can also be transferred into application and used for the estimation of image areas, which captured multiple reflections. Thus for these areas specific masks are generated and can be applied in real measurements to reconstruct multiple reflection free surfaces.

The rapid developments in the micro camera industry, driven by the smartphone sector, offer a wide range of innovations with respect to the performance and miniaturization of endoscopic instruments. For the fast 3D inspection of inaccessible components such as turbine blades in partially disassembled aircraft engines, a borescopic fringe projection system was developed. This study provides a methodology for the comparison of different camera and projection configurations within borescopic fringe projection. Furthermore, the current limits for the use of multimedia sensors in metrological applications are shown and quantified. The projection unit of the developed measuring system is based on a digital micromirror device, which generates structured light that is imaged into the measurement scene by means of an objective lens and a borescope. Threedimensional, high-resolution reconstructions are carried out via chip-on-the-tip miniature cameras based on the MIPI interface by forming a triangulation base with the projection unit. To enable inspections in confined spaces, the cameras are connected to external framegramer boards. In this study, 1/6” and 1/4” sensors with fixedfocus lenses are evaluated to assess the trade-off between the physical sensor size and the possible reconstruction accuracy. Typical camera parameters such as the sensitivity with respect to the signal-to-noise ratio are determined by means of a standardized test setup. In addition, the application in the triangulation system is evaluated through the modulation signal strength as well as the suitability for typical system calibrations based on the widely used pinhole camera model in combination with a distortion polynomial correction according to the approach of Conrady and Brown. Finally, the sensors are compared regarding 3D reconstructions of calibrated geometric features in accordance with ISO/IEC Guide 98-3:2008 and VDI/VDE 2634-2.

The regeneration of aircraft engines provides a key approach in order to reduce operating costs of these complex capital goods. The efficient and resource-saving maintenance of aircraft engines is particularly challenging, as they are made from a variety of different parts with locally adapted properties and different functionalities, which therefore also differ in the requirements in surface quality. The engine parts are manufactured and repaired on different machines, such as milling or turning machines. The subsequent quality check is realized with the help of highly specialized metrology systems. In case of so-called aircraft blisks, tactile coordinate measuring machines are used to measure the blisks surface data in regions with limited accessibility. The state-of-the-art regeneration procedure is therefore time-consuming and costly, as the parts need to be moved and mounted several times. In this paper, we present a blisk regeneration approach, which is meant to allow the inline quality monitoring of the regeneration process within a milling machine by means of a rigid endoscopic fringe projection system. The presented approach is meant to be time- and resource-saving as the fringe projection system is directly used in the blisk repair environment. To this end, we present the developed measurement system, outline the planned system integration into the milling machine and define challenges that arise due to the calibration of optical measurement systems within the production environment. The borescope with a chip-on-the-tip camera at the measuring head offers the possibility to drive into limited space and to perform high-precision 3-D measurements.