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[ 1 ] Gonzalez Fernandez, G.; Plogmeyer, M.; Zanger, F.; Biehl, S.; Bräuer, G. & Schulze, V. . (2020), „Effect of tool coatings on surface grain refinement in orthogonal cutting of AISI 4140 steel“, Procedia CIRP 87, S. 176-180.
Abstract:
Recrystallization mechanisms leading to the generation of ultrafine grains (UFG) by surface severe plastic deformation (S2PD) at low temperatures (< 0.5Tm (melting temperature)) have been investigated over the last years. Material removal processes like broaching impose large plastic strains along the shear plane during chip formation, leading in many cases to changes in the workpiece subsurface microstructure. In this work the influence of the cutting material on surface grain recrystallization were studied on broaching of AISI 4140q&t steel. Orthogonal cutting tests were carried out in dry conditions on a broaching machine using tools with different coatings. Uncoated cemented carbide inserts were geometrically prepared using fixed abrasive grinding processes and then coated by physical vapor deposition (PVD) with Al2O3 and CrVN thin films. Workpiece subsurface layers were analyzed after machining by Focused Ion Beam (FIB-SEM) and X-ray diffraction (XRD). The presented results show the influence of the cutting material on the final microstructure of the machined workpieces through the determination of the final grain sizes and dislocation densities.

[ 2 ] May, M. C.; Kuhnle, A. & Lanza, G. (2020), „Digitale Produktion und Intelligente Produktionssteuerung“, wt Werkstattstechnik online, Band 4, S. 255-260. https://doi.org/10.5445/IR/1000119555
Abstract:
Im Rahmen der stufenweisen Umsetzung von Industrie 4.0 erreicht die Vernetzung und Digitalisierung die gesamte Produktion. Den physischen Produktionsprozess nicht nur cyber-physisch zu begleiten, sondern durch eine virtuelle, digitale Kopie zu erfassen und optimieren, stellt ein enormes Potential für die Produktionssystemplanung und -steuerung dar. Zudem ermöglichen digitale Modelle die Anwendung intelligenter Produktionssteuerungsverfahren und stellen damit einen Beitrag zur Verbreitung optimierender adaptiver Systeme dar.

[ 3 ] Wirth, F.; Nguyen, C.; Hofmann, J. & Fleischer, J. (2020), „Characterization of Rectangular Copper Wire Forming Properties and Derivation of Control Concepts for the Kinematic Bending of Hairpin Coils“. Procedia Manufacturing, Hrsg. Elsevier Ltd., S. 678-685.
Abstract:
As a result of the continuously growing demand for electric vehicles, innovative production technologies must be developed to fulfill the high automotive requirements for productivity and quality in the manufacturing of electric drives. By providing advantages regarding the degree of automation, the productivity as well as the attainable filling factors in comparison to established round wire winding technologies, the hairpin technology shows a high potential for meeting the requested specifications but also technological weaknesses, especially concerning the process reliability. The referring production process of stators is normally based on the spatial forming of open, hairpin-shaped coils of enameled flat copper wire as well as subsequent joining and contacting processes. Consequently, the hairpin coils represent the elementary components of the process chain and can be either shaped by robust tool-bound or flexible kinematic bending processes that enable the shaping of different contours at moderate tool costs. In this paper, the essential mechanical forming and product properties of flat copper wires with different dimensions and insulation coatings are characterized by means of uniaxial tensile tests as well as metallographic analyses of the material structure, at first. Subsequently, the identified forming properties are correlated to the applied manufacturing processes drawing, rolling as well as continuous extruding and considered as limits of possible material variations. To evaluate the effect of fluctuating wire qualities on the robustness of kinematic hairpin bending processes, the fabrication tolerances are analyzed by finite element simulations, using the example of elementary kinematic bending operations and modeled changes of the material properties. Based on the knowledge of material-based process tolerances, different control concepts for the kinematic bending of hairpin coils are derived and compared based on technical as well as economic aspects.

[ 4 ] Wirth, F. & Fleischer, J. (2019), „Influence of Wire Tolerances on Hairpin Shaping Processes“. 2019 9th International Electric Drives Production Conference (EDPC), Hrsg. IEEE, S. 1-8.
Abstract:
Due to the increasing sales of electric vehicles, new production technologies must be developed for meeting the growing demand for high productivity and quality in electric drives manufacturing. In comparison to conventional winding technologies, the hairpin technology provides significant advantages regarding the ability for automation, the productivity as well as the attainable filling factors, but also exhibits technological weaknesses concerning the process reliability. Since the shaping of hairpin coils represents the initial core process of the winding production by hairpin technology, geometric tolerances of the hairpin contour after shaping have a major impact on the downstream manufacturing processes. Especially the insertion of the coils into the stator slots as well as the twisting and contacting of the open coil sides are highly affected by variations in the positioning and orientation of the hairpin legs. Besides the process-based deviations caused by vibrations and tool displacements, the tolerances of hairpin contours are frequently induced by fluctuations of the geometric and material properties of the wire – like the dimensions and radii as well as the Young’s modulus and flow curve. In this paper, a holistic analysis of geometric and material tolerances of flat wires and their effect on the accuracy of hairpin shaping processes is shown. For this purpose, essential material properties of flat winding wires are characterized by means of tensile tests at first and subsequently used as boundary conditions for a numerical sensitivity analysis of a tool-bound hairpin shaping process. The FE-based analyses are carried out in Abaqus FEA using a fully parametrized simulation model that is validated by means of CT measurements. The derived knowledge about interdependencies between fluctuations of wire properties and the reliability of hairpin shaping processes enables the cost-effective definition of wire tolerances in compliance with quality specifications.

[ 5 ] Weinmann, H. W.; Töpper, H. & Fleischer, J. (2020), „Coil2Stack: Ein innovatives Verfahren zur formatflexiblen Batteriezellherstellung“, ZWF Zeitschrift für wirtschaftlichen Fabrikbetrieb, Band 115, Nr. 4, S. 241-243. 10.3139/104.112192
Abstract:
Die wirtschaftliche Herstellung von Lithium-Ionen-Batteriezellen in verschiedenen Formaten und aus unterschiedlichen Materialien fordert flexible Anlagen für die Stapelbildung. Im Rahmen dieses Beitrags werden deren Prozesse, aktuell verfügbare Lösungen sowie Trends in der Materialentwicklung analysiert, um ein neuartiges Anlagenkonzept abzuleiten, welches den Forderungen nach Flexibilität bezüglich Zellformat und Material gerecht wird und bisher bestehende Defizite ausgleicht.