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Effiziente KSS-Zufuhr in additiv gefertigten Fräswerkzeugen
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Laser-based powder bed fusion of metals (PBF-LB/M) is an emerging technology with enormous potential for the fabrication of highly complex products due to the layer-wise fabrication process. Low-alloyed steels have recently gained interest due to their wide potential range of applications. However, the correlation between the processing strategy and the material properties remains mostly unclear. The process-inherent high cooling rates support the assumption that a very fine martensitic microstructure is formed. Therefore, the microstructure formation was studied by means of scanning electron microscopy, hardness measurements, and an analysis of the tempering stability. It could be shown that additively manufactured Bainidur AM samples possess a bainitic microstructure despite the high process-specific cooling rates in PBF-LB/M. This bainitic microstructure is characterized by an excellent tempering stability up to temperatures as high as 600 °C. In contrast to this, additively manufactured and martensitic-hardened specimens are characterized by a higher initial hardness but a significantly reduced tempering stability. This shows the potential of manufacturing products from Bainidur AM for high-temperature applications without the necessity of a post-process heat treatment for achieving the desired bainitic microstructure.
Metal powder bed-based Additive Manufacturing (AM) technologies, such as Electron Beam-Melting (EBM) and Laser Powder Bed Fusion (LPBF), are established in several industries due to the large design freedom and mechanical properties. While EBM and LPBF have similar operating steps, process-specific characteristics influence the component design. The differences in the energy coupling lead to differing solidification conditions, microstructures, and, thus, mechanical properties. The surface finish and geometrical accuracy are also affected. As opposed to LPBF, EBM powder layers are preheated prior to selective melting. In this study, similar volume energy densities in LPBF and EBM were used to manufacture Ti6Al4V test geometries to assess the process transferability. Since the energy coupling of LPBF and EBM differ, heat source absorption was considered when calculating the volume energy density. Even when a similar volume energy density was used, significant differences in the component quality were found in this study due to specific respective process constraints. The extent of these constrains was investigated on voluminous samples and support-free overhanging structures. Overhang angles up to 90° were manufactured with LPBF and EBM, and characterized with regard to the relative density, surface roughness, and geometric compliance.
The growing global energy demand from industry results in significant ecological and economical costs. Aiming to decrease the impact of machining operations, an increasing number of research activities and publications regarding energy efficient machine tools and machining processes can be found in the literature. This keynote paper provides an overview of current machine- and process-related measures to improve the energy efficiency of metal cutting machine tools. Based on an analysis of the energy requirements of machine tool components, design measures to reduce the energy demand of main and support units are introduced. Next, methods for an energy efficient operation of machine tools are reviewed. Furthermore, latest developments and already available energy efficiency options in the machine tool industry are discussed. The paper concludes with recommendations and future research questions for more energy efficient machine tools.
In this review, the present situation of H13 tool steel formed by selective laser melting (SLM) is introduced in detail. This review shows the current academic exploration and achievements in this field through the three aspects of microstructure, defects, and mechanical properties. We presented the distribution of the alloy elements and the different crystal morphology. We summarize the main defects of this alloy prepared by SLM from three aspects: the rough surface, cracks, and low density. The mechanical properties of H13 tool steel formed by SLM are also introduced. All in all, it shows a wide application prospect of SLMed H13 steel.
As a result of the material-specific segmented chip formation occurring during the machining of titanium alloys, the tools used can be set into vibration significantly depending on the given process conditions. In addition to an increased tool wear, this often leads to not being able to achieve the required workpiece qualities. With the use of additively manufactured tool holders for turning TiAl6V4, a passive damping of such chip-induced tool vibrations can be realised. The decisive factor is the production of specially structured hollow elements in the tool holder shafts, which can be realised by the additive manufacturing process. The tools’ vibration amplitudes were significantly reduced on the one hand due to the resulting vibration-optimised tool design, and on the other hand due to the internal friction of additional filling materials applied into the shafts hollow elements.
The purpose of this document is to investigate the influence of heat treatment on the mechanical properties of parts from MAR 300 (EN 1.2709) produced by LPBF. In order to compare the influence of the heat treatment on the parts properties, some parts were in the state solution annealed and others age hardened tested. For the quality in the LPBF the feedstock powder as starting material is of great importance. Therefore, powder characterization has been performed in order to work out ageing effects after multiple use. As a major ageing effect an increasing oxygen content could be identified which might affect process and parts quality. For industrial acceptance, AM parts need to be produced to the best available tolerances and with well-understood mechanical properties. For this purpose, the mechanical properties of the LPBF samples have been analysed and are compared to those properties for conventional samples. In this investigation, the mechanical tests (hardness test, tensile test and notch impact resistance) have been performed in horizontal and vertical directions of manufacturing by LPBF. The hardness increased from 333~341 HV10 to 640~656 HV10 after heat treatment. Simultaneously, the ultimate tensile strength (Rm) increases from 1056~1096 MPa to 1964~2102 MPa, while the break elongation (εtot) is reduced from 11.3~16.0% to 2.0~4.5%. Aged samples show a significant decrease in toughness in the Notch Impact Test. A specifically designed ball joint test setup has shown that the frame manufactured by LPBF provides comparable results as a conventionally manufactured frame and is robust and suitable for the prototype production and test of car headlamps.
The focused cutting fluid supply on the rake face of cutting tools has proven its positive impact on tool wear and chip formation in many machining processes. However, the realization of internal coolant channels in indexable milling cutters is difficult. Traditionally manufactured milling tools feature drilled coolant channels. Hence, the channels are restricted to being straight holes with intersections. In this paper, an additively manufactured tool with improved coolant channels was compared to a conventional tool when machining AISI 4140+QT. The additive tool resulted in lower tool wear and different vibration behavior compared to the conventional tool.
High-pressure cutting fluid supply has a major influence on tool wear and chip formation, especially in difficult-to-cut materials, such as titanium alloys and quenched and tempered steels. The titanium alloy TiAl6V4 features high temperature strength, low thermal conductivity and a low E-modulus. Therefore, high mechanical loads and high temperatures occur in the contact zone between work piece and tool, which is the reason why machining of this material is accompanied by high tool wear. In contrast to machining steel, only a low fraction of the generated heat is dissipated by the chip, which thermomechanically accelerates tool wear mechanisms. Machining of quenched and tempered steel on the other hand is characterized by high abrasive wear due to hard particles, because of the martensitic microstructure. The focused high-pressure cutting fluid supply between the emerging chip and the rake face of the tool showed its potential to reduce thermomechanical induced wear mechanisms in many examinations during turning, resulting from the more effective cooling and lubrication of the contact zone. However, engagement conditions in milling differ substantially from turning, which is the reason for the demand of experimental investigations. In this paper, the tool life and chip formation was examined in face milling with indexable inserts and internal cooling channels that were focused to the rake faces of the inserts. The number of cooling nozzles and their orientation were varied. The cutting fluid was supplied internally through the milling tool with a pressure of p = 80 bar and constant volumetric flow rates. The results show major differences in chip morphology and tool wear depending on the number and orientation of the cooling nozzles. Moreover, different wear mechanisms were identified in reliance to the work piece material and the cooling nozzle orientation and number.
Band 1 des fünfbändigen Werkes behandelt das Spanen mit geometrisch bestimmter Schneide. Zu den Themen Schneidkantenpräparation, Hartzerspanung, Werkzeugdynamik und Spannsysteme sind völlig neue Kapitel entstanden. Aktuelle Forschungsergebnisse mit Praxisbezug wurden in die Kapitel Grundlagen der Zerspanung, Kühlschmierstoffe, Standvermögen und Simulation integriert. Ansätze der Prozessmodellierung und der statistischen Versuchsmethodik erweitern das Kapitel zur Prozessauslegung und Prozessüberwachung in der 9. Auflage. Das Buch stellt die wesentlichen Verfahrensprinzipien dar und erklärt die zu Grunde liegenden Wirkzusammenhänge. Es basiert auf den Vorlesungen Fertigungstechnik I und II, die an der RWTH Aachen gehalten werden.
Die Zielgruppen
Ingenieure mit Interesse an moderner Produktionstechnik und Studenten der Fachrichtungen Maschinenbau, Produktionstechnik, Konstruktion und Produktentwicklung sowie Berufspraktiker
Einfluss von KSS-Produkten auf den Werkzeugverschleiß beim HPC-Fräsen von Titan-Strukturbauteilen
- M Lange
FEM-basiertes Softwaresystem für die effiziente 3D-Gewindebohrsimulation und Werkzeugoptimierung mittels CFD-Simulation
- E Oezkaya
Hochdruck-Kühlschmierstoffzufuhr in der Zerspanung
- H Sangermann
A Practical Guide to Design for Additive Manufacturing
- O Diegel
- A Nordin
- D Motte
Surface anomalies in turning of difficult-to-cut materials with high-pressure coolant supply
- T Cayli
High-pressure cutting fluid supply in milling
- T Lakner
Beanspruchungs- und fertigungsgerechte Gestaltung additiv gefertigter Zerspanwerkzeuge
- T Scherer