Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Modeling of the wet immersed tumbling process with the Discrete Element Method (DEM)
    ( 2021)
    Uhlmann, Eckart
    ;
    Fürstenau, J.-P.
    ;
    Kuche, Yves
    ;
    Yabroudi, Sami
    ;
    Polte, Julian
    ;
    Polte, Mitchel
    Immersed tumbling is an industrially established process for finishing of components made of metal, ceramic or plastic. In this process, the components are completely surrounded by a wet, abrasive medium, which allows burrs to be removed and surfaces to be polished. In order to gain specific insights into the influence and flow properties of the abrasive media used in this process, numerical approaches using the Discrete Element Method (DEM) with the Rocky DEM software are presented within these investigations. A complete process simulation could be realised by means of a digital machine tool. The immersed tumbling process with cone-shaped polymer abrasive media is implemented by use of a liquid bridge model. The results were validated by experiments with an industrially used immersed tumbling machine tool and for the first time allow sound statements about the contact conditions and interactions of the abrasive media with the workpiece.
  • Publication
    Development of a machining strategy for diamond slide burnishing burnishing tools made of polycrystalline diamond (PCD)
    ( 2020)
    Uhlmann, Eckart
    ;
    Polte, Mitchel
    ;
    Polte, Julian
    ;
    Kuche, Yves
    ;
    Wendorf, S.
    ;
    Siebel, D.
    High demands on product quality force companies to reduce production costs. Due to the growing international competition, optical surfaces for tool and mould making need to be produced economically. These surfaces are commonly produced using ultra-precision cutting. However, the efficiency is limited due to low feed velocities vf, small depth of cut ap and associated long process times tPr. An innovative manufacturing process represents diamond burnishing, which can be carried out directly after the high-precision milling process. For this purpose, super-hard materials made of single crystalline diamond (SCD) are currently used as tool materials. Since the material costs are high and the availability is limited, SCD needs to be substituted. An innovative substitution material is polycrystalline diamond (PCD). Within this paper, a machining strategy for the high-precision production of PCD spheres for diamond slide burnishing tools is presented. The processes grinding, p olishing and electrical discharge machining (EDM) were applied. Therefore, the manufacturing costs, the surface roughness, the shape accuracy as well as the concentricity accuracy were analysed. Based on these investigations, an efficient and economical machining strategy for the production of high-precision spherical geometries made of PCD can be provided. First results showed that the prefered machining strategy uses a cross-process chain consisting of grinding and polishing. Thereby, the advantages of both processes with the fast manufacturing of the macro-geometry by the grinding process as well as the high surface qualities, which can be achieved by the polishing process, are combined.
  • Publication
    Development of monolithic ceramic milling tools for machining graphite
    ( 2020)
    Uhlmann, Eckart
    ;
    Polte, Mitchel
    ;
    Polte, Julian
    ;
    Kuche, Yves
    ;
    Hocke, Toni
    Due to the international competition, continuous increases in productivity, product quality and reduction of production costs are required. Especially, the development of milling tools made of innovative cutting materials and application-specific tool geometries are in focus to overcome these challenges. Besides copper, graphite is the most important electrode material for electrical discharge machining (EDM). The machining of graphite leads to high tool wear due to a strong abrasive effect. Short tool life has a considerable influence on the economic efficiency of manufacturing processes. Currently, for the machining of graphite cost intensive diamond coated carbide tools are applied. In order to reduce machining costs, innovative cutting materials and dedicated manufacturing processes have to be applied. First results show a great potential of ceramics as tool material for machining graphite. The aim of this investigation is the characterisation and identification of novel ceramic cutting materials and the evaluation of an innovative tool micro-geometry especially designed for machining graphite. Therefore, the cutting material properties such as hardness, fracture toughness and wear resistance of four ceramic materials were investigated. Various hardness tests and particle blasting tests were carried out. Based on this investigations to manufacture the ceramic milling tools, a specific and innovative tool micro-geometry with defined angles was used. Thereby, a suitable cutting ceramic was identified, which represents a promising approach for an optimised machining of graphite.
  • Publication
    DEM-simulation of particle behaviour during cutting edge preparation of micro-milling tools by immersed tumbling
    ( 2020)
    Uhlmann, Eckart
    ;
    Polte, Mitchel
    ;
    Polte, Julian
    ;
    Kuche, Yves
    The micro-milling process is widely used in industry for the manufacturing of complex geometries for a wide range of materials. To increase the tool life and cutting length the cutting edge preparation could be successfully established. Within preliminary investigations the immersed tumbling process was identified as the most promising process for cutting edge preparation of micro-milling tools. The process enables a reproducible cutting edge preparation with constant cutting edge radii as well as low chipping of the cutting edges. For a profound understanding of the preparation process and the process mechanisms further knowledge about the particle interactions with cutting tools as well as the particle flow mechanisms needs to be obtained. Therefore, the process simulation using discrete element methods (DEM) offers the possibility of an improved understanding of the process behaviour. In this investigation simulation studies about the cutting edge preparation of micr o-milling tools using the immersed tumbling process will be presented. The DEM with the software ROCKY DEM from the company ESSS, Florianópolis, Brasil, was used and a process model was derived. The investigations show that the software can be successfully used for the visualisation of the immersed tumbling process and the flow mechanisms can be examined more closely.
  • Publication
    Verschleißverhalten neuartiger Mikrofräswerkzeuge mit Schneiden aus CBN bei der Hartzerspanung
    ( 2018)
    Uhlmann, Eckart
    ;
    Polte, Julian
    ;
    Polte, Mitchel
    ;
    Kuche, Yves
    ;
    Wiesner, Hagen Maximilian
    In der Mikroproduktionstechnik bei der Zerspanung mit geometrisch bestimmter Schneide und Werkzeugdurchmessern von D < 1mm stellt der Werkzeugverschleiß einen entscheidenden Faktor für die Entstehung hoher Fertigungskosten dar. Ein großes Anwendungsfeld der Mikrozerspanung ist die Fertigung hochpräziser Spritzgusswerkzeuge für die Serienfertigung von Präzisionskunststoffteilen. Gefordert werden dabei hohe geometrische Genauigkeiten und niedrige Oberflächenrauheitskennwerte. Um diese Anforderungen zu erfüllen, ist eine stetige Forschungsarbeit notwendig. Ein Ansatzpunkt zur Optimierung der Fertigungsprozesse ist der Einsatz neuartiger Schneidstoffe und Werkzeuggeometrien.
  • Publication
    Influence of cutting edge micro-geometry in micro-milling of copper alloys with reduced lead content
    ( 2018)
    Uhlmann, Eckart
    ;
    Kuche, Yves
    ;
    Polte, Julian
    ;
    Polte, Mitchel
    Especially copper-zinc alloys (CuZn) with good machining properties are used for electrical components and fittings. By using copper alloys with lead content of 1 % < Pb < 3 % an improved chip breakage can be achieved. Legal regulations require the reduction of lead and demand further knowledge about the effect of the material properties in interaction with the used micro-milling tools. In this contribution the cutting conditions of copper as well as four copper alloys were examined. The results show considerable differences in the resultant surface roughness and burr formation. Furthermore, the influence of two different tool geometries and variied cutting edge micro-geometries were investigated while machining CuZn21Si3P. Thereby, tools with increased cutting edge radii rv showed increased active forces Fa, burr height h0 and decreased surface roughness.
  • Publication
    Wear behaviour of HIPIMS coated micro-milling tools with cutting edge preparation for machining steel moulds
    ( 2018)
    Uhlmann, Eckart
    ;
    Kuche, Yves
    ;
    Polte, Julian
    ;
    Polte, Mitchel
    Micro-milling is an appropriate process for the industrial production of precision parts in the mould and die industry. Decisive for a long tool life is the wear resistance, which can be improved by cutting edge preparation technologies and tool coatings. Especially the improvement of the coating technology with the high power impulse magnetron sputtering (HIPIMS) provides improved tool wear behaviour and longer path length lc. Further studies compare two different HIPIMS-coatings of micro-milling tools for machining the mould steel X13NiMnCuAl4-2-1-1. Furthermore, the tool wear could be reduced due to cutting edge preparation using immersed tumbling process. In consequence of the increased cutting edge radii rβ the measured active forces Fa increased slightly. Best results were achieved for micro-milling tools with cutting edge preparation and AlTiN coating.
  • Publication
    PKD-Glattdrückwerkzeuge für den Werkzeug- und Formenbau
    ( 2018)
    Uhlmann, Eckart
    ;
    Polte, Mitchel
    ;
    Polte, Julian
    ;
    Guhde, Sebastian
    ;
    Kuche, Yves
    ;
    Kappel, Thomas
    Es wurden Glattdrückwerkzeuge mit Sphärenkopf aus polykristallinem Diamant der Firma Baublies AG, Rennigen, genutzt. Das Werkzeugkonzept orientiert sich dabei an den aktuellen Herausforderungen beim Werkzeug- und Formenbau sowie an handelsüblichen Zerspanwerkzeugen. In diesem Beitrag sind das Werkzeugkonzept, der Versuchsaufbau und die ersten Ergebnisse zur Kraftmessung dargestellt. Darüber hinaus werden die erreichbare Härtekennwerte und die Rauheitskennwerte in Abhängigkeit verschiedener Prozessparameter sowie zu den Ausgangswerten verglichen.