Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Application of Micro Structured, Boron Doped CVD-diamond as mEDM Tool Electrodes
    ( 2018)
    Uhlmann, Eckart
    ;
    Oberschmidt, Dirk
    ;
    Bolz, Robert
    High precision cavities are used for micro injection and micro embossing tools in the field of tool making and are mainly used for small batch or mass production of micro parts. In order to fabricate a large quantity of parts, wear resistant tool materials are required. In possession of a high hardness and a high Young's Modulus, such materials are often hard or even impossible to machine by conventional fabrication processes. Being independent of the work piece's mechanical properties, Micro-Electrical Discharge Machining (mEDM) is predestined for this case. mEDM is based on the modification of state of the art process technologies and universal machine tools applied for electrical discharge machining operations [1], [2]. Besides the adjustment of the electrical parameters, the mEDM-process is also determined by the tool electrode's material which has a big influence on the material removal rate VW, the electrode's wear behavior, as well as the process results concerning surface quality and dimensional accuracy [3]. Experimental investigations aim at decreasing the wear of tool electrodes using novel electrode materials. To assure an efficient process, short production times and low tool wear TH are demanded. Therefore, electrodes with excellent electrical and thermal conductivity along with a high mechanical strength have to be used. Boron doped CVD-diamond is fulfilling these criteria. Microstructures within thin CVD-diamond foils are realized by direct structuring utilizing laser ablation and by indirect structuring using micro-structured copper substrates in the CVD-process, which transfer the micro-structure onto the growing diamond layer. Experiments were conducted in order to identify suitable EDM-parameters for different workpiece materials, namely steel 90MnCrV8, silicon carbide SiSiC and tungsten carbide K40F, which lead to lower tool wear TH and high accuracy.
  • Publication
    Boron-doped CVD diamond micro-end mills for machining titanium
    ( 2018)
    Uhlmann, Eckart
    ;
    Polte, Mitchel
    ;
    Polte, Julian
    ;
    Oberschmidt, Dirk
    In industry micro-milling tools made of cemented carbide are widely used. However, these micro-milling tools suffer from fast and random tool breakage during the machining of hard to machine materials. Therefore, in preliminary work micro-milling tools with cutting edges made of boron doped chemical vapour deposition (bdCVD) diamond were developed. In this work new micro-milling tools were successfully applied for machining titanium grade 2. Comprehensive cutting tests were carried out to analyse the influence of the spindle speed n, the feed per tooth ft, and the depth of cut ap on the surface roughness. Further experiments addressed the wear behaviour of the developed micro-milling tools. After a path length lc of 10 m a maximum width of flank wear land VBmax of 29 µm were observed.
  • Publication
    Ductile machining of brittle materials for manufacturing micro-optic components
    ( 2018)
    Uhlmann, Eckart
    ;
    Oberschmidt, Dirk
    ;
    Rolon, D.A.
    ;
    Kühne, S.
    ;
    Jagodzinski, M.
    ;
    Malcher, M.
    Due to the geometry and specification of micro-optic components, these may not be ground or polished, therefore they demand other manufacturing processes such as ultra-precision (UP) machining with defined cutting edge tools. Despite previous studies, the machining of brittle materials remains a challenge for manufacturing those components in UP processes. For example, ductile machining of silicon is extensively studied, however, ductile machining of materials such as Zerodur®, GaP, U.L.E.® and glass is still a challenge to overcome. Therefore, this paper aims at reporting the ductile or part-ductile machining of silicon and Zerodur® pieces in UP processes. Experiments were carried out using UP-shaping and plane turning processes in an UP-machine tool. Moreover, monocrystalline diamond tools were employed. During UP-turning experiments, the process forces were measured. The machining results were obtained by White Light Interferometer (WLI) of the representative mach ined surfaces. In order to complement the experiments, simulations were performed in finite element software to comprehend the influences of the rake angle on ductile machining of those materials. After the UP-shaping experiments, the depth of cut was determined for each of the mentioned materials together with the main influence of each process parameter. Furthermore, a reduction of parameter ranges for UPturning experiments was accomplished. Using Design of Experiments for UP-turning tests, the main influences of process parameters were observed and detailed, together with tool geometry optimization and recommendation for further experiments. The local optimum of process parameters was found as well as the accomplishment of ductile removal during the machining tests. These results and simulation models are going to be further used for a more detailed process description, as analogous tests and optimization of UP processes such as micro-milling.
  • Publication
    Diamond burnishing for mould and die industry
    ( 2018)
    Uhlmann, Eckart
    ;
    Oberschmidt, Dirk
    ;
    Guhde, Sebastian
    ;
    Polte, Mitchel
    ;
    Polte, Julian
    Special ultra-precision processes are necessary to machine surfaces for optical applications with required surface roughness Ra < 30 nm. The use of ultra-precision cutting results in low feed f and significantly reduced cost-efficiency. Diamond burnishing can be a cost-effective alternative. The process reduces the surfaces roughness and generates residual stress, which is advantageous for the workpiece's fatigue strength. However, diamond burnishing is mostly used for post-processing of rotating parts. Applications of diamond burnishing by linear motion, e. g. in mould and die making, are not common. The article shows first investigations to manufacture surfaces with optical quality on milled parts made of steel X37CrMoV5-1, copper CW008A, brass CW612N and aluminium 5083. The experiments were carried out on a 5-axis milling machine tool PFM 4024-5D, PRIMACON GMBH, PeiÃenberg, Germany. The feed velocity, the penetration depth, and the stepover were varied as input para meters. Vickers hardness and the surfaces roughness were measured as reference criteria. Thus, the ability for the surface improvement by diamond burnishing of complex shaped surfaces could be shown.
  • Publication
    Mikro- und Makrozerspanung von PM-Stählen
    ( 2016)
    Uhlmann, Eckart
    ;
    Richarz, Sebastian
    ;
    Oberschmidt, Dirk
    Voraussetzungen für die wirtschaftliche Zerspanung von gehärteten Stahlwerkstoffen sind neben entsprechend steif ausgelegten Maschinen insbesondere optimierte Bearbeitungsprozesse und geeignete Werkzeuge. Neu- und Weiterentwicklungen im Bereich der Schneidstoff- und Beschichtungstechnologien zeigen hierbei großes Potenzial für eine wirtschaftliche und prozesssichere Hartdreh- und -fräsbearbeitung von Stählen mit Rockwellhärten um 65 HRC. Ziel der Arbeiten am IWF war daher die Erarbeitung einer Fertigungsstrategie bestehend aus Schneidstoff, Werkzeuggeometrie und kinematischen Zerspanungsgrößen, die ein prozesssicheres und wirtschaftliches Hartdrehen und -fräsen ermöglicht. Der makroskopisch zu zerspanende pulvermetallurgisch hergestellte Schnellarbeitsstahl HS6-5-3, Werkstoffnummer 1.3344 (auch AISI M3 oder PM23), lag in einer anwendungstypischen Kernhärte von 65±3 HRC vor. Die Ergebnisse zeigen, dass die Hartbearbeitung von pulvermetallurgisch erzeugten Stählen auch im Härtebereich von 65 HRC prozesssicher möglich ist. Für experimentelle Untersuchungen zum Mikrofräsen wurde der Werkstoff PM X190CrVMo20 eingesetzt. Im Ergebnis wurde eine Werkzeuggeometrie entwickelt, mit der es möglich ist, die Mikrozerspanung von PM-Stählen hoher Härte zu ermöglichen. Werkzeugbruch konnte durch diese Entwicklung als Hauptversagenskriterium eliminiert werden. In Zerspanversuchen konnten Aussagen zu geeigneten Schneidstoffen und Beschichtungen sowie Werkzeuggeometrien als auch Richtwerten beim Werkzeugeinsatz erarbeitet werden.
  • Patent
    Getriebeeinrichtung
    ( 2014)
    Oberschmidt, Dirk
    ;
    Uhlmann, Eckart
    The invention relates to a transmission device, comprising a drive module that can be rotationally driven about a driving axis (3). In order to ensure uniform loading of a tool that is to be drivable by means of the drive module, it is provided that the drive module has a base (1, 2, 26, 27, 28, 31 32) rotatable about the driving axis and an output element (12, 13) for transmitting a rotational motion to a functional element, the output element being mounted rotatably about an output axis (12a) in relation to the base, wherein the base is rotatable in relation to an arrangement of teeth (4a), in particular a stationary arrangement of teeth, and has a planet gear (5), which is mounted rotatably about a first auxiliary axis (8) and which revolves on a circular path (20) during the course of rotation of the base, is driven by meshing with the arrangement of teeth, and interacts with the output element (12, 13) directly or by means of one or more additional gears.
  • Patent
    Einrichtung zur Beaufschlagung eines Fluids mit wechselndem Druck
    ( 2014)
    Oberschmidt, Dirk
    ;
    Uhlmann, Eckart
    Die vorliegende Erfindung bezieht sich auf eine Einrichtung zur Beaufschlagung eines Nutzfluids mit wechselndem Druck mit einer Versorgungseinrichtung (1), die einen Verbindungskanal (6) aufweist, der ein Hydraulikfluid führt, sowie mit Schaltmitteln (5), die den Verbindungskanal (6) wahlweise mit einem ersten Druckreservoir (3) mit einem ersten Druck oder mit einem zweiten Druckreservoir (4) mit einem zweiten Druck verbinden, und mit einer Arbeitseinrichtung (2), die eine Arbeitskammer (12) zur Aufnahme des Nutzfluids, einen in der Arbeitskammer (12) mündenden, durch eine erste Verschlussvorrichtung (26) verschliessbaren Zuleitungskanal (12) für das Nutzfluid und einen in der Arbeitskammer (12) mündenden, durch eine zweite Verschlussvorrichtung (27) verschliessbaren Ableitungskanal (14) aufweist, wobei die Arbeitskammer (12) durch einen Kammerkolben (9); auf der Sekundärseite einer Kolbenanordnung (8, 9) druckbeaufschlagbar ist, deren Primärseite einer Druckkraft entsprechend dem in dem Verbindungskanal (6) herrschenden Druck ausgesetzt ist.
  • Patent
    Maschinenbaugruppe, Fertigungsmaschine mit Maschinenbaugruppe sowie Verwendung und Verfahren zur Fertigung von Rotationsbauteilen
    ( 2014)
    Oberschmidt, Dirk
    ;
    Uhlmann, Eckart
    ;
    Eßmann, Jörg
    ;
    Herfert, Frank
    ;
    Polte, Mitchel
    Die Erfindung betrifft eine Maschinenbaugruppe 100 zur Verwendung in einer Fertigungsmaschine 1000, insbesondere in horizontaler Ausrichtung einer Drehachse D in einer Horizontal-Fertigungsmaschine, mit - einer an einem Aufnahmeträger 4 angebrachten Werkstückaufnahme 30 mit einer ersten Seite 31 und einer zweiten Seite 32 und - einer ersten und einer zweiten Werkzeugaufnahme 10, 20, wobei - die erste Werkzeugaufnahme 10 auf der ersten Seite 31 der Werkstückaufnahme 30 und die zweite Werkzeugaufnahme 20 auf der zweiten Seite 32 der Werkstückaufnahme 30 angeordnet ist. Erfindungsgemäss ist vorgesehen, dass die Werkstückaufnahme 30 eine Hauptspindel 33 mit einer von der ersten zur zweiten Seite 31, 32 verlaufenden Drehachse D aufweist und die Hauptspindel 33 zur Aufnahme eines Werkstücks entlang der Drehachse D ausgebildet ist.
  • Publication
    Development of a versatile and continuously operating cell disruption device
    ( 2013)
    Uhlmann, Eckart
    ;
    Oberschmidt, Dirk
    ;
    Spielvogel, Anja
    ;
    Herms, Katrin
    ;
    Polte, Mitchel
    ;
    Polte, Julian
    ;
    Dumke, A.
    Cell disruption is a recurrent unit operation in biotechnology. Interesting biotechnological products like proteins, lipids or biopolymers are synthesized intracellularly and are often not secreted. Furthermore, cell-free biotechnology uses defined fractions of the cytoplasm for in vitro protein synthesis. Bacteria, yeast, algae and filamentous fungi are surrounded by rigid cell walls that have to be disrupted by physical, chemical or mechanical methods in order to retain the valuable cell content. High pressure homogenization is a widely used procedure to disrupt cells and it has been applied to bacteria, algae and yeast. However, the mode of cell disruption has not been fully elucidated and performance is not predictable, thus time consuming iterative cycles are always necessary to define the best parameters for each microorganism, chemical environment and the corresponding product. Therefore, physical parameters of different biological systems were analyzed and boundary conditions defined in order to construct an adjustable disruption device to allow economical efficient, predictable and adjustable cell disruption processes.