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
    Manufacturing, replication and assessment of microfluidics for blood plasma separation
    ( 2016)
    Uhlmann, Eckart
    ;
    Hein, Christoph
    ;
    Polte, Mitchel
    ;
    Polte, Julian
    ;
    Spielvogel, Anja
    ;
    Huth-Herms, Katrin
    ;
    Oberschmidt, Dirk
    Point of care diagnostics gain importance with regard to novel diagnostic techniques. Future applications, for example based on cell-free DNA, are prenatal or cancer diagnostics. With regard to these methods a large influence of natural blood degradation during full blood storage and transport before laboratory based separation restricts possible applications. With a point of care plasma separation device, the plasma can be separated from full blood directly after blood collection. Thus, diagnostic markers remain undamaged and allow a highly specific detection. Targeting microfluidics for point-of-care blood plasma separation, this work presents the development of a microfluidic blood plasma separation device along a novel process chain. Besides system design and manufacturing technologies for prototypes, the development of technologies for replication, closure of microfluidics and affecting of surface properties are under the special scope of this investigation.
  • 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.
  • Publication
    Process development and optimization in the die-sinking m-EDM of micro molds for the dental industry
    ( 2015)
    Uhlmann, Eckart
    ;
    Domingos, David C.
    ;
    Oberschmidt, Dirk
    ;
    Zanatta, A.M.
    ;
    Gomes, J.O.