Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    A time domain simulation approach for micro milling processes
    ( 2012)
    Uhlmann, Eckart
    ;
    Mahr, Frederik
    Prediction of Process Machine Interactions (PMI) can be achieved using models for conventional milling processes in the time and frequency domain. However, instabilities such as regenerative chatter can also be observed in micro milling processes using filigree cemented carbide end mills. The dominant chatter frequencies are basically related to the end mills eigenfrequencies. Nevertheless, the dynamic characteristics of the machine tool structure and the work piece must not be neglected. In this paper a comprehensive time domain process model is presented. The machine tool dynamics are considered as non-coupled oscillators based on measured frequency response functions at the tool holder. The end mill is modeled as rotating Euler-Bernoulli beam with variable boundary conditions at the tool clamping. At first, the parameter identification for a geometric cutting force model is described. It contains the cutting edge radius as a time-depended parameter. Thereafter, the modeling and parameter identification of the structural parts are presented. A stability criterion is defined with special regard to the tool deflection at the TCP. Finally, simulation results at different stable and unstable operating points for full immersion cutting are discussed in detail and compared to experimental tests.
  • Publication
    Machine tools for hybrid micro manufacturing
    ( 2010)
    Eßmann, J.
    ;
    Uhlmann, E.
    ;
    Langmack, M.
    Two hybrid machine tools are presented. The first hybrid machine tool combines micro milling and laser ablation. It is designed for the manufacturing of dies and molds for micro replication. An integrated measurement device is used for acquisition of the workpiece geometry. The benefits are pointed out with respect to workpiece materials, geometry features, surface quality and overall manufacturing time. The second hybrid machine tool realizes a combination of laser machining and electrical discharge machining for drilling. The machine tools application area is manufacturing of complex shaped holes with low diameter and high aspect ratio.
  • Publication
    Design concept for micro milling machine tools based on dynamic dislocation compensation
    ( 2009)
    Uhlmann, E.
    ;
    Eßmann, J.
    Firstly, the technological capability of increasing the jerk values for the machine tool axes movement is investigated in this paper analytically and in experimental studies for micro milling. Following this, the influence of different jerk values on surface topography and roughness has been investigated with a set of experiments. Secondly, the demands on the design of machine tool frames for the realisation of high jerk values are discussed and a new concept for micro milling machine tool frames is proposed. The concept is based on a mechanical structure as the frame, which is of a stiff design in the direction perpendicular to the respective machine tool axis and of a compliant design in the direction of the respective machine tool axis. The compliancy allows for compensation of the dynamic dislocation by use of correction movements of the machine tool axes. An open control system is used capable of integrating complex models of the mechanical structure. These models and additional sensors are evaluated simultaneously during machine tool run time so that they become part of the machine tool control. A test setup is shown, representing a single machine tool axis with a compliant base. The dynamic dislocation has been compensated by integrating a laser interferometer and a mathematical model of the dislocation has been integrated.