milling

C. Brecher (a), (c), M. Weinzierl (a), A. Rashid (b), R. Schmitt (c), D. Köllmann (c)

(a) Fraunhofer Institute for Production Technology IPT, Germany
(b) System 3R Intl. AB, Sweden
(c) Werkzeugmaschinenlabor (WZL), RWTH Aachen University, Germany

Abstract

The set-up of ultraprecision machining processes is characterized by manual process steps which require a lot of personal skill and experience to full fill sub-micron requirements in form accuracy. Besides the fact that these manual process steps require a lot of time, they individualize each ultraprecision machined work piece and therefore prevent ultraprecision machining processes from becoming universal and cost efficient machining processes for high precision work pieces. To overcome this deficit, automation solutions are developed within the European Integrated Project (IP) »Production4μ« which enable the realization of efficient ultraprecision process chains with a high level of accuracy. In this paper, a sub-micron referencing system is introduced, which has been developed within this IP to contribute to the
high accuracy process chains by enabling the automated and repeatable clamping of work pieces with submicrometer deviations from their original position. This does not only enable the efficient combination of different machine-tools and processes but also allows for an increase in product quality.

J. Fleischer, M. Deuchert, C. Kühlewein, C. Ruhs
Institute of Production Science (wbk), Universität Karlsruhe (TH), Kaiserstrasse 12, 76131 Karlsruhe, Germany

Abstract

The geometry of micro milling tools currently in use have been adopted from macro tools, assuming that chip formation and process kinematics are analogical in both types of tools [1]. Experience has proved that micro tools respond to influences in a very different way than macro tools [2]. Oftentimes, structural details such as the rake angle and the twist angle impede further miniaturization and are impossible to achieve with conventional manufacturing techniques. Therefore it is necessary to get a comprehensive understanding of the entire process by taking a structure mechanical and cutting technological approach to micro milling tools in order to be able to optimize them. Another objective consists in the production of these miniaturized milling tools by means of force-free procedures such as laser ablation and electrical discharge machining.
The present state of research already puts the deficits of the currently available tools on display. Insufficient manufacturing tolerances of ±10 μm, constitute a substantial change of cutting conditions for the commonly used lateral infeed or feed per tooth of a few micrometers. Sometimes, only one cutting edge is engaged, which results in increased wear and, therefore, reduced durability, increased cutting forces, minor surface quality and a higher probability of milling cutter breakage. For that reason, a single-edged geometry has been proposed. It guarantees clear adjustment of the process parameters feed per edge and lateral infeed. For that purpose, stability analyses of simple stylus geometries have been conducted by means of FEM simulations. The resulting tool with a diameter down to 30 μm was machined on the EDM-machine at the wbk (Sarix SX 100). First tests have been carried out that prove the ability of these tools to cut steel.

G. Lalev (1), P. Petkov (1), N. Sykes (2), V. Velkova (1), S. Dimov (1), D. Barrow (2)

(1) Manufacturing Engineering Centre, Cardiff University, Newport Road,Cardiff, CF24 3AA, UK
(2) metaFAB, Cardiff University, Newport Road, Cardiff, CF24 3AA, UK

Abstract

A cost effective methodology for pattering of Nano Imprint Lithography (NIL) templates with different length scale features is proposed. The approach relies on selecting the optimum processing window of different technologies for cost effective micro and nano patterning. Very promising results were obtained when first fused silica templates were structured by F2 laser ablation at 157 nm without inducing phase transformation of the material. It was demonstrated that nanoscale features and complex 3D microscale features could be machined with a Focused Ion Beam (FIB) over the existing topography produced by laser ablation. Thus, a large area (up to several square centimetres) of the NIL templates is easily patterned with micro- and even meso-scale features by laser ablation while nano- and micro-scale features could be introduced by FIB machining.

P V Petkov, S Scholz and S Dimov
Manufacturing Engineering Centre, Cardiff University, Queen's Buildings, The Parade, Newport Road, Cardiff, CF24 3AA, UK

Abstract

Laser milling with microsecond pulses is a thermal material removal process usually associated with detrimental effects such as heat affected zones (HAZ), a recast layer and debris. Process optimisation can lead to considerable reduction of the above mentioned negative effects. In this context, the research investigates the effects of tool path optimisation and material removal strategies on the resultant surface quality and edge definition. The conducted experimental study shows clearly that the applied milling strategies have a significant effect on the resulting surface topography and the edge definition. Also, the research demonstrates that by optimising the laser path and material removal strategies it is possible to reduce significantly the thermal load when milling micro features, and thus to minimise HAZ and other secondary effects.

G. Bissacco (a), T. Gietzelt (b), H.N. Hansen (c)

(a) Department of Mechanics and Innovation (DIMEG), University of Padova, via Venezia 1, 35131Padova, Italy
(b) Forschungszentrum Karlsruhe Institut für Mikroverfahrenstechnik, 76021 Karlsruhe, Germany
(c) Department of Mechanical Engineering (MEK), Technical University of Denmark (DTU), Produktionstorvet 2800 Kgs. Lyngby, Denmark

Abstract

This paper discusses the issues related to force measurement in micro milling and presents the results of the experimental investigation performed in an on going Cross Divisional Project within the 4M network of Excellence, aiming at force analysis and process characterization in micro milling. Reliable force measurement in micro milling is shown to be a challenging task. Measured forces are affected by contributions coming from the machining system. Based on the performed measurements, tool engagement has been demonstrated to occur at each tooth passing, even at feeds per tooth as low as 2 μm.