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1 INTRODUCTION
Miniaturisation has become widespread, with a broad range of applications in many fields including microelectronics (mobile phones and sensors), motor vehicles, medicine (implants, micro- dosage), biomedicine, the chemical industry and watch-making. However, there is a clear imbalance between the ease with which batch-fabricated micro-components can be produced in silicon compared to the difficulties and the cost associated with their manufacture in other materials. In micro-manufacturing, machining equipment and techniques can be roughly grouped into
“ultraprecision processes”, including micromilling, and processes based on silicon machining techniques - typically found in the electronics industry and known more precisely as “micro- machining processes” [13].
Among micro-manufacturing processes, this study centres on micromilling, and more specifically on the experience obtained from the micro-milling machine present at the Technology University of Delft, NL, shown in Fig. 1.1.
This thesis work is a part of a project research of the Laboratory for Precision Manufacturing and Assembly at TU Delft in the Netherlands. The purpose of the project is to develop a reliable industrial micro-milling process for moulds with micro features made of hardened steel, powder metallurgy materials or aluminium, with less throughput time, lower cost and less tool wear [51]. In order to gain fundamental knowledge of the process of micro-milling, the researchers have built a dedicated experimental milling setup.
Nowadays the requirements of the die and mould industry are changing, passing from a macro- to a micro-scale and from high-speed to ultra-precision machine. To achieve the finishing requirements of the mould sector, the micro-milling machine tools have to guarantee some performances, such as geometric accuracy, high stiffness of the machine’s components, high performance at high speed, etc.
This report presents some methods to analyse three different performances of the micro-milling machine under exam, namely stiffness, dynamic accuracy and geometric accuracy. Some tests have been done to verify these performances by using specific designed experimental setup.
The remainder of this work evolves as follows.
A study of the state of the art of the micro-milling technology is done, trying to find the specific requirements of the micromilling technology on machine tools.
Fig. 1.1-Micro-milling setup at the TU Delft
8 An analysis of the current machine tool evaluation methods is presented, in order to draw an error budget of our setup.
Three main performances of the machine are analysed and tested with specially designed experimental setup, using dedicated instruments.
The results and the conclusions are then developed for each performance and some recommendations for future improvement are given.
