Laser micromachining of the miniature functional mechanisms

Abstract

The actual performance of a miniature mechanism significantly depends on the geometric quality of the machined part and specific features therein. To fabricate functional parts and features with accuracy and precision within +/- 1 μm or less, the laser micromachining system requires the capabilities of following the desired toolpath trajectories with minimum dynamic errors, high positional repeatability, and synchronization of laser firing events at precise time-and-location to ablate the material. The major objectives of this study are to fabricate miniature functional mechanisms using precision laser micromachining method, explore the machining challenges and evaluate the geometrical quality of the machined parts in terms of accuracy, precision and surface quality. Two functional mechanisms based on electro-thermal actuation have been studied. Several machining challenges related to the corner accuracy, the asynchronization of motions and, the laser-on/off events in space and time with respect to the part geometry have been addressed. The source of inaccuracies primarily stems from the geometric complexity of the mechanism that consists of several features, such as, arcs, radii, lines, curvatures, segments and pockets, along with their dimensional aspect ratio. Such a complex design requires a large number of inconsecutive trajectories to avoid thermal deformations. Copper and nickel foils with a thickness of 25 and 12.5 µm respectively were used in the fabrication of the prototypes. The machining challenges were successfully tackled and the geometrical performance of the fabricated prototypes was evaluated. Local feature accuracies within 0.1 - 0.2 µm have been recorded.