Angled glass micromachining with a 6DOF spark-assisted chemical engraving system: Error characterization and tool-angle compensation

Abstract

As a common engineering material, glass possesses several unique properties that make it promising for micro-electro-mechanical systems (MEMS). However, micromachining glass structures is demanding because its hardness and brittleness challenge conventional manufacturing methods. Spark-assisted chemical engraving (SACE) has been proposed as an alternative process that uses localized high-temperature chemical etching to remove glass. Most conventional SACE machines based on cartesian system provide three degrees of freedom in tool motion, limiting machining mainly to 2D contours or 2.5D structures. This paper explores the use of a six-degree-of-freedom (6DOF) SACE system to machine inclined and multi-slope glass structures. When the tool electrode is tilted, the orientation change may alter local electrolyte flow and gas-film behaviours, contributing to non-uniform material removal, non-parallel cut walls, and angle-dependent errors. Several uncorrected cuts with programmed angles from 0° to 45° were analysed via cross-sectional micrographs, revealing bottom-wall angular errors of up to 1.73°. A linear compensation model was established to estimate these errors and generate compensated tool commands, successfully reducing the residual angular error to within 0.26° in validation cuts. Finally, two compensated frustum structures demonstrate discrete multi-slope machining, with confocal-microscope estimates broadly consistent with the intended wall geometries.