Title: Process control for ultrasonic hole-drilling in hard brittle materials

Authors: Kossi Agbeviade; Emmanuel Deghilage; David Hoover; Elia Deschenaux; Jacques Giovanola; Daniel Kremer

Addresses: Ecole Polytechnique Fédérale de Lausanne, EPFL – IGM-LCSM, Lausanne, 1015, Switzerland. ' Ecole Polytechnique Fédérale de Lausanne, EPFL – IGM-LCSM, Lausanne, 1015, Switzerland. ' Ecole Polytechnique Fédérale de Lausanne, EPFL – IGM-LCSM, Lausanne, 1015, Switzerland. ' Ecole Polytechnique Fédérale de Lausanne, EPFL – IGM-LCSM, Lausanne, 1015, Switzerland. ' Ecole Polytechnique Fédérale de Lausanne, EPFL – IGM-LCSM, Lausanne, 1015, Switzerland. ' Ecole Polytechnique Fédérale de Lausanne, EPFL – IGM-LCSM, Lausanne, 1015, Switzerland

Abstract: Ultrasonic drilling offers a solution to bore sub-millimetre holes of high diameter-to depth ratio in difficult to machine brittle materials. A key aspect of the process is to maintain a proper gap between tool and workpiece. This paper presents the successful solution developed to address this issue. In our approach, we vibrate the workpiece and control the motion of the tool, which is constrained by an aerostatic bearing and generated by a voice coil actuator. We use the voice coil to measure the force acting between tool and workpiece. We measure the tool displacement with an Eddy current sensor. Using the two sensor measurements, we developed a control algorithm in which the tool is displaced in such a way as to maintain the tool-work piece interaction force constant. The paper presents experimental details of the characterisation of the control loop and results of drilling experiments.

Keywords: ultrasonic drilling; ceramics; glass; deep microholes; mechatronics; cascade control; process control; brittle materials; hard materials; tool displacement; tool-workpiece interaction.

DOI: 10.1504/IJMMS.2012.046522

International Journal of Mechatronics and Manufacturing Systems, 2012 Vol.5 No.2, pp.106 - 119

Received: 19 Nov 2010
Accepted: 30 Aug 2011
Published online: 20 Aug 2014 *

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