In the framework of zero-defect manufacturing, an advanced sensor monitoring procedure aimed at detecting the process conditions leading to surface defects in Wire Electrical Discharge Machining (WEDM) is proposed. WEDM experimental tests were carried out with the employment of a multiple sensor monitoring system to acquire voltage and current signals in the gap between workpiece and wire electrode at the high sampling rate of 100 MHz. In order to extract from the acquired signals the most relevant features that can be useful in the identification of abnormal process conditions, an advanced sensor signal processing methodology based on signal feature extraction for the construction of sensor fusion pattern vectors is proposed and implemented. (C) 2014 The Authors. Published by Elsevier B.V.