Precision Engineering 35 (2011) 339–347 Contents lists available at ScienceDirect Precision Engineering journal homepage: www.elsevier.com/locate/precision A novel method of determination of wire lag for enhanced profile accuracy in WEDM S. Sarkar a,∗ , M. Sekh b , S. Mitra a , B. Bhattacharyya a a Production Engineering Department, Jadavpur University, Kolkata 700032, India b Production Engineering Department, H.I.T., Midnapore(E) 721657, India article info Article history: Received 4 April 2010 Received in revised form 20 October 2010 Accepted 6 January 2011 Available online 13 January 2011 Keywords: WEDM Wire offset Profile accuracy Wire lag compensation Gap force abstract Wire bending due to gap force is a major cause of imprecision in WEDM applications. To achieve higher precision and accuracy the knowledge of gap force and wire lag is extremely essential. In the present research, an in depth study on wire lag phenomenon has been carried out. A novel method to measure gap force intensity and wire lag under any given machining condition has been proposed by developing an analytical model. Experiments were carried out to verify the proposed model. Beside this, the impact of wire deflection on profile accuracy during cutting cylindrical job has been investigated. Based upon the developed analytical model an effective method has been proposed to eliminate this inaccuracy using wire lag compensation technique. The research finding will lead to better understanding of the gap force phenomena and will promote significant development in the domain of high precision WEDM. © 2011 Elsevier Inc. All rights reserved. 1. Introduction The cutting speed, surface finish and taper angle are improving markedly day by day since the beginning of wire electrical dis- charge machining (WEDM). But, wire bending, which is a major cause of cutting imprecision, is still hampering the part accuracy for various applications. When cutting out a sharp corner or curved profile, the bending of the wire creates a geometrical error on the workpiece. This error can be of the order of a few hundred microns; which for some applications becomes unacceptable [1]. Several research efforts have been given for improving the accu- racy in WEDM. Dekeyser and Snoeys [2] proposed off-line path modification strategy to enhance the profile accuracy. Later Dauw and Beltrami [1] developed on line wire path control system using an on line optical wire position sensor. Hsue et al. [3] addressed the unsteady phenomena of the machining parameters at the cor- ner using the concept of discharge angle. To reduce the machining errors of corner parts, Lin et al. [4] developed a fuzzy control strat- egy to improve corner accuracy through reduction of wire lag near corner by increasing the pulse off time. Using Taguchi method- ology Puri and Bhattaharyya [5] minimized corner inaccuracy in trim cutting operation through optimization of process parame- ters. Sanchez et al. [6] proposed a technological data base system in which experimental knowledge and numerical simulation of the ∗ Corresponding author. E-mail address: mail.dr.sarkar@gmail.com (S. Sarkar). process allow the user to select the optimum cutting strategy, either by wire path modification or by cutting regime modification. Yan et al. [7] claimed improvement in corner accuracy using on line closed loop wire tension control system. A corner error simulation method was proposed by Fuzhu et al. [8] to predict the actual corner profile under different cutting condition. Sanchez et al. [9] studied how the number of finishing cut and cutting speed limitation influ- ences the corner accuracy on different thickness workpiece. Lin and Liao [10] proposed an effective-wire-compensation scheme to specify the wire location matrices required to improve the precision of the machining results while manufacturing components with tapered features or complex profile. Dodun et al. [11] investigated the error in machining of small corner angle in thin parts. From the review of the past research, it is found that the pro- cedure to improve accuracy can broadly be classified in to two categories. The first procedure is to modify the cutting parame- ters (pulse on time, pulse off time peak current etc.) in order to reduce the wire deflection [2,4–6,9]. This methods result in low- ering of cutting speed at the corner. The second procedure is to modify the wire path to correct the geometrical inaccuracy in an on-line [1,6,11] manner. In the second procedure, although the cut- ting speed is not reduced but accuracy level is comparatively poor compared to first procedure for smaller angle [6]. To implement the either of the above procedure the knowledge of wire deflec- tion for a given machining parameter setting is extremely essential. Some researchers attempted to measure the wire displacement using optical sensor [1] or electrical contact between wire and workpiece [12]. But it is not an easy task to measure the wire posi- 0141-6359/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.precisioneng.2011.01.001