Corner Accuracy Research Articles

Enhancing die corner accuracy through trim cut in WEDM

Wire electrical discharge machining (WEDM) is one of the promising methods to produce precision dies and machine tools. In the present work, die corner accuracy achievable through trim cutting operation has been analyzed in the presence of a higher wire lag arising due to the higher workpiece thickness, acute corner angle, and higher flushing nozzle height. The influence of the corner error (uncut area left between the actual profile and the desired profile) generated in the first cut (rough cut) on the considered responses, namely volume removal rate, corner accuracy, surface roughness, and dimensional shift, has been analyzed by setting three different parameters during the first cut of the trim cutting operation. It is established that the trim cutting operation is a superior strategy for improving die corner accuracy than the pulse parameter modification strategy. Nevertheless, the high pulse parameter setting in rough cut was preferred for achieving greater productivity while the low pulse parameter setting in rough cut was chosen to achieve better corner accuracy at the cost of lower productivity.

Genetic Algorithm Based Fuzzy Logic Controller for Wire-EDM Machine

Wire tension as well as wire feed should be controlled tightly for the geometry and corner accuracy of wire-EDM. A closed-loop wire tension control system for Micro-Wire-EDM is presented to guarantee a smooth wire transport and a constant tension value. To keep smooth wire transportation and avoid wire breakage during wire feeding, the reel roller is modified and the clip reel is removed from the wire transport mechanism. A genetic algorithm-based fuzzy logic controller (FLC) is proposed to investigate the dynamic performance of the closed-loop wire tension control system. Theoretical analysis and experimental research demonstrate that the developed wire transport system can result in satisfactory transient response, steady-state response and robustness. The proposed FLC can obtain faster transient response and smaller steady-state error than PI controller.

Experimental investigation on die corner accuracy for wire electrical discharge machining of Monel 400 alloy

The experimental research presented in this article explores the wire electrical discharge machining of Monel 400 alloy. An L-18 orthogonal array has been used for experimentation by considering machine controllable factors (i.e. wire tension, pulse-on time, pulse frequency, peak current and servo voltage) and machine uncontrollable factors (namely flushing nozzle height, workpiece thickness and corner angle) as process parameters. Using Taguchi methodology, the influence of the process parameters on the responses, such as material removal rate, surface roughness and corner error, were studied. The impact of pulse parameters modification in corner accuracy improvement has been analyzed. Finally, using Taguchi’s additive model predictions and Pareto optimality approach, a sample technology table for a specific machining condition has been reported for ready use.

Application of genetic algorithm-based fuzzy logic control in wire transport system of wire-EDM machine

Wire tension as well as wire feed should be controlled tightly for the geometry and corner accuracy of wire-EDM. In this paper, a closed-loop wire tension control system for Micro-Wire-EDM is presented to guarantee a smooth wire transport and a constant tension value. In order to keep smooth wire transportation and avoid wire breakage during wire feeding, the reel roller is modified and the clip reel is removed from the wire transport mechanism. A genetic algorithm-based fuzzy logic controller is proposed to investigate the dynamic performance of the closed-loop wire tension control system. Experimental results demonstrate that the developed wire transport system can result in satisfactory transient response, steady-state response and robustness. The proposed genetic algorithm-based fuzzy logic controller can obtain faster transient response and smaller steady-state error than a PI controller.

On the influence of cutting speed limitation on the accuracy of wire-EDM corner-cutting

The wire electro-discharge machining (WEDM) process is widely used in the manufacturing of high-hardness steel precision tooling. Even though the process is characterised by its high accuracy level (sufficient even for micromachining applications), the development of enhanced generators that produce more energetic discharges yielding cutting speeds as high as 500 mm 2/min has resulted in stronger forces acting on the wire. These forces, together with the low rigidity of the wire, especially in the cutting of parts of high thickness, are responsible for wire deformation that has a direct influence on the accuracy of the part, mainly on wall-flatness and corners. In this work a study on the corner geometry generated by the successive cuts (roughing and finishing) is presented. Errors at different zones of the corner are identified and related to the material removed during each cut. Limitation of cutting speed allows a certain control on the amount of material actually removed by the wire. The influence of different aspects such as work thickness, corner radius and number of trim cuts is discussed. The main conclusion is that a corner accuracy optimisation procedure must consider the errors generated by the previous cuts.

Combined Power and Path Control Method to Improve Corner Accuracy of Rough Cuts by Wire EDM (2st Report)

Combined Power and Path Control Method to Improve Corner Accuracy of Rough Cuts by Wire EDM (2st Report)

Combined Power and Path Control Method to Improve Corner Accuracy of Rough Cuts by Wire EDM (1st Report)

Combined Power and Path Control Method to Improve Corner Accuracy of Rough Cuts by Wire EDM (1st Report)

ワイヤ放電加工の加工精度に関する基礎的研究 ５ 休止時間制御を用いた小円弧凹コーナＲ荒加工の加工時間短縮方法

This paper describes a control method to improve the accuracy of a concave corner with small radius R on the rough cut of wire EDM. A well-known off-time (pulse interval time) control method has an advantage in terms of corner precision but it takes a long time to cut the corner. In this paper, methods to reduce the machining time of the off-time control method are discussed. The off-time control method is combined with the overcut method, the servo voltage control method and the simple path modification method. The proposed method is found to be useful for improving the corner accuracy and reducing the machining time. The machining time was decreased from 90 to 28 seconds, and it was shorter than 34 seconds of the dwell over cut method proposed in a previous study. The residual error of the corner shape was decreased to 15μm. The procedure and expressions used to calculate the control values are described.

Fundamental Study of Accuracy of Wire EDM (2nd Report)

This present paper investigates about accuracy of rough convex corner and convex corner R. Previous some reports proposed methods to improve corner and corner R accuracy of wire EDM. One method controls EDM conditions and other method modifies a program path at the corner and corner R, and 3rd method is a on-line system which detects wire deflection and corrects a contouring path. But 1st method has problems that the corner accuracy is insufficient and it lacks details to decide EDM parameters. Also 2nd method has a problem that the accuracy on top surface differs from that on middle cross section surface of a work piece. In addition 3rd method is only useful for special machines. In this paper we propose a combined power and path control method to improve the convex corner and corner R accuracy which is useful for ordinary operators. In the method, discharge power is adjusted so that the error of convex corner and corner R on the top or bottom surface of the work piece decreases within a desired value. The program path is corrected so as the residual error on the middle surface of the work piece to be 0.

ワイヤ放電加工の加工精度に関する基礎的研究 （第４報） オーバーカット‐ドウェル方式による小円弧凹コーナＲの荒加工精度の改善方法

The previous 2nd and 3rd reports described methods by which to improve the accuracy of the convex corner, corner R and large concave corner R on the rough cut of a workpiece, where the wire discharges symmetrically on front surface of the wire. The present paper describes methods by which to improve the accuracy of the concave corner having small radius corner R on the rough cut, where the wire discharges asymmetrically on the wire surface. A new method that combines the dwell operation method with the over cut method is proposed. The procedure and expressions used to calculate these control values based on a wire deflection model are described. In addition, the advantage of high wire tension is discussed. The proposed method was found to be useful for improving the concave corner accuracy and saving machining time.