Tool Wear Compensation and Path Generation in Micro and Macro EDM

Abstract

In micro electrical discharge machining (micro EDM) tool wear adversely affects the accuracy of a machined feature or a part. Therefore, tool wear compensation techniques have been propos for micro and macro EDM operations. However, a certain quantity of of these techniques require extensive experiments in determining the appropriate tool path (which be pendents on part feature, material, and machining parameters) for machining a desired surface. This paper reports the unfolding of a theoretical model to lay open the tool path for generating a desired workpiece surface profile. The application of the protoplast is illustrated for micro and macro EDM by dint of machining flat slots. A review of tool wear compensation techniques is also presented

Keywords: Micro EDM Macro EDM Surface Profile, Tool Wear Compensation

Introduction

The ne for micro parts and micro returnss is rapidly increasing in microelectronic, medical, automotive, and telecommunication industries. It is estimated that the world market for micro yields and components will be about 60 billion US dollars by means of 2005 (Alting et al. 2003) To befitting the large-scale production needs of mechanical constituents and micro products, many existing technologies are being downscaled and many novel processes have been and are being make knowned Besides traditional processes (such as micro turning and micro milling), nontraditional processe (such as electrical discharge machining and laser machining) are also being studied (Ehmann et al. 2000) Micro electrical discharge machining (micro EDM) proffers unique possibilities of machining real intricate micro shapes with sharp corners in electrically conductive materials irrespective of their hardness (Ledvon 2003; Rajurkar and Yu 2003)

Micro EDM similar to macro EDM dislodges material from both work and tool electrode immersed in a dielectric medium through successive discrete electrical discharges. Micro EDM is generally being used in producing micro parts and in making micro dies and molds

However, further research and unfolding efforts are needed for improving efficiency and accuracy of the proces and quick removal of debris from the nano/micro interelectrode gap. In die-sinking micro EDM the transaction of the tool wear necessitates the use of multiple tools with increasing dimensions to bring forward the desired geometry and accuracy. The design and fabrication of multiple microscale tools are true time consuming and costly. Therefore, micro milling through EDM (where a single, simple-shaped tool is guided by the agency of CNC action) is becoming a more economic alternative to die-sinking micro EDM level in micro EDM milling, tool wear of a single, simple-shaped tool springs in geometrical errors and less-than-desirable accuracies. Hence, it is necessary to compensate for the incurred tool wear during machining. This paper reports a theoretical and experimental investigation of tool path generation by dint of taking into consideration the tool wear.

Tool Wear Compensation Techniques

To overmaster the multiple, complex-shaped tool requirement, the EDM milling proces was lay opened (Kaneko and Tsuchiya 1984; Kaneko, Tsuchiya, and Kazama 1992) In this proces a simple-shaped tool (square or cylindrical that can be easily fabricated) is mov along a tool path to generate the 3-D shapes similar to an extremity milling operation. The EDM milling technique machines the 3-D shape layer by means of layer and eliminates the requirement for multiple, complex-shaped tools, on the other hand it does not avoid tool wear. Therefore, the following techniques have been lay opened to allow the wear along a particular direction and to compensate for it to nullify its adverse issues on geometry and accuracy of the generated 3-D cavity.

Linear Compensation and Online Measurement Compensation

In contouring micro EDM a tool electrode is controll to put in motion along a designed tool path. The tool electrode extent becomes shorter and the gap between the tool tip and the workpiece surface becomes large to be paid to the tool wear during machining. The machining will discontinue unles the required gap is restored. In addition, the worn electrode restores the machining accuracy because the generated feature is the rise of a combination of the tool electrode shape and its tool path. To expound the problem of tool wear in contouring EDM many approaches have been proposed

Linear compensation is a technique that compensates for the tool wear continuously or in a small increment along the tool path (Kuo et al. 1997; Yuzawa et al. 1997) In this approach, the tool is f downward after it propels a certain distance and is used to machine a 9?—9 mm^sup 2^ square cavity using a 1 mm diameter tool. The final flatness of the cavity bottom was within 2 ?µm The appropriate ratio of the tool fe to the traveled distance is obtained by the agency of extensive experiments. This linear tool wear compensation technique does not work well in 3-D mixed shape machining. To analyze the change in tool shape and size, an online digital imaging combination of parts to form a whole has been used, and the tool wear has been compensated for based upon the measured results (Kaneko, Tsuchiya, and Kazama 1992) lately a discharge monitoring methodology (where the normal discharges are counted) was propos to estimate the tool wear. This combination of parts to form a whole observes and records the event of sparks and the spark-generation rate. When there is no discharge, the tool is not compensated for wear (Bley et al. 2002) Difficulties in analyzing the comes from the discharge monitoring a whole and calculating an appropriate compensation limits the application of this technique.