Characteristics and processes of micro EDM

Characteristics of Micro EDM.

1. The material removal in micro EDM relies on electrical and thermal effects, and the processability of the material primarily depends on its conductivity and thermal properties, rather than mechanical properties such as hardness and strength. This machining method breaks through the limitations of traditional cutting processes and is not restricted by tool materials. It enables the use of soft tools to machine hard workpieces, making it suitable for machining any difficult-to-cut conductive materials, such as diamond, cubic boron nitride, and other hard materials.
2. Since there is no direct contact between the tool electrode and the workpiece during the machining process, there is no macroscopic cutting force. Therefore, it is suitable for machining low-stiffness workpieces, and the electrode can be very thin. Moreover, the shape of the tool electrode can be easily replicated onto the workpiece, making it suitable for machining workpieces with complex surface shapes. The use of numerical control technology also enables the simple machining of complex-shaped workpieces.
3. The machining process is simple and controllable, and the pulse parameters can be adjusted within a wide range. Rough, semi-finish, and finish machining can be performed continuously on the same machine tool. It is easy to achieve process automation, digital control, and intelligent control.
4. Micro EDM is mainly suitable for machining conductive materials such as metals, and semiconductor and non-conductive materials can only be processed under special conditions. Additionally, the machining speed is relatively slow. Therefore, in actual production, the majority of the stock is typically removed using cutting methods first to improve production efficiency before proceeding with micro EDM.

Micro EDM Processes.

1. Micro EDM Forming.

   Micro EDM forming refers to the use of micro-energy power supplies and small electrodes to discharge the workpiece, aiming to achieve surface forming. In fields such as aerospace, precision instruments, and automobile manufacturing, micro-holes (holes with diameters smaller than 0.1mm) are widely applied due to their unique functional structures. Examples include damping sleeves in high-pressure compressors in aircraft engines, damping tubes and rings in high-pressure turbine front and rear shafts, electron microscope gratings, and automobile engine fuel injectors, among others. In the machining of micro-holes in difficult-to-machine materials, conventional micro-machining methods have low accuracy and poor machining quality. However, micro EDM technology has the advantages of non-contact machining, no apparent macroscopic force, and the ability to “defeat hardness with flexibility,” providing unique advantages in the machining of micro-holes in difficult-to-machine materials and achieving efficient micro-hole machining.
   

2. Wire Electrical Discharge Grinding (WEDG).

   Wire Electrical Discharge Grinding (WEDG) refers to the reverse copying machining of the electrode blank using a moving wire electrode. During the machining process, there is relative motion between the wire electrode and the guide, with the guide making micro-feed movements radially while the workpiece rotates and makes axial feeds. This machining method of in-situ electrode production avoids errors caused by secondary clamping and improves machining accuracy. Moreover, the continuous wire feeding mode compensates for wire electrode loss, avoids concentrated discharge and short circuits, and facilitates continuous EDM. Since the electrode wire and the electrode blank undergo point discharge machining, the shape of the tool electrode is only related to the trajectory of the forming motion, making it easy to achieve automated tool electrode shaping. Currently, wire EDM grinding technology is widely used in the preparation of micro-tools for applications such as micro-ultrasonic machining and micro-electrochemical machining.

3. Micro Wire EDM Cutting.

   The basic principle of micro wire EDM cutting is to use a moving fine metal wire as the electrode to perform pulsed spark discharge on the workpiece. It relies on the relative transverse cutting motion between the wire electrode and the workpiece to achieve cutting and shaping of various two-dimensional, three-dimensional, and complex multi-dimensional surfaces. Due to the use of a smaller-diameter wire electrode in the machining process, it can be used to process micro-irregular holes, narrow gaps, and workpieces with complex shapes. Microelectrode arrays have extensive applications in the fields of life sciences and micro-group hole machining, such as cultivating various tissue systems in medicine and machining group micro-holes. The processing methods mainly include LIGA (Lithography, Electroplating, and Molding) method, spark-assisted ultrasound compound reverse copying method, and micro wire EDM cutting method. The LIGA method is expensive, time-consuming, and involves complex processes. Although the spark-assisted ultrasound compound reverse copying method is simple, effective, and inexpensive, it has long processing times and low efficiency. The micro wire EDM cutting method has the advantages of high machining accuracy, achieving micrometer-level surface quality, and being able to process most conductive materials. It possesses unique advantages in the machining of microelectrode arrays.