Development of High-precision Micro EDM System
L-shaped,angle aluminum,angle aluminum profile Jiangsu Yuejia Metallic Technology Co.,Ltd , https://www.yuejiametal.com
**Abstract:**
A micro EDM (Electrical Discharge Machining) system has been designed and developed to meet the demands of precision microfabrication. The system integrates a horizontal-axis V-shaped ceramic spindle, a macro and micro servo system using piezoceramics, a tool electrode copying system, a reading microscope, and an electrical control unit. This system has successfully achieved machining of micro-shafts with diameters less than 4.5 μm and micro-holes with diameters less than 8 μm. The development represents a significant advancement in micro-EDM technology, demonstrating high precision and stability in micro-scale manufacturing.
**Keywords:** Microfabrication; EDM; Piezoelectric ceramic; Micro shaft; Micro hole
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**1. Features of Micro EDM**
Although the basic principle of micro EDM is similar to that of conventional EDM, the surface quality and processing accuracy are influenced by several unique factors. The surface finish depends on the size and depth of the craters formed during discharge, which relates to the energy of each single pulse. Meanwhile, the accuracy of the process is affected by the discharge gap, system stability, and electrode wear.
Micro EDM operates using a pulsed power supply, where high-frequency discharge energy is delivered to the gap between the electrode and the workpiece. The high-temperature thermal effects lead to material removal, enabling precise machining. However, due to the extremely small dimensions involved—typically between 5 to 100 μm—special considerations are required to achieve the desired accuracy and surface quality. Key characteristics of micro EDM include:
**(1) Small Discharge Area:**
The electrode used in micro EDM typically ranges from 5 to 100 μm in diameter. For electrodes smaller than 5 μm, the discharge area is less than 20 μm². This limited area makes it difficult to distribute discharges evenly, leading to instability and challenges in maintaining consistent machining performance.
**(2) Low Single Pulse Energy:**
To ensure precision and surface quality, the material removed per pulse must be controlled within 0.01 to 0.10 μm. This requires each discharge pulse to have an energy level between 10â»â¶ and 10â»â· J or even lower, significantly reducing the risk of over-removal and ensuring fine control.
**(3) Small Discharge Gap:**
In EDM, the gap between the electrode and the workpiece is crucial for stable operation. In micro-EDM, this gap is often as small as a few micrometers, making it essential to maintain stability to avoid short circuits and ensure accurate machining, especially when drilling micro-holes.
**(4) Difficulties in Tool Electrode Preparation:**
Creating and installing micro-electrodes is a major challenge in micro-EDM. Traditional methods involve secondary mounting on the machine tool, which introduces errors in alignment and verticality. The introduction of Wire Electrical Discharge Grinding (WEDG) has improved electrode preparation, but it still requires a highly precise EDM system with sub-micron rotational accuracy.
**(5) Challenges in Chip Removal and Spark Stability:**
Due to the small discharge area and gap, chip removal becomes difficult, increasing the likelihood of short circuits. A sensitive feed servo system is necessary to quickly retreat the electrode in case of abnormal discharge, thus improving pulse utilization and protecting the electrode.
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**2. Overall Design of the Micro EDM System**
Based on the analysis of micro EDM characteristics and existing research, a prototype micro EDM system was developed. It consists of mechanical and electrical components. The mechanical part includes a horizontal-axis V-shaped ceramic spindle, a macro-micro servo system using piezoceramics, a micro-electrode copying system, and a reading microscope.
The horizontal-axis layout improves chip removal efficiency by allowing gravity to assist in ejecting debris. This design also enhances the roundness of micro-holes and increases machining speed. The spindle uses a high-precision V-shaped ceramic support, ensuring rotation accuracy within 1 μm.
The macro-micro servo system combines a stepper motor and piezoceramic actuator to provide both large stroke movement and ultra-fine positioning. This ensures high precision and fast response during micro-EDM operations.
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**3. Micro EDM Machining Experiment**
The system was tested with micro-shafts and micro-holes. A micro-shaft with a diameter of 4.5 μm was successfully machined, and a micro-hole with a diameter of 8 μm was also produced. These results demonstrate the system's capability to achieve sub-micron precision, confirming its potential for advanced micro-manufacturing applications.
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**4. Conclusion**
This paper presents a detailed study of micro EDM, including the design and implementation of a high-precision micro EDM system. The system features a horizontal-axis V-shaped ceramic spindle, a macro-micro servo system with piezoceramics, and a micro-electrode copying mechanism. The successful machining of micro-shafts and micro-holes confirms the system’s effectiveness. These achievements place the system at the forefront of domestic and international micro-EDM technology, marking significant progress in China’s micro-manufacturing capabilities.