In electrical discharge machining (EDM) of small holes, electrode wear is a key factor affecting machining accuracy and efficiency. The high temperature generated by high-frequency pulse discharge continuously erodes the electrode, causing changes in its shape, which in turn affects the dimensional accuracy and surface quality of the small holes.
To address this issue, systematic countermeasures need to be formulated from multiple dimensions such as material properties, process parameters, and structural design, and effective control of electrode wear can be achieved through technical optimization.
1. Scientific Selection of Electrode Materials
The physical properties of electrode materials directly determine their anti-wear ability. Tungsten wire electrodes, with their high melting point and good thermal conductivity, have a wear rate that is more than 40% lower than that of brass electrodes when processing difficult-to-cut materials such as cemented carbide, making them particularly suitable for deep small hole machining. Although brass electrodes have lower costs, they are prone to melting and wear during high-energy discharge, and are more suitable for shallow holes or scenarios with low precision requirements.
2. Precise Regulation of Processing Parameters
Optimization of pulse parameters is crucial for controlling electrode wear. Using a combination of high peak current and narrow pulse width can concentrate the discharge energy on the workpiece, reducing thermal erosion of the electrode.
For instance, when processing small holes with a diameter of less than 0.5mm, setting the pulse width to 5-20μs and increasing the pulse interval to more than three times the pulse width can not only ensure discharge efficiency but also provide sufficient cooling time for the electrode, reducing wear caused by continuous high temperatures.
Parameter matching of the working fluid system is equally important. When using deionized water as the working fluid, improving the filtration accuracy to below 5μm can reduce abnormal discharge caused by impurities, avoiding local overheating and wear of the electrode.
Reasonably controlling the working fluid pressure (usually 0.3-0.8MPa) ensures that the eroded debris in the discharge gap is promptly discharged, reducing secondary discharge erosion on the electrode. For machining small holes with a depth-to-diameter ratio greater than 10, a pulsating fluid supply method can be adopted to enhance debris removal through pressure fluctuations, indirectly reducing electrode wear.
3. Optimal Design of Electrode Structure and Path
Improvements in electrode structure can effectively reduce wear. Adopting a stepped electrode design, which separates the front processing section from the rear guiding section, allows the electrode to continue being used through feed compensation after the front end is worn, extending the overall service life.
For processing special-shaped small holes, designing the electrode head as a tapered type reduces the discharge area while enhancing the cooling effect, lowering the local wear rate.
Intelligent planning of the machining path can balance electrode wear. By presetting the electrode wear compensation amount in the numerical control system, the electrode feed rate is adjusted in real-time during processing to offset dimensional deviations caused by wear.
Using a spiral feed path instead of a linear feed ensures that all parts of the electrode participate in discharge evenly, avoiding excessive local wear. For deep hole machining, a segmented tool lifting strategy is implemented, and the electrode position is calibrated during each lifting process to ensure the final hole shape accuracy.
4. Dynamic Control of the Machining Process
A real-time monitoring system is an important means for wear control. An infrared thermometer is used to monitor the temperature change of the electrode, and the pulse energy is automatically reduced when the temperature exceeds the threshold.A current sensor is used to detect the discharge current waveform, identify abnormal discharge, and adjust parameters in a timely manner. Some equipment is equipped with an online electrode wear measurement function, which can calculate the electrode diameter change in real-time through image processing technology, providing data support for compensation control.
Addressing electrode wear in EDM small hole machines requires a comprehensive technical solution. Through the collaborative optimization of materials, parameters, structure, and control, electrode wear can be controlled within a reasonable range, while ensuring the accuracy and efficiency of small hole machining, providing reliable technical support for precision small hole machining.