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October 12, 2025

Abnormal Problems and Analysis of Electrical Discharge Machining in Die and Mould Manufacturing

**1. Introduction** Electrical Discharge Machining (EDM) is a crucial process in mold manufacturing, especially in the production of plastic molds. Most plastic mold components are typically finished using EDM to achieve high precision and surface quality. The quality of the machining directly impacts the performance of the mold assembly and the accuracy of the molded parts. Any abnormalities during the process can lead to unnecessary rework, potentially resulting in scrapped workpieces, extended mold production cycles, increased costs, and reduced overall mold quality. Therefore, preventing processing anomalies is essential for ensuring efficient and high-quality mold manufacturing. These anomalies can manifest as issues during machining or as quality problems after the process. **2. Common EDM Problems and Analysis** **(1) Unqualified Machined Dimensions** The dimensions of machined mold parts are critical. EDM typically achieves an accuracy of around 0.005 mm, but different areas of the mold may have varying requirements. Some parts require strict dimensional control. If the actual size falls outside the acceptable tolerance range, it results in defective parts—either too large or too small. Several factors influence the final dimension: - **Electrode Scaling:** The spark gap between the electrode and workpiece affects the final size. Proper electrode scaling is essential. If the spark gap is smaller than expected, the part will be undersized, and vice versa. The scaling depends on the type of part—structural or molding parts—and requires careful consideration of polishing allowances and machining parameters. - **Electrode Size and Translation Control:** The actual size of the electrode has a significant impact on the final result. When using electrode translation, controlling the amount of movement is key to achieving accurate dimensions. - **Electrode Calibration Accuracy:** Inaccurate calibration can increase the projected area, leading to oversized parts. Small electrodes often have lower calibration accuracy compared to larger ones. - **Electrical Parameter Adjustment:** Parameters like current and pulse width affect the spark gap. Adjusting these properly ensures stable discharge and consistent dimensions. - **Electrode Wear:** Electrode wear reduces the final size. Controlling this wear is important for maintaining dimensional accuracy. - **Depth Control:** The depth of the machining process must be carefully controlled. Factors such as tool setting and residual machining allowance play a role in ensuring proper depth. **(2) Poor Surface Quality** Surface quality issues include carbon buildup, roughness that doesn't meet specifications, and excessive surface metamorphic layers. - **Carbon Deposition:** This occurs due to unstable discharge conditions, especially during finishing. Proper parameter settings and oil flushing methods help prevent this issue. - **Roughness Issues:** Surface roughness is affected by electrode condition, material, and machining allowance. Finishing processes require careful polishing to meet required standards. - **Excessive Metamorphic Layer:** High discharge energy can create thick altered layers, reducing the wear resistance and lifespan of the part. Controlling discharge energy is vital to avoid this. **(3) Position Deviation** Misalignment between the electrode and workpiece is a common problem. Ensuring secure clamping, accurate positioning, and regular checks during processing helps prevent deviations. **(4) Processing Abnormalities** Several abnormal phenomena can occur during EDM, including low efficiency, excessive electrode wear, unstable discharges, electrode deformation, and “powdering” during hole machining. - **Low Efficiency:** This is often due to improper electrical parameters, poor working fluid quality, or excessive machining allowances. Optimizing parameters and ensuring good chip evacuation improves efficiency. - **Excessive Electrode Wear:** Caused by incorrect pulse widths, improper polarity, or excessive current. Monitoring and adjusting these factors can reduce wear. - **Unstable Discharge:** Indicated by irregular sparks, uneven currents, or unusual sounds. Adjusting parameters and checking for impurities can stabilize the process. - **Electrode Deformation:** More common in thin electrodes, caused by thermal stress. Controlling current and ensuring adequate cooling prevents deformation. - **“Powdering” in Hole Machining:** Gas accumulation at the bottom of the electrode can cause violent discharge. Proper ventilation and gas removal techniques are necessary to avoid this. **(5) Human Error** Human mistakes, such as incorrect coordinates, wrong electrode selection, or program errors, can also lead to processing defects. Training and attention to detail are essential to minimize such errors. **3. Conclusion** Preventing abnormal processing in EDM is crucial for improving mold quality and production efficiency. A thorough understanding of each step in the process, attention to detail, and continuous improvement in technical skills are essential to ensure consistent and high-quality results.

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