What are the advantages and disadvantages of graphite electrodes compared with traditional metal electrodes?

Advantages

1. Faster Machining Speed
   Graphite electrodes offer discharge machining speeds 2–3 times faster than copper electrodes, particularly evident in the machining of thin-rib electrodes. With a cutting resistance only 1/5 that of copper, graphite enables higher machining efficiency and significantly reduces processing time.

2. Lightweight
   Graphite has a density only 1/5 that of copper, reducing the load on machine tools and minimizing equipment wear, making it particularly suitable for large molds and electrodes.

3. Low Thermal Expansion Coefficient
   Graphite’s thermal expansion coefficient is only 1/30 that of copper, ensuring minimal deformation during high-temperature machining and maintaining higher machining accuracy, especially for deep, narrow ribs and thin-walled parts.

4. Low Wear
   During discharge machining, carbon atoms in the dielectric fluid decompose at high temperatures and form a protective film on the graphite electrode surface, compensating for electrode wear. In contrast, copper electrodes tend to produce burrs, requiring additional manual finishing.

5. Burr-Free and Easy to Polish
   Graphite electrodes leave no burrs after machining, eliminating the need for post-processing and facilitating automated production. Additionally, their low cutting resistance simplifies grinding and polishing.

6. Cost-Effective
   With rising copper prices in recent years, graphite electrodes remain relatively stable in cost. Moreover, graphite electrodes are 30%–60% cheaper than copper electrodes of the same volume.

7. Excellent High-Temperature Performance
   Graphite electrodes have a sublimation temperature of up to 3650°C, far exceeding copper’s melting point (1083°C), ensuring stability in high-temperature environments and suitability for high-power, high-current machining applications.

8. Superior in Machining Complex Shapes
   Graphite electrodes are easily shaped into complex geometries, meeting the demands of precision molds and irregularly shaped parts, whereas copper electrodes face greater challenges in machining complex shapes.

Disadvantages

1. Lower Mechanical Strength
   Graphite electrodes have relatively low mechanical strength, making them prone to chipping at sharp corners, especially during rough machining. Light cuts with high feed rates are required to avoid corner breakage or fracturing.

2. Dust Generation
   Machining graphite electrodes produces significant dust, necessitating specialized sealing and dust extraction systems to protect machine tools and operator health.

3. Poor Performance in Wire EDM
   In wire electrical discharge machining (Wire EDM), graphite electrodes exhibit cutting speeds approximately 40% slower than copper electrodes and are prone to wire breakage, making them unsuitable for high-precision wire cutting applications.

4. Surface Roughness Limitations
   Achieving surface roughness levels below VDI12 (Ra0.4μm) is challenging with graphite electrodes. For mirror-finish discharge machining, copper electrodes remain the preferred choice.

5. Difficulty in Recycling
   Graphite electrode scrap has low recycling value and is challenging to repurpose, increasing usage costs and environmental impact.

6. Brittleness and Susceptibility to Fracture
   Graphite electrodes are brittle, especially thin or narrow electrodes, which are prone to breaking under external forces, requiring careful handling.

7. Unsuitable for Fine Surface Discharge Machining
   For fine surface discharge machining requiring surface finishes below VDI12 (Ra0.4μm), graphite electrodes underperform compared to copper electrodes, making it difficult to meet high-precision surface requirements.