1. Discharge energy and microstructure
In EDM, discharge energy is one of the key parameters. Higher discharge energy will produce a larger heat-affected zone on the mold surface when removing mold material. At the microscopic level, this may lead to changes in the grain structure of the material, such as grain growth, grain boundary melting and recrystallization. For example, for some carbide precision molds, excessive discharge energy will cause the hard phase particles on the surface to be unevenly distributed and cause local aggregation or dissolution, thereby reducing the hardness and wear resistance of the mold surface. This change in microstructure directly affects the service life of the mold. During the subsequent stamping or injection molding and other molding processes, the surface of the mold is more likely to be worn and scratched, which in turn affects the accuracy of the mold and the quality of the molded product, reducing the effective work of the mold. frequency.
2. Pulse width and micromorphology
Pulse width has a significant impact on the micromorphology of the mold. A longer pulse width will make the discharge last longer and form deeper and wider discharge pits on the mold surface. The shape, size and distribution of these pits will change the roughness of the mold surface. Taking injection molds as an example, a rough mold surface will affect the flow and filling performance of the plastic melt, resulting in a decrease in surface quality of the molded product, and defects such as flash edges and flow marks may occur. At the same time, this uneven micromorphology can easily become a stress concentration point when the mold is subjected to repeated molding pressure, accelerating the generation and expansion of fatigue cracks on the surface of the mold, and ultimately shortening the life of the mold. On the contrary, a suitable pulse width can obtain a more ideal surface micromorphology while ensuring processing efficiency, and reduce the adverse impact on the life of the mold.
3. Pulse interval and material heat accumulation
The pulse interval determines the time interval between two discharges, which plays a key role in the heat accumulation of the mold material. If the pulse interval is too short, the heat generated by the previous discharge has not been fully dissipated, and the next discharge starts again, which will continue to increase the temperature of the mold material. This heat accumulation on the microstructure may cause thermal stress inside the material, which may lead to microscopic cracks. For precision molds, these microscopic cracks will continue to expand during subsequent use, eventually leading to cracking and failure of the mold. For example, when processing some high-precision stamping dies, unreasonable pulse interval settings may cause fine cracks in the mold in the early stages of use. As the number of stampings increases, the cracks expand rapidly, greatly reducing the expected life of the mold.
4. Electrode materials and processing effects
The choice of electrode material is also closely related to the microstructure and life of the mold. Different electrode materials have different discharge characteristics and wear rates during EDM. For example, copper electrodes have good electrical conductivity and processing stability, but wear quickly when processing certain high-hardness mold materials. The wear of the electrode will affect the stability of the discharge gap, which in turn affects the processing accuracy and microstructure of the mold surface. If the discharge gap is unstable, it will lead to uneven processing of the mold surface and local over-processing or under-processing. The microstructure is manifested by inconsistent material removal, uneven surface hardness and uneven structure. This unevenness will reduce the overall performance of the mold, making it more susceptible to local damage during use, thereby reducing the service life of the mold. Therefore, reasonable selection of electrode materials based on mold materials and processing requirements is critical to optimizing mold microstructure and extending service life.
