How to distinguish the difference between the quality of graphite mold?

1. Average particle diameter of the material

The average particle size of the material directly affects the discharge status of the material. The smaller the average particle of the material, the more uniform the discharge of the material, the more stable the discharge conditions, and the better the surface quality.

For forging and die casting molds with low surface and precision requirements, coarser particles such as ISEM-3 are usually recommended. For electronic molds with high surface and precision requirements, it is recommended to use materials with an average particle size below 4μm to ensure the accuracy and surface finish of the machining mold. The smaller the average particle size of the material, the smaller the loss of the material, and the greater the force between the ion groups. For example, ISEM-7 is often recommended to meet the requirements of precision die casting and forging molds. However, when customers have high accuracy requirements, TTK-50 or ISO-63 materials are recommended to ensure less material loss, so as to ensure the accuracy and surface roughness of the mold. At the same time, the larger the particle, the faster the discharge speed, the smaller the roughing loss. The main reason is that the discharge energy is different due to the different current intensity during discharge. However, the surface finish after discharge also changes with the change of particles.

2. The inherent resistivity of the material

According to our statistics of material properties, if the average particle of the material is the same, the discharge rate with high resistivity will be slower than that with low resistivity. For materials with the same average particle size, the strength and hardness of the material with low resistivity will be slightly lower than that of the material with high resistivity. That is, the discharge rate and loss will be different. Therefore, the selection of materials according to the practical application is very important. Due to the particularity of powder metallurgy, the parameters of each batch of materials have their representative values, and there is a certain fluctuation range. The discharge effect of graphite materials of the same grade is very close, and the difference in application effect caused by various parameters is very small. Material The choice of graphite electrode material is directly related to the discharge effect. Whether the material is suitable determines the discharge speed, machining accuracy and surface roughness to a large extent. Mastering the above points will have a great effect on identifying the grade of graphite materials.

3. Bending strength of the material

The bending strength of the material is a direct reflection of the strength of the material, which shows the compactness of the internal structure of the material. The discharge resistance of materials with high strength is relatively good, and graphite products should choose materials with better strength as far as possible for electrodes with high precision requirements. For example, TTK-4 can meet the requirements of general electronic connector molds, but some electronic connector molds with special accuracy requirements can use TTK-5 materials, the same particle size, but slightly higher strength.

4. Shore hardness of the material

In the subconscious understanding of graphite, graphite is generally considered to be a relatively soft material. However, the actual test data and application show that the hardness of graphite is higher than that of metal materials. In the special graphite industry, the general hardness test standard is Shore hardness measurement, and its test principle is different from metal. Due to its layered structure, graphite has excellent cutting properties during cutting. Its cutting force is only about 1/3 of copper, and the processing surface is easy to handle. However, due to its high hardness, the loss of cutting tools will be slightly greater than that of cutting metal tools. At the same time, the high hardness material has a good control over the discharge loss. In our EDM material system, there are two materials to choose from, one with slightly higher hardness and the other with slightly lower hardness, to meet the needs of customers with different requirements. For example, the average particle size of 5μm materials are ISO-63, TTK-50; The materials with average particle size of 4μm are TTK-4 and TTK-5. Materials with an average particle size of 2μm include TTK-8 and TTK-9. Mainly considering the various types of customers on the discharge and processing of the emphasis.