Modern wire cutting power supplies have strict requirements on electrode wires. It must be able to withstand large cutting currents with peaks in excess of 700 amps or averages in excess of 45 amps, and the transmission of energy must be very effective in order to provide the high-frequency pulse current required to achieve high surface finish (above 0.2Ra). This depends on the resistance or conductivity of the electrode wire. Copper is one of the materials with the highest electrical conductivity, and it is used as a benchmark for measuring other materials. The electrical conductivity of copper is marked as 100% IACS (International Annealed Copper Standard), while the electrical conductivity of brass is 20%.
1. Mechanical characteristics
Tensile strength is a measure of a material's ability to resist fracture when subjected to a radial load. It is scaled by the weight that a unit cross-sectional area can support, such as imperial PSI (pounds per square inch) or metric N / mm2 (newtons per square millimeter). Copper is the material with the lowest tensile strength (245N / mm2), while molybdenum is the highest (1930N / mm2). The tensile strength of wire-cut molybdenum wire depends on the choice of materials and various heat treatment and stretching treatment processes. Electrode wire is sometimes divided into "soft wire" and "hard wire", which have their own advantages for different devices and applications.
This is directly related to the "soft" or "hard" of wire-cut molybdenum wire. The soft wire does not have the memory ability to recover to a straight line when it is drawn off the axis, so it cannot be used for automatic threading, but this has no effect on cutting, because tension is added to the wire cutting molybdenum wire during processing. The soft wire is suitable for the equipment that the upper and lower guide wire nozzles cannot be tilted to cut at a large incline more than 7 degrees. Hard wire is the best choice for automatic threading machine. At the same time, because of its high tensile strength, it has a strong ability to resist wire jitter caused by current and washing force during cutting.
Elongation is the percentage change in wire length caused by tension and heat during cutting. The elongation of soft wire can be as large as 20%, while the hard wire is less than 2%. When the soft wire is processed at an inclination, the wire cutting molybdenum wire with a high elongation can ensure the geometric accuracy of the inclined plane, and the softer electrode wire generates less vibration when sliding in the guide wire nozzle. However, after the wire-cut molybdenum wire enters the cutting area, the soft wire has a greater degree of jitter than the hard wire, so it must be compromised.
线切割 技术发展的早期(1969年到七十年代中期)，对线切割钼丝几乎没有做任何的研究，用的是现成的电机和电缆上的紫铜丝。 In the early days of the development of wire cutting technology (1969 to the mid-seventies), almost no research was done on wire cutting molybdenum wire, using copper wires on ready-made motors and cables. Today, high-efficiency and high-precision wire cutting machines require electrode wires with geometric characteristics with minimal errors. The final process of wire cutting molybdenum wire manufacturing is to use multiple jewel wire drawing dies to obtain smooth, excellent roundness, and a wire diameter tolerance of +/- 0.001mm. On the other hand, there are some wire-cut molybdenum wires that are intentionally designed to have a relatively rough surface, which can increase the cutting speed.