Improvement in Dimensional Accuracy of Drawn Micro Shaped Wire

摘要

Shaped wire drawing round-to-octagon, round-to-hexagon and round-to-square copper wire drawing has been investigated. Significant technological advancements have been achieved in the fields of electronic equipment, precision instruments and micromachines, and considerable attention is being paid to the technology for manufacturing high-quality shaped microwires. However, the drawing of shaped wires with a diameter of 1 mm or less is not easy; in addition, there are important requirements in terms of the accuracy in dimensions, residual stress and mechanical properties. Furthermore, the demand to reduce fabrication costs is increasing in the market. To satisfy these requirements, the level of overall ability in integrating the drawing technology is important. In particular, the unaccuracy in dimensions and wire breaks during drawing are directly related to the drawing cost. Many methods, including the slab method, that are used in round wire drawing cannot be applied to the drawing of shaped wires. Therefore round-to-shaped wire drawing has been simulated by 3D-FEM. The authors drew the shaped microwire from a round wire by changing the die half-angle and one-pass reduction, and examined a few points about the drawing stress, dimensional accuracy (diameter, magnitude of corner R) and residual stress. The results reveal that the optimal die half-angle for shaped microwire drawing with a hexagonal die (600 mu m) and square die (400 mu m) is slightly greater (alpha=12 approx 18 deg) than that for round wire drawing and that the suitable one-pass reduction is about 25 approx 35 percent. It is clearly shown that the lower the die half-angle or the larger the one-pass reduction, the smaller the residual stress level is.