トーラス形状工具を用いた薄肉銅円管の高縮径率回転成形

抄録

Thin-walled copper tubes of various shapes are required to reduce the environmental impact of products by improving the performance of their heat exchangers. Tubes of various outer diameters along the longitudinal direction are conventionally manufactured by rotary swaging. However, the shape of the die is just transferred and thin-walled copper tubes are prone to torsion due to friction. To solve these problems, we applied the flexible ball-spin forming (FBS) method, in which ball-spin tools are pressed against a rotating circular tube at an arbitrary axial position. The FBS method was suitable for the flexible diameter reduction of thick tubes, whereas it caused polygonal or torsional defects in the case of thin tubes. Therefore, in this paper, we propose a method of spin forming using a torus-shaped tool for thin tubes. This method can hold tubes in the circumferential direction and maintain a near-circular shape. As a result, the tube diameter was effectively reduced and a reduction ratio of up to 57.1 % was achieved.