| 摘要 |
PURPOSE:To form a core bar of rotary recording sheets with a high precision and improve the yield of production by forming preliminarily many notches at proper intervals in the part where a step should be formed with drawing and performing drawing thereafter. CONSTITUTION:For example, a steel plate 1 of SUS430 having 0.3mm. thickness is used, and this steel plate 1 is subjected to the first lancing to form semicircular cuts 3 and 3 in two positions facing each other along a circle having a diameter larger than that of a product. Next, the steel plate 1 is subjected to the second lancing to form semicircular cuts 5 and 5 in positions shifted from the first cuts by 90 deg.. Many notches 6, 6- are formed at equal intervals in the base-shaped part, where a step should be formed, by punching. Thereafter, prescribed drawing is performed; and thus, the drawing processability of the part, where a step should be formed, of materials is improved, and the occurrence of cracks is prevented, and the dimensional precision is improved. |
