| 摘要 |
PURPOSE:To prevent frequent occurrences of defective products, by detecting the change of pressing force applied to a piercing pin by a strain gauge and thereby recognizing the degree of wear of the pin. CONSTITUTION:With the progress of wear of the head 11 of a piercing pin, the hole diameter of a pierced blank 13 becomes gradually smaller, and at last, simultaneously with the completion of piercing, the pierced blank bites the shoulder 14 of the peripheral body with high pressure, and more pressing force acts on the shoulder 14 from the whole periphery. Accordingly, at upper limit position of advance of a punch 18, once lowered pressing force is raised again. An upward change of pressing force is directly reflected by a strain gauge 20. When wear reaches the limit, the machine is stopped at once, and the piercing pin 10 is replaced with new one. |
