| 摘要 |
PURPOSE:To accurately bring shaft centers of a stem and container in line, by emitting a light beam parallel to the shaft center of the stem from a light beam generator provided on the outer surface of the stem, introducing to a photodetector provided on the outer surface of the container, then calculating an eccentricity value based on a detected signal of the photodetector. CONSTITUTION:A heated hollow billet, while inserting a mandrel in its inner surface, is pushed into the container 1 by the stem 2, the stem 2 is pressed to advance to push out the hollow billet and to make it into a pipe. The plural laser beams are emitted parallel to the shaft center of the stem 2 from plural laser beam oscillators 3a, 13a, etc., provided on the outer surface of the stem 2 of this extruder and these beams are received by the plural photodetectors 4a, 14a, etc., provided on the outer surface of the container 1. When the shaft cents of the container 1 and the stem 2 are brought in line, the straight line connecting the receiving positions of the laser beam is to cross the shaft center of the container 1, and based on the detected signal of the photodetector, the shift of the shaft center is calculated and based on this calculated value, the position of the container 1 is shifted.
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