PURPOSE: To obtain a cylindrical member being free from an underfill part and a burr, etc., by controlling a penetration quantity of a pair of mandrels, based on a difference of a proceeding condition of a plastic deformation of both side end parts, when bringing the cylindrical member to plastic working from a columnar billet.
CONSTITUTION: Before and behind both side end parts of a columnar billet 2, a light source 17 for projecting a beam 16 to a side end outside peripheral edge part of the billet 2, and a light quantity detector 18 for detecting the beam 16 from this light source 17 are placed. Each detector 18 is connected to a control device 19 for controlling an operation of a mandrel driving device 15 for driving a pair of mandrels 14, respectively. In case a proceeding state of a plastic deformation of the left end side of the columnar billet 2 is faster than that of the right side, a detected light quantity by the light quantity detector 18 of the left side becomes larger than that of the right side. In this case, a penetration quantity of the mandrel 14 of the right side is set so as to be more than a penetration quantity of the mandrel 14 of the left side, and a part of the billet 2 is made to flow to the side where the proceeding state of the plastic deformation has been delayed. In this way, the proceeding states of the plastic deformation in both side end parts of the billet 2 become roughly equal, and the generation of an underfill part and a burr is prevented.
SHIODA HIROSHI
TAURA RYOJI
MASUMOTO MASANORI
SUZUKI KENJI
CATERPILLAR MITSUBISHI LTD