| 摘要 |
PURPOSE:To increase mechanical strength, while the occurrence of bottom breakage and constriction is prevented and high grade molecular orientation is imparted to its side wall by heat setting the body of a can after the side wall and bottom part of a preform has been proheated at a prescribed temperature and after the preform has been formed by squeezing. CONSTITUTION:A cylindrical bottomed perform 1 provided with a cylindrical side wall 2 and a bottom part 3 is molded by injection molding of plastic. Said preform 1 is preheated in such a condition that the temperature of the side wall 2 is equal to the transition point of plastic glass or higher, and the temperature of the bottom part is lower than the transition point of plastic glass by at least 3 deg.C. The occurrence of the bottom breakage or the constriction in the wiping process continuously carried out is prevented. Next, the side wall 2 of the preform 1a supported by a punch 12 is engaged with a wiping die 13, and it is formed by squeezing. The lug part 5 on the edge of the obtained wiped can is cut off, and the flange 6 is formed on an opening end. There, heat setting is applied to the body of the squeezed can 1b, and heat resistance and mechanical strength are contrived to be improved. Finally necking 7 is formed, and a can body 1c is obtained. |
