| 摘要 |
PURPOSE:To improve manufacturing efficiency at the formation of a heating cylinder by reducing the dimension of an end opening of a pipe material to a specified dimension by drawing, uniformly correcting thereafter the thickness of the end section of said opening by drawing and also uniformly correcting the thickness of a base section by drawing. CONSTITUTION:Drawing comprising a plurality of processes is applied in a stepwise manner to the circumferential wall of an end 1a of a pipe material 1 to stepwise enlarge a protruded section of a step 3, while the end opening 2 is gradually made smaller. Thereafter, the end periphery of a punch is engaged with the step 3 to apply drawing comprising a plurality of processes to the circumferential section of the end 1a in a stepwise manner, in which the step 3 is bent outwardly by stages to increase the curvature thereof, while the end opening 2 is gradually made smaller. And drawing is applied to the end 1a so that its opening 2 has a specified dimension and then the thickness of the end 1a is made uniform by drawing, while the dimensions of other parts are corrected to specified ones and further the thickness of a base section 1b of the material 1 is made uniform by drawing. As a result, manufacturing efficiency in the formation of a heating cylinder can be promoted.
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