Rollers are mainly the work of the three-driven roller to ensure that any thickness of the material sent to a good rolling function.

三个工作辊均为主驱动辊，保证对任何厚度的材料有良好的送进卷制功能。

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However, the deformation is more uniform with regard to billet in contact with the work surface of punch, material thickness decreases less, therefore, the purpose of calibration has been reached.

而与模具工作表面相接触的管坯，其变形则较为均匀，材料壁厚减薄较小，达到扩径整形的目的。

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