科研之友
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摘要
A pointing process is a pre-work operation to facilitate the feeding of a rod to pass through a drawing die. After performing the pointing process, the drawing material is inserted into the drawing die and the jaw pulls the end of the material. A bar pointing turning machine, which is universally used for the pointing process, causes a breaking of drawing material easily in the shape-drawing process. Because a shape-drawing process requires a higher drawing load and a smaller cross-sectional area of the pointed zone of drawing material, a pointing process which is to prevent the breaking of the drawing material through a work-hardening effect at an early stage of the drawing process is necessary. In this study, a four-roll squeeze pointing machine (RSPM) as a new automatic pointing machine is introduced. RSPM has been developed to improve the productivity of the pointing process as well as the shape-drawing process by preventing the breaking of the drawing material. The ductile fracture criterion based on Cockcroft-Latham's theory was used to predict the breaking of drawing material and any defects during the pointing process. A tool design method for the RSPM and a feasible pointing size for the conventional pointing machine are proposed. In addition, the drawing materials manufactured using a conventional pointing machine and the RSPM are compared through finite element (FE) simulations and experiments.
