Improving Chucking Accuracy and Repeatability by Reducing Kinematic Redundancy

In this paper, the effect of kinematic redundancy on chucking, especially, on the positioning accuracy of a cylindrical workpiece was investigated. No previous research on the effect of kinematic redundancy on the positioning accuracy and the repeatability of a workpiece in chucking has been reported, even if kinematic principle has been known for a long time. Starting from the description of the issues, a series of systematic experiments was carried out. It was demonstrated that the nonrepeatability and the chucking error proportionally increase as the kinematic redundancy increases. Also, it was shown that kinematic redundancy had a significant effect on the positioning accuracy of chucked workpieces, especially the workpieces with a relatively higher length/diameter ratio. The contact area between the workpiece and the jaws was reduced to the extent, which does not hurt the chucking rigidity and the safety to reduce kinematic redundancy. It was shown that the concentricity of the workpieces was improved as much as ten times by just minimizing the kinematic redundancy in the finish hard turning of the rings of a taper roller bearing.