Improvement of Machining System by Using In-Process Proof Testing of Cutting Tools

切削过程中切削刃脆性破坏的发生不仅会对刀具本身、而且会对工件和机床造成不可预料的损伤，而且会导致自动化制造系统的可靠性大大降低。在这项研究中，IPT（过程中的验证测试）的概念，在断续切削已提出。在这种方法中，通过修改切削条件，使切削刀具预先承受比实际切削中预期的切削力更大的切削力，从而淘汰弱刀具，另一方面，继续使用幸存的刀具。首先应用断裂力学和统计学方法阐述了IPT概念的理论基础，然后在陶瓷刀具的断续数控车削过程中进行了IPT试验，并从验证试验比和验证试验周期两个方面对IPT的性能进行了检验。采用IPT后，平均刀具寿命显著延长，分散量显著减少，并从加工经济性的角度讨论了IPT的性能。存活刀具平均寿命的延长一方面降低了换刀成本，另一方面也降低了因IPT增大而淘汰的刀具数量的增加。从理论上得到了IPT使生产成本降低的边际条件，从而证实了通过选择合适的验证试验条件，IPT在降低生产成本的同时，对提高刀具的可靠性是非常有效的。

Occurrence of brittle failure of the cutting edge during cutting operation may substantially cause unexpected damage not only to the tool itself, but also to the workpiece and machine tool, furthermore it may result in considerable deterioration of the reliability of the automated manufacturing system.As a new method for assuring the reliability of cutting tools, IPT (In-process Proof Testing) concept in interrupted cutting has been proposed in this study. In this method, cutting tools are preliminarily subjected to a cutting force greater than that expected in actual cutting by modifying the cutting condition, so that weak tools are eliminated, on the other hand, surviving tools are successively used in service. The theoretical basis for the IPT concept was first described by applying fracture mechanics and statistics.IPT experiments were then conducted during interrupted CNC turning on ceramic cutting tools, and the performance of the IPT is examined in terms of the proof test ratio and period. By employing the IPT, the mean tool life is considerably elongated and the amount of scatter is remarkably reduced.The performance with the IPT is also discussed from the view point of machining economics. The elongation of the mean tool life of survivors reduces both the tool changing cost tool cost, on the other hand, the increase in the number of eliminated tools due to IPT enlarging of them. The marginal condition above which the production cost becomes less with IPT was theoretically obtained.Consequently, it was confirmed that by selecting appropriate proof test conditions, the IPT is very effective in reducing the production cost as well as the improving the reliability of the cutting tool.