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

刀具在加工过程中发生脆性失效，不仅会对刀具本身造成不可预知的损坏，还会对刀具本身和机床造成不可预知的损伤，进而导致自动化制造系统的可靠性大大降低，为保证刀具的可靠性提供了一种新的方法。在这种方法中，通过改变切削条件，使刀具初步承受大于实际切削时预期的切削力，从而淘汰了薄弱的刀具，而幸存的刀具则陆续投入使用。首先从断裂力学和统计学的角度阐述了IPT概念的理论基础，然后进行了断续数控车削陶瓷刀具的IPT试验，并从验证试验率和验证试验周期两个方面对IPT的性能进行了检验。通过采用IPT，刀具的平均寿命显著延长，分散量显著减少。从加工经济性的角度对IPT的性能进行了讨论。幸存者平均刀具寿命的延长一方面减少了刀具更换成本和刀具成本，另一方面也减少了因IPT扩大而被淘汰的刀具数量。从理论上得到了IPT降低生产成本的边际条件，从而证实了通过选择合适的验证试验条件，IPT在降低生产成本和提高刀具可靠性方面是非常有效的。

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.