The novel method for tool life monitoring

To ensure a reasonably good precision on machining micro-lens arrays in ultra-precision machining, the tool life must be monitored without removing the single point diamond cutting tool from the tool-holder. In this paper, a method is presented to monitor the condition of tool nose radius. The prime objective is to spot when the tool starts to wear significantly. Initially, because of the good roundness of the tool nose, the wear is expected to be slow. However, when the roughness begins to deteriorate, the rate of wear will increase tremendously because of the friction induced adhesion occurred at localized zones sandwiched between the workpiece and the tool. The method proposed in this paper aimed at identifying when the roundness is no longer smooth relative to the cutting conditions and to the workpiece materials used. The profile of quasi-circular channels, which were machined by single pass grooving, was measured by an optical profiling system. A model was proposed to assist in reconstructing the groove profile at the time the tool still remained in contact with this portion of the groove. By comparing the reconstructed profile with the measured profile, the effect of adhesion on deforming the profile could be estimated. In our experimental work on single point diamond machining of Aluminum 6061, no adhesion happened at the depth of cut between 1-1.5um while significant adhesion was observed when the depth of cut was larger than 2um. This inferred that the tool used in this work was no longer fit for machining with depth of cut beyond 2um but was still good enough to be used to perform shallow cutting.