In the process of cutting, the heat in the cutting area gradually accumulates at the arc of the tool tip, and the crescent depression wear occurs on the front edge and the back face also appears. Under each parameter, the maximum wear depth of crescent depression wear does not exceed 0.03mm, so the later tool face wear reaches 0.3mm to determine tool failure. The serial numbers of tool life test parameters correspond to the serial numbers of figures 2 and 3.
Figure 1 shows the failure morphology of the flank under various parameters. When the feed rate is 0.05mm/tooth, the flank wear at each cutting speed is concentrated in the arc area of the tool tip, and the secondary flank wear is less. When the feed rate increases to 0.2mm/tooth, the flank wear area extends to the flank of the pair at each cutting speed, and the flank of the pair has a certain degree of wear. This is because the feed rate increases, the cutting length of the secondary cutting edge increases, and the wear degree of the flank becomes larger.
Figure 2 shows the flank wear curve of the tool varying with time under various parameters. It can be seen from Fig. 2 (a) and Fig. 2 (b) that the wear curve under each cutting parameter appears rapid wear phenomenon in the early stage, and then enters the stable wear stage. When the feed rate is constant, the tool life decreases with the increase of cutting speed, and the maximum tool life 29.8min appears when the cutting parameters are v=800m/min and f=0.05mm/tooth, and a long stable wear period occurs. When the cutting parameters are v=1600m/min and f=0.05mm/tooth, the minimum tool life 5.5min appears, and the stable wear period is almost not seen, and the tool wear is fast. This is due to the poor toughness of PCBN cutters. under the condition of intermittent milling, the higher the speed is, the greater the impact frequency of the tool is and the lower the tool life is. It can be seen from figure 2 (c) that when the cutting speed is constant and the feed is 0.05mm/tooth, the tool life is generally longer than that when the feed is 0.2mm/tooth, which is consistent with the variation of the cutting force with the feed and the cutting temperature with the feed. In addition, compared with the large feed, the tool life decreases greatly when the feed is small. This is because when the feed rate is small, the tool wear area is small and concentrated at the tip arc; when the feed rate is large, the longer secondary cutting edge participates in the cutting, and the secondary flank participates in the wear, which shares the wear at the tip arc.
Figure 3 shows the change of the flank wear and volume removal of the tool, which is recorded as 1 volume per 3600mm3. As can be seen from the figure, when the feed rate is 0.2mm/tooth, the material removal amount of the workpiece at each cutting speed is larger than that when the feed rate is 0.05mm/tooth, which is 5.57 times when the cutting speed is 1600m/min, and the lowest is 2.27 times when the cutting speed is 800m/min. When the feed rate is 0.2mm/tooth, the material removal of the workpiece in 1200m/min is greater than the other two parameters. Combined with cutting force analysis and surface roughness analysis, better surface roughness and higher tool life can be obtained at cutting speed 1200m/min and f=0.2mm/tooth.