| Improved machining processes provide economic benefits through increased productivity and product quality. The main goal of this study was to improve the CNC router performance through extending the life of the cutting tool when machining wood-based products. There were two main objectives: (1) to determine the relationship between tool wear, panel chipping, and tool spindle vibration; and (2) to demonstrate the use of a process monitoring and control technique for extending tool life, and reducing panel chipping when machining wood-based products. The relationship between tool wear, panel chipping, and tool spindle vibration was established through conducting an extensive background work. As for the demonstration of the application of a process monitoring and control system, a feedback control technique, where the spindle speed was increased based on the tool spindle vibration level, was compared with three other cutting scenarios: (1) a control test with a constant spindle speed of 18,000 rpm; (2) a test with a constant low spindle speed of 12,000 rpm; and (3) a step function cutting with the spindle speed increased at regular intervals. Each situation cut two 0.6 x 1.2 m (2 x 4 ft.) panels of melamine-coated particleboard on a CNC router with a 10% cobalt grade tungsten carbide insert at 12.7 m/min (500 ipm) of feed speed in a climb cutting direction. After each test, tool wear, and panel chipping of the melamine layer of the particleboard were measured. At a constantly low spindle speed of 12,000 rpm, tool life was increased, but the panel chipping was adversely affected due to a larger chip load. A constantly high spindle speed of 18,000 rpm produced lower panel chipping; however, it resulted in a higher rate of tool wear. Increasing the spindle speed at regular intervals showed a lower tool wear, and panel chipping; however, it provided no clue about when to systematically increase the spindle speed. The feedback control technique utilized the tool spindle vibration to regulate the spindle speed that could greatly extend the useful life of the cutting tool. A cost-benefit analysis was also done on the different spindle speed settings to determine their performance based on ease of use, cost of implementation, and the actual extent of tool life improvement obtained. The results of the cost-benefit analysis showed that the step function test produced the lowest cost per product while the highest was produced by cutting at 18,000 rpm. The 12,000 rpm had the second highest cost per product whereas the feedback control had a comparably low cost per product, and came in second for the lowest cost per product. In terms of tool life, the feedback control technique had a 33% increase when compared to the 18,000 rpm test. |
