On-line Monitoring of Drill wear Using Stereo Microphone When Drilling CFRP Composite Materials

The condition of the cutting tool when drilling composite materials is the controlling factor for the quality of hole produced, and the strength and integrity of assembled structural parts are highly influenced by the quality of the drilled holes. Inspecting the condition of the drill between or during the drilling process is not practical or economical. Because of this and the high rate of tool wear when drilling composite materials, it is necessary to find a way to monitor the condition of the cutting tool without interrupting the drilling process. In an attempt to tackle this problem, a new approach of on-line tool wear monitoring method using an air-coupled stereo microphone is proposed. An experimental investigation was conducted on multi-directional carbon fiber reinforced plastic (CFRP) composite material using a high speed steel (HSS) drill. The result shows that, the amplitude of the acoustic signal from the microphone decreases when the amount of flank wear increases and the thrust force increases with the increase of the flank wear. This result demonstrates that the proposed approach can be used as an effective and economical tool for on-line monitoring of cutting tool condition.