Effect of router tool wear on AE count rate

This work is a part of the study that will establish the feasibility and limitation of using acoustic emission (AE) to monitor the peripheral cutting process of wood, and discusses the effects of wood fiber direction and tool wear on the acoustic emission signals, surface finish roughness and cutting force for routing. For sensing of AE signals, a non-contact technique with a transducer was used. The results obtained can be summarized as follows : (1) The AE count rate slightly decreased from 0° grain angle to about 15-30° grain angle taking the lowest value, and then increased to reach maximum at the grain angle of 135-150°. At the grain angle of 165°, the AE count rate showed a little lower value than that of 150°. The edge recession affected the AE count rate. The greater the edge wear, the greater the AE count rate. However, there was no significant change in AE count rate at the gram angles of 15° and 30°. Moreover, even though the tool became severely worn, an increase in feed speed gave little effect on the AE count rate while cutting with the grain. (2) The cutting force-grain angle relationship was almost steady at the initial stage of cutting edge. As the bit became severely worn, the relationship dramatically changed and a parabolic relation between two variables with an extreme at the grain angle of 60° became evident, and in a addition, an increase in feed speed did not affect the cutting force. For every cutting condition, the greater the edge recession, the greater the cutting force. (3) The surface roughness, lowest at the grain angle of 0°, slightly increased till 120° and then rapidly became rough reaching maximum at the grain angle of 150°. At the 165° grain angle the surface finish showed a lower value than of 150°. An increase in feed speed did not affect the change in R_z value while cutting with the grain. However, the greater the cutting wear, the worse the surface finish quality.