Forced Chatter Sound in End-Milling Processes for Bamboo Fiber Extraction Using a Machining Center

In this study, we attempted to fabricate a self-adhesive molded product made entirely of bamboo. The raw materials were bamboo tube chips cut using a machining center. The chips can be made parallel to the vascular bundles with adjustable dimensions. However, the vibration inherent in the working material during the cutting process could potentially affect the chip shape. Therefore, we evaluated the effect of workpiece-specific vibration on fiber shape. Additionally, cutting sound, which is considered highly correlated with workpiece vibration suppression, was examined. The results showed that the first- (x-parallel) and second-order (y-parallel) intrinsic vibrations decreased the mean fiber width and increased its standard deviation. Cutting sound was also evaluated. The correlation between cutting sound and vibration acceleration was high when the natural to intermittent cutting frequency ratio was an integer. Under other conditions, cutting sound peaks were observed at integer multiples of the intermittent cutting frequency, and the maximum peak occurred at the frequency closest to the natural frequency. Subsequently, a natural frequency calculation method using the cutting sound was proposed. When this equation was applied to actual cutting sounds, the natural frequency was predicted with high accuracy. The results indicate that the spindle speed could be set to avoid the workpiece natural vibration using the cutting sound.