The Drilling Vibration Behavior of a Twisted Microdrill

The dynamic characteristics of a microdrill in the drilling process were investigated in this study. The trend toward higher density printed circuit boards requires smaller holes, down to 0.3 mm in diameter, to be drilled through the board layers. To improve quality, produce a higher production rate, and avoid drill breakage, the dynamic characteristics of the microdrilling process must be studied. A stepped pretwisted beam is used to simulate the microdrill. A moving Winkler-Type elastic foundation is used to approximate the drilling process. A time-dependent vibration model for drilling is presented. The rotating speed, pretwisted angle, and thrust force effects of the microdrill are considered. The numerical analysis indicates that the natural frequency is reduced suddenly as the microdrill moves into a workpiece.

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