PURPOSE: To smoothly discharge chips by drilling a drilled plate which is being vibrated to generate air flow at a drill edge.
CONSTITUTION: Two-layer printed boards 5 are pushed against an EX-axis moving table 6 by a board hold-down 9, an alternating current is applied to a vibrator 11 to give the printed board 5 vibration, and a drill 4 is fed in such a state. The rotating number of a spindle is 70,000rpm and the machining speed per turn of the drill is 20μm. Also, the vibration frequency is 20kHz and all the amplitude is 10μm. As a result, the feeding speed of the spindle 1 is nearly 23.3mm/sec, meaning that 20,000 vibration frequencies are applied thereto while the drill 4 advances nearly 23.3mm, and so a drill feeding distance per vibration is about 1.17μm. If there is vibration at all the amplitude of 10μm for a feeding distance of 1.17μm, a sufficient gap is made at the edge of the drill 4, where greater wear resistance is provided.
EGAWA TSUNEO
TANIMOTO TATEO
NAKAMURA KATSUMI
