| 摘要 |
PROBLEM TO BE SOLVED: To accurately machine a small hole in a short time. SOLUTION: A punch 12 bites a substrate slightly with an upper mold 13 lowered at first, so that both a recessed part 16 and a projected part 17 in shallow depth are thereby formed up in the substrate. Next, the upper mold 13 is lowered down while being slightly vibrated in the vertical direction A by allowing ultrasonic vibration with its amplitude less than 0.1 mm to be applied to the punch 12 from an oscillator. After a through hole 18 is newly formed up, the hole is deburred. Punching force of the punch 12 and ultrasonic vibration of the oscillator are applied to the substrate 10 in an overlapping mode in a state that tension stress is incurred in the glass fibers 10b of the substrate 10 so that the glass fibers 10b are thereby broken, and epoxy resin 10a is simultaneously softened so as to let the through hole 18 as shown by a broken line be thereby formed up.
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