DRILLING METHOD AND RELEVANT DRILLING MACHINE FOR STACKED BOARDS, PARTICULARLY FOR PRINTED CIRCUITS

摘要

To reduce dead times and waste of dummy boards necessary for preparing individual packages of stacked boards to be drilled, the latter are loaded on the table in a single stack and are drilled from the top in groups formed of a predetermined limited number of boards, drilling only partially into the next board to be drilled. The drilled boards are carried out of the stack which is reapproached to the drilling head. The drilling restarts by following the impression left by the tool in the preceding cycle on the partially drilled board. The numerically controlled drilling machine includes a table vertically movable to bring the stack against a fixed stop. A slide transversely movable after each drilling cycle engages the already drilled boards and carries them to an unloading support external to the table. The numerical control corrects for the positions of the holes upon each cycle by sensing with an optical sensor the impressions left by the tool in the preceding cycle on the partially drilled board following those unloaded.