Tool path-generating method, drilling method, and tool path-generating device

A hole machining method for machining first and second holes extending in a Z-axis direction in a surface of a workpiece by a machine tool that comprises X-, Y-, and Z-feed axes for relatively moving a rotating tool mounted to an end of a spindle which rotates about a rotation axis and the workpiece arranged to face the spindle, in three-axis directions of X, Y, and Z, orthogonal to each other, in which a direction of the rotation axis of the spindle is set at the Z-axis, the hole machining method characterized by:

• calculating distances in the X-axis and Y-axis directions between a position for end of the machining of the first hole and a position for start of the machining of the second hole;
• determining an X-axis reference value obtained by dividing the distance in the X-axis direction by a maximum acceleration of the X-feed axis as well as a Y-axis reference value obtained by dividing the distance in the Y-axis direction by a maximum acceleration of the Y-feed axis;
• setting a higher value of the X-axis reference value and the Y-axis reference value at a maximum reference value;
• multiplying the maximum reference value by a maximum acceleration of the Z-feed axis to determine a retraction distance in the Z-axis direction;
• generating a connection path having a shape of an ellipse of which a major or minor axis is a line segment of which both ends are at the position for the end of the machining of the first hole and the position for the start of the machining of the second hole, and which extends into a plane perpendicular to an XY plane, wherein the retraction distance is ½ of the minor or major axis of the ellipse;
• moving the rotating tool from the position for the end of the machining of the first hole in the workpiece to the position for the start of the machining of the second hole in the workpiece along the connection path;
• and
• driving the rotating tool toward an interior of the workpiece along the rotation axis.