Controlling feed operations of a machine tool and work-piece relative to a programmed fixed cycle

A controller for machine tool which is provided for a machine tool having a feed mechanism for relatively moving a tool and a workpiece, and which controls the operation of the feed mechanism according to a machining program related to a fixed cycle,

• the controller for machine tool comprising:
• program storage means for storing the machining program related to the fixed cycle;
• program analyzing means for analyzing the machining program stored in the program storage means and extracting a fixed cycle command;
• parameter setting means for determining an accuracy level on the basis of the fixed cycle command extracted by the program analyzing means and setting parameters which correspond to the accuracy level and relate to the control of the operation of the feed mechanism, the accuracy level being graded into a plurality of grades depending on how high machining accuracy is prioritized as compared with machining time in machining;
• and
• drive control means for controlling the feed mechanism on the basis of the fixed cycle command extracted by the program analyzing means and the parameters set by the parameter setting means, and thereby relatively moving the tool,
• wherein:
• the drive control means is configured to, for an intersection portion of two linear movement paths, relatively move the tool along an arc-shaped movement trajectory which depends on the parameters set by the parameter setting means, the movement trajectory touching the linear movement paths and being more distant from the intersection portion when the grade of the accuracy level is lower;
• the parameter setting means is configured to recognize machining type on the basis of the fixed cycle command;
• when the recognized machining type is finishing, the parameter setting means determines the accuracy level to be the highest grade of accuracy level and sets the parameters corresponding to the determined accuracy level;
• and
• when the recognized machining type is rough cutting, the parameter setting means virtually sets a vertical corner portion where two straight lines intersect with each other, and then determines the accuracy level to be the lowest grade of accuracy level among such accuracy levels that an arc-shaped movement trajectory of the tool moving around the virtual corner portion which depends on the parameters does not intersect with a linear offset line which is obtained by offsetting the two straight lines inwardly by a finishing allowance which is recognized from the fixed cycle command, and sets the parameters corresponding to the determined accuracy level, the movement trajectory touching the straight lines and being more distant from the virtual corner portion when the grade of the accuracy level is lower.