Machine tool

A machine tool comprising:

• a table defining a plurality of machining regions;
• a spindle head movable relative to the table in a first direction;
• a spindle supported by said spindle head for undergoing machining of a workpiece;
• a column supporting said spindle head, said column being movable in a second direction perpendicular to the first direction and in a third direction perpendicular to both the first and second direction;
• a plurality of palettes each detachably mounting the workpiece, the plurality of palettes including means for moving each of said plurality of palettes into and away from an associated machining region, means for clamping each of said plurality of palettes when each palette is moved to a predetermined position within the machining region, and means for producing a clamped palette indicative signal when each of said plurality of palettes is clamped in the predetermined position;
• first detection means for detecting the movement of said spindle head and producing a first detection signal when said spindle head moves out of a first predetermined range in the first direction;
• second detection means for detecting the movement of said column and producing a second detection signal when said column moves out of a second predetermined range in the second direction;
• third detection means for detecting the movement of said column and producing a third detection signal when said column moves out of a third predetermined range in the third direction;
• control means responsive to the clamped palette indicative signal and the first, second and third detection signals for controlling the movements of said spindle head, said column and said plurality of palettes;
• first storage means for storing a plurality of machining programs and program numbers assigned to the plurality of machining programs for identifying each of the machining programs, each machining program containing a series of machining control data blocks;
• a central processing unit for sequentially supplying the machining control data blocks to said spindle, said spindle head and said column in accordance with the machining program stored in said first storage means, said machining control data block including column end position data indicative of an end position to which the column is finally moved from a preset position;
• setting means for setting an allowable movement range of said column over each of the plurality of machining regions;
• second storage means for storing the allowable movement range of said column;
• stroke over checking means for checking whether the end position to which said column is finally moved from the preset position is included within the allowable movement range of said column, said checking means indicating a stroke over status when the end position is out of the allowable movement range of said column;
• and
• prohibiting means for prohibiting the machining control data block from being supplied to said column when said stroke over checking means indicates the stroke over status.