Machine tool system and method of replacing pallet of the device

A machine tool for machining a workpiece mounted on workpiece mounting table by moving a spindle having a tool mounted thereon in directions along the X-axis, the Y-axis and the Z-axis with respect to the workpiece, said machine tool comprising:

• a spindle support structure comprising a base adapted to be located on a floor surface and having guides extending in the direction along the X-axis on the upper and lower portions thereof, an X-axis slider guided along said guides on the upper and lower portions of said base to move from side to side in the direction along the X-axis, said base of said spindle support structure having longitudinal spaces extending in the direction along the X-axis and opening downwardly in the upper and lower portions of said base, respectively, and each of said longitudinal spaces accommodates therein a guide for guiding and supporting said X-axis slider and an X-axis feed means for moving said X-axis slider in the direction along the X-axis, a Y-axis slider guided on said X-axis slider to move upwardly and downwardly in the direction along the Y-axis, a Z-axis slider guided on said Y-axis slider to move forwardly and backwardly in the direction along the Z-axis, and a spindle head mounted on said Z-axis slider to be rotatable in at least one of directions along the A-axis, the B-axis and the C-axis, said spindle head rotatably supporting said spindle;
• a workpiece support structure disposed in opposed relation to said spindle support structure and including a workpiece mounting table having two opposed pallet mounting surfaces and pallet securing means arranged thereon, said workpiece mounting table supported to allow for rotational indexing about a horizontal axis extending in the direction along the X-axis;
• and
• rotationally indexing means for turning said workpiece mounting table of said workpiece support structure by 90 degrees or 180 degrees to allow said two opposed pallet mounting surfaces to be positioned in an upwardly directed horizontal position or a transversely directed vertical position, said workpiece being mounted on said workpiece mounting table or demounted therefrom when one of said pallet mounting surfaces is in said horizontal position, said spindle support structure machining said workpiece mounted on said workpiece mounting table when one of said pallet mounting surfaces is maintained in vertical position;
• and
• chip discharge means interposed between said spindle support structure and said workpiece support structure for discharging chips produced in the machining area to the outside of the machining area.