Method of machining workpiece using machine tool, and machine tool

A machine tool comprising:

• a bed;
• a plurality of supporting jigs having an adjusting mechanism for adjusting a vertical support position and a load cell detecting a support load, and supporting the bed at predetermined support positions;
• a workpiece holder disposed on the bed for holding a workpiece;
• a tool holder disposed on the bed for holding a tool;
• a feed device moving the workpiece holder and the tool holder relative to each other along guides provided on the bed;
• and
• a numerical controller generating a position control signal in accordance with a machining program for machining the workpiece into a target shape with the tool, and numerically controlling operation of the feed device in accordance with the generated position control signal,
• the machine tool further comprising;
• a motion locus estimator calculating height positions or variation positions relative to a reference height position at target positions set on the guides based on the support loads detected by the load cells of the supporting jigs and an influence coefficient matrix defining degrees of influence of the support loads detected by the load cells upon the height positions at the target positions, and estimating, based on the calculated height positions or variation positions at the target positions, a motion locus of relative motion of the tool and the workpiece moved along the guides by the feed device;
• a motion error calculator calculating motion errors between the motion locus estimated by the motion locus estimator and a preset reference motion locus at predetermined intervals in a motion direction;
• and
• a motion error judgment part outputting an alarm signal at least when a maximum value of the motion errors calculated by the motion error calculator exceeds a predetermined reference value or when a variation value of the motion errors in the motion direction exceeds a predetermined reference value, and
• the numerical controller being configured to, when generating the position control signal, generate, based on the motion errors calculated by the motion error calculator, such a position control signal that the motion errors have been compensated for.

A machine tool comprising:

• a bed;
• a plurality of supporting jigs having an adjusting mechanism for adjusting a vertical support position and a load cell detecting a support load, and supporting the bed at predetermined support positions;
• a workpiece holder disposed on the bed for holding a workpiece;
• a tool holder disposed on the bed or holding a tool;
• a feed device moving the workpiece holder and the tool holder relative to each other along guides provided on the bed;
• and
• a numerical controller generating a position control signal in accordance with a machining program for machining the workpiece into a target shape with the tool, and numerically controlling operation of the feed device in accordance with the generated position control signal,
• the machine tool further comprising:
• a motion locus estimator calculating height positions or variation positions relative to a reference height position at target positions set on the guides based on the support loads detected by the load cells of the supporting jigs and an influence coefficient matrix defining degrees of influence of the support loads detected by the load cells upon the height positions at the target positions, and estimating, based on the calculated height positions or variation positions at the target positions, a motion locus of relative motion of the tool and the workpiece moved along the guides by the feed device;
• a motion error calculator calculating motion errors between the motion locus estimated by the motion locus estimator and a preset reference motion locus at predetermined intervals in a motion direction;
• a motion error judgment part outputting an alarm signal at least when a maximum value of the motion errors calculated by the motion error calculator exceeds a predetermined reference value or when a variation value of the motion errors in the motion direction exceeds a predetermined reference value;
• and
• a position corrector successively receiving the position control signal generated by the numerical controller, generating a correction signal for the received position control signal based on the motion errors calculated by the motion error calculator, and adding the generated correction signal to the positon control signal in the numerical controller.