Method and Device for Preparing Error Map and Numerically Controlled Machine Tool Having Error Map Preparation Function

A method for preparing an error map of a numerically controlled machine tool which has a linear feed axis and a rotational feed axis and in which a main spindle and a table are movable relative to each other, said method comprising steps of:

• defining a plurality of measurement points in a movable range of said linear feed axis and said rotational feed axis;
• positioning said rotational feed axis to plural rotation angles at said measurement points and processing three mutually orthogonal surfaces of a test piece or work piece in a shape of rectangular parallelepiped attached to said table at each of said rotation angles thus positioned,
• measuring an inclination of a processed surfaces obtained when said rotational feed axis is positioned to one of said plural rotation angles and said test piece or work piece is processed at one rotation angle relative to that positioned to other rotation angle to determine an attitude error at each rotation angle,
• measuring said processed surfaces of said test piece or work piece to determine, for each rotation angle, a position of intersection point of three planes containing said processed surfaces that are processed at said rotation angle,
• determining a position error at each measurement point from difference of position between an intersection point of three planes containing said processed surfaces obtained when said rotational feed axis is positioned to said one rotation angle and said test piece or work piece is processed at said one rotation angle and an intersection point of three planes containing said processed surfaces obtained when positioned and processed at an other rotation angle, and said attitude error, and
• storing said position error and said attitude error in correspondence to a position of said linear feed axis and said rotation angle of said rotational feed axis.

A method for preparing an error map of a numerically controlled machine tool which has a linear feed axis and a rotational feed axis and in which a main spindle and a table are movable relative to each other, said method comprising:

• defining a plurality of measurement points in a movable range of said linear feed axis and said rotational feed axis;
• positioning said rotational feed axis to plural rotation angles at said measurement points and processing three mutually orthogonal surfaces of a test piece or work piece in a shape of rectangular parallelepiped attached to said table at each of said rotation angles thus positioned,
• measuring processed surfaces of said test piece or work piece to determine, for each rotation angle, an inclination of said processed surfaces and a position of intersection point of three planes containing said processed surfaces that are processed at a rotation angle,
• determining an attitude error at each measurement point from a difference between an inclination of said processed surfaces obtained when said rotational feed axis is positioned to one of said plural rotation angles and said test piece or work piece is processed at one rotation angle and an inclination of said processed surfaces obtained when positioned and processed at other rotation angle,
• determining a position error at each measurement point from a difference of position between an intersection point of three planes containing said processed surfaces obtained when said rotational feed axis is positioned to said one rotation angle and said test piece or work piece is processed at said one rotation angle and an intersection point of three planes containing said processed surfaces obtained when positioned and processed at other rotation angle, and said determined attitude error, and
• storing said position error and said attitude error in correspondence to a position of said linear feed axis and said rotation angle of said rotational feed axis.

A numerically controlled machine tool which has a linear feed axis and a rotational feed axis and in which a main spindle and a table are movable relative to each other, said numerically controlled machine tool having an error map preparation function comprising:

• a test piece or work piece attached to said table,
• a measurement device having a sensor provided on said main spindle for measuring processed surfaces of said test piece or work piece with said sensor at a desired measurement point,
• a computation section that computes a position error and an attitude error for said measurement point based on measurement data measured with said measurement device and coordinate values of said measurement point,
• a storage section for storing said position error and said attitude error computed by said computation section in correspondence to a position of said linear feed axis and a rotation angle of said rotational feed axis at said measurement point.