Patent ID: 8676527

Claim:
An industrial machine comprising: a base surface; a column and a support that stand along a Z-axis perpendicular to the base surface; a beam that is provided between the column and the support; a slider that is movable on the beam; a ram that is held on the slider in a manner movable in a Z-axis direction; a temperature detecting unit that detects a temperature T c of the column, a temperature T s of the support and a temperature T r of the ram; a Z-axis scale that is provided to the ram and is provided with graduations for measuring a movement amount of the ram in the Z-axis direction; a Z-detector that is provided to the slider to read the graduations of the Z-axis scale, and a shift amount calculating unit that calculates a Z-axis shift amount of the ram along the Z-axis direction resulting from a temperature change of each of the column, the support and the ram, wherein the shift amount calculating unit calculates the Z-axis shift amount based on the temperature T c of the column, the temperature T s of the support and a temperature T r of the ram detected by the temperature detecting unit, reference position data indicating a positional relationship between the column, the support and the ram when the column, the support and ram are at a predetermined reference temperature, a compensation factor for calculating a dimensional change amount Δ C of the column, a dimensional change amount Δ S of the support, a dimensional change amount Δ Z of the ram in the Z-axis direction resulting from the temperature change, and position coordinate x of the slider, the reference position data comprises: a distance L 1 from the base surface to the Z-detector at the reference temperature; a distance L 2 from an end of the ram opposed to the base surface to a fixed position of the Z-axis scale in the ram at the reference temperature; a distance X 0 from a center axis of the column to a center axis of the slider when the slider is set closest to the column; a distance X 1 from a center axis of the support to the center axis of the slider when the slider is set closest to the support; and a distance X 2 through which the slider is movable in an X-axis direction, the compensation factor comprises: a thermal expansion coefficient α c for the column; a thermal expansion coefficient α s for the support; and a thermal expansion coefficient α r for the ram, and the shift amount calculating unit calculates the Z-axis shift amount by using an expression below, ( Z -axis shift amount)=( X o +x ) 3 ×(Δ S−ΔC )/( X 0 +X 1 +X 2 ) 3 +ΔC−ΔZ where: ΔC=(T c −T 0 )×L 1 ×α c ΔS=(T s −T 0 )×L 1 ×α s ΔZ=(T r −T 0 )×L 2 ×α r , and T 0 : the reference temperature.