In addition to the axial stiffness of the bearing, the factor that affects the maximum thermodynamic zero is the temperature distribution in the lengthwise direction of the lead screw. Figure 1 shows a thermal image of a screw after a few hours of reciprocating operation at a distance of 150 mm. It is clearly identifiable that even after a few hours, the heating of the lead screw is almost limited to the area in which the screw nut moves. Therefore, the ball screw heat and elongation are very local.