Abstract: The conventional methods for fixture analysis are based on the point-kinematic model, which ignores the curvatures of workpiece and locators. Even if CARLSON presented a quadratic method considering the curvature of workpiece, the effect of locators’ curvatures should not be neglected especially when the locators’ curvature is large with respect to the workpiece curvature. The signed distance function from surface to surface is defined, the first and second differential properties are analyzed and its 2nd Taylor expansion is derived. Then the new quadratic sensitivity equations are derived and a new method of fixtures locating analysis is presented. The proposed method considers not only the curvature of workpieces but also that of locators. The examples show that the proposed method has higher precision than the linear method and the CARLSON’s method.

Key words: Fixture analysis, Sensitivity equation, Signed distance function