Incorporating Geometric Feature Variation with Kinematic Tolerance Analysis of 3d Assemblies

INCORPORATING GEOMETRIC FEATURE VARIATION WITH KINEMATIC TOLERANCE ANALYSIS OF 3D ASSEMBLIES Jeffrey G. Dabling Department of Mechanical Engineering Master of Science As technology increases and performance requirements continually tighten, the cost and required precision of assemblies increase as well. There exists a strong need for increased attention to tolerance analysis to enable high-precision assemblies to be manufactured at lower cost. Methods for tolerance analysis of 2D and 3D assemblies have been developed and are in use in both research and commercial applications. These methods are usually very complex, and are usually best implemented in some type of automated software. However, existing variation analysis software does not yet have an industrywide user base. In an effort to greatly increase the proportion of companies with variation analysis capability, Paul Faerber [Faerber 1999] developed the TAKS method (Tolerance Analysis Using Kinematically-Derived Sensitivities), allowing the creation of a tolerance model from a kinematic mechanism using equivalent variational mechanisms (EVMs). Such a model can then utilize much more widely used kinematic analysis software to perform tolerance analysis on an assembly, and even increment the position of the mechanism for conducting analyses at every desired position very quickly. However, the TAKS method was limited to 2D and did not incorporate geometric feature variation. This thesis expands upon Faerber’s work to develop a kinematic analogy to 3D tolerance analysis that also allows for inclusion of geometric feature variation sources. Libraries of 3D EVMs are introduced that incorporate both dimensional and geometric variation in a kinematic model. Methods of incorporating these equivalent joints into a kinematic model are set forth and analysis techniques are explained. The use of a commercial kinematic software package to automate the analysis is also demonstrated.