Kinematic Simulation Of The Nipper Mechanisms On Combing Machine Considering The Tolerance Of Manufacture And Assembly

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. This thesis takes advantage of all the achievements in tolerance analysis and considers every kind of errors in mechanism, and as result performs tolerance analysis in 3D。Paul Faerber [1999] developed the Tolerance Analysis Using Kinematically-Derived Sensitivities (TAKS) method, 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. The thesis expands Paul Faerber’s tolerance analysis theory and develops the kinematic analogy to 3D tolerance analysis that also allows for inclusion of geometric feature variation sources. All the errors included in mechanism or assembly can be considered in the vector loop used for tolerance analysis from two angles as followed, dimension errors and geometric errors. Based on the equivalent exchange ideology, the length error in the vector loop of assembly can be displaced by slider joint, and similarly the angular error by revolute joint. The equivalent exchange ideology is also used to displace the dimension and geometric errors that exists in the mechanism/assembly kinematic nodes, namely adds joints. As results of the equivalent exchange, it’s easy to get Equivalent Variational Joints(EVJs) and Geometric Equivalent Variational Joints(GEVJs). By using the method above, the errors can be equivalently modeled and finally gets the Equivalent Variational Mechanism(EVM) for the original mechanism. EVM enables performing the tolerance analysis using software ADAMS. Firstly, model EVM in ADAMS, and then input a virtual unit speed for each independent variational source, finally simulate by single step so that to extract each error’s tolerance kinematic sensitivity. Then to performs tolerance analysis for kinematic mechanism in different positions, trigonometric functions will be used to modify the static assembly. At the end of the thesis, these methods expressed above is used to perform tolerance analysis of the nipper mechanisms on combing machine, and in the practical analysis example, tolerance sensitivities are also extracted. As long as getting these tolerance sensitivities, the key of the question in the precision design of textile machine can be easily caught.In a word, every kind of errors in mechanism/assembly is considered by means of the equivalent exchange ideology so as to get EVM, and then realize tolerance analysis using software ADAMS. The results demonstrate that the method in this thesis enable computer aided tolerance analysis using ADAMS, solve the defect of DLM, and insure a reliable tolerance analysis method.