Research On Assembly Error Modeling Of CNC Machine Tools Based On Meta-action

As one of the most important key pushing areas in Made in China 2025 Strategy,assembly is a key process to realize the product quality,and assembly precision is an important measurement index of assembling process.Regarding CNC Machine Tools as the research object,Meta-action Assembly Unit as the error carrier,error impress course in assembly process is modeled systematically,with great practical guiding significance to assembly process controlling.The main work of the paper are followed:?The basic theories of the assembly accuracy were expounded.The widespread using model and their characteristic ? research status were analyzed.Technical framework of assembly error modeling of CNC Machine Tools was established.?The functional decomposition approach “function-motion-action” was used to analyze its assembly process structurally,then,it was decomposed down into basic action: meta-action;and the concept of Meta-action Assembly Unit was defined.The deviation source that affects meta-action assembly unit precision is clustered into four types: form error,position error,assembly position error and kinematic error.Based on analysis of different fit modes,feature deviation source and error transfer in junction surface were expressed by SDT.Analyzing the peculiarity of error transfer in assembly process,the conclusion that model should be built respectively was drawn.?Error transfer process inside Meta-action Assembly Unit was modeled.Expressing the relationship of coupling and nesting vividly,error linkage model was introduced as the basic unit of part error relationship,linkage network and linkage matrix was construct as structured error relationship model.Assembly error transfer path search method based on error linkage model is proposed,searching all possible paths by traversal algorithm,and highest precision is put forward as the basis of distinguishing error transfer effective path,then the effective transfer path of error component are obtained.The effectiveness and practicability of the error linkage mode and research method is verified by a case of worm drive MAU.?Error transfer process between Meta-action Assembly Units was modeled.In order to express the assembly relationship between each assembly unit and logical relationship between geometry features,the frame chart of assembly errors propagation based on meta-action was constructed;Thirdly,in order to provide guiding comments on assembly process,multi-level state space model was built to predict final assembly precision of NC Machine Tools on the basis of propagation and accumulation of geometry errors;Finally,the effectiveness of multi-level state space model was demonstrated by an example of Z axis feed motion assembly unit from a certain machining center.