Research On Prediction Method Of Assembly Accuracy Of Meta Action Unit Considering Error Of Part

Assembly precision is an important indicator to ensure the quality of mechanical products.Scientific and reasonable prediction of assembly accuracy in the product design stage is an effective means to check whether the tolerance design of parts is reasonable,and provides an important basis for error compensation and tolerance optimization of products.This paper proposes a mechanical product assembly error modeling method using meta-action unit as the error transfer carrier,and performs assembly precision modeling for the meta-action unit,which lays a foundation for the next assembly accuracy prediction,control and analysis of the whole machine.Specific research content includes:(1)Common joint surfaces of meta-action unit parts and extraction of geometric elements and their error modeling.Compared with complex mechanical products,the number of parts in the meta-action unit is small,and the type of joint surface is simple.By classifying the main joint faces of typical meta-action unit parts,the common joint faces are plane joint faces,The cylindrical joint surface,the special shape joint surface in the bearing,and the corresponding geometric elements are plane,cylinder and cylinder axes.Based on SDT,the mathematical expression of the error of common geometrical elements in meta-action unit parts is given.The error variation of geometric elements under multi-tolerance coupling is analyzed by an example.The variation inequalities of each error component are established,and the error components are Constrained inequality.At the same time,based on the failure rate p of the constraint equation,the calculation method of the actual distribution law of each error component parameter of the geometric element under the constraint inequality limitation is derived.(2)The assembly error transfer path solving method of meta-action unit with complex mating relationship is analyzed.By introducing the concepts of error transfer properties,combined joint faces and movable joint faces,the error transfer properties of the common joint faces of meta-action units are discussed,and the joint face error model is established.In view of the influence of parallel joint surface interaction on the error transfer properties of each joint surface,the concept of joint surface constraint strength is introduced,and the solution method of the error transfer property of parallel joint surface is given.The meta-action unit assembly model is established by analyzing the structure of the meta-action unit.The assembly model of the meta-action unit contains the information of the key geometric elements,the coordination relationship,the error transfer properties of the joint surface,etc.,and realizes the meta-action unit part.Integrated expression of assembly information.Based on the meta-action unit assembly model,the error propagation path search method is proposed.Based on the error transfer property of the joint surface,the complex error transfer process in the meta-action unit is decoupled,which lays a foundation for the assembly accuracy modeling of the meta-action unit.(3)A meta-action assembly accuracy prediction model is constructed.According to the error transfer property of the joint surface and the error transfer path,combined with the Jacobian spin theory,the meta-action assembly error model is established,and the assembly precision prediction is realized.Combined with the reliability theory,the meta-The assembly accuracy indicator of the action.Taking the prediction of gear-turning meta-action assembly accuracy as an example,the rationality and feasibility of the method are verified.