| With the full implementation of the manned space flight and lunar exploration project,the requirements for the manufacture of aerospace products have become higher and higher.In aerospace-related products such as rockets and satellites,a large number of new aerospace integral parts with reduced structural characteristics,such as shell valves and board parts,are widely used because they can effectively shorten the assembly cycle and enhance the strength of the body.However,the new aerospace valve body parts have many holes,complex structures,large amounts of material removal,and high precision requirements,The completion of machining requires multiple clampings,which results in transmission and accumulation of part errors,affecting the machining accuracy of parts and limiting the production efficiency of space valves.In order to solve the above problems,this paper aims at the problem of influence of error accumulation on accuracy of multiple installations of aerospace valve parts.With the goal of reducing error accumulation,the fixture positioning planning method for valve housing multi-process manufacturing parts is studied.A fixture design method for aerospace valve housing parts based on clamping features aiming at reducing error accumulation.Firstly,on the basis of analyzing the coupling transfer mechanism between the spacecraft valve part reference,fixture and tool error,the model of error accumulation and transfer of spacecraft valve parts is established,and the error state transfer equation is obtained.By designing fixtures to reduce the number of fixtures to reduce the error accumulation,a fixture positioning scheme for valve multi-process parts manufacturing was proposed.Secondly,the inference rules of candidate set features of valve housing parts are studied.Analyze the factors affecting the clustering of valve parts processing features,calculate the fuzzy similarity among various features,and use the webbing method to complete the part clustering grouping based on the similar relationship matrix.According to the relationship between the process constraints and geometric tolerances of the part features,the vector discriminant method was used to complete the inference of the candidate set feature.Then,the positioning mode and positioning reference are selected during fixture design,and the fixture design is completed.According to the established analytic hierarchy model,the standard deviation and membership theory are used to complete the construction of the judgment matrix at each level,and the optimal positioning reference ranking is obtained.Combined with the limited degrees of freedom,the positioning reference and positioning modes are selected.By designing corresponding positioning elements,the fixture design is completed.Finally,the fixture design experiment was verified.By constructing the valve part system structure framework and using MATLAB to compile the calculation program,the reasoning of positioning reference is completed.The feasibility of this design method was verified with certain type of valve housing part. |
