Study On Uncertainty Base On Double Tolerance Principle Coaxiality Error

With the rapid development of advanced manufacturing technology in China,the high-precision manufacture,manufacture quality assessment and control technology of hole/shaft parts have made an urgent request in the fields of space,automobile and national defense.The use function of these hole/shaft parts is often affected by the geometric quality,and the precise evaluation method and its uncertainty are an important index to influence the geometric quality of the parts.Hole/shaft parts are generally constructed by a cylindrical surface with complex requirements,and the manufacturing cost can be reduced on the premise of ensuring the assembly property when the maximum material requirement is simultaneously applied on the reference and the coaxiality tolerance of the measured element of the cylindrical surface of hole/shaft parts.At present,most of the research of uncertainty evaluation of the coaxiality error for the double-tolerance principle is limited to the measurement uncertainty,while the study of the method for evaluating the conformity of the part in a few literatures is expanded from the measurement uncertainty to the compliance uncertainty,but it is generally limited to the part with a simple shape tolerance and a tolerance of the form and position of applying tolerance principle with a datum or a measured element,and the part of the coaxiality error for the double-tolerance principle is not applicable.Therefore,this paper takes a certain type spool of enterprise as the research object,aiming at the shortcomings in the above uncertainty evaluation research,the uncertainty of the coaxiality error of the double-tolerance principle is evaluated based on the GUM method and the Monte-Carlo method,and the research content mainly includes the following aspects:(1)This paper discusses the research background and significance of the subject,and analyzes the research progress and present situation of the form and position error evaluation method based on the double tolerance principle and uncertainty,and further expounds the main research contents of this paper.(2)This paper introduces the evaluation method of coaxiality error of double tolerance principle and the uncertainty theory of new generation GPS,including the theoretical basis of error evaluation method and tolerance marking of coaxiality of double-tolerance principle,the limit equivalent diameter of the measured cylinder,the evaluation process of the coaxiality error and the basic concept of the uncertainty of new generation GPS and judgment principle.(3)The uncertainty of coaxiality error of double tolerance principle based on GUM method is studied,according to the orthogonal experimental design,the test index and three influencing factors are determined,the related test scheme is worked out,and the measurement method is optimized.According to the definition of the specification uncertainty,the extraction,association and filtration specification of its constituent factors are analyzed,and the components of specification uncertainty are synthesized,and obtaining the specification uncertainty.Based on the black box model of uncertainty evaluation,the implementation uncertainty is calculated.Finally,the compliance uncertainty is combined and an example is given to verify it.(4)The uncertainty of the coaxiality error of the double-tolerance principle based on the Monte-Carlo method is studied,the probability density distribution of the input quantity is analyzed,and the uncertainty of the coaxiality error of the double-tolerance principle is evaluated according to the basic process of the uncertainty evaluation,and the validity of the method is verified by an example.The example shows that the result of the compliance uncertainty is reduced by 28.9% and the coverage interval is shortened by 35.2% based on the GUM method compared with the Monte-Carlo method.The method makes the uncertainty evaluation result more reliable,at the same time,the area of the compliance uncertainty is further reduced,the qualification rate of the product inspection is improved.(5)In order to facilitate the engineering designers to operate the uncertainty evaluation software,the uncertainty evaluation platform of coaxiality error based on double tolerance principle is designed in MATLAB.The platform can carry out the key dimensions and tolerances of the parts inputting,the coordinate data of the measuring points of the parts importing,the coaxiality error evaluation,the uncertainty of the GUM method evaluation and the uncertainty of the Monte Carlo method evaluation.The operation interface is simple,intuitionistic and simplifying the operation of the error evaluation.