Research On Dimensional Completeness Check And Tolerance Optimization Design Technology Of Key Parts Of Marine Diesel Engine

Dimensional completeness inspection and tolerance design and optimization technology have always been important research contents in the field of CAD,CAPP and CAT.With the rapid development of computer technology and the gradual advancement of digital factories,product manufacturing information has gradually evolved from traditional two-dimensional annotated engineering drawings to three-dimensional annotated digital model.Three-dimensional dimensioning is a key link in digital definition technology and paperless design and production,which directly affects the processing,measurement and assembly of products.Based on this,it is of great significance to realize the completeness check of the dimensioning information and the optimal design of the dimension tolerance for improving the product design efficiency and quality performance.Based on the production status and actual needs of the shipbuilding industry and the characteristics of the key components of the marine diesel engine,this paper builds a system structure based on the three-dimensional MBD model for dimensional integrity check and tolerance optimization design.Based on the thorough investigation of the current research status,specific research has been carried out on the two key technologies.The research contents and results are as follows:(1)A specific inspection method is proposed for the two dimension error forms of redundant and missing.Through the virtual decomposition of dimensions and the construction of a three-dimensional dimensioning conversion model,the inspection of non-linear dimensions are converted into the inspection of linear dimensions,and the inspection of three-dimensional dimensions is converted into the inspection of two-dimensional dimensions.Use the computer to realize the automatic dimension completeness inspection of the three-dimensional model to ensure the accuracy of the dimension annotation and improve the design efficiency.(2)According to the definition of the dimensional chain,combined with its closedness and relevance,the dimensional node is used as the search unit,and the direction of the dimensional vector is used as the basis for judgment to realize the automatic extraction of complex dimension chains and judgement of the increase and decrease loops.The tolerance design function provides a basis for the follow-up tolerance optimization design.(3)Analyze the shortcomings of the existing tolerance analysis and allocation methods,establish a tolerance-cost model suitable for key parts of marine diesel engines,which comprehensively consider various influencing factors such as processing technology,manufacturing cost,assembly performance,equipment condition and so on.Matlab is used to realize the solution of multi-objective tolerance optimal allocation based on particle swarm algorithm.(4)On the basis of the above theory,complete the independent research and development of the dimensional completeness inspection and tolerance optimization design software system,including software function module design and interface design.Using the secondary development tools of NX combined with Visual Studio and Matlab,a prototype system of dimensional completeness inspection and tolerance optimization design was initially realized,and the practicability and effectiveness of the functional modules were verified.