Study Of The Design Technology Of Computer-aided Dimensional Tolerances

China is a traditional agricultural country, and then from the traditional agriculture to modern agriculture, the agricultural mechanization level is an important sign. At the same time, China is a developing country, the broad masses of peasants are not wealthy. Therefore, at the same time ensure the quality, how to effectively reduce costs has become an important issue.Computer-aided tolerance design is one important part of mechanical design. Computer-aided tolerance design is to improve the precision machinery manufacturing and cost effective means of one, so the optimization of manufacturing precision machinery and computer aided manufacturing, computer-aided tolerance design has a necessary link. it not only influences products' quality, but also react on the manufacture cost. At the sametime, Computer Aided Tolerance (CAT) is one of the core technology in integrationof CAD and CAM, it is the bottle-neck of integration of design and manufactureinformation.Is this, domestic and international scholar to calculator assistance size business trip design carry on extensive of research.The model of cost-tolerance is an important issuer about the optimal design of precision for product.Manufacturing environment has been recognized as a variable, non-linear and complex major factor.In this paper, i based on an environment variable manufacturing and establish the costs - Tolerance Model.It closely linked to actual machining process.The relation of Cost - tolerance is more precise.As the manufacturing environment change the model can be easy to be adjust. It does not need to spend a number of expenses and time-consuming to experiment.The model has in general use.It is applicable to various Optimal Design of precision abaot machine product .It this article describes that it take VB as development tool, use ACCESS to establish dimension tolerence database, realize that dimension tolerence can be auto search.It is based on AutoCAD software for graphics support,and achieve automatic marking of dimensional tolerances in AutoCAD.This paper through the research on the new method of CAT establish a new method of dimension chain automatic generation .Monte Carlo method in this paper as a statistical experimental methods used in tolerance analysis, Studied and proposed the synthesis smallest cost law. Then focus on the theoretical derivation and validation example of the comprehensive smallest cost method. The example proved that using the comprehensive smallest cost method to conduct tolerance- assignment can reduce the processing cost and receive the good economic efficiency.The research of the item can exaltation product assemble success rate and quality, decline low cost, shorten a product development period.Pass research and calculator of this item assistance business trip design software in the meantime of development, push CAT technique of development, make the CAT get behind with the situation of CAD/CAM to get improvement, for CAT and CAD/CAM of further integration lay foundation.