Evaluation System Development Of Products’ Geomentric Deviation Based On NGPS

A perfect life cycle of a product is beginning with its design. The designer designthe products consist of the parts which can complete the corresponding functionsaccording to the functional requirements of products. Product design is done underideal conditions. But because of various uncertainties, there is no ideal environment,which leads to deviation throughout its productive process. My job is to determinewhether the products meet the tolerance requirements, namely to evaluate geometricalerrors of the products. Each deviation corresponds to a product tolerance.Based on the research of National Nature Science Fund Project‖Study for thethree-dimensional tolerance design and optimization method of product function (No.51005002)‖, the evaluation of geometrical error is studied and evaluation algorithmsof all kinds of geometric deviation are proposed. And a geometric deviationassessment system is developed with Visual C++.Firstly, the existing geometric deviation evaluation, mainly on form deviations, issummarized, and the related development status of GPS is analyzed in detail. Theevaluation significance of geometric deviation is proposed based on NGPS.An appropriate frame of reference or benchmark system must be firstlyestablished before evaluate the geometric deviation of products. And fitting methodsmust be used for fitting actual benchmark elements in order to establish the idealframe of reference or benchmark system. So various fitting methods (mainly the leastsquares method and the minimum area method), which are used for various geometricelements, are firstly studied. Then the principles and methods to establish variousframe of reference or benchmark system are studied in detail. Then the evaluationalgorithms of geometrical deviations are studied on the basis of the study above,including the form deviation of flatness error, straightness error, roundness error,cylindricity error and positional deviations of parallelism error, vertical error,inclination error, and location error and so on. The evaluation products are moredetailed classified according to the different status of geometric elements andevaluation methods, and evaluation algorithms of geometrical deviation are designedfor each category.Finally, a geometrical deviation system based on NGPS is developed. Visual C++programming language, MFC and OpenGL are used for developing the software ofthe system. At last, the usage of this system is introduced by evaluating straightnesserror in2D with least square method as an example. At the same time, the feasibilityof designed evaluation algorithms above is proved.