Computer aided tolerance control in process planning of precision parts

Pao Yue-kong Library Electronic Theses Database

Computer aided tolerance control in process planning of precision parts

 

Author: Chow, Yiu-keung
Title: Computer aided tolerance control in process planning of precision parts
Degree: M.Sc.
Year: 1994
Subject: Tolerance (Engineering) -- Data processing
Process control -- Data processing
Hong Kong Polytechnic -- Dissertations
Department: Multi-disciplinary Studies
Pages: x, 103 leaves : ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1182959
URI: http://theses.lib.polyu.edu.hk/handle/200/4109
Abstract: In this thesis, a detailed review of tolerance charting technique is performed. It reveals that since the introduction of tolerance chart in the early l950s, development was rather sluggish. It was due to the large amount of tedious calculation and easy to make computation error involved in the manual development of a tolerance chart. With the computer explosion in the 1980s, research on computerised tolerance charting became active and fruitful. The introduction of Graph Theory has enriched the theoretical background of tolerance chart. Three trees can be generated from blueprint dimensions, stock removals, and working dimensions of a tolerance chart. By specially ordering the vertices and defining the directions for each edge of the combined SRBP and working dimension tree, a pure Graph-theoretic method for dimension chain identification is presented. A methodology for the development of a complete automatic tolerance charting system is formulated. A path tracing algorithm is used to identify the dimension chains for the functional and stock removal equations. The derived system of linear equations is then solved by the Gauss-Jordan elimination method to obtain the working dimensions. A linear programming model is formulated for optimisation of working tolerances. The objective function seeks to maximise the cumulative tolerance of each working dimension. The constraints include tolerance chains of stock removal and blueprint dimensions, and the process capability of each machining process involved. The model is then solved by the Revised Simplex method. With the computed working dimensions and tolerances, a modified tolerance chart is completed and ready for printing. The above methodology is successfully implemented on an IBM personal computer. Tolerance chart examples drawn from the literature are used for testing the validity of the software.

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