Tolerance Control and Location Surfaces
A sequence of machining operations involves a series of set-ups for holding and locating the workpiece while it is being machined so that the required design specifications can be economically achieved. To this end the sequence of machining operations and the selection of location surfaces must be based on the practicality of locating and holding the workpiece and on the dimensional relationships between machined features of the part. These are aspects of fixture design previously discussed as workpiece control. Geometric and mechanical control are concerned with practicalities of fixture design and dimensional control deals with the dimensional relationships between machined features. Good dimensional control is guaranteed if the workpiece is located on one of the pair of surface features related by a dimension while the second surface is machined. (This is axiom 7). While this ideal should be strived for, consideration of geometric and mechanical control may make it impossible to achieve. If surfaces not referred to by the dimension are used for location then manufacturing tolerance stacks are inevitable.
KeywordsMachine Surface Location Surface Final Dimension Design Dimension Nominal Dimension
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- 1.Marks CT. Tolerance charts control production machining. American Machinist March 1953; 97 (5): 114–116Google Scholar
- 2.Drozda TJ, Wicks C (ed). Tool and manufacturing engineers handbook, vol 1. Society of Manufacturing Engineers, Dearborn, Mich, 1988.Google Scholar
- 4.Britton GA, Whybrew K, Sermsuti-Anuwat Y. A manual graph-theoretic method for teaching tolerance charting. International Journal of Mechanical Engineering Education, October 1992; 20 (4): 273–285.Google Scholar
- 5.Wade OR. Tolerance control in design and manufacturing. Industrial Press, New York, 1967.Google Scholar
- 6.Gadzala JL. Dimensional control in precision manufacturing. McGraw- Hill, 1959.Google Scholar
- 7.Eary DF, Johnson GE. Process engineering for manufacturing. Englewood Cliffs, NJ, Prentice-Hall, 1962.Google Scholar
- 8.Sermsuti-Anuwat Y. Computer-aided process planning and fixture design (CAPPFD). PhD thesis, University of Canterbury, 1992.Google Scholar
- 9.Robinson DF, Foulds LR. Digraph: theory and techniques. Gordon and Breach Science Publishers, New York, 1980.Google Scholar
- 10.Ling KC. Development of computerised tolerance charting system. Project report, School of Mechanical and Production Engineering, Nanyang Technological University, 1992.Google Scholar