Solutions in Limit Deviations for Optimum Dimensional Structures of Technological Processes of Machining

Abstract

In the paper the analysis of the dimensional structure of different manufacturing process is made. There are shown that the different schemes of the designer sizes result in a different level of an optimality of a dimensional structure. At definition of number of the technological sizes as criterium of a optimality it is necessary to allow both formation of the intermediate sizes and the effect of errors compensation. The effect of errors compensation is the reason for the change of the sizes nominals and its limit deviations. The detail subjected to machining, is characterized by constructive dimensional links which reflect, eventually, its functionality. The character of the constructive dimensional links is defined by the designer who takes into account the technological features of machine tools, but not in detriment of functionality. Therefore, carrying out of the dimensional analysis on a joint of these two phases is very important with the purpose of improvement of dimensional adaptability to manufacture of made details. One of criterions of this optimality has the structural nature. The manufacturing process is considered optimum, if in the structure of all technological dimensional chaines number of the technological sizes is minimum. This condition executes if to each designer size there corresponds in a technological dimensional chain the unique technological size, and in dimensional circuits for machining allowances, each machining allowance is determined by two technological sizes or one technological size and one size on blank. For different variants of the linear dimensions are shown the way in which are changing the limit deviations of technological sizes and respectively of the constructive sizes of the equivalent details.