Abstract: English letters with subscripts are used to illustrate the components which various elements within the assembly belong to and the condition of location of the components so that correct relationships of mounting dimensions can be established based on it. “Target size” as a concept is put forward for specifying such principles as “independence” and “integrity”, which should be followed when target sizes are selected. Based on “finding the shortest path” and “giving high-precision priority”, two essentials of establishing path diagrams are put forward and the basic path diagram of mounting dimensions, which is the only shaping path of each target size, is hereby confirmed. In accordance with the process features and the customs of size marking of each component, the basic path diagram is optimized for the establishment of the final path diagram of mounting dimensions; thereby, reasonable marking modes for the dimensions of each component are found out. Moreover, after the path diagram has been confirmed, a mode system of mounting dimensions can be established for the target sizes in the ensemble, and a complete model of total correlative mounting dimensions can be obtained. Under the drive of the entire target sizes and the tolerances, the dimensions and the tolerances of all the components can be solved so that the demands of computer-aided design of tolerance and parameterization can be better met.

Key words: Marking mode, Model of dimensions, Path diagram of dimensions, Target size