In view of the existence of discrete variables for material diameter

medium diameter and number of operating in spring design

and that of the machine error changed the spring’s dimensions and characteristic

the multi-target optimal design model was set up with the purpose of the lightest weight of breaking spring

the minimum rigidity error and the minimum rigidity deviation at the specified change of the spring’s dimensions.The model was determined by mixed discrete optimization method and effective ratio method

etc.

the optimal solution satisfied all restrain conditions.