# Features and design principles of mold springs

1. Design principle of mold spring

①. The selection of allowable stress of spring materials should be mainly considered to ensure the fatigue life of the spring. The dynamic life of the spring is generally divided into three categories: Type Ⅰ, which bears alternating loads for 106 times; Type Ⅱ, which bears alternating loads The frequency is 103-105; Class Ⅲ, the number of alternating loads is less than 103;

②. The material width-thickness ratio (a/b) should not be too large, and the winding of the spring should not be too small.

③. When designing non-rectangular shaped cross-section springs, it is necessary to derive and draw curves or calculation formulas in different rotation ratios, different width to thickness ratios, deformation correction coefficients and shear stress correction coefficients.

④. According to the given conditions and constraints, choose a design method that is simple to calculate and select reasonable parameters.

2. Characteristics of mold spring

In recent years, with the development of the mold industry, the number and varieties of mold springs have been increasing. Special-shaped cross-section mold springs have the characteristics of long life, large rigidity, and small size. However, the development of design theory has been relatively slow. At present, except for square section strong springs In addition to the more mature design method, the design method of other cross-section strong springs is basically based on the empirical design formula obtained through the test of the specific section. Zhengyi Spring now gives an introduction to the characteristics and design problems of this type of spring.

Let’s first compare a square section with a round section coil spring. In the same space, the load-bearing capacity of a square section wire spring is 43-48% higher than that of a round section spring. Obviously, a rectangular spring is more than 50%.

It can be seen from the analysis that if the advantages of special-shaped cross-section material springs cannot be fully used, they will not produce economic benefits. Generally, they are often used in the following situations: the design load cannot be achieved with round cross-section materials; the spring installation space is small; instead of round Cross-section composite spring; when the required deformation cannot be achieved with the round material spring; where strict spring characteristics are required.