Design and performance evaluation of multi-helical springs fabricated by Multi Jet Fusion additive manufacturing technology

Springs are mechanical devices which are used quite extensively in different industries and mechanisms. Traditionally, springs have been manufactured by wrapping a hot wire around a rotating mandrel. This process has certain limitations because it is difficult to vary the spring parameters such as pitch and wire diameter. However, through the use of AM processes, with the complexity-for-free approach, it is possible to design and manufacture springs with variable spring parameters. Furthermore, it is also possible to create springs with multiple helices as opposed to traditional springs with a single helix. In this study, 32 springs with different numbers of helices, variable pitch profiles, variable wire diameters, and constant mass were designed. The springs were manufactured for experimental validation using HP MJF 520, which is a hybrid AM process. The stiffness of these springs was calculated analytically, through FEA, and experimentally validated. It was observed that increasing the number of helices in a spring leads to an increase in the stiffness of the spring. Furthermore, springs with variable pitch profiles and variable wire diameters have greater stiffness as compared to springs with constant parameters. However, with the increase in stiffness, the fatigue life of the springs decreases exponentially. Improvement in the stiffness of the springs without increasing the mass and therefore cost can lead to new and improved designs. These springs show great potential for industries where weight is an important consideration, such as aerospace and automotive. As these springs have a higher stiffness for the same mass, they can lead to designs with a light weight, and lower package volumes.