Project Overview:
Additive manufacturing provides many diverse and highly flexible processes to manufacture geometries that are difficult or impossible to recreate with traditional manufacturing methods. For example, with SLA, we can create highly customizable geometries from various polymer materials to obtain specific part characteristics. This process can be leveraged to manufacture polymer springs that have customized load-deflection curves. The goal of this project is to investigate the physical properties of additively manufactured springs. The material, print orientation, and geometry of the spring will be varied and the SLA process will be used. Ultimately, load versus displacement and mass versus stiffness plots will be created as the source of comparison. This data will be collected to provide insight on how material, orientation and geometry in an SLA manufacturing process effects the performance of a spring.
Manufacturing Considerations and Parameters:
The Form 2 SLA additive manufacturing technology will be used at the University of Wisconsin – Madison Makerspace to create the test springs. Several springs will be manufactured for each print to explore the repeatability of the results. Additionally, support structure will be used as necessary to create the springs.
Two classical spring geometries will be studied: coil springs vs wave springs. Models of both geometries are pictured below. Both geometries have advantages. Coil springs have the advantage of longer travel distances and are less expensive to manufacture while wave springs require half as much of the working height of a coil spring and don’t torsionally load in compression
Figure 1 – Geometric differences between coil (top) and wave (right) springs
Print orientation can change the characteristics of 3D printed parts, so three orientations (0, 45, and 90 degrees) will be used to understand how the anisotropy alters the spring characteristics. In addition, we will use three different polymers, from highly flexible material to rigid polymer as available in the Makerspace. A full description of the experiment parameters can be seen in the figure below.
Figure 2 – Test plan for SLA manufactured springs
Proposed Analysis:
To compare the effect of geometry, material, and print orientation on spring stiffness, the spring curves will be measured using a compression test machine. These springs, plotted as load vs deflection will be measured in compression only to restrict the scope of the study. We will be communicating with Professor Wendy Crone, a mechanics of materials professor in Engineering Physics, to gain access to the appropriate testing equipment. With the spring curves, we can compare the effect of material, orientation, and geometry on spring curve as well as the interaction between independent parameters (e.g. flexible material wave spring vs rigid material coil spring) to better understand the characteristics of 3D printed polymer springs. We will also compare the mass vs stiffness of the spring to understand if similar stiffness characteristics can be achieved with a reduction in material.
Robert Bradley, Quinn Burzynski, Asher Elmquist, Mitchell Langer