Mechanical properties of snap-fits fabricated by selective laser sintering from polyamide

Snap-fits provide a quick, simple and reversible way to join larger additively manufactured parts. They take up little space and are flexible in their placement. The mechanical properties of snap-fits fabricated by selective laser sintering are not well explored. While the mechanical properties of the bulk material are available, these do not sufficiently describe the behavior of thin and flexible structures. The purpose of this research is the investigation of the mechanical properties of SLS-fabricated snap-fits. We explored the influence of geometric parameters, orientation during the manufacturing process and post-processing by chemical vapor smoothing as well as stress cycling. In a series of experiments, we measured the retaining force applied along the axis of the joint as well as the force necessary to open the snap-fit by pressing sideways. Based on literature, we formulated the relationship between geometry and mechanical properties. The resulting formulas were tested experimentally and corrected if necessary. The results show that the effective flexural modulus is 45% lower in cantilever snap-fits with width and thickness of less than 3 mm compared to bulk material. Smoothing reduced the flexural modulus as well as the friction even further.