A parametric study of the repeatability of 3D printed LEGO®-like mechanical couplings

Abstract

Parts made using Additive Manufacturing (AM) are limited in size to the build area of the 3D printer being used. Embedded elastically averaged locators can be used to join AM parts into assemblies, resulting in a piece larger than the build area, yet the design and placement of these locators must enable sufficient accuracy and repeatability of the couplings. In this thesis, locator design was formulated and verified using contact area, interference, and stiffness of the couplings as the design variables. A LEGO®-like coupling design was printed out of ABS on an Afinia H480 Fused Deposition Modeling (FDM) printer and measured with a ZEISS MICURA Coordinate Measuring Machine. The accuracy of each coupling was determined by measuring the radial misalignment between the base and the top of the coupling, and the repeatability of each coupling was determined by calculating the standard deviation of the radial misalignment after decoupling and re-coupling five times. The couplings were displayed accuracy on the order of 10 [mu]m and repeatability on the order of 1 [mu]m. Varying interference, contact area, and stiffness had a statistically insignificant effect of accuracy. Varying interference had a statistically insignificant effect on repeatability, increasing contact area increased repeatability by 0.75 [mu]m, or 15%, and increasing increased repeatability by 0.57 [mu]m, or 12%.