© Copyright 2016, Mary Ann Liebert, Inc. 2016. The recent creation and growth of desktop three-dimensional (3D) printing has led to a new way of building objects. In the manufacture of pieces using Open-Source 3D printing it is very common to use a range of infill patterns and densities with the aim of reducing printing time and material consumption. However, it is not well understood how these factors influence the characteristics of the pieces obtained. Due to the differences with FDM technology, it is necessary to evaluate the strength of the pieces manufactured with this technology. In this work, the influence of two controllable variables, such as pattern and density of the infill has been evaluated. A series of test pieces with different density characteristics and infill patterns were produced using an open-source 3D printer. The results obtained show that the influence of the different printing patterns causes a variation of less than 5% in maximum tensile strength, although the behavior is similar. The change in infill density determines mainly the tensile strength. The combination of a rectilinear pattern in a 100% infill shows the higher tensile strength, with a value of 36.4 Mpa, with a difference of less than 1% from raw ABS material.