In the present work, an explicit finite element analysis technique is introduced to analyze the thermal stress fields present in the additive manufacturing process. To this purpose, a finite element matrix formulation is derived from the equations of motion and continuity. The developed code, NET3D, is then applied to various sample problems including thermal stress development. The application of heat to an inclusion from an external source establishes an initial temperature from which heat flows to the surrounding body in the sample problems. The development of thermal stress due to the mismatch between the thermal strains is analyzed. As mass scaling can be used to shorten the computation time of explicit analysis, a mass scaling of 108 is employed here, which yields almost identical results to the quasi-static results.