Protomold president Brad Cleveland believes that the mechanical properties of plastic parts made on additive machines don't come close enough to those of injection-molded and machined plastic parts, which creates design engineering difficulties. So Design News asked Cleveland to back up his assertions about material properties — and he did. Protomold hired an independent materials testing lab, Stork Materials Technology, to run ASTM tensile and flexural tests of three kinds of ABS parts — injection molded, CNC machined and fused deposition modeled (FDM) — on a Stratasys machine. The study tested the FDM part in different orientations to account for the anisotropy found in additive parts. It also tests the molded part in two different gating configurations. The study, whose results are summarized in these tables below and which can be downloaded in full here, shows a significant strength advantage for machined and molded ABS grades.