This article studied the demolding of an array of injection molded micro-structures based on a design of experiments (DOE) method. The demolding force (F-d) to eject an array of 4 x 5 micro-ridges from the cavity of a mold was calculated indirectly. It was found that mold temperature had a significant effect on the demolding force: the demolding force decreased as mold temperature increased and as the part substrate thickness also increased. The demolding force is a combination of the adhesion force and friction force that exist between a molded feature and the microcavities of a mold. When the processing parameters were optimized to minimize the demolding force during the ejection process, it was found that the adhesion force had a bigger influence than the friction force. POLYM. ENG. SCI., 56:810-816, 2016. (c) 2016 Society of Plastics Engineers