Effect of injection velocity on the filling behaviors of microinjection-molded polylactic acid micropillar array product

Microinjection-molded products with microfeatures are widely used in the biomedical field, microlens, etc. In this paper, a microinjection mold with venting design is fabricated for producing a polylactic acid (PLA) micropillar array product. The effect of injection velocity on the filling fraction is investigated. Results show that the farthest microcavity in the array to the sprue is readily filled with PLA melts at the given injection velocity conditions, while the nearest microcavity is the worst one in term of filling fraction, although increasing injection velocity can efficiently improve the entire filling fraction. By seriously analyzing the temperature and pressure from a simulation point of view, it reveals that the special geometrical structure of the product provides the condition which causes all the significant and interesting filling phenomena to appear in the experiment and simulation. This mechanism is beneficial to understand the filling behaviors of microfeatures and helps us to improve the replication of the product.