The effect of water-silica slurry impacts on PolyLactic Acid (PLA) processed by Fused Deposition Modeling (FDM) under different conditions were investigated. The studied factors were building orientation, layer thickness, and slurry impact angle, where Taguchi design was used. The results showed an increase in the specimens’ weights after the slurry erosion tests. This weight gain was eventually attributed to the synergistic effect of water absorption and the embedment of solid particles within the specimens. An analysis of variance (ANOVA) test was conducted and concluded that the layer thickness and impact angle are the significant factors influencing the weight gain resulting from absorbed water. Moreover, impact angle was the most significant factor for the weight gain resulting from embedded slurry particles.