Fused Deposition Modelling (FDM) has been becoming a widely used additive layer-by-layer manufacturing process, is used to produce complex geometries in a short period without tooling or human involvement. One of the challenging problems of FDM products is the surface roughness. In this article, a slurry was applied to the surface of FDM Polylactic Acid (PLA) products to enhance the surface roughness. The developed technique lessens the asperities of the surface and makes it softer. The controllable factors are layer thickness, building orientation, and slurry impact angle. Experimentally, a test rig was utilized to investigate the effect of the three factors on surface roughness. Numerically, an Adaptive Neuro-fuzzy Interference System (ANFIS) was developed to map roughness with the contributing factors. The results showed that the effect of slurry gave a good surface quality and the surface roughness …