Effect of Process Parameters on Dimensional Inaccuracy of Solidified Polylactic Acid Parts Fabricated by 3-Dimensional Printing Process

Abstract

Rapid prototyping is a manufacturing process that fabricates products by adding layer of a specified material. Products made using rapid prototyping are not only limited to be used as a prototype, rather they are also being used as functional parts. But the functional use of a rapid prototyped product is often constrained due to dimensional inaccuracies in the product. These dimensional inaccuracies are mostly caused due to unevenness of the surface profiles and shrinkage of the part. The parameters that govern the surface profile and shrinkage of a product depend upon the process used to fabricate it. In this present work, an attempt has been made to study the effect of various process parameters on dimensional inaccuracies of solidified PolyLactic Acid (PLA) parts fabricated using Fused Filament Modelling (FFM) process. Central Composite Rotatable Design (CCRD) has been used to design experiments. Four parameters namely surface orientation, layer thickness, part bed temperature and extrusion speed have been selected for studying surface roughness while for studying part shrinkage, five parameters have been selected viz. part orientation, layer thickness, raster angle, part bed temperature and part length. Analysis of Variance (ANOVA) has been used to identify the significant parameters followed by regression to correlate the response with process parameters. Statistical models have been developed to predict surface roughness and shrinkage of a part along x, y and z axis. The process parameters have been optimised using trust region based MATLAB technique to obtain the minimization of the responses. The models have been validated within the pre-selected domain of process parameters. It is concluded that surface orientation and layer thickness are key factors that affect surface roughness while shrinkage is mainly affected by part orientation, layer thickness and part dimensions.