Surface appearance of poly lactic acid due to variations in material extrusion processing parameters.

The study examines the impact of Material Extrusion (MEX) process parameters on the surface quality of polylactic acid (PLA) components, utilizing a straightforward image analysis method for distinguishing products realized with varying process parameter sets. The research aims to establish a relationship between process variations and product characteristics, with a primary focus on surface roughness and grayscale variations. Process parameters such as flow rate, nozzle temperature, and fan speed significantly influence the surface roughness and appearance of PLA parts. These parameters alter the shape of raster deposition, resulting in a different peak-valley arrangement, which in turn impacts surface quality and grayscale variations. The study evaluates grayscale image analysis to assess color shifts induced by processing conditions, for a scanning direction perpendicular to the printing direction. The results of grayscale analysis were compared with surface roughness, achieving a significant match. Variations in surface roughness and grayscale values were substantial, ranging between 50% and 60%. The PLA specimens were finally tested under uniaxial tensile tests to determine Young's modulus, tensile strength, and strain at break, evaluating changes in mechanical performance. The flow rate and fan speed were crucial factors because they caused changes in raster density, raster adhesion, and mechanical properties. However, the mechanical test results revealed that the variations were more significant than 5% but lower than 10%.