Application of Response Surface Methodology for Modeling and Optimization of the Top Surface Ironing Process in Parts Produced by MEX 3D Printing

This study analyzes the influence of material extrusion (MEX) 3D printing and ironing parameters on parts made of polylactic acid (PLA), such as top surface roughness and flatness. Surface ironing is one of the post-processing methods. It is an interesting alternative to the most commonly used mechanical or chemical treatments. It does not require the use of any additional devices or substances; however, it can only be used on flat surfaces, requires additional time for application, and a flush may form at the edges of the ironed surface. The Response Surface Methodology (RSM) was used for modeling the analyzed processes. The presented methodology assumes a two-stage approach. First, the printing process of the top surface is optimized. Then, the ironing of the top surface is optimized. Improvement of surface roughness and flatness was adopted as the optimization criterion. The influence of extruder temperature, printing speed, and filament flow used during printing of the top surface, as well as extruder temperature, ironing speed, and distance between passes used during ironing, was examined. The significance of the influence of the analyzed parameters was determined using ANOVA and Pareto diagrams. The use of the applied research methodology and created mathematical models allows for determining the relationship between the optimal extruder temperature, extrusion flow, speed, and distance between passes during ironing while ensuring high process efficiency. The ironing resulted in a fivefold reduction in the Ra and an eightfold reduction in the FLTq parameters. A surface with Ra = 1.09 μm and FLTq = 3.4 μm was obtained.