Surface roughness of 3D printed materials: Comparing physical measurements and human perception

This study concerns the perceived roughness of 3D printed material samples (print process: fused deposition modelling, or FDM), generated across changes in print speed, build angle, and layer height. Physical sample surface roughness parameters Ra and Rq were first obtained via optical scanning. Next, using a custom-designed apparatus, surface roughness perception was assessed via a psychophysical procedure that identified the just noticeable difference in roughness through the sense of touch alone. By comparing both data sets, this study concludes that for FDM-printed materials, objective surface roughness parameters (Ra, Rq) cannot adequately predict users' haptic experience. This finding is of importance for all 3D printing applications where equally perceptible roughness is desired. As a whole, the study highlights the role of 3D printing as a new tool for the science of haptics and as a means for generating new material qualifies by design.