Experimental Research on the Dimensional and Geometrical Deviations of Features-of-Size Produced by Material Extrusion Processes

A major advantage of Additive Manufacturing (AM) processes is their ability to produce components with complex surfaces and sophisticated structures. However, several functional requirements of end-use AM parts, related to interchangeability and assemblability, are still strongly dependent on tightly toleranced Features-of-Size (FoS), as defined in current ISO-GPS standards. The paper presents an experimental approach for evaluating the dimensional and geometrical deviations of FoS produced by AM Material Extrusion processes (MEX) where the material is joined by thermal reaction bonding (MEX-TRB), such as Fused Deposition Modeling (FDM). A set of custom, primitive based test components are manufactured by low-cost and professional MEX-TRB printers, in different materials and orientations. The FoS linear and form deviations, as per ISO 14405-1 and ISO 1101, of the produced components are then evaluated by a Coordinate Measuring Machine (CMM). With the use of regression analysis, a statistical model is created, presenting and categorizing those defects. Finally, the development of a hybrid experimental/theoretical model for the prediction of linear and form deviations in MEX is presented and discussed.