Forming the properties of parts obtained by FDM by modifying the surface layer using mechanical and physical-technical treatment

This study focuses on the processes and phenomena related to post-processing of FDM articles in the form of mechanical, thermal (laser), or chemical action, as well as their influence on the set of FDM-printed parts’ properties. At present, the lack of a methodological basis for the choice of post-processing methods creates obstacles in the attempt to improve the operational properties of articles and is an important problem in additive engineering. The paper investigates the post-processing of articles obtained by the method of layer-by-layer arrangement of plastic filament from the point of view of changing their mechanical and physical-technical characteristics due to the formed modified surface layer. It was noted that post-processing can be performed by mechanical action (blade cutting or abrasive processing), physical-technical, thermal (for example, laser), and chemical (etching, application of adhesive layers). As a result of such actions, a modified layer of a certain thickness is formed on the surface of the article, the structure, and properties of which will differ from the base, and its features can significantly change the operational properties of the article as a whole. The analysis of various post-processing options was performed on the basis of the functional transformation of the input parameters of the workpiece into the output ones, which made it possible to link the regularities in the formation of stresses, thermal fields, and fields of motion of matter from the parameters of the state of the surfaces, which change in the process of post-processing from the initial to the final one, and which are reflected by combinatorial sets. This approach allows one to avoid duplication of operations or individual transitions, determine the expediency of using certain techniques, increase the reproducibility of the additive process, and ensure the reliability of the finished article as a whole. The dependence of FDM articles’ properties on the state of the surfaces has been established; the corresponding functional dependences have been proposed for determining the thickness of the modified layer formed by certain mechanical or physical-technical influences. It is shown that the use of sharply sharpened tools makes it possible to obtain for PLA Ra = 3.0…3.6 μm, Rz = 20…40 μm during turning, milling, and drilling; for ABS, respectively, Ra = 1.2…1.6 μm, Rz = 5…8 μm, with a modified layer thickness of 0.15–0.65 mm and 0.1–0.25 mm, respectively. Laser exposure modifies the layer at a depth of 0.2…0.5 mm; chemical treatment with ketone vapors forms a layer with a thickness of 0.3…1.1 mm and is determined by the temperature of the saturated vapor, as well as diffusion rate