PurposeThe purpose of this paper is to develop a novel post-processing technique of fused deposition modeling (FDM) parts to improve surface roughness and reduce heat absorption and for high-temperature application in thermoforming process. Design/methodology/approachThe current technique consists of chemical treatment, drying and aluminum coating. First, surface morphology was investigated using FDM specimens with a flat surface. The heat absorption characteristic was also analyzed by Taguchi-based design of experiment and modified lump-capacity model. In addition, dimensional accuracy and uniformity were investigated under high-temperature conditions, which were similar to a typical thermoforming process, with specimens having concave and convex grooves. FindingsIt was verified that the proposed post-processing technique could efficiently improve surface quality of FDM parts with the arithmetic average surface roughness of 2.06 µm. In addition, the coated aluminum layer was found to reflect the heat radiation, resulting into a sufficient reduction of heat absorption. From the investigation of dimensional accuracy and uniformity, it was found that the current technique produced maximum change of 0.11 mm and uniform thickness of an aluminum layer within 0.07 mm. Originality/valueThe present study establishes a novel post-processing technique, enabling to treat the surface of FDM parts for high-temperature applications. It provides a simple way of using typical FDM parts for a thermoforming process as the mold cores. Furthermore, it can be used in other rapid tooling technologies, consequently widening the application areas of FDM.

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In this article, jackfruit seed starch plasticized with common plasticizers was developed and characterized. At the first step, the research papers that dealt with the fabrication and characterization of starch-based bioplastics were synthesized and analyzed. Next, jackfruit seeds were selected as a source for starch because of their large availability, low price or even free, and high starch capacity. Afterward, a starch-based bioplastic fabrication procedure was proposed. From preliminary tests, plasticizers were sufficiently selected, including water, glycerol, natri bicarbonate, and acid citric. Using different combinations of these plasticizers, four types of bioplastics were then fabricated to study the effect of the plasticizers as well as to characterize the properties of the corresponding bioplastics. A cutting tool for ASTM D412 type A standard tensile testing specimen was then designed and fabricated. Using these dog-bone specimens, tensile results showed that the hardness of the fabricated bioplastic was positively proportional to the ratio of the starch. Furthermore, from SEM characterization, the bioplastic specimens were fully plasticized. Although the fabricated bioplastic has lower mechanical properties than petroleum-based plastics, its environmental friendliness and high potential added value promise to be a material of the future.

In this study, we investigated warpage and corner lifting minimization for three-dimensional printed parts generated by macro-size fused deposition modeling (FDM). First, the reasons for warpage were theoretically elucidated. This approach revealed that the thermal deformation and differential volumetric shrinkage of the extruded molten plastic resulted in warpage of FDM parts. In addition, low adhesion between the deposited model and the heated or non-heated printing bed may intensify warpage further. As a next step, initial small-size and medium-size models were used to identify parameters to manage and minimize warpage in a way that would reduce material consumption and running time. Finally, a macro-size model was built to experimentally investigate and verify the technical solutions to minimize the warpage of FDM parts. In conclusion, an improved part with reduced warpage was efficiently produced after detailed consideration of thermal effects and adhesion force. Potential exists to widen the application scope of FDM technology in manufacturing for processes like thermoforming that involve mold core fabrication with heating. This technology, which has applications not only in mechanical engineering but also in related engineering fields, is convenient and could readily be applied to practical manufacturing industries.

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