Investigations on friction stir joining of 3D printed parts to overcome bed size limitation and enhance joint quality for unmanned aircraft systems

Abstract

3D printing technology is making its mark in automotive, aerospace, and bio-medical-related industries. It is considered a viable option for the direct manufacturing of final parts. However, it is not possible to print longer parts in a single attempt due to the bed size limitation of printers. This problem can be addressed by employing a polymer joining technique as a secondary operation. Moreover, low mechanical strength and inferior geometrical qualities like the flatness of the joined parts restrict its real-time industrial application. Here, an attempt is made to join a longer part (typical of an aircraft wing) using friction stir welding technique. Joining was performed on 3D printed similar/dissimilar thermoplastic parts. Tensile test results showed that friction stir welding of 3D printed parts (for both similar/dissimilar) produced relatively weaker joints compared to the base material. Various important process parameters of 3D printing and friction stir welding technique, namely part infill percentage, material combination, tool rotational speed, traverse speed, and tool pin taper angle were optimized by means of ANOVA. Optimization was aimed at maximizing the weld strength, elongation, hardness, and desired flatness. The results suggested that the material combination and tool pin taper angle play a significant role in the weld's strength as well as its geometric properties (flatness). The results were validated by adopting the optimized parameters for successful joining of the wing section of an unmanned aerial vehicle. A span of 320 mm, with a metrological acceptable flatness value of 0.41 µ/m could be successfully achieved on an existing 3D printer whose bed size limit was 240 mm.

An overview on joining/welding as post-processing technique to circumvent the build volume limitation of an FDM-3D printer

“…Initially applied only for welding aluminum and its alloys, the technique was extended to titanium, magnesium alloys and dissimilar metals. Off late, it is also applied to join thermoplastics and 3D printed parts (Malik and Kailas, 2020; Tiwary et al , 2020). The FSW process consists of a rotating tool with a shoulder and a pin that moves along the weld seam, resulting in extreme stirring action, reaching a state, which softens the metals/plastic.…”

“…The parameters with which 3D printing is done also play a critical role during FSW of 3D printed parts affecting the final strength of the joint. Tiwary et al (2020) attempted FSW on 3D printed similar and dissimilar thermoplastics overcoming the printing volume limitation. Tensile strength, the flatness of the weld and the hardness of the weld was also investigated and reported.…”

“…A mechanism by which the joint nears or exceeds the base material’s strength has to be developed. There is a need to address the effect of joining techniques on the surface finish and dimensional integrity of joined parts. The authors could find only one article addressing this issue (flatness of the joined parts) (Tiwary et al , 2020). There is a need to address the aging factors such as the influence of radiation, humidity and temperature on the joined parts.…”

“…There is a need to address the effect of joining techniques on the surface finish and dimensional integrity of joined parts. The authors could find only one article addressing this issue (flatness of the joined parts) (Tiwary et al , 2020).…”

Academic Insights and Perspectives in 3D Printing: A Bibliometric Review

“…It has gained popularity in consumer-maker communities and the media as well as scientific researchers in many areas [2][3][4]. With recent increasing interests, this technology is continuously expanding into areas such as automotive [5][6][7], aerospace [8][9][10], electronic [11][12][13], medicine [14][15][16], biology [17][18][19], architecture [20][21][22], Appl. Sci.…”