Master of Science / Material extrusion is a common form of 3D printing that has historically been limited to producing prototypes, models, and low load-bearing parts. This is primarily because parts are manufactured layer-by-layer, resulting in poor adhesion along the build direction, and machines struggle to print with high-strength polymers, which tend to shrink significantly as they cool. However, one way to address these limitations is to use fiber-reinforced materials in combination with multi-axis deposition strategies. In material extrusion, embedded fibers will align themselves along the deposition path, providing structural, thermal, and chemical improvements. Multi-axis toolpathing can enable the deposition of this fiber-filled material in full 3D along a part's expected stress paths. This is possible using a complex kinematic system like an industrial robot arm that can rotate the angle of the tool relative to the part as it is printing. The objective of this work was to develop and test a tool capable of multi-axis continuous carbon fiber reinforcement, which required a dedicated cutting mechanism to shear the fiber at the end of each deposition path, control over the amount of fiber used, and a slender tool profile to avoid collisions during multi-axis printing. The findings of this work revealed that while the use of continuous carbon fiber further reduced the adhesion between deposition paths, it substantially improved the strength of the part along them. To validate the multi-axis capability of the system, a toolpath was generated for a curved tensile bar. The results showed that the continuous carbon fiber multi-axis toolpath resisted a load 820.57% higher than an XY-planar sliced part printed with traditional filament, confirming the effectiveness of the presented approach. Multi-axis motion can also be used for avoiding support material requirements. In traditional 3-axis material extrusion, steep overhanging features often require additional, sacrificial material to be printed underneath. This leads to longer print times, more material waste, and a poor surface finish left behind on the final part. To minimize the amount of support material required, various techniques have been explored, including changing the toolpath, part geometry, or material processing parameters. However, none of these techniques have been successful in eliminating the need for supports entirely. A promising approach to address this issue is multi-axis material extrusion, where the angle of the printing tool and the direction of the layers can be precisely controlled during the printing process. This technique can be used to ensure that the tool is always extruding material onto a well-supported surface, rather than over thin air. However, research to date has not yet fully explored how the range of achievable overhang features changes as the tool is rotated. To address this knowledge gap, this work used an industrial robot arm equipped for material extrusion to investigate the relationship between tool angle, build direction, and achievable overhang threshold. The results showed that the same overhang limitations that exist in the XY plane will rotate with the tool and are unaffected by gravitational forces. These findings provide valuable insights for advancing the use of multi-axis material extrusion in the production of complex and intricate 3D objects without the need of supports.

We study a novel structure employing the woven continuous carbon fiber (CCF) epoxy composite with high electromagnetic (EM) shielding. The influences of wove type, number and angle of overlapped plates upon the shielding effectiveness (SE) of wove CCF epoxy composite are investigated. The minimum SE of the single, double, and triple plain or balanced twill woven CCF composite plates were measured to be as high as 50 dB, 60 dB, and 70 dB, respectively. More than 100 dB of SE was obtained for the triple overlapped plain wove CCF composite at frequency of 0.9 GHz. The weight percentage of single CCF composite plate required for electronic application was 4.8% only, which was less than one quarter of the carbon fiber (CF) content and the performance of SE was 10 dB higher in comparison with long CF filled liquid crystal polymer composites. The SE calculated theoretically is consistent with that measured by the experiment. We have demonstrated a new woven CCF epoxy composite with high EM shielding. This work may lead to the development of effective shielding for plastic optical transceiver modules to prevent electromagnetic interference (EMI) for use in low cost and lightwave communication systems.