The importance of additive manufacturing (AM) to the future of product design and manufacturing systems demands educational programs tailored to embrace its fundamental principles and its innovative potential. Moreover, the breadth and depth of AM spans several traditional disciplines, presenting a challenge to instructors yet giving the opportunity to integrate knowledge via creative and challenging projects. This paper presents our approach to teaching AM at the graduate and advanced undergraduate level, in the form of a 15-week course developed and taught at the Massachusetts Institute of Technology. The lectures begin with indepth technical analysis of the major AM processes, then focus on special topics including design methods, machine controls, and applications of AM toward current industry needs and emerging materials and length scales. In lab sessions, students operate and characterize desktop AM machines, and work in teams to design and fabricate a bridge having maximum strength per unit weight while conforming to geometric constraints. The class culminates in a semester-long team design-build project; in a single semester of the course, teams created prototype machines for printing molten glass, soft-serve ice cream, biodegradable (chitosan) material, carbon fiber composites, performing large-area parallel extrusion, and for in situ optical scanning during printing. Several of these projects led to patents, future research, and peer-reviewed publications. We conclude that AM education, while arguably rooted in mechanical engineering, must be truly multidisciplinary, and education programs must embrace this context. We also comment on our experiences adapting this course to a manufacturing-focused master's degree program and a oneweek professional short program.2
Significant improvements to the production rate of additive manufacturing (AM) technologies are essential to their cost-effectiveness and competitiveness with traditional processing routes. Moreover, much faster AM processes, in combination with the geometric versatility of AM, will enable entirely new workflows for product design and customization. We present the design and validation of a desktop-scale extrusion AM system that achieves far greater build rate than benchmarked commercial systems. This system, which we call 'FastFFF', is motivated by our recent analysis of the rate-limiting mechanisms to conventional fused filament fabrication (FFF) technology. The FastFFF system mutually overcomes these limits, using a nut-feed extruder, laser-heated polymer liquefier, and servo-driven parallel gantry system to achieve high extrusion force, rapid filament heating, and fast gantry motion, respectively. The extrusion and heating mechanisms are contained in a compact printhead that receives a threaded filament and augments conduction heat transfer with a fiber-coupled diode laser. The prototype system achieves a volumetric build rate of ~127 cm 3 /hr, which is ~7-fold greater than commercial desktop FFF systems, at comparable resolution; the maximum extrusion rate of the printhead is ~14-fold greater (282 cm 3 /hr). The performance limits of the printhead and motion systems are characterized, and the tradeoffs between build rate and resolution are assessed and discussed. The combination of high-speed motion and high deposition rate achieved by the FastFFF technology also poses challenges and opportunities for toolpath optimization and real-time deposition control. High-speed desktop printing raises the possibility of new use cases and business models for AM-where handheld parts are built in minutes rather than hours. Adaptation of this system to high-temperature thermoplastics and filled composite resins, which require high extrusion forces, is also of interest.
Evaporative self-assembly of semiconducting polymers is a low-cost route to fabricating micrometer and nanoscale features for use in organic and flexible electronic devices. However, in most cases, rate is limited by the kinetics of solvent evaporation, and it is challenging to achieve uniformity over length-and time-scales that are compelling for manufacturing scale-up. In this study, we report highthroughput, continuous printing of poly(3-hexylthiophene) (P3HT) by a modified doctor blading technique with oscillatory meniscus motionmeniscus-oscillated selfassembly (MOSA), which forms P3HT features ∼100 times faster than previously reported techniques. The meniscus is pinned to a roller, and the oscillatory meniscus motion of the roller generates repetitive cycles of contact-line formation and subsequent slip. The printed P3HT lines demonstrate reproducible and tailorable structures: nanometer scale thickness, micrometer scale width, submillimeter pattern intervals, and millimeter-to-centimeter scale coverage with highly defined boundaries. The line width as well as interval of P3HT patterns can be independently controlled by varying the polymer concentration levels and the rotation rate of the roller. Furthermore, grazing incidence wide-angle Xray scattering (GIWAXS) reveals that this dynamic meniscus control technique dramatically enhances the crystallinity of P3HT. The MOSA process can potentially be applied to other geometries, and to a wide range of solution-based precursors, and therefore will develop for practical applications in printed electronics.
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