Lighting : LIGHTING Aug-Sep 2018
28 LIGHTING MAGAZINE | August/September 2018 August/September 2018 | LIGHTING MAGAZINE 29 thermal properties. The results showed that higher thermal conductivity values were achieved for components printed using filaments with metal filler materials and that thermal conductivity values strongly depend on the print orientation. However, the achieved thermal conductivity values may not be sufficient to meet the thermal management needs of higher power LEDs with smaller footprint heat sinks. In general, commercially available filament materials currently do not possess the thermal properties needed to challenge the existing extruded or machined heat sinks5. However, it is worthwhile to continue research in this direction because the thermal performance of a heat sink depends on its geometric form as well (Figure 3). With 3D printing, system engineers and designers can create heat sink designs that can meet not only the performance requirements but also add aesthetics to the light fixture that are not possible with traditional manufacturing methods. Electrical Traces: In LED lighting systems, electrical traces are often used to conduct electrical current between different electrical and electronic components (Figure 4). Making electrical conductors in 3D orientations is important for constructing a practical Figure 5. Examples of conceptual 3D printed optics and remote phosphor optical components. Figure 6. Examples of 3D printed LED luminaires. light fixture. The LRC studied whether electrical traces can be 3D printed with suitable electric and geometric properties. The study found that nanoparticle-based silver inks and liquid metal conductive inks could achieve a resistivity comparable to copper; however, these materials cannot be processed using unmodified FFF-type 3D printers. Future improvements are required to make 3D printing a viable option for making functional electrical connections in SSL fixtures. Optics: Optical component manufacturing is one area where 3D printing has already gained footing (Figure 5). The potential benefits include ease of creating complex geometric designs and speed of manufacturing. The LRC analyzed how print resolution and orientation using the SLA method affected light transmission and light scatter. The results showed that post-processing, print orientation, and print resolution are all important factors to be 3D printed pendant fixture 3D printed table lamp 3D printed wall sconces considered. A print resolution better than 50μm can produce adequate optical performance for lighting applications. Nevertheless, the longevity of 3D printed optical components is not known and requires further investigation. CHALLENGES THAT NEED ADDRESSING The potential benefits for 3D printing in the SSL industry are clear, but challenges need to be overcome in order to successfully explore these opportunities. These challenges include the availability of suitable materials to meet the required functions of the printed subcomponents. An integrated approach is also needed to combine different parts to fabricate a product with multiple materials and functionalities (Figure 6). Finally, faster fabrication and integration are required to meet the needs of LED luminaire fabrication and use in various applications, such as on-demand fabrication. Overcoming these technical challenges will aid not only the SSL industry, but also other industries that require electrical, thermal, optical solutions such as consumer electronics, medical, automotive, and aerospace. The LRC is in the process of establishing an alliance among researchers, manufacturers, and other organizations to help overcome the technical barriers impeding the use of 3D printing and make it a viable resource for the SSL industry. On behalf of the alliance, the LRC will conduct research, demonstration, educational, and industry-wide consensus building activities to help the lighting industry realize the benefits of 3D printing and add value for users of solid-state lighting. Learn more at http://www.lrc.rpi.edu/ programs/solidstate/3DPrinting.asp. For more information about participating with the LRC in its SSL 3D printing research, contact N Narendran, firstname.lastname@example.org REFERENCES 1 Columbus, L. 2017. The state of 3D printing, 2017. Forbes, 23 May 2017. 2 Narendran, N., et al. 2017. Opportunities and challenges for 3D printing of solid-state lighting systems. Proc. SPIE 10378: 10378-35. 3 Krishnan, S., et al. 2012. Design of complex structured monolithic heat sinks for enhanced air cooling. IEEE Trans. CPMT 2(2): 266–277. 4 Kalsoom, U., et al. 2016. A 3D printable diamond polymer composite: a novel material for fabrication of low cost thermally conducting devices. RSC Adv. 6: 38140–38147. 5 Terentyeva, V., I.U. Perera, and N. Narendran. 2017. Analyzing theoretical models for predicting thermal conductivity of composite materials for LED heat sink applications. Proceedings of the IES 2017 Annual Conference, August 10-12, Portland, Oregon. *Lighting Research Center, Rensselaer Polytechnic Institute, Troy, New York www.lrc.rpi.edu/ programs/solidstate Figure 4. Example of 3D printed functional electrical traces with electrical and electronic components. 3D printed circuit board Functional circuit board CAD model of circuit board The LRC is in the process of establishing an alliance among researchers, manufacturers, and other organizations to help overcome the technical barriers impeding the use of 3D printing and make it a viable resource for the SSL industry.
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