Abstract:
Additive manufacturing (3D printing), combined with computer aided design, is transforming the modern manufacturing industry. Using high temperature techniques such as “selective laser sintering”, fabricators are given access to a wide range of starting materials. The sustainability of the approach could be improved through the direct use of concentrated sunlight to sinter these powders. Using inexpensive components, the cost can also be decreased to enable utilization by microbusinesses, especially those operating in remote, off-grid locations. For achieving this goal a high resolution prototype has been developed and constructed using a Fresnel lens design. To determine the feasibility of the method, two dimensional sintering tests were conducted on a commercial Nylon 12 powder. The effects of the most influential parameters on this process were determined through the implementation of a simplified model and dimensional analysis.
The most important parameter for the description of the process was found to be the dimensionless ratio of incoming radiative power to power required for sintering or melting. For conditions in which only a single phase transformation takes place, this parameter was found to remain constant, with a mean of 6.84 and variance of 0.04. The limits of the power to speed ratio were also determined, achieving thicknesses as low as 0.3 mm for the selected powder and lens combination. The measured parameters demonstrate the feasibility of high resolution 3D printing using the proposed technique, provided that tailored control strategies are developed. A major limitation was found to be the focal spot size of the lens, which determines the track width. This can be improved from the current value of 3 mm through the use of a cast glass lens.
