Optical Metrology For Advanced Manufacturing

PROJECT NUMBER: 98

AUTHOR: Morgan Trexler, Mechanical Engineering | MENTOR: Jeff Squier, Physics

ABSTRACT

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Current additive manufacturing (AM) techniques struggle to provide feedback on part quality in-situ. As a result, AM parts require extensive post process testing for certification. In laser based AM processes, a 200+ watt laser melts metal powders at the fusion surface. At the fusion surface, one of three characteristic interactions occurs: powder absorption, melting, or keyholing. Our goal is to create a feedback system that determines characteristic interactions in-situ for optimizing print quality in real time. Reflective measurements offer one possible route for determining the characteristic interaction because different fusion surface textures absorb different amounts of light. Such measurements of absorption at the fusion surface have been done with integrating spheres showing that powder absorption reflects low amounts of light, melting reflects almost all incoming laser light, and keyholing absorbs almost all incoming laser light. Integrating spheres can be used for reflective measurements to determine characteristic interactions, but are not viable for in-situ use due to geometry and longevity constraints. Thus we propose using a photodiode to measure back reflection on the axis of the laser beam. Back reflection photodiode measurements provide a cheap and potentially effective in-situ measurement for characteristic interactions while avoiding the constraints that limit integrating sphere commercialization. By providing more extensive feedback during the printing process, reflective measurements could eventually detect printing failures and part properties minimizing optimization times.

VISUAL PRESENTATION

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AUTHOR BIOGRAPHY

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Morgan is a junior in mechanical engineering with a passion for 3D printing. During high school, he built a 3D printer from scratch to be able to manufacture files he designed but he also really enjoyed understanding the printing process. When he came to Mines, he sought out opportunities to research with metal 3D printing, finding Jeff Squier from the physics department. Morgan has played a crucial role in researching metal 3D printing feedback technologies at Mines. One day he hopes to be able to integrate the techniques he is developing into commercial metal 3D printing.

Sponsored by Phillips 66