Browsing by Author "Phillips, Timothy Bryce"

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    Development of a feedforward laser control system for improving component consistency in Selective Laser Sintering
    (2019-06-18) Phillips, Timothy Bryce; Beaman, Joseph J.; Milner, Thomas; Crawford, Richard; Seepersad, Carolyn; Fish, Scott
    Selective Laser Sintering makes up a significant portion of the polymer additive manufacturing market and is often the process of choice for structurally significant polymer components. With its expanding market, especially among end-use components, comes a growing need for improving reproducibility. Components built using Selective Laser Sintering display a large range among their mechanical properties and it has been shown that the thermal history of the building process has a strong influence over these variations. Temperature fluctuations of just a few degrees can mean the difference between scrapped parts or those with excellent mechanical and dimensional properties. This dissertation will introduce a novel method of reducing temperature and mechanical variations among parts. Physical simulations and empirical measurements of laser-polymer interaction are evaluated and used to guide development of an advanced laser power controller. The feedforward control system developed uses thermal imagery and dynamic surrogate modeling to systematically modulate laser energy impinging on the polymer surface to homogenize post-sintering temperatures. Results from thermal and mechanical tests will be presented, showing the laser control system is capable of reducing standard deviations by up to 57% for post-sintering temperature and 45% for ultimate flexural strength.
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    In-situ laser control method for polymer selective laser sintering (SLS)
    (2016-05-05) Phillips, Timothy Bryce; Beaman, Joseph J.; Fish, Scott
    This thesis investigates thermal issues of the Selective Laser Sintering process. A method for controlling laser energy deposition in order to normalize post-sintering temperatures is presented. Infrared sensors are used to provide feedback for in-situ control of laser power with the goal of reducing the influence the pre-sintering thermal profile has on the post-sintering temperatures. By actively controlling the laser during its scanning, the post-sintering temperatures can be more accurately controlled, resulting in mechanical and geometric improvements in part quality.