Effects of Laser Window Degredation on Laser Power and Distribution in Laser Sintering

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Date

2013

Authors

Fulcher, Ben
Leigh, David K.

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University of Texas at Austin

Abstract

Laser power is a key parameter in the laser sintering (LS) process, and tight control on laser power is necessary to produce quality parts with desirable mechanical properties. Unfortunately, temperature limitations hinder real-time monitoring and feedback of laser power within the process chamber. Therefore, in order to maintain consistent laser power during an LS build, the laser window, which provides a barrier between the processing chamber and the laser housing, must remain clean throughout the build. However, material outgassing leads to the buildup of condensation on the window, thereby reducing the amount of energy imparted to the powder bed. The buildup of condensation also necessitates frequent cleaning of the laser window and significantly reduces its life. Thus, laser window replacement is a large source of cost in a production environment. To compensate for the loss of laser power through the window, current practice is to steadily increase the laser power at the laser source during the build. This practice can be largely inaccurate, as it is difficult to predict the loss of laser power through the window at various stages in a given LS build. Thus, to achieve consistent mechanical properties in this manner, a trial and error-based approach is used. The study presented in this paper aims to characterize laser power and distribution for various levels of laser window degradation. In addition, methods to reduce or eliminate the buildup of condensation on the laser window are explored in an effort to improve the consistency of part quality, as well as to reduce maintenance requirements and costs.

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