Multiple material selective laser sintering

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Jepson, Larry Ray

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The components making up modern devices must in general fulfill functional requirements which vary spatially throughout the component and are satisfied by the properties of the materials making up the component. Thus, it is necessary to vary the material properties in a spatial sense to properly match the spatial variation in functional requirements. Since material properties are an intrinsic characteristic of the material composition, this desire translates to a need to vary the material composition based on the variation of the functional requirements. This problem may be described in abstract terms as: How to control the spatial variation of material properties in a component to match the corresponding spatial variation in functional requirements? Recent developments in the field of Rapid Prototyping (RP) offer new opportunities to control material composition during fabrication. Selective Laser Sintering was chosen as the RP technology for further investigation. Specifically, a redesign of the current powder delivery subsystem will lead to the development of a new process, Multi–Material Selective Laser Sintering (M2SLS). A tungsten carbide / cobalt drill bit insert was selected from the petroleum industry as a specific component to narrow the scope of our problem. Thus, a specific hypothesis may be given as: The desired matching of material properties to functional requirements may be achieved via the fabrication of drill bit inserts containing functional gradients with the Multi-Material Selective Laser Sintering (M 2SLS) process. A set of feasibility experiments were conducted to gain insights into the behavior of material gradients during laser sintering. The creation of these samples represents the first fabrication of FGM samples using the traditional SLS process. Following this work, the M2SLS workstation was designed and fabricated. This work represents a significant functional enhancement beyond the basic processing abilities of the traditional SLS process. Finally, a series of verification tests were conducted to ensure correct operation. Results predict the ability to deposit and laser sinter multiple materials to create a gradient of material composition. However, poor atmospheric processing control results in generally poor part quality similar to that experienced in the initial development efforts of traditional SLS.




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