Applications such as layered manufacturing, or in general, solid free-form fabrication, pose a major challenge on online process control. For these parts to be functional, it is imperative that their mechanical and structural properties are strictly kept within respective tolerances. To that end, no internal or external defects, especially voids, can be tolerated. Since these parts are made layer by layer, it is then necessary to inspect top surface and boundary of each layer before the next layer is deposited. Two issues are of major concern here: (1) Inspection must be nondestructive, that is, layer surface and boundary must not be touched by the inspecting instruments, (2) the time window for inspection and any corrective measures should not exceed the maximum time limits necessary for two adjacent layers to properly bind together. Here, we present a closed loop online process control model where the process feedbacks are obtained from a 3D imaging system, and where the process dyn...
Yuan Cheng, Mohsen A. Jafari