Adaptive direct metal/material deposition process using a fuzzy logic-based controller

The laser aided direct metal/material deposition (DMD) process is a layered manufacturing process able to produce a three-dimensional (3D) part directly from a computer aided design image. A closed-loop feedback control system is considered as a requirement to ensure dimensional accuracy. For conventional control methods, the effectiveness of process control strongly relies on accuracy of the analytical model of the system behavior. However, development of such an analytical model is quite difficult and impractical, since coupled process variables cause the complexity and nonlinearity of the DMD process. Fuzzy logic-based control, which no model but only knowledge of the process is required for decision making using this control technique, is attempted to overcome the difficulty. A proportional integral differential such as a fuzzy logic-based controller was developed for adaptive deposition during the DMD process. The controller has the capability of continuously tracking the reference height by varying the laser power adaptively, thus depositing a clad line with varying deposition height and a layer with a curved surface. This feature provides a potential of building 3D parts with nonlinear geometry such as overhang, while maintaining the accuracy of surface curvature. Simulation was performed tuning up fuzzy controller parameters with an experiment-based fuzzy logic model of the DMD process and simulated results were compared with experimental results to verify the performance of the controller.