OPTIMIZATION OF LAYER TIME IN LARGE SCALE ADDITIVE MANUFACTURING WITH FIBER REINFORCED POLYMER COMPOSITES

A method to optimize layer deposition time (a.k.a. layer time) was developed for large-scale additive manufacturing (AM) using physics-based simulations. A long layer time leads to deposition of new layer on an over-cooled surface resulting in weak bonding or debonding, cracking, or warping between layers. On the other hand, a short layer time results in a high temperature of the structure due to insufficient cooling and thus, the structure may not be stiff enough or collapse during manufacturing. To this end, optimizing layer time in additive manufacturing is crucial to obtain a high-quality product. The recommendation for quality printing to deposit a new layer when the temperature of the top layer is slightly higher than the glass temperature of the material. Approximating cooling as an exponential function of time, an optimized layer time can be obtained based on a target temperature while maintaining a minimal print time. In this study on layer time optimization, a large-scale deposition system (LSAM ^TM, Thermwood Corporation) was used printing carbon fiber-reinforced polycarbonate (CF/PC). Three different layer times were investigated experimentally, and a series of thermal images were obtained using infra-red (IR) camera during the entire manufacturing process. AM process simulations were performed using finite element method for three different layer times. The temperature profiles from numerical simulations matched well with the experiments. Using these temperature profiles, optimization for layer time was performed.