Additive manufacturing processes (referred to here as three-dimensional printing, or “3D printing”) are used to prototype and fabricate complex three-dimensional objects out of a variety of materials, including polymers, metals and ceramics. These techniques have been used to manufacture objects that can withstand heavy loads and forces such as automotive parts, aeronautical components, and other industrial parts at accuracies down to tens of microns.
Conventional approaches to 3D printing use extrusion-based direct-write methods for thermoplastics and stereolithography (SLA) based photo-polymerization for both thermoplastics and thermosets. However, such techniques often result in printed polymers that are lightweight but relatively weak.
More recent implementations utilize fiber-reinforced polymer composites and automated fiber placement printers to print continuous carbon fiber, Kevlar, and fiberglass reinforced polymer. However, these robotic placement printers are limited to reinforcement fibers with large lengths and geometries, fiber orientation controls limited to the X-Y plane, and the dispensing being limited to the trajectory of the toolpath. This results in reduced physical strength, stiffness, and thermal properties of the part when the trajectory of the toolpath, and therefore alignment of reinforcing fibers, are determined by the geometry requirements of the part instead of the ideal alignment of fibers for these properties.