Heat transfer simulation of material extrusion additive manufacturing to predict weld strength between layers

Poor strength of material extrusion additively manufactured parts has limited the process's adoption for direct manufacturing of end-use products. These weaknesses are present at material interfaces as a result of material extrusion's typical deposition. The variety of possible part geometries, along with the multiple toolpath options to deposit material, results in a unique thermal profile that causes varying strength across the part at the material interfaces. Prior research showed that by utilizing polymer weld theory alongside thermal profile information at the layer interfaces, one can predict tensile strength for different designs. However, these thermal profiles are unique at each point of a part's cross-section, making them challenging to obtain experimentally or analytically. Therefore, this work presents a framework to obtain these interfacial thermal profiles computationally and directly from the programmed material deposition toolpath. A heat transfer simulation technique based on finite difference method is demonstrated and validated experimentally through thermocouple measurements. The practical potential of this simulation is then demonstrated by using the evaluated thermal profile alongside polymer weld theory to estimate the strength of structures with different infill densities and complex internal cavity designs.