The process in AM is thermally driven, and temperature gradient, flow, and distribution are crucial to the development of elastic modulus, strength, deformation/warpage, shape, surface finish, residual stresses, and density.  Similarly, in the polymer-based 3D printing technology, i.e., FDM, temperature distribution and heat flux dictate surface finish, dimensional accuracy, and precision, as well as mechanical strength of printed components. 

The first step toward understanding distortions and residual stresses in the FDM parts is understanding the thermal flow and temperature distribution of highly non-linear and complex phenomena during layer-by-layer deposition of materials.  Thermally related phenomena (i.e., convection and radiation heat transfer, phase changes, and deposition advection) are particularly crucial during fabrication and cooling phases. 

 

The processes of formation and production in FDM involve all mechanics of heat transfer: radiation, convection, and conduction as well as bonding, melting, diffusion, solidification, phase transformation, and microstructural revolution, as shown in Fig. 1.  Radiation plays a significant role in the high-temperature regions, specifically during the first phase of material deposition and bonding.

From the heat transfer perspective, modeling conduction, radiation, and convection are crucial, especially when one deals with material properties and boundary conditions that depend on temperature.  A researcher needs to incorporate radiation, transient conditions, and natural or forced convection together with moving boundaries, continually varying conditions, and material properties in order to realize an acceptable computational simulation of FDM processes.