# title
Experimental and numerical investigation of the thermal behaviour of polylactic acid during the fused deposition process

# abstract
Fused deposition modelling (FDM) has become the most popular additive manufacturing process worldwide since the early 2000s. However, limited understanding of its deposition process greatly hinders the future growth of the technology. In order to optimise and control the deposition process, modelling and predicting the thermal behaviour change of the material during such a process is required. In this paper, the thermal behaviour of FDM process was studied both experimentally and numerically; effects of nozzle temperature, platform temperature, extrusion speed, and layer thickness on effective diffusion time, maximum vertical distortion, and maximum thermal stress were evaluated. It is shown that the developed simulation model could predict the effective diffusion time with the error of less than 13% in 6 out of 9 experimental conditions, relatively lower than the existing simulation and theoretical prediction models. Both the experimental and numerical results suggested that polylactic acid would have the longest diffusion time at high nozzle temperature, high platform temperature, low printing speed, and high layer thickness. And the numerical model revealed that reducing extrusion temperature, slowing printing speed, decreasing layer thickness are beneficial of reducing the vertical distortion and residual thermal stress.