Mechanistic cutting force model: Identification of cutting coefficients in finish milling of polylactide (PLA) 3D-printed parts

Finishing the parts obtained by Fused Filament Fabrication (FFF) is a promising approach to overcome its inherent limitations, such as poor surface roughness and dimensional accuracy. However, specific thermal properties of polymers, such as low melting temperature and low thermal conductivity, influence the cutting process and may, therefore, also affect the modeling of cutting forces. Unlike metals and composites, investigations into cutting forces models of polymers, including polylactide (PLA), are at a very early stage. Yet, these models have the potential to enhance the reliability of the polymer milling process. Furthermore, the use of finish milling on 3D-printed PLA parts is rising, particularly with the recent development of hybrid manufacturing machines, which increases the need for suitable cutting models. Therefore, this paper proposes to study a mechanistic model, as this type of model has shown a good compromise between simulation time and precision for other materials. The developed model is based on an inverse analysis to identify cutting coefficients from measured forces. Finish milling tests were conducted on PLA samples using various feed rates, cutting speeds and cutting fluid conditions. The identification of the cutting force model was performed on each sample individually then on the whole database using an iterative method. The good agreement between simulation and experiments in stable cutting conditions demonstrate the applicability of the model.