New boundary conditions for simulating the filling stage of the injection molding process

Purpose The purpose of this paper is to develop new boundary conditions for simulating the injection molding process of polymer melts. Design/methodology/approach The boundary conditions are derived and implemented to simulate real-life air vents (used to allow the air escape from the mold). The simulations are performed in the computational libraryOpenFOAM (R) by considering two different fluid models, namely, Newtonian and generalized Newtonian (Bird-Carreau model). Findings A detailed study on the accuracy of the solverinterFoamfor simulating the filling stage is presented, by considering simple geometries and adaptive mesh refinement. The verified code is then used to study the three-dimensional filling of a more complex geometry. Originality/value The results obtained showed that the numerical method is stable and allows one to model the filling process, simulating the real injection molding process.This work is funded by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT (Portuguese Foundation for Science and Technology) under the projects UID-B/05256/2020, UID-P/05256/2020 and MOLDPRO-Aproximacoes multi-escala para moldacao por injecao de materiais plasticos (POCI-01-0145-FEDER-016665).The research of L.L. Ferras was partially financed by the Portuguese Funds through FCT within the Projects UID-B/00013/2020, UID-P/00013/2020 and the scholarship SFRH/BPD/100353/2014.The authors would like to acknowledge the Minho University Cluster (NORTE-07-0162-FEDER-000086) for providing the HPC resources that contributed to the research results reported within this paper

Multi-objective optimization of plastics thermoforming

The practical application of a multi-objective optimization strategy based on evolutionary algorithms was proposed to optimize the plastics thermoforming process. For that purpose, in this work, differently from the other works proposed in the literature, the shaping step was considered individually with the aim of optimizing the thickness distribution of the final part originated from sheets characterized by different thickness profiles, such as constant thickness, spline thickness variation in one direction and concentric thickness variation in two directions, while maintaining the temperature constant. As far we know, this is the first work where such a type of approach is proposed. A multi-objective optimization strategy based on Evolutionary Algorithms was applied to the determination of the final part thickness distribution with the aim of demonstrating the validity of the methodology proposed. The results obtained considering three different theoretical initial sheet shapes indicate clearly that the methodology proposed is valid, as it provides solutions with physical meaning and with great potential to be applied in real practice. The different thickness profiles obtained for the optimal Pareto solutions show, in all cases, that that the different profiles along the front are related to the objectives considered. Also, there is a clear improvement in the successive generations of the evolutionary algorithm.This research was funded by NAWA-Narodowa Agencja Wymiany Akademickiej, under grant PPN/ULM/2020/1/00125 and European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Grant Agreement No 734205–H2020-MSCA-RISE2016. The authors also acknowledge the funding by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT (Portuguese Foundation for Science and Technology) under the projects UID-B/05256/2020, UID-P/05256/2020, UIDB/00319/2020, MORPHING.TECH— Direct digital Manufacturing of automatic programmable and Continuously adaptable patterned surfaces with a discrete and patronized composition (POCI-01-0247-FEDER-033408)