Simulating injection moulding of microfeatured components

Numerical simulation of injection moulding of a microfeatured component is reported in this paper.  The simulation is divided in two; first a large scale simulation of the main geometry is performed and then a microscale simulation of the structural details using the pressure from the large scale simulation as a boundary condition. The simulations show that even though the polymer solidifies in less than 5 ms, there is enough time to make a good replication of the microfeatures as has also been shown experimentally. It is also possible to isolate different physical effects influencing the replication. The shear heating in the microfeature is in this case not important. However, the shear thinning within the microfeatures helps replication significantly. The shear stress at the wall is in the lower range of where wall slip has been reported to occur for other polymer melts. Even though wall adhesion is not considered in these simulations, it is shown that the adhesion energy is comparable in size with the pressure-volume work required to push the polymer into the microfeature and could therefore be an important factor influencing replication.