Effects of Mold Surface Roughness on Compressible Flow of Micro-Injection Molding

Authors: Nguyen Q. M. P., Chen X., Lam Y. C., Yue C. Y.

Abstract:

Polymer melt compressibility and mold surface roughness, which are generally ignored during the filling stage of the conventional injection molding, may become increasingly significant in micro injection molding where the parts become smaller. By employing the 2.5D generalized Hele-Shaw model, we presented here the effects of polymer compressibility and mold surface roughness on mold-filling in a micro-thickness cavity. To elucidate the effects of surface roughness, numerical investigations were conducted using a cavity flat plate which has two halves with different surface roughness. This allows the comparison of flow field on two different halves under identical processing conditions but with different roughness. Results show that polymer compressibility and mold surface roughness have effects on mold filling in micro injection molding. There is in shrinkage reduction as the density is increased due to polymer melt compressibility during the filling stage.

Keywords: Compressible flow, Micro-injection molding, Polymer, Surface roughness

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1072056

References:

[1] H. L. Zhang, N. S. Ong and Y. C. Lam 2007 Effects of surface roughness on microinjection molding Polymer Engineering and Science 47 2012-2019
[2] H. L. Zhang, N. S. Ong and Y. C. Lam 2008 Experimental investigation of key parameters on the effects of cavity surface roughness in microinjection molding Polymer Engineering and Science 48 490-495
[3] H. L. Zhang, N. S. Ong and Y. C. Lam 2008 Mold surface roughness effects on cavity filling of polymer melt in micro injection molding International Journal of Advanced Manufacturing Technology 37 1105- 1112
[4] N. S. Ong, H. L. Zhang and Y. C. Lam 2008 Numerical simulation of cavity roughness effects on melt filling in microinjection molding Advances in Polymer Technology 27 89-97
[5] N. S. Ong, H. L. Zhang and Y. C. Lam 2009 Three-dimensional modeling of roughness effects on microthickness filling in injection mold cavity International Journal of Advanced Manufacturing Technology 1-9
[6] C. A. Hieber and S. F. Shen 1980 A finite-element/finite-difference simulation of the injection-molding filling process Journal of Non- Newtonian Fluid Mechanics 7 1-32
[7] H. H. Chiang 1991 A unified simulation of the filling and postfilling stages in injection molding, part 1: Formulation Polymer Engineering and Science 31 116-124
[8] H. H. Chiang, C. A. Hieber and K. K. Wang 1991 A unified simulation of the filling and postfilling stages in injection molding. Part ii: Experimental verification Polymer Engineering & Science 31 125-139
[9] Q. M. P. Nguyen, X. Chen, Y. C. Lam and C. Y. Yue 2011 Effects of polymer melt compressibility on mold filling in micro-injection molding Journal of Micromechanics and Microengineering 21
[10] Y. C. Lam, X. Chen, K. C. Tam and S. C. M. Yu 2003 Simulation of particle migration of powder-resin system in injection molding Journal of Manufacturing Science and Engineering 125 538-547
[11] U. R. A. Theilade, E. Kjoer and H. N. Hansen The effect of mold surface topography on plastic part in-process shrinkage in injection molding 2003 Nashville, TN