Having a high-quality mesh that best represents the geometric characteristics of a complex model is much desirable for attaining accurate mold-filling analyses. Thus, deciding the appropriate type of meshing for mold-filling analyses has become essential if the accuracy is of the highest concern.
What is Boundary Layer Mesh (BLM)?
Boundary Layer Mesh (BLM) is a powerful pre-processing tool for complex geometries. It allows users to generate inward multiple layers of prismatic meshes out of the triangular surface mesh of the object, followed by filling up the internal space with quality-controlled tetrahedral mesh. CAE solvers including mold-filling software can capture the variable distributions more accurately with much less number of elements of a BLM mesh than an isotropic tetrahedral mesh.
For example, constructing a satisfactory mesh for a complex conformal cooling channel is not an easy task. Also, due to the unique feature of a conformal cooling design, it poses a great difficulty to fully capture the curvatures in meshing. A Boundary Layer Mesh (BLM) can be applied to solve this problem. A BLM mesh can precisely capture the drastic changes of temperature and velocity near the cavity during the filling process so users can accurately detect viscous heating and warpage problem in advance. That is to say, a BLM mesh is a powerful pre-processing tool for complex geometries.
Fig. 1: A complex conformal cooling design (left) and its 3D solid meshing (right) using BLM for accurate mold-filling analyses.
Recent Advanced Enhancements in Boundary Layer Mesh (BLM)
However, in the past, the time and the human efforts spent on preparing a high-quality BLM mesh could be substantial because it required a great deal of manual work and the mesh generated was error-prone. Hence, despite the fact that a BLM mesh might be the best option for simulation accuracy, users might choose an easier and quicker method for mesh generation in order to save time and efforts in the pre-processing stage.
In order to alleviate the burden of mesh preparation, numerous improvements in BLM mesh generator have been made to improve the functionalities of BLM mesh technology significantly:
l Automatic BLM Mesh Creation: One of the greatest improvements is the automatic BLM mesh creation. This latest technology can effectively help advanced users build high quality boundary layer meshes with ease. It also reinforces meshing capabilities to generate high-resolution solid mesh for complex geometric features. For instance, gate location is one of the most common design changes. However, it is very time-consuming to rebuild the mesh every time when the gate location is changed. Through the automatic BLM mesh generating function, users can reserve the solid mesh of the cavity model, and can only rebuild the mesh of the new gate location area. This enhancement can help users ensure the mesh quality and speed up the mold design and build process.
Fig. 2: A. Automatic BLM mesh generation: Original gate position B. Delete the BLM solid mesh of runner
C. New gate position D. Automatically generate a BLM solid mesh
l Mesh Fix Wizard: The BLM mesh generator will monitor the mesh quality and alert its users if there is any mesh defect. In the past, these defects could only be manually fixed. Now, a Mesh Fix Wizard is available to offer a quick fix on mesh defects and ensures mesh quality for accurate mold-filling simulation results.
Fig. 3: Users can utilize a useful tool, Fix Wizard to correct/fix mesh defects such as free edges, t-connect edges, overlap elements, etc to ensure accuracy of mold-filling simulation.
l Efficient Solid Meshing for Complex Runners and Cooling Channels: The recent development of BLM technology unleashes the limitation that users cannot directly import the the complete geometry of runner or cooling system from CAD into mold-filling software without any modifications. Now, a complete meshing for a complex runner or cooling channel design is possible. This improvement not only reduces the time for mesh preparation but also offers high accuracy for flow prediction of both melt and coolant.
Fig. 4: Solid meshing of the runner (left) and the simulation result for temperature contour (right).
l Support Various Industry-specific Molding Processes : The BLM technology can be applied in diverse molding processes, including multiple component molding (MCM), 3D cooling channel, compression molding, powder injection molding (PIM), MuCell, gas-assisted injection molding, water-assisted injection molding, co-injection molding, and bi-injection molding.
In short, with the recent advancements in BLM mesh technology, the tasks and the time involved in a BLM mesh preparation has become greatly efficient. Also, the mesh quality has been strengthened to improve its functionality. Particularly, when meshing a complex geometry, using a BLM mesh is the most appropriate type of meshing that can fully capture its distinctive geometric characteristics; therefore, the accuracy of mold-filling analyses can be further ensured.
Dr. Ellen (Shu-Ping) Hu is a program manager in the R&D Division of CoreTech System (Moldex3D). She received her Ph. D from the Department of Civil Engineering of National Taiwan University. Her main research interests include computational fluid dynamics, mesh generation and computational geometry problems. She can be reached at: [email protected]
Editor's note: The author is a PlasticsToday contributor. The opinions expressed are those of the writer.