Page 12 - Moldex3d training Manual

The placement of the gate can greatly impact the temperature of the weld line as the weld line can be
placed later in the fill for higher shear heating, or early in the fill to maintain the temperature out of the
gate.
2.1.3.2.3 Weld Line Migration
After the weld line is created and the melt front progresses, the material on the weld line will move due
to the momentum of flow. If Weld Line Migration occurs, the weld line is stretched out to where the melt
fronts are more mixed than when they originally met, increasing the overall strength of the weld line.
The earlier in the flow a weld line occurs, the more time it uses to stretch out. This effect is also dependent
on the temperature of the weld line as a hotter weld line will typically migrate more due to the lower
viscosity of the material on the weld line.
2.1.4 Meshing Theory
To run simulation, the imported model must be converted into a series of mesh elements. Moldex3D
simulation uses a Finite Volume Method (FVM) for the calculation style, which requires the use of solid
elements.

Solid elements in Moldex3D are split into the following types, increasing in calculation quality:
- Voxel Elements: Block style elements which can be used to approximate the volume of the
geometry. This style is used in the eDesign meshing type.
- Tetrahedral Elements: Four-sided triangular element. Tetra elements are commonly used in
Finite Element Analysis (FEA) and are used in Moldex3D in the BLM meshing style. Tetrahedral
elements are sufficient for heat transfer and displacement calculations but are not of high enough
quality for FVM analysis. This mesh element type will be used to connect the Prism layers in the
BLM structure discussed later, as well as define the heat transfer components of the modeling.
- Prismatic Elements: Wedge-like element in the form of triangular prisms. Prism elements are the
first of the two higher quality element types. This type is used as an extrusion of the surface mesh,
which allows for mesh consistency and reduces the overall number of elements for the meshing.
These elements are used in the Boundary Layer of the BLM style of meshing.
- Hexahedral Elements: Box-like elements aka rectangular prisms. Hexa elements are the highest
quality element available for their computational advantages. The resolution provided by this
type of element enables high-order calculations and allows for the lowest element count. These
elements may be used occasionally in the BLM style of mesh, but will be required for advanced
analysis types, such as Advanced Hot Runner, Optics, and IC Encapsulation.

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