Feb 1, 2019
A useful parameter to evaluate the quality of an element is the aspect ratio.
In simulation triangular elements are the main factor in meshing the surface of a part.
The aspect ratio can be determined in different ways.
In Moldex3D for example, the aspect ratio is calculated based on two circles.
The inside circle is touching every edge of the triangle tangential, while the outer on goes through all the edges of the element.
The aspect ratio equals twice the inner radius divided by the outer radius of the circles.
An equilateral triangle has an aspect ratio of 1, a triangle with no surface area has an aspect ratio of 0.
The higher the aspect ratio, the better the quality.
In Moldflow there are different ways to calculate an aspect ratio.
Using one strategy the aspect ratio lies between 0 and 1 similar to Moldex3D.
Another strategy leads to an aspect ratio that starts by 1,16 to infinity. Hereby the smallest value represents the best quality.
Injection Molding Simulation: In
Moldex3D, the aspect ratio is twice the inner radius (blue) divided by the outer radius (yellow) of the circles.
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This glossary of plastic industry is provided by PLEXPERT Canada Inc.
May 29, 2019
Volume meshes can be made out of different element types.
A lot of times pure hexahedron or tetrahedron are used.
The BLM-mesh is ideal for the exact display of the boundary area.
BLM stands for Boundary Layer Mesh.
The boundary layers are made out of prisms with triangular surface.
The inside is filled with tetrahedrons.
Especially in injection molding simulation, this mesh type is preferred.
Simulation: Cut through a volume meshed with
BLM.
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This glossary of plastic industry is provided by PLEXPERT Canada Inc.
Jan 11, 2019
Initially developed at the IKV in Aachen, Germany, Cadmould is a popular 2.5D injection molding simulation software in Germany.
Based on the shell approach the computation times are short and it is possible to modify wall thickness without changing the geometry.
Development and sales of the software are done by the company Simcon.
Filling, cooling and warpage can be simulated. Additional modules are available for other processes.
Simulation: A filling and cooling result visualized in the
Cadmould viewer.
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This glossary of plastic industry is provided by PLEXPERT Canada Inc.
Mar 8, 2019
Square or triangle elements are mostly used to generate a mesh for a simulation.
When two or more nodes of one element fall on the same coordinate the element is called a degenerated element.
This way a square can become a triangle, a line or even a point.
Depending on the used program the multiple nodes will be joined automatically to one node or need to cleaned up manually.
Degenerated elements exist in volume elements as well.
A hexahedron can degenerate to a prism or tetrahedron.
Degenerated elements lead to wrong results in the simulation or even block the start of an simulation.
Simulation: When two points of a square fall onto the same coordinates a
degenerated element is built.
Related topics:
Aspect Ratio
This glossary of plastic industry is provided by PLEXPERT Canada Inc.
Nov 20, 2019
For a finite element (FE) calculation the body to be calculated is described using many small elements.
The elements may be points, linear, planar or solid.
The division into smaller parts (finite elements) is called meshing or discretization.
It looks like a mesh, which is laid over the part.
Today simulation programs take over the discretization partially or completely automatically.
This way an idealized model is produced to be processed for the calculation.
It is important to pay attention to the mesh density: The absolute value of all results always depends on the mesh density. Therefore, it is important that the same mesh density is chosen for each calculation variant so that differences in the calculation results are not due to different element sizes. It should also be noted that the numerical complexity and thus the calculation time increases overproportionally as the number of elements increases.
Each element is assigned certain properties.
Flat elements, for example, can be assigned the wall thickness, or line elements their cross section.
For each individual element the correspondign equations are calculated.
These are for example the deformation do to loars, the speed due to changes in volume flow, or the temperature change due to heat input.
For the entire component, the individual equations are combined in an overall matrix. Therefore it is possible to calculate arbitrary complex geometries.
Simulation:
Discretization with shell elements on the surface of a box
Related topics:
Aspect Ratio
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This glossary of plastic industry is provided by PLEXPERT Canada Inc.
