Jan 28, 2019
Geometry data is delivered as points in a cartesian coordinate system after a 2D-/3D-surface scan or a CT analysis of a part.
The sum of all points is called point cloud.
On the base of the point cloud triangle elements will be created in order to visualize the skin of the scanned object.
A return of the data into a CAD model is possible based on a point cloud as well as on the base of the generated triangle element-mesh.
It has to be noted, that the quality of the CAD surfaces show imurities.
May 6, 2019
A solid, made by a parallel shift of a polygon is called prism.
In the FEM, prisms with triangular footprints are commonly used.
Its advantage is an unstructured mesh in two directions, and, at the same time, one structured main direction.
Based on the surface mesh out of triangular -elements prism- elements are extruded into the part.
Different layers of the so built prism-elements are possible. In combination with tetraeder-elements (in the remaining part), a blm mesh is built with a high accuracy and less elements. Therefore, the calculation time can be reduced.
The special form of the triangular footprint based prisms allows, in the runner system for injection molding simulation, an orientation of the fibers in flow direction inside the runner without a secondary preferred direction.
Mar 8, 2019
For a 2.5D injection molding simulation a surface mesh is needed.
All surfaces of the chosen CAD model will be covered with triangle elements to build a closed mesh.
A surface mesh can be generated automatically with a CAD-System by exporting it as stl-file. This format is often used in rapid prototyping processes.
But the quality of such a mesh is not accurate enough for an injection molding simulation.
The mesh carries the geometry information and need to be optimized.
It is important to have a high amount of elements as well as to make sure that each element has a good aspect ratio.
Simulation: The prepared mesh for the usage in the next simulation.
Related topics:
This glossary of plastic industry is provided by PLEXPERT Canada Inc.
Mar 8, 2019
A pyramid-like 3D-object, with 4 triangle elements is called tetrahedron (Tetrahedral Element).
In simulation tetrahedrons are used to build a volume mesh.
In a first step the surface of a part will be meshed using triangle elements.
The triangle elements will be used as a base for the first layer of tetrahedrons going into the part.
Depending on the size and orientation of the base triangle element tetrahedrons with a critical aspect ratio can be created.
The random orientation of a tetrahedron elements lead to a not preferred direction.
This can lead to longer computation times.
Simulation: A pyramid-like 3D- object – called
tetrahedron (
Tetrahedral Element).
Related topics:
Volume Mesh
Surface Model
This glossary of plastic industry is provided by PLEXPERT Canada Inc.
Mar 8, 2019
Shrinkage and warpage can be seen if plastic material is processed and cooled down in the mold and later after ejection.
In order to compensate shrinkage the mold design is modified using a factor, which is very often based on experience.
The given dimension of the part is multiplied by the factor to enlarge the part and create a cavity based on the new dimensions.
A filling simulation can be done to predict warpage due to fiber orientation, stresses, etc. as well as the shrinkage of a part during production.
In order to compensate warpage the cavity is modified in the oposite direction of what can be seen as part warpage.
This modification is called tool adaptation.
To do this in a best way the simulation result warpage is multiplied with a factor of -1 and exported as .stl file for example.
In the CAD system the mold cavity is adjusted taking care of that no undercuts are build in.
It is essential that, based on the new cavity geometry a new simulation is done in order to verify the desired results.
If this simulation shows good results the tool adaptation can be implemented into the mold.
Simulations: Left:
part warpage; right:
tool adaption.[/caption]
Related topics:
Reverse Engineering
This glossary of plastic industry is provided by PLEXPERT Canada Inc.
