Week - 5 - 2D meshing for Plastic components
For the given Plastic Bottle Cap model, check for the geometrical errors and take the mid surface by suitable mid surfacing techniques. PID and Thickness assignment has to be done for all the mid surfaces. Mesh the same with the given element Quality criteria. (Refer to the table below for the Quality criteria)
S.No Quality Criteria Value
1 Target/Average length 1
2 Minimum Length 0.5
3 Maximum Length 3
4 Aspect 3
5 Warpage 15
6 Skewness 45
7 Jacobian 0.7
8 Minimum Quad Angle 45
9 Maximum Quad Angle 135
10 Minimum Tria Angle 30
11 Maximum Tria Angle 120
10 Tria Percentage 15
Note:
- There might be some Failed elements near Triple CONS or at smaller regions that are bounded by two Triple CONS. Keep those OFF elements as it is if not possible to solve.
- Elements other than those regions should pass the above-mentioned quality criteria and the features in the model have to be captured properly with good mesh flow. Depending upon this you will be awarded marks.
Write a detailed report on your approach to the challenge and also mention which method you used to extract the mid-surface along with the reason.panels.
Steps involved in ANSA
- Import the geometry
- Geometry clean up:
To ensure that all the surfaces are connected properly Faces>Topo tool is used for all the edges of each individual component at a time. Next, geometry check is performed by going to Checks>Geometry and running it for parameters as shown in the image below. Initial 4 errors were found. Auto fix option could able to fix, most except 1 needle face errors.
Below figure shows some of the error.
After clearing all the errors.
The next, step is to extract the mid surfaces for each component and keep them in separate property ID. Mid-surfaces are extracted using the manual method i.e. offsetting the surfaces of either face to the middle. Or by mid-surface → skin option. First, the thickness of each component is measured using the Measure tool from Utilities>Measure. The thickness is not uniform it has variable thickness, hence the component is plastic component. Next, the mid surface is extracted using the Offset tool by going to Faces>Offset and selecting all the surfaces on one face. Then, half of the thickness is given as the offset value, the direction is checked and offset. Now, the property is assigned to the extracted mid surface by going to Faces>Set PID and assigning to the respective property.
Prepare the mid surfaces for meshing. For that, switch to the Mesh module. First, the shell element length is altered by going to Perimeters>Length and all the CONS are selected and target element length 5 is fed as length value. The same is done for all the Macros (surfaces).
Cons2 curve under curve option is used to generate the curves.
Delete option is used to delete the surfaces
Deleting the curves after generating the surface.
Midsurface using offset option.
Quality criteria are configured by going to Utilities>Quality Criteria. And, the quality criteria file is saved for future reference. The created quality criteria parameters are shown in the image below.
mesh parameters are configured by going to Utilities>Mesh Parameters. There, target length, minimum element length, and maximum element length are configured
A mesh is a network that is formed of cells and points. A meshing is the process of subdividing the structure from infinite number of points to the finite number of node and elements. This process is also known as discretization. We used “BEST” option for meshing to generate FE elements on each and every surface of model. This tool generates the mesh using the best algorithm applicable.
During meshing we have to take care of quality criteria. Because on click of meshing option, it will generate improper meshing. So we have to improve meshing pattern in order to satisfy the quality criteria.Using reconstruct function in shell mesh, we have achieved high quality shell mesh. To achieve the overall quality, reconstruct function examine the current mesh and performs re-meshing in order to optimize the overall quality of mesh.After performing meshing on Bottle cap, component will look like as shown in picture
Mesh quality is important and mesh flow. Mesh quality and mesh flow is obtained by the following options.
Grid>Paste, to paste the nodes and move tria backward
Elements>Split, to split an element and move tria forward
Elements>Swap, to move the tria left or right
Elements>Join, to join two trias to make a quad
After modifying the mesh, Shell Mesh>Smooth tool is used to smoothen the flow of the mesh. Any elements failing for quality criteria are also fixed by either remeshing or smoothing the elements. The created mesh is shown below,
Challenges in the project:
Feature were more as it plastic component, feature is important as well quality of the mesh. Most of the mesh were failing for minimum length which needs a compromise between the quality and the feature. Intricate shape ribs were more. It is quite tricky to generate the midsurface also to mesh this component. After meshing few elements are failed due to of triple CONS
SHELL AS SOLID
In order to assign thickness, we have to make sure our thickness value should be in property identity. So to activate thickness at final stage, we have to check the draw shell as solid under presentation parameters.
LEARNING OUTCOMES
- Learnt to work on plastic model from mid surfacing object as the cap had many feature.
- Learning on improving mesh flow since mesh flow is something that cannot be absolutely perfect in components such as this.
- Learnt to check all the areas for minimum element length and to alter where elements might fail for minimum length. Similarly, CONS which are not essential to define a feature are removed by joining the surfaces.
- Learnt to achieve better mesh flow, even in complex problems.
- Learned how to applying thickness to every faces separate
Conclusion:
Importing the geometry, geometry cleanup, mid surface extraction, and 2D meshing of the given cap model were successfully done. All the features in the model are captured properly with good mesh flow.