Week - 4 - 2D meshing for Plastic components

Week 4 Challenge: 2D Meshing of Plastic Components

Aim: Checking for the geometrical errors, taking the mid surface, and meshing the given Plastic Bottle Cap model with given element Quality criteria. (Refer to the table below for the Quality criteria)

Given sheet metal model: Plastic Bottle Cap model

Given Quality criteria:

S.No	Quality Criteria	Value
1	Average Length	1
2	Minimum Length	0.5
3	Maximum Length	3
4	Aspect Ratio	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 Angel	120
12	Tria Percentage	15

Procedure steps followed:

1. Check for Geometrical errors and fix them.
2. Extract mid surfaces manually for all different thicknesses using various mid surface techniques.
3. Update the mesh quality criteria with the given
4. The meshing of the component mid surfaces
5. Assigning different PID to different areas of the component in according to various thickness.
6. Switching on Draw Shell as Solid in 'Quality Criteria' Dialog box

Procedure:

1. Checking for Geometrical errors and fixing them for all components

After importing the given model into ANSA, checking for geometry cleanup is done from

Tools -> Checks -> Geometry -> Execute

Before Executing Geometry check After Executing the Geometry check

After Geometry cleanup

There are only two errors 'Needle Faces' and these are solved by Auto fixing them through clicking on the actions icon in after check window -> Fix

2. Extracting mid surfaces for all components after measuring the thickness of the components

After geometry cleaning is done, the thickness of different areas of the component is measured and stored for extracting the mid surface.

Since the given model is having variying thickness we use different techniques to extract mid surface.

By dividing the whole part and storing it to different store locks we can extract mid surface easily.

The techniques used to extract mid surfaces include

(1) TOPO -> Curves -> Middle

Here we use this by forming curves at middle of the part and using

TOPO -> Faces -> New

we form new surfaces which represents exact middle surfaces

we use the same technique above to extract middle surface for this area.

Then by using these curves we form new surface.

(2) technique

Here we use TOPO -> Faces -> Middle -> Single

to form middle surfaces directly, but the middle surfaces formed using this will have gaps where there are two surfaces intersects and also this can be used for only single surfaces extraction.

We use TOPO -> Faces -> New to close those gaps

Using this technique we extract middle surface

And using TOPO -> Faces -> Extend -> Target, we can fill the gap of this formed surface and the adjacent mid surface.

The cyan CON indicates the extended and intersected surfaces.

(3) Using TOPO -> Faces -> Offset -> Faces

We can extract mid sufaces which are having uniform thickness

This part has uniform thickness and we use this technique

By giving the offset value we form mid surface

when extracting mid surfaces keeping the same PID makes it easier to mesh

The complete mid surfaces of the component is shown as below

Given component

The extracted mid surface with same PID in shadow mode and Hidden mode

3. Update the mesh quality criteria with the given

We update the given quality criteria and mesh parameters to further proceed to meshing

Quality Criteria

Mesh Parameters

4. The meshing of the component mid surfaces

After updating the quality criteria we can proceed to mesh the component

Using

we mesh the component for within given quality criteria

The final meshed component

5. Assigning different PID to different areas of the component in according to various thickness.

After meshing is done, we can now assign PID to areas according to varying thickness

This can be done using MESH -> Macros -> Edge2Perimeter

we can divide the mesh into different macros and using 'Set PID' and selecting the faces with same thickness

we can assign a differnt PID and the thickness of that area.

After assigning PID to different areas a different color is assigned to differentiate it.

After Assigning different PID according to their thickness

-> For the areas with varying thickness we take average of two extremes as the thickness of that area or Macro

6. Switching on Draw Shell as Solid in 'Quality Criteria' Dialog box

After assigning PID we switch on 'Shell as Solid' in "Quality Criteria -> Presentation Parameters" the component will be shown with the given thickness in mesh

After swithching it on. we can see the final component with thickness switched on

Learning Outcomes:

• Cleaning of Geometry.
• Generating mid surfaces using feature selection, entity selection, Curves, Faces ->New, Extend and other different techniques.
• Meshing of component using different (Best, Map) Algorithms
• How to effectively use split, swap, join, paste commands in Mesh module for removing Trias and
  rotating Quads.
• Assigning PID using Edge2Perimeter

Conclusion:
Geometry cleanup and 2D meshing of given Bottle Cap model is done using ANSA v22.0