Week - 4 - 2D meshing for Plastic components

Aim:

Create 2D meshing for the given Bottle Cap model considering the below stated quality criteria. Midsurface thickness is to be assigned for each shell element.

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

Steps:

• Geometry Clean-up.
• Midsurface extraction by offset & Middle option.
• Midsurface extraction for Thread.
• Meshing the midsurface.
• Set PID and assign thickness for each shell element.

Procedure:

1. Clean up the CAD model using Topology module and remove the inconsistence in entities.

2. Switch on to entity mode, isolate each part & check for errors with the help of Boolean operations.

3. Define material as given in the statement or standard material will be steel as default.

4. Check CAD topologies using checks manager, check parameters such as triple con, single con, etc.

    

5. If there are any errors in geometry, auto-fix whichever is possible. Errors which cannot be auto fixed, right click on the error & select show only. The actual error will be displayed which has to be fixed. Similarly perform check geometry until the result passes completely.

6. Generate mid surface of the given model using Offset -> Faces. Activate the cross hatch lines and select the face to be offset by clicking the centre of cross hatch in that particular face. After selecting the face click on middle mouse button to confirm the action. Enter the offset value equal to half of the model thickness. Depending upon the arrow mark, enter positive or negative sign for the offset value. Similarly extract mid surface for all different thickness.

7. Midsurface of outer Ribs is extracted by single middle option. Similarly perform same action for all the outer ribs.

8. Midsurface of small ribs is extracted by multi middle option. Similarly perform same action for all the inner ribs.

9. Midsurface of tooth is extracted by curve middle and then creating new face.

10. Make visible only the mid surface & lock the view. Check for unnecessary single Cons and perform a topology. Once all the surfaces are associated with neighbouring surface, orient the mid surface to meet uniformity. Assign a separate property for each shell element by set PID option. Cross check the property assigned by switching to PID mode. At the end, perform check geometry and de-select single Con option and execute.

            

11. Switch to mesh module and check for colour representation. Measure the element length by measure option. As per the requirement, assign element length by length -> Perimeters. Enter the element length value and perform the action.

12. Check for node length at critical or small places. If the length does not pass the criteria, de-feature the model without compromising any fillet or critical CAD geometry.

13. Set up the quality criteria by pressing F11 key. Based on the quality requirement, key in the values and range.

14. Switch over to mesh module. Start meshing the most critical face which has got features and holes. Select best mesh option and select the area to be meshed and middle mouse click to perform action. Turn on hidden mode and check for quality of mesh. If there are any errors in quality of mesh, use mesh improvement tools like Reconstruct, Smooth, Fix Quality, improve, etc. to eliminate the quality errors.

15. Assign thickness properties by selecting the mid surface and rename accordingly. Verify by clicking F11 > Presentation Parameters>draw shell as solids> apply.

Learning Outcome :

• Extraction of Mid surface using different methods and option.
• Geometric error fixing while taking mid surface.
• Managing Triple Cons.
• Maintain quality as much as possible.
• Meshing with very minimum trias.

Conclusion :

The given Bottle Cap Model is meshed considering to the prescribed quality criteria, each mid surface element is assigned with a separate PID.

With minimum number of Trias and off elements, 2D meshing is completed.