Week - 4 - 2D meshing for Plastic components

AIM:

To perform geometry clean up and shell mesh the given model of a bottle cap with given quality criteria.

Methodology:

The methodology for the given element is as follows:
1. Perform a Geometrical Check ( if Errors present fix them)
2. Extraction of Mid surface
3. Assigning Thickness to Mid surface.
4. Giving the Quality Criteria.
5. Creating a mesh
6. Adding thickness to the meshed element.

PROCEDURE

Import the Bottle Cap part ansa file.

Clean up the geometry of the given bottle cap.

FIG 2: CLEANED UP GEOMETRY OF BOTTLE CAP.

• Measure Thickness on few edges and coons to generate the midsurface for the component.
• Set the Property IDs and Material IDs.
• Under the Mesh module change the set the Length of Perimeter and Macros to 1mm.
• Check visually for unorganised faces, delete it and create a new face with commands under Topo Module.
• Now go to Checks > Geometry.
• Select all the checkboxes except Sharp edges and Unmeshed macros and click execute.
• Errors like Triple cons , needle faces , cracked faces, single cons may appear.
• Select all errors , right click the mouse and select Autofix.
• Correct the errors by commands like hotpoints delete , insert , release.
• Commands like Faces > Delete , Topo, Orient Commands like Cons > Release , Project, Break

Generate Midsurface.

• The commands used for generating midsurface manually are faces > Offset because thickness can be easily measured for each part.
• First Generate Midsurface for larger parts and then go for features like ribs , threads.

FIG 3 : MIDSURFACE MANUALLY EXTRACTED FOR THE BOTTLE CAP

• Use commands like Faces>Extend , Intersect, Set PID for features to get a proper mesh.
• Topo the faces properly after extraction.

Set the Quality Criteria.

FIG 4 : QUALITY CRITERIA SETUP

Set the Mesh Parameters.

FIG 5 : MESH PARAMETERS UNDER BASIC TAB

FIG 6 : MESH PARAMETERS UNDER FIX QUALITY TAB

Generating Mesh.

Select the Entire part and select the perimeter length to be at 1mm from the Mesh module.

1. Use commands like Shell Mesh>Reconstruct, Smooth to get rid of errors.
2. Use commands like Elements > Split, swap( to reorganise quad and tria elements).
3. Use commands from Perimeter > Number , Num+/-
4. Use commands like Macros > Cut , Join for reconstructing Mesh forms.
5. Try to reduce the trias as much as possible and keep the quads in the majority of mesh to improve the quality of mesh.
6. There must not be numbers mentioned in OFF under the shell quality card.
7. Thus the meshing process is completed.

FIG 7 : GENERATED MESH IN SHADOW VIEW

FIG 8 : GENERATED MESH IN HIDDEN VIEW UNDER SPECIFIED QUALITY CRITERIA

Assign Thickness to the mesh.

Go to Quality Criteria > Presentation Parameters and select the Draw Shell as Solid Check box. When switched to the Mesh Modules tab , The thickness can be viewed.

Release the entire meshed part for separating FE elements by using MESH module > Elements > release.

FIG 9 : MESHED BOTTLE CAP WITH THICKNESS

FIG 10 : MESHED BOTTLE CAP WITH THICKNESS

Result:

1. A geometry clean up was performed.
2. mid-surface was generated.
3. The mid-surface was meshed as per the required quality parameters.

Learning outcomes:

Understood the challenges encountered when meshing a complex geometry.

Importance of defeaturing for attaining good quality.

Mid-surfacing regions with varied thickness.