Week - 4 - 2D meshing for Plastic components

AIM : To achieve the good quality mesh of the given 2D model of Plastic cap by using ANSA tool, the procedure consists of Topo cleanup, Extracting the Mid surface, Defeaturing and finally meshing by constraining the following parameters as inputs ,

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
12	Tria Percentage	15

PROCEDURE:

A.TOPO CLEANUP

1. Import the given Plastic Cap Model into the Ansa, carefully study and understand the model.
2. Give the Topo command to entire Model assign the property index for each individual components /feature by selecting the faces and utilizing the Commands storage lock, OR, INOT , neighbour all.
3. Now check for the Geometry checkup which is available Tools --> Check --> Geometry for Sharp edges, Unchecked Faces, Triple Cones, Cracks, Single Cones(which are missed in Topo during selection and neglect the outer perimeter single cones) , Needle faces,Overlap Faces.
4. Fix the errors automatically by the FIX option. If any errors are not fix during the automatic, fix them manually especially triple cones by using the commands release, INOT, OR, neighbor all, Cut etc. which is useful to resolve the errors.
5. Repeat the point no. 3 & 4 for all the individually property components which are stored in property index.
6. After resolving all the issues, measure thickness randomly for all the individual parts and define them.

B. MIDSURFACE EXTRACTION

1. Assign the Orient to all the components in the same direction for each property index. Develop the Mid surface by using the OFFSET command for all the components of property index and assign the offset value.
2. Since there are many faces, to select the entire face activate crosshatch and keep the face selection in inclined feature area.
3. Assign the property Index by using the storage lock for the each mid surface.
4. Give Topo for the mid surface and check the geometry for error. Fix the errors automatic if any use the manual method as mentioned in TOPO cleanup for all the property features.

C. DE- FEATURING

1. After mid surfacing, De-feature the midsurface without altering the Original Geometry size and shape.
2. Defeature is defined as removing of additional curves, Hotpoint’s, cones which are used during the Modeling of geometry it can be done by using the commands such as number of Hotpoint’s (+/-), Cut, join, Delete , Hot points etc, whichever is used to defeature.
3. Make suitable rectangular planes on the faces by using the command (Mesh -> Macros -> Project cut) to get suitable quads mesh in undisturbed and regular pattern. Delete the construction cons after completing the mesh by using the join option mentioning Reconstruction as keep in option list.

B. 2D MESHING

1. Enter the input constraints of mesh as given aim in the command (Utilities -> Mesh Parameters and Quality)
2. Mesh the given mid surface by selecting the features separately and mesh by using command (Mesh -> Mesh Generation -> best).
3. Use the command (Mesh -> Shell Mesh -> Reconstruction) to get the fine mesh without any errors.
4. Refine the Mesh by using the Commands (Swap, Paste, Split, join, etc) to get the refine mesh and to avoid the opposite trias, rotating quads and trias at perimeter of features like hole, edge perimeter etc and resolve all the error in OFF of mentioned mesh parameters.
5. After completing the Mesh, check the unmeshed areas if any and enable the thickness and enable the thickness Quality Criteria -> Presentation Parameters -> enable draw shell as solid.

Learning Outcomes:

1. A Clear understanding on meshing and Ansa tool in especially working difference between on plastic components and sheet metal models.
2. Complications of Extracting the Midurface in Plastic components where feature dimensions are very small and variation in thickness for single feature.
3. Meshing effects of one feature with respective other which are attached together.

Result & Conclusion:

Attached Ansa file consists of final mesh and images are attached here.