Week - 4 - 2D meshing for Plastic components

                                   2D meshing for Plastic component ( Bottle Cap ) using ANSA

AIM:-

For the given Plastic Bottle Cap model, to check for the geometrical errors and also to take the mid surface by suitable mid surfacing techniques. And the meshing to be done for the given component for the given quality element criterias.

Given quality criterias for meshing:-

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

CAD MODEL:-

Plastic component given for meshing ( Bottle Cap ) :-

Procedures for Meshing a 2D component:-

i) Importing the CAD model into ANSA:-

The cad model is imported into the Ansa software by clicking File ---> New command.

ii) Geometry Checks:-

Then the important step is to check the geometry of the CAD model. This will helps us to clear all the surface errors, unwanted cons and also for any dissruptions placed in the CAD model. 

This can be done by giving the command Tools ---> Checks ---> Geometry. And when you check for the geometry, some of the errors will be thrown out by ANSA.

These errors can be automatically resolved by the ANSA by using the command Right click + Fix in the geometry check dialog box, and will make the geometry clean as follows:-

And after clearing all the geometrical errors and when you excecute the geometry check, It will appear as follows:-

And hence all the CAD models were check for clean geometry and all their surface imperfections are fixed in the geometry check. And once again release all the cons and give Faces ---> Topo.

Then Faces ---> Orient command is used to check the orientation is proper in all the faces of the CAD geometry.

iii) Mid-surface extraction:-

Once the geometry is clean, then the midsurface is extracted from the provided CAD model. The following steps are followed to extract the midsurface for the different thickness component.

Before extracting the Mid surface of the components, its important to measure their thickness. And this can be achieved by using the command Utilities---> Measure. And by chosing the extreme end of two hotpoints we can get the thickness of the geometry. After measuring the thickness, for the seperate thickness of different components seperate PID's are also created.

And to do the midsurface Faces ---> Offset command is used and the face to be extracted is selected and then the offset value is gives and the surface is extracted.

For components like ribs, Faces ---> Middle command is used to extract the mid surface.

And after creaating the mid surface, the Faces ---> Extend command is used to attach the midsurface to the base of the parent geometry.

To create the mid surface for the thread portion in the model, initially Curves ---> Middle command is used to create a curve in the middle portion of the teeth.

And then project the curve using Cons ---> project, and hence the curve will get projected to the surface. And then a new surface is created by using Faces ---> New command and the curve and the projected cons are selected and then the new surface is created in between the curve and cons as follows:-

And by this way, the mid surface for the entire component is seperated and the final mid surface of the component will look as follows:-

FINAL EXTRACTED MID SURFACE :-

iv) Fixing Quality criteria and Mesh parameters:-

Once the Mid surface is generated, the CAD model is now ready for the meshnig. And for that the quality criteria for the mesh is defined using the command Utilities ---> Quality Criteria ( or by clicking F11 )

The quality criteria dialog box will appear as follows and our qiven quality criterias are defined in the dialog box.

Then switch to 'Presentation parameters' tab , In Graphics division put tick mark for Elements% and choose the Details on demand effect as 'More details'

Then choose Utilities ---> Mesh parameters and give the target length as 5 and give the following setup to the meah parameters dialog box.

v) Meshing:-

Finally the Meshing will be done to the extracted mid surface components. To start with meshing in the Modules tab, choose Mesh icon.

Then choose Perimeters ---> Length command and choose the entire component and give the target length of the mesh value as 1. (user can choose their own value). The same should be also done for the Macro to get a smooth surface before mesh.

And then the model should be checked for the de-featuring. If we see any cons or hotpoints which will tends to fail the quality criteria, they can be suppress using Macros ---> Cut + Right click and Hotpoints ---> Delete options. Similarly, the minimum length error can be solved by taking peak value of the fillet and by suppressing the nearby cons.

After when all the defeaturing works are done, the complex component can be subdivided into batches to obtain better quality mesh and that can be achived by Macros ---> Cut command and then meshing can be applied for the indiviual places. 

And Perimeter ---> Slide option is used to slide the holes in the component and make the perimeters almost parallel, to get an proper mesh in the component.

Finally choose Mesh Generation ---> Best Mesh command and choose the faces to be meshed one by one like a flow.

And then the meshing will be done segment by segment in a proper flow and the complete meshing is achieved.

The elements are then modified according to the quality criterias provied by using the following commands.

So, after obtaining the mesh, the above things to be taken care and the tria elements can be mostly avoided by using the following commands:-

Elements ---> Split , Elements ---> Swap, Grids ---> Paste These commands are used to move the trias forward and backword and also to split them . Elements ---> Join command is also used to reshape many tria elements and by using these  comannds we can achieve the above conditions and the tria elements can be avoided.

Shell mesh ---> Reconstruct and Shell mesh ---> Smooth commands are also used to obtain the smooth elements in our meshed model.

And hence, when our meshes are failing to fill the quality criterias provided, they can be cleared with the help of the above steps and commands provided.

After meshing, go to Utilities ---> Quality criteria ---> Presentation parameters ---> Draw shell as solid to covert the CAD model again back to its original parent position with meshing.

FINAL MESHED COMPONENT:-

Learning outcomes:-

The new learnings are , almost all of the options are covered in this bottle cap challenge. The new things which I have learnt again is How to Extend a face, How to create a new face, The purpose of curve option, Different options to take a mid surface like offset, middle etc., and also all the mouse and keyboard controls become quite familiar once i complete this challenge.

Conclusion:-

Hence the given Bottle cap is meshed according to the quality criterias provided.

CLICK THE LINK BELOW TO SEE THE COMPLETED MODEL:

ANSA MODEL:- https://drive.google.com/file/d/1KNd3x_LAO3ajZbQYhbAJzxVkijWj64Pd/view?usp=sharing