Meshing a Bottle cap in ANSA pre-processor

Aim: Meshing a bottle cap for pre-processing in ANSA Pre-processor.

Procedure: The component to be meshed is a bottle cap. Examining the part concludes that the thickness not more than 3mm at any section of the component. Also, the component is almost symmetrical and can be meshed by Midsurfacing. The quality of the mesh elements is given in the following table.

S.No	Quality Criteria	Value
1	Target/Average length	1
2	Minimum Length	.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

These are the quality criterias to be satisfied by the elements in the mesh.

1.Geometry cleanup: The first thing after importing the component is to perform topo on the geometry. Next, check for geometric errors and fix them manually or by auto fix option. All the cracks, single cons, triple cons etc should be removed before proceeding for midsurfacing. The below image shows the errors in the geometry.

Images below show the geometry before and after performing Topo on the imported model.

2.Midsurfacing: The most time consuming and difficult task among all the steps is midsurfacing. The understanding of the complete geometry is the most important aspect for midsurfacing. Every feature in the geometry should be studied perfectly so as to carry out a perfect midsurface of it. Otherwise there is no meaning in performing the mesh using midsurface, as it would not give accurate result.

In this model there are a lot of features, and they need to be captured accurately. The two sets of threads, the outer grip ribs and the inner fitting ribs are to be mainly looked after acurately.

The tickness at different curves and features is different. This should be taken care of before offsetting any surface or taking middle of any cross section.

The complete model after and before midsurfacing looks as shown below.

3.Setting PID: PID is nothing but a property identity given to any surface, so as to keep the record of the material, its thickness, color, name etc., and is convenient to access any material seperately when needed to modify or correct any errors.

4.Meshing: Once the midsurface is created, now is the time to mesh it. Before meshing, set the quality criteria and mesh parameters. The table at the start of this report shows us the quality criterias, and the mesh parameters are the target length, maximum length and minimun length of the element. Here it is 1, 3 and 0.5 respectively.

The mesh is generated by selecting the 'BEST' option in the mesh generation button in the mesh module. The generated mesh is to be checked for failures as per the assigned quality criteria. Modulate the mesh to remove the failures is commonly achieved with the commands such as 'Reconstruct', 'Smooth', 'Split', 'Swipe' etc.

The first image attached below is the screenshot of the mesh I could achieve, and the second shows the same with enabled thickness using 'Draw shell as solid option'.

Learning Outcomes: The auo midsurfacing command is also tried out in this part to achieve the midsurface and mesh on the bottle cap. But it turns out that the software could not capture all the features especially the threads and the ribs and hence is inaccurate. Though it is time saving, it can only be accurate for simple parts with less features.

Below is the automidsurface FEA model and it shows the failures it has achieved. The distortion in the features and ribs is seen here, also the coloured areas show different types of failure for each color.

Conclusion: The bottle cap is corrected for geometric errors and is meshed by taking automidsurface casting option and also by manual midsurfacing. The result which was accurate was of manual midsurfaced part. The quality criterias have been met succesfully and thickness of every part is assigned to it.

The below link will help you to download the meshed model.

https://drive.google.com/file/d/1AwpYGUyOHhU8E94_7SGPkv0-CFofAlEV/view?usp=sharing