Week 4

Mid Surface Extraction and Meshing of a Bottle Cap Model using ANSA.

Objective:

To extract the midsurface and generate 2D mesh for the given bottle cap according to the given element quality criteria using ANSA.

S. No	Quality Criteria	Value
1	Target Length	1
2	Minimum Length	0.5
3	Maximum Length	3
4	Aspect Ratio	5
5	Skewness	45
6	Warpage	15
7	Jacobian	0.7
8	Min. Quad Angle	45
9	Max. Quad Angle	135
10	Min. Tria Angle	30
11	Max. Tria Angle	120
12	Tria percentage	15

Introduction:

          The component provided was bottle cap in ‘iges’ format. The bottle cap has many features with varying thickness. Hence, the mid surface is extracted for each feature and 2D mesh is generated by satisfying the given quality criteria.

Geometry cleanup:

The given component is checked for geometrical errors using checks manager. The errors displayed is cleared using auto fix and tools from hot points, cons, faces & surfaces.

Midsurface Extraction

• The midsurface is extracted separately for each feature of the bottle cap.
• The midsurface for features having uniform thickness is generated using tool offset option.
• The midsurface for curved features are extracted using tool curves>middle option, since it has varying thickness.
• The midsurface of semicircular cross-sectional threads is extracted as rectangular cross-sectional threads, since it is impossible to capture semicircular cross-sectional threads.
• Since, it is time consuming to extract midsurface one by one for all the teeth of bottle. The midsurface of one tooth is extracted. Using rotate command and copy option the mid surface is duplicated by 35 numbers at 10 degree.

Midsurface extraction of teeth of bottle cap

Bottle cap midsurface outer view

Bottle cap midsurface inner view

Assigning shell property and thickness

• The midsurface of each feature of bottle cap with varying thickness are assigned with new PID’s.

Meshing:

• The quality criteria & mesh parameters values are entered.
• The perimeter length value assigned is 1 mm.
• Using best mesh option each macro area is selected and meshed.
• The quality criteria are achieved by using tools like cut, join, Num +/-, reconstruct, smooth and split options.
• The tria percentage is reduced by deleting unwanted construction lines without losing the feature.
• The smooth mesh flow is achieved by creating small macro areas and restructuring the mesh.

The meshed model of bottle cap 

Bottle cap meshed final view

Learning Outcomes:

• Learnt the usage of various tools of ANSA software.
• Able to fix the geometrical errors for given model.
• Able to extract midsurface for features with varying thickness.
• Able to mesh the given model by satisfying the quality criteria.

Conclusion:

          The given bottle cap model is imported to the ANSA software and the geometrical errors are fixed. The midsurface for each feature of bottle cap is extracted and thickness is assigned. The midsurface is meshed successfully by satisfying the quality criteria.