Week 4 - Mid-surfacing and Meshing of Bottle Cap using ANSA

Objective: For the given model, we have to check for geometrical errors, create the mid-surface, mesh with given Quality criteria and assign thickness. Also, we have to write a detailed report on methods used to extract mid-surface.

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

Meshing Process:

Importing the model: Firstly, we imported the model from the storage in .STEP format to ANSA software.

Geometry Check: From ‘Checks Manager’ using ‘Geometry’ we checked for any geometrical errors. And fixed using Auto Fix options, however for some manual fixing was required. Corrected the “UNCHECKED SURFACES’.

Extracting Mid-surface: Now for extracting mid-surface, we had to use different approaches depending on the area of the surface. Below are the methods used for the midsurface along with the reason for using the same.

1.Faces>Offset: For the surfaces having similar top and bottom thickness we could use the offset method. For example mid-surface for the top surface could be extracted using the same. However, for surfaces having varying thickness we had to use the Weld Spot and then by projecting it to other face we could measure the average thickness of the face and create the mid-surface uaing the offset method.

2.Faces>Middle: Using the method we can create the mid-surface between two faces, hence for the Ribs and teeth we could use this method. For outer teeth we could use Middle>Single. However, for teeth we have to use Middle>Multi as inner and outer surfaces were not same.

3. Curve>Middle and Faces>New: For surfaces where the above method can give desired results we have to opt for other option. Using the curve middle we can create a curve between two cons and then projecting the curve created we can create a new surface between them. For the threads we had to create the middle curve then aftr projecting the curve we could create a mid-surface for threads.

Some mid-surface entities were extended upto parent geometry to cover the fillet region.

De-featuring: In order to prepare the model for the meshing we removed unnecessary cuts and hotpoints from the surface. Extended few surfaces to the mid-surface.

Meshing- To mesh the model, we started from the centre of the model, for that we used Mesh Generation>Best. In order to get lesser number of trias and off elements, we used different approaches for a better mesh. In order to create better mesh, we used Shell Mesh>Smooth, Reconstruction and Grids>Move. Tried to reduces number of trias and eleminate opposite trias.

[Some areas having multiple triple cons overlapping each other, the off elements could not be fixed there hence, after discussion with Support Engineer, off elements were reduced to minimum possible number.]

Assigning Thickness: Created a new PID for each part and assigned thickness assigned for each macro area, the thickness assigned is same as thickness of parent geometry of that part. Total of 16 PIDs were created. Same PIDs has been assigned to parts having similar thickness.

Learning Outcome: By doing this challenge, leaned to model the plastic components. Learned to create mid-surface of surface having different thickness at each end. Learnt to use tools like Extend, Intersect, Grid>Move, Weld Spot etc.

Conclusion: Modelling of the plastic component was done, mid-surface using different techniques was done. Created mesh, and reduced off elements by using different tools and brought to minimum possible number.