2D meshing for Plastic components

Objective:

To extract the mid surface and mesh the given bottle cap component using given quality criteria and assign correct thickness to the property.

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

Given cad model:

Procedure:

• Import the model first.Now check the geometry for any errors like singlecon, needle face,crack surfaces using checks-geometry tool in menubar. after that select execute and select all the errors and right click-fix to fix those errors.

• Now select mesh-perimeter-length tool and give 1 as a value to refine the macros and perimeter of the model for good resolution to see the component.

• Now use not, or, inot tools to separate the surfaces for taking midsurfaces.

• First measure the thickness of the model to get a idea to extract the midsurface for the macros.

• Now the thickness of the two surfaces are same overall we should use offset option topo-faces-offset. assign value as half of the thickess and select the faces to offset. give negative value when the arrow in opposite side.click ok and click no to delete the surface for further reference.

• The model has varying thickness in some surfaces. those surfaces are extracted by using middle tool in topo module topo-faces-middle-(single or multi). for ribs we can use both but the surfaces are single. use middle-single. now select the first surface then click second surface. now click ok to accept surface. now the midsurface is generated.

• Here we have some threads in the bottle cap. it has trapezium shaped surface for those surfaces take midcurve to get a exact mid surface topo-curve-middle select the two curves one by one and click ok to get mid curve. now project the midcurve to midsurface topo-cons-project and now use those curves to create new surface using topo-faces-new.the midsurface is generated for threads.

• we have some ribs having varying thickness in the inner bottom of the model. use topo-faces-middle to get a midsurface for the rib and now extend the free edge topo-faces-extend select free edge and select the midsurface and the midsurface connected with the another major midsurface.

• Now transform the ribs around the surface as copy by using Transform-copy-rotate select the midsurface of rib and select rotate now give X & dx value for axis of rotation and give the copies and click finish to get a ribs. For create axis of rotation we have to create COG points topo-points-on COG select the circle 1 and create COG point and select a cirle 2 above some height use those points for x & dx value.

• Now get a midsurface for teeths in the model. we can use midcurve option to create a midcurve and project the opposite side con to the midsurface and now click the midcurve and projected curve to create the new surface.

• Follow the same procedure for transform the teeth. Here we have some more steps to create the copy. select angle tab. give value as 360/26 and click ok. now the teeths are created around the surface.

• Now assign the thickness for the midsurfaces. we have some varying thickness surfaces so that we have to create gradual thickness variations under one surface.we can create property easily. select property-new-pshell-assign thickness-assign name.

• Now we can move to mesh the model. first set the mesh parameters. give target element length as 1mm, min length as 0.5mm, max length as 3mm. select ok.

• Now give quality criteria for the mesh. Select quality criteria and assign values as given in the above. select presentation parameters. select elements percentage.now click ok.

• First select the macros and select best mesh in the mesh generation (mesh-mesh generation-best). now the mesh is generated in the selected macros. follow the same procedure for mesh generation.
• Now use reconstruct tool for remesh the exsiting mesh (mesh-shell mesh-reconstruct).

• Now Use split, paste, swap option for reduce the opposite trias, back to back trias in the exsiting mesh in the model (mesh-element-split/swap) (mesh-grids-paste).
• Split- the tool used to split the elements by edges and by nodes and used to move forward the tria.
• Paste- the tool used to move the tria to backwards by pasting the nodes.
• Swap- the tool used to swap the tria to next element.

• Now the mesh are generated. check for quality criteria and the failed elements are corrected using tool like smooth,reconstruct,fix quality, move in the mesh module. finally the mesh are generated for the given model.

• Some elements around the triple cons are failed for minimum length, aspect ratio. Those elements are under OFF elements.

• Now select the draw shell as solid tool in presentation parameters tab to see the thickened solid pattern of the mesh.

Final component images:

Final Meshed Component:

final shell elements represented as solid componenet:

Learning outcomes:

• Learnt to use the different kind of tool to create midsurface, to create a surface using midcurve, to transform the pattern of surface in the model.

Note: I'm using ansa's latest version 21.0.1. so i was imported my model as iges and fem (optistruct) by the idea given by my support engineer and upload it in this challenge.

Conclusion:

The given bottle cap model is meshed with given quality criteria using midsurface and assign various thickness among the surfaces.