Week - 4 - 2D meshing for Plastic components

Abhishek Anil Patil | 23/06/2022

Objective

Week 4

For the given Plastic Bottle Cap model, check for the geometrical errors and take the mid surface by suitable mid surfacing techniques. PID and Thickness assignment has to be done for all the mid surfaces. Mesh the same with given element Quality criteria. (Refer the table Below for the Quality criteria)

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

Note:
1. There might be some Failed elements near to Triple CONS or at smaller regions which are bounded by two Triple CONS. Keep those OFF elements as it is if not possible to solve.
2. Elements other than those regions should pass the above-mentioned quality criteria and the features in the model have to be captured properly with good mesh flow. Depending upon this you will be awarded marks. (Refer “Model Requirements” in “Grading Policy” to know what to be done in the model)

Write a detailed report on your approach for the challenge and also mention which method you used to extract the mid-surface along with the reason.( Refer “Report Requirements” in “Grading Policy” to know what to be added in the report)

Click here to Download the Model

Total mark for this challenge is 150 marks.

Assignment Help:

1. Click here to know how to take mid surface for Teeth, Threads and to know How to perform ‘Rotate’ command to copy Mid surface entities.

2. To Assign thickness for the varying thickness ribs, Split the surface into multiple surfaces by using the “CUT” command and give different thickness values such that it captures varying thickness components in the best possible way.
3. Before submitting the model, Assign proper thickness to midsurface and compare the same with Parent geometry by performing “Draw shell as solid” in Quality criteria > Presentation parameters. (If thickness assigned is not proper then so necessary corrections after comparing it with parent geometry provided)

CAD model

Procedure

Geometry cleanup

All the single cons are stitched to double cons using Topo

Orient is used to orient all surfaces in one direction

Using checks à geometry à execute, shows geometry errors that can be fixed.

After performing these checks the model looks as shown below

Midsurface

There are different options to create Midsurface

Since the bottle cap is very small and complex in shape, it is difficult to use auto Midsurface option

So Midsurface is created manually for each surface

Measure thickness using Measure tool

Use Offset to give half of thickness and create the Midsurface

Surfaces having variable thickness is created using Curves à middle

Or surfaceàmiddleàmulti

Here the rib section has variable thicknesss so the facesàmiddleàmulti option is used

Here the outer ribs also have variable thickness so the curvesàmiddle option is used to create a mid line

These are created for all surfaces and then using surfaceàcoons options joined to create a surface

Threads

The threads, using the middle option a mid curve is created

That curve is projected on the Midsurface of the perpendicular face using

Consàproject

Then usings surfaceàcoons thse cons are joined to form the midsurface for a thread

Meshing

Using Mesh à length à applying target length as 1mm

Assigning mesh parameters, target length is 1mm, min length is 0.5mm,

Quality Criteria

The above quality criteria are specified below

Best mesh was used to generate the mesh

Three are some bad elements near the triple cons

Even after reconstruction, reshaping and smoothing these elements still fail in quality

After completing meshing

Go to qualitu criteriaà presentation parameters à draw shell as solid

The 2D mesh will appear as a solid with appropriate thickness for each misurface

We can switch on the 3D model and check if there are any inconsistencies

Total elements =9203

Tria =361

Tria % = 3.9%

Off = 252

Conclusion

We learned the process for midsurfaceing and meshing of plastic components

We learned different methods of variable thickness Midsurface generation