Week - 4 - 2D meshing for Plastic components

AIM : For the given PLASTIC BOTTLE CAP, checking of its GEOMETRICAL ERRORS and assigning PIDs followed by MID SURFACE EXTRACTION of the same and is to be SHELL MESHED using ANSA.

INPUT : The given component model is of a plastic bottle cap.

It has the number of features like outer ribs,internal threads internal ribs etc.

QUALITY CRITERIA FOR MESHING :

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

WORKING PROCEDURE :

• The model is imported to ansa and initially checked for any GEOMERTICAL ERRORS using CHECKS MANAGER>GEOMETRY. The following two errors occured in the model which is then rectified and geometrically correct model is obtained.

• As the model is now good to go for the MID SURFACE EXTRACTION, the component given has a number of features whose mid surfaces are extracted using different methods.
• For convinience the different features are assigned to different PIDs given as follows;

• The OUTER RIB's mid surface is extracted using FACES>MIDDLE in TOPO DECK.
• The INTERNAL THREAD's mid surface extracted by creating CURVES between CONS using CURVES>MIDDLE, and the a surface is created using this curve and its projection in the base using FACES>NEW>FITTED.

• The feature named FEAT 1's mis surface is extracted by FACES>MIDDLE. and then stitched.
• the feature named FEAT 2's mid surface is taken by FACES>MIDDLE.
• the feature named FEAT 3's mid surface is taken by taking offset using FACES>OFFSET.
• For the feature named FEAT 4, the mid surface is taken for one of it by creating a curve in between cons and projecting the con of the other end to the mid surface of base. after that a new face is created using FACES>NEW>COONS to obtain a mid surface. As these feature are 26 in number so for the rest 25 of it, the mid surface of one is copied using TRANSFORM>COPY, but before it two points at different heights are to be made to fix the axis of rotation which is done using POINTS>ON COG. Thenafter the ROTATION is made and after confirming the ENTITY the angle is taken 360/26.

• For the base panel the mid surface is taken by offset and also by FACES>MIDDLE.

existing surface option is used such that the cons can be joined.

• After stitching all the midsurfaces together again a geometry check is performed but this time by disabling single and triple cons.

• After all the necessary steps the model is forwarded to the MESH DECK, where initially all the given QUALITY PARAMETERS and MESH PARAMETERS are fed.

• Initially the complicated features are meshed using MESH GENERATION>BEST and improvised and smoothen by using SHELL MESH>RECONSTRUCT and SHELL MESH > SMOOTH.
• After meshing all the unmeshed faces and eliminiating possible tria elements both opposite to each other and at perimeters the meshed obtained is,

MESHED AND SHOWN AS A SHELL MESHED AND SHOWN AS SHELL AS SOLID

CONCLUSION : The provided plastic bottle cap model is rectified from all its existing errors and topology is done. The midsurface is extracted using various techniques and then meshed properly with limited tria saturation of about 2.54% and with 56 off elements which are found uneliminatable due to the congestion of triple cons.

LEARNING : In the given assignment plenty of new challenges occured like to remove as many off elements by all possible ways, and also came to know the use of ROTATION command by creating points at different heights, which in turn proved out to save plenty of time.