Week 3 - 2D meshing for sheet metal

Aim-

The main objective of this project is to do preprocessing of the given hood of car i.e. to do geometry cleanup, extraction of mid-surface, mesh generation of model. To provide thickness and material to mid-surface & mesh, also to satisfy the quality criteria mentioned below,

Procedure-

• We start with the model import i.e to open the model in ANSA software for that go to file>>open>>file location>>select file >>hit open.

• Given model has total four parts in all, 1. inner ectract, 2. outer extract, 3. latch reinforcement & 4. hinge re inforcement.

Inner Extract

Outer Extract

Latch Reinforcement

Hinge Reinforcement

• Once We imported the model we first refine the models and check the exact shapes of component.
• For that we can go to Auxiliaries>>Fine>>click on the cons to refine, but using this will take a lot of time. So, to reduce that we will go to mesh tab>>perimeters>>length, select perimeter and length as 1 and hit ok, then select macros and do the same thing.

• Now we have to check the model geoemtry for that go to tools>>check>>geometry>>hit ok. A new window will open click execute and it will run the check window if there is any error it will show the errors or say geometry is ok.
• If errors are found then right click on edges>>click on fix and error will be fixed.

• Now we have to check that all the faces in the mmodel are grey of yellow in color as as the face should have same color for further result generation if some faces have different colors the go to Topo>>macros>>orient>>select visible, since will take the most common face as main and convert all the faces to same color. of select face to orient.

Note- This can be viewed in Ent mode in drawing styles.

All faces not oriented.

All faces oriented in same color.

• We have to check the thickness of each part for that go to utilities tab>>measure>>select nodes>>check thickeness to ensure proper thickness, measure it on 4 to 5 areas and then ensure.
• After measurement it is observed that the inner extract and outer extract having same thickness as 0.75mm & hinge reinforcement and latch inforcement as 1.2mm.
• Now next step is to generate mid-surface, there are two ways to do that 1st is by offset method and 2nd by mid-surface skin method.
• We will 1st method, for this again have two ways by going part by part or by feature selection.
• For 1st offset method type go to topo>>faces>>offset>>face>> select face>> as per direction off arrow set the offset value as +ve or -ve.
• For 2nd offset method type go to topo>>faces>>offset>>face>> click on feature & select any face which will cause all faces selection on same side>> as per direction off arrow set the offset value as +ve or -ve.

• Red lines are free edges which indicates that we have offseted mid-surface properly, to see that go to !not command in focus tab and check the mid surface.

1. Inner Extract

2. Outer Extract

3. Latch Reinforcement

Hinge Reinforcement

• Now we have to assign the property and thickness to it, for that go to property>>right click >>new>>assign name to it and add required thickness.

• Now go to Topo>>faces>>set PID>>select faces and asiign that property to it.
• Before heading to mesh we have to set element size, for that go to utilities>>mesh parameters>>set the values as per below snap.

• Now we have to set quality criteria for taht again go to utilities>>quality criteria(F11 key)and set quality criteria.

• To set all the cons and node to required elemnt length go to mesh>>perimeters>>length>>select all cons and set the size as 5 hit ok.

• We have to check the length of each part for that go to utilities tab>>measure>>select nodes>>check lengths to ensure min. & max. length of each for proper element creation, measure it on 4 to 5 areas and then ensure.
• Now to get the proper mesh flow will devide all the surfaces in some strategic fragments to get good mesh flow and latter we can remove it.
• To generate that go to mesh>>modules button>>macros>>cut or by projection cut.
• In below snaps Orange coloured cons (edges) are joined macros and yellow one are newly generated.

• In order to solve this Min length error, we have to toggle (suppress) the top and bottom double cons at the fillet region of a mid surface (Toggled cons will be represented as Orange colour lines). This is called ‘defeaturing’ the midsurface. (Refer the below snap).

• To generate mesh go to mesh generation>>best>>select and select required faces for meshing.
• For Generating mesh of inner extract we have to generate mesh and by tranform and symmerty using three point we have to mirror remaining half and to get mesh of other half.
• While generating mesh we have to ensure that no trais are touching each other & no back to back trais and low trai concentration.

• If there is any quality issue it can see observed as per below snap.

• When issue is resolved it will disapper.
• now to check thickness is applied or not, then go to quality criteria>>presentation parameters>>check draw shell as solid and hit apply then ok.

• From above snap it is clear that thickness is applied properly.

Learning Outcome-

• Leant about ANSA GUI, Basic Commands.
• Learnt about geometry cleanup, measurement taking, mid surface generation.
• mesh element size declarition, quality criteria setting, quality checking and error removal.

Conclusion-

• Geometry cleanup, mid-surface creation and mesh generation on given hood assembly.
• Quality criteria achievement and error removal.