Meshing a interior plastic component of a side door

Objective :-

• To perform geometry clean up for Side-door plastic component model.
• Extract the FE structure or mid-surface by all the three method discussed below
  • Take the mid-surface manually.
  • Take the mid-surface using auto mid-surface.
  • Use the mid-surface using combination of both auto mid-surface and manuall mid-surface.
• Mesh the geometry with the Target element size of 4 mm
• Set Quality criteria for shell as shown in table below

Various Steps that are followed by me to cleanup the geometry, Extracting mid surface, Meshing and then Setup Quality criteria for the model in ANSA :-

Step 1 : Import the model

• Import the model to the ANSA. File - Open -Select - Import
• Check if the model is only showing by its edges then it is in wireframe mode so click on the below shadow icon to convert it into solid mode.
• When we are importing the model by default it is in entity mode so we convert it into PID(Property ID) mode.
• If edges showing the same color as the modle so to change it go to Quality criteria - Presentation parameters and check the Draw CONS in PID, MID...mode like in ENT mode in Visualization option and then click on Apply.

Fig : Side door plastic component Model (Wireframe and Solid)

Step 2 : Check for the geometry error

• After all the above step done, Now we can check for any errors in the geometry so click on the tick mark icon above And then open for geometry checkup and click on Execute.
• If it gives green check mark in status column so it means our geometry has no error but in our case it shows various of error so we have to clear all this error before mid-surface extraction.

Fig : Check for geometry error in side-door plastic component by Geometry check tool.

• So by the above figure we observe that, we have many errors in our geometry so first of all clean all the errors using TOPO module.

Step 3 : Clean up the geometry

• In this first of all we are using the inbuild function of ANSA to Automatic fix the gemotry error. For this right click on error in geometry check and then select Fix option. So ANSA try to clear for the error as much as possible.
• If some error left then we are using the TOPO Modules Buttons tools of ANSA to manually fix the error. we patches the cons and clear all the intersection error so we can generate the mesh properly.
• We have various tool to patch the single cons and intersection.
• For this model we generally use Coons, delete face, topo, project, new faces, Extrude, Extend, cut, project cut and intersects command.

Fig : Cleaned geometry of side-door plastic component

Step 4 : Midplane Extraction, Meshing and Check for Quality criteria.

We have three cases for midplane extraction.

CASE I : Mid-surface Extraction by manually.

Calculation for the thickness of model :

• For this first of all we have to calculate thickness of the model. 
• To calculating the thickness we placed Weld spot on the outer surface of the model and then project it on the outer surface.
• Now by the use of Measure tool we can calculate the thickness of the model by using these weld spot.

Fig : Thickness of the model

• So as shown by the above fig approximately 2.8 mm overall thickness of the model

Extracting mid-surface using Offset tool :

• For extracting mid plane we are using Offset tool in Faces and giving the offset value to 2.8/2 mm to the main surface and for rib 3/2, 2/2, 3.5/2 mm.
• When we are offseting the surface and rib it get seperated from each other by the offset distance of the surface as shown in the fig below.

Fig : Seperated Rib from the surface

• To solve these we are using different tool from TOPO modules buttons. For this Extend, Extrude, Intersects and delete tool is very useful.

Assigning the PID and thickness

• For setting up the PID first we have to ensure that in visualization Cross Hatches mode is ON so by that we can select the face for naming.
• So, now go to Modules Buttons - Faces - Set PID and select for Faces/Shells, now click on the faces that we want to give name and then click the middle mouse button for property help.
• In property help go to New and Give the name for the faces and then click on OK.
• Now name the property and thickness to the component.
• So now in the property help double click on the face that we have named to assign the name to that face.
• At last we go to the property and check all the faces are named correctly or not.

Fig : We provided seperate PID and thickness for all component.

Mesh generation

• For creating the mesh on the model first of all we have to switch the module from TOPO to MESH.
• So, now go to Modules Buttons - Perimeters - length and select for perimeters, now select the edges or directly left click and drag a box around the body so all the edges directly selected.
• After that click the middle mouse button for open the length parameters dialog box and provide the length as 4 mm and then click on \'ok\' to apply.
• So, now for mesh generation go to Modules Buttons - Mesh generation - Best mesh and select \'mixed\' in element type, now left click and drag a box around the body that we have to mesh.
• After that click the middle mouse button to apply.

Fig : Model after meshing

Setting up for the quality criteria in shells

• For this go to the quality criteria tool and tick on parameters like skewness, min length, max length etc. as shown in above table and set the failed criteria for it.

• No we have various of skewness and length error so by the use of tool (MV surf, Split, Swap, Reconstruct, Cut, etc) we remove all the error.

• In the above fig Off indicates the quality criteria error.

Fig : Quality criteria error.

Solving the Quality Criteria Error

• Now we have various of skewness and length error so by the use of tool (MV surf, Split, Swap, Reconstruct, Cut, etc) we remove all the error.

Fig : Model after all the quality criteria error solved.

Final Model after all the geometry error, mesh error and quality Criteria error Solved.

CASE II : Mid-surface Extraction using auto mid-surface.

Midplane Extraction

• For extracting mid plane out of the full geometry we are using tool Mid.surface - Casting  and after that drag on the screen to select for the geometry and then giving the input as shown below.

Calculate Midplane thickness

• For giving the thickness to the FE geometry we are using tool Mid.surface - Calculate thickness  and after that giving the input as shown below (Make sure that both the FE and Geometry is visible for this step).

Fig : Model in FE mode after giving thickness to it.

Setting up for the quality criteria in shells

• For this go to the quality criteria tool and tick on parameters like skewness, min length, max length etc. as shown in above table and set the failed criteria for it.

• No we have various of skewness and length error so by the use of tool (MV surf, Split, Swap, Reconstruct, Cut, etc) we remove all the error.

• In the above fig Off indicates the quality criteria error.

Fig : Quality criteria error in shells.

Solving the Quality Criteria Error

• Now we have various of skewness and length error so by the use of tool (MV surf, Split, Swap, Reconstruct, Cut, etc) we remove all the error.

Fig : Model after all the quality criteria error solved.

Final Model after all the geometry error, mesh error and quality Criteria error Solved.

CASE III : Mid-surface Extraction using combination of both auto mid-surface and manual mid-surface.

Midplane Extraction

• In this method, first of all the whole model is mid-skinned by auto mid-surface extraction and then by using manual mid-surface extraction edit wherever the mid plane surface is missing or deformed.

Auto mid-surface Extraction 

• For extracting mid plane out of the full geometry we are using tool Mid.surface - Casting  and after that drag on the screen to select for the geometry and then giving the input as shown below.

• So, when we are extracting mid-surface bu automatic method the whole extracted mid surface is in FE mode as shown below.

• So, to do manual mid skinned on the surface getting defformed we have to convert whole mid skinned model from FE mode to geometry mode.
• For this go to Mesh module - Elements - To Surface and then drag the mouse on the model to select and then click on middle button of mouse to confirm.

Checking for the geometry error in the mid surface

• Now we can check for any errors in the geometry so click on the tick mark icon above And then open for geometry checkup and click on Execute.

Fig : Geometry error

Clean up the geometry

• In this first of all we are using the inbuild function of ANSA to Automatic fix the gemotry error. For this right click on error in geometry check and then select Fix option. So ANSA try to clear for the error as much as possible.
• If some error left then we are using the TOPO Modules Buttons tools of ANSA to manually fix the error we patches the cons and clear all the intersection error so we can generate the mesh properly.

Fig : Cleaned geometry

Assigning the PID and thickness

• Assigning diffrent PID to the Surface and Ribs to provide proper thickness to it.

Fig : Model after assigning different PIDs for thickness

Mesh generation

• For creating the mesh on the model first of all we have to switch the module from TOPO to MESH.
• So, now go to Modules Buttons - Perimeters - length and select for perimeters, now select the edges or directly left click and drag a box around the body so all the edges directly selected.
• After that click the middle mouse button for open the length parameters dialog box and provide the length as 4 mm and then click on \'ok\' to apply.
• So, now for mesh generation go to Modules Buttons - Mesh generation - Best mesh and select \'mixed\' in element type, now left click and drag a box around the body that we have to mesh.
• After that click the middle mouse button to apply.

Fig : Model after meshing

Setting up for the quality criteria in shells

• For this go to the quality criteria tool and tick on parameters like skewness, min length, max length etc. as shown in above table and set the failed criteria for it.

• No we have various of skewness and length error so by the use of tool (MV surf, Split, Swap, Reconstruct, Cut, etc) we remove all the error.

• In the above fig Off indicates the quality criteria error.

Fig : Quality criteria error in shells.

Solving the Quality Criteria Error

• Now we have various of skewness and length error so by the use of tool (MV surf, Split, Swap, Reconstruct, Cut, etc) we remove all the error.

Fig : Model after all the quality criteria error solved.

Final Model after all the geometry error, mesh error and quality Criteria error Solved.

Conclusion :-

• Extracting the mid-surface by using Auto method took less time. By this method user can save lots of time, but the accuracy is much poor.
• Extracting the mid-surface using manual method is much accurate but it take lots of time.
• Extracting the mid-surface using combination of both auto mid-surface and manual mid-surface is more preferred because by this user can obtained good surface and also save lots of time.

Google drive Link for the final model :- 

Manual :- https://drive.google.com/open?id=1ggkNcJeI_K2MGLYWtPY2FMnhXNbhIN8P

Auto :- https://drive.google.com/open?id=1juBvAVRODqgKqiASN5LIwzvPm_jOPpeR

Combination :- https://drive.google.com/open?id=1hw9Q5WU13pBMkxMsayX-IdxxGjs3z5Kn