Interior Plastic model - Side door meshing using ANSA

IP SUBSTRATE - SIDE DOOR MESHING - ANSA

The objective of this project is to perform meshing for given IP substrate side door model using ANSA. The model is cleaned and checked for errors, then using the given element size, is meshed accordingly. For these IP models, we are going to perform a mid surface casting mesh and check for mesh quality

For this meshing process, the following steps are necessary.

1. Geometry checks and Surface cleaning (if any)
2. Mid-surface extraction
3. Calculate thickness
4. Mesh quality check

Model

Geometry checks and Surface cleaning (if any)

First of all, we need to input the mesh quality parameters as such and then start working on the geometry.

To ensure that the separate entity extraction of each part is precise, we perform geometry checks on the models and fix any error that occurs.

There are a lot of unchecked faces and so they are all deleted and other extra faces are corrected and joined using topo option.

We make necessary changes in the geometry and plug in holes using fill hole and creating new surfaces using New option until the geometry is clean.

Mid-surface extraction

For this step, we need to select the mid-surf option in the faces tab and hold it to select the casting option.

Now, we need to enter the parameters such as minimum thickness allowed in the geometry, the element type and length.

The following parameters are the standard for all the models.

1. Minimum thickness = 1 mm

2. Target element length = 4mm

3. Element type = Mixed

4. T-junction treatment = Direct T (second option)

After this, ANSA calculates the mid-surface for the whole selected geometry and performs meshing too.

Remember that we have are using ANSA\'s help in creating the mid surface now. After this step is done, we have to create the same mid surface with just our own tools manually and again using little help from ANSA.

Now we have to check the mid-surface created using the option check mid-surf in the mid-surf tab itself. Any errors are fixed automatically by clicking the fix button. Remember to have the outer geometry in transparent mode to see through the mesh at mid-surface. This is also done so that the mid check and thickness could be alotted too.

This is the process for just one of the types of mid-surface extraction. It took exactly 6 mins for ANSA to calculate mid surface and extract it from the given geometry. For manually performing this operation, we cannot select the whole geometry and perform offset function. We have to separate particular entities of the IP and then work on them separately so that we get a complete mid surface and then mesh it.

For example, separate entities like these are taken from the bigger IP part and used to create the mid surface.

For this, we utilize the offset function and select only the front components of one side. After that, we estimate the thickness of that section, say 3 mm, and give input as 1.5 mm or -1.5 mm, depending upon the direction of extraction.

The best mesh option is used to create mixed mesh of given length 4 mm. Likewise, we can do for the entire component again and again, manually once, and also using mid-surface extraction at times to get from ANSA. Both the other files are also connected and checked for mesh quality.

Extra protrusions in the geometry are cleaned and filled using fill hole option. These are changes made for the manual extraction of mid surface easier.

After all the changes are made, the model is meshed properly and then the mesh quality check step starts.

Calculate thickness

Now that the mid-surface mesh has been created, we can assign thickness to the mid-surface created to resemble the CAD model itself. ANSA does this too automatically by the calculate thickness option in the same mid-surf tab.

We have to provide parameters like the maximum thickness allowed in the assignment, which can be provided as 5 mm as standard for all the models. We can also select the PID creation option with intervals of 0.5 mm for each thickness assignment. This provides separate PIDs for each thickness assigned and after that, the user can examine and change thickness at certain areas where it has been incorrectly assigned by the computer.

Mesh Quality check

Quality criteria to be followed:

Target Element Length-4mm

S.N	Quality Criteria	Value
1	Aspect Ratio	3
2	Skewness	45
3	Warping	15
4	Taper	0.5
5	Min. Length	2mm
6	Max. Length	6mm
7	Min angle Quad	45
8	Max angle Quad	135
9	Min angle Tria	30
10	Max angle Tria	110
10	Tria %	15

The above given quality criteria is entered in the mesh quality checkbox and then the errors are shown. All errors are fixed manually using the reconstruct option or the MV. surf option too.

User utilizes tools learnt from previous experience to solve all the errors in the meshing until it is all fixed.

Like wise, the same process is followed for the manually edited geometry and mid surface extracted model. We delete extra protrusions and then create mesh equally across the geometry.

Hence, we have performed mid surface extraction and mesh quality checks using three methods:

1. Automatic mid-surface

2. Manual mid-surface

3. Manual + Automatic mid-surface