ANSA Week 7 Challenge - Batchmesh and casting

OBJECTIVE

To mesh the component as per the given quality criteria using three different methods. The first being the standard and manual process. The second being via the casting algorithm and the third using the batchmesh procedure.


COMPONENT IMAGE

QUALITY CRITERIA

PROCEDURE
CASE 1 - MANUAL MESHING

1. As is customary with meshing, in order to facilitate the meshing process, we need to 'prepare' the component and that involves getting rid of deformities, stray single cons, hot points, etc. This model requires a topological cleanup so we can make use of the topo tool via Faces > Topo from the topo deck. With the tool activated, we can highlight the entire component and proceed. This fixes all the single cons, which are now correctly portrayed as double cons, since it is supposed to be a closed volume.



The model is also oriented properly using the orient tool, accessible via Faces > Orient.

2. Then, a geometry check and cleanup need to be carried out and ANSA has a tool that takes care of that. The checks tool can be accessed from the upper toolbar: Checks > Geometry. With all components visible, the checks can be 'executed'. The geometric discrepancies will be highlighted by the tool and they can all be selected, right clicked and fixed by clicking 'fix' as shown in the screenshot.



3. At this juncture, with the model having undergone the geometry cleanup, it is a good idea to save the current instance so it can be made use of when attempting the other cases.

4. Since it's a manual process, I decided to go with manual midsurfacing (via offset tool) instead of the auto midsurface tool. But before that, we need to measure the thickness. This is done using the 'measure' tool from the top toolbar.



On measuring various regions, we can conclude that the thickness is definitely 1mm.

5. To offset the component, we can make use of the Faces > Offset tool from the topo deck. One side of the component is selected with the help of the 'Feature Area' option on the bottom toolbar. On the window that appears when we proceed, we can enter the offset value (which is half of the thickness). Care must be taken to ensure that the value entered is according to the offset direction.



After we click OK, ANSA creates the offset face and we can choose to delete or keep the original faces (I kept them). We can then isolate the midsurface for the next step.

6. We can now assign the thickness property to this midsurface. Doing this will also help separate it from the main component. This is done via the 'Set PID' tool via Faces > Set PID. The midsurface is selected and on proceeding, we get the property window, where we can create a new property and assign the thickness (T). After the new property is created, we just need to double click the property (in this case 'Thickness Property') for ANSA to apply it onto the midsurface.

7. With the property assigned, we can move onto preparing the component for meshing. To start off, we can assign the quality parameters as per the challenge. We need to access the 'mesh parameters' and 'quality criteria' options from the top toolbar. And then we can assign the values as per the table. The target length would be 3mm, mesh type would be 'mixed' & the minimum and maximum lengths would be 1mm and 5mm respectively.

And the given values are entered in the 'quality criteria' window:

Finally, we can change the con resolution to 3mm via Perimeters > Length from the mesh deck:

8. Next, we need to prep the model itself by adjusting hole orientations, suppressing certain cons and making cuts elsewhere to ensure the mesh doesn't have failed elements as well as ensure that the mesh flow is 'linear'. For hole orientations, the Perimeters > Slide tool can be used. It lets us orient holes as per our requirement. To control the number of nodal segments on each con, we can make use of Perimeters > Num +/-. And finally, for the cuts, we can use the 'cut' tool via Macros > Cut. All these tools are available in the mesh deck.

9. Care is taken to ensure we mesh outwards from any particular region, preferably a region in the centre of the component. After meshing a region, analyze the mesh and see if it can be improved. If it can be improved, we can make use of the 'Reconstruct' tool from the Shell Mesh section in the mesh module. It basically remeshes the selected mesh keeping the quality criteria in mind and tends to produce a better mesh. The tool gives the option to rerun the tool so we can ensure the produced mesh is up to the standards we are looking for.



This process is repeated until we mesh the entire component.

10. Usually, remeshing the region fixes discrepancies and in addition to that, if our cuts are proper, we needn't worry about stray tria formations (opposite trias, trias touching feature lines, etc.). But if that does happen, we can make use of the swap, split and join tools (can be accessed from the 'Elements' section in the mesh deck). These tools can be used to 'move' trias away from feature lines or just cancel them out with their opposites (if available in the vicinity).

After making these fixes, we can make use of the 'Smooth' tool via Shell Mesh > Smooth to optimize the mesh flow.

11. This is what the final mesh looks like:

CASE 2 - CASTING

1. This process is very straightforward. All we need to do is let ANSA take care of the midsurfacing and meshing. We can make use of the saved component (mentioned in #3 of case 1) which has already undergone geometry fixes. In addition to that, we need to ensure the quality parameters and criteria have been entered.

To access the casting tool, we need to go to Faces > Mid. Surface > Casting available in the topo deck. After entering the information highlighted in the following screenshot and proceeding, the casting algorithm takes it from there. The process takes some time.




2. Using the !Not tool, we can isolate the generated midsurface+mesh:

As we can see, the mesh flow isn't that good overall, except in select regions and there are several elements failing the quality criteria.

Especially when it came to hole capturing and cuts, the casting algorithm seemed to be off the mark in a lot of places.



CASE 3 - BATCHMESHING

1. Another straightforward process that generates the mesh albeit this one requires the midsurface to be generated beforehand. Using the same saved file (from #3 in Case 1), we can go through the offset process again to generate the midsurface. After that, we need to assign it a model ID via the model browser (after the midsurface is isolated):


2. After creating this new model entry (and naming it), we can move onto the batchmesh process. The batchmesh tool can be accessed via its namesake in the top toolbar or by pressing Ctrl+B. On the batch mesh window, we need to go to New > Meshing Scenario. This creates a batchmesh instance.

Now, this instance needs to work on something. For that, we need to assign a model and that is done by double-clicking the 'Meshing_Scenario_1' content (which would be 0 now). Doing so opens the contents window where we can select the midsurface (Which I named 'Midsurface'). Selecting it moves it from the 'pending items' box to the 'meshing scenario' box.



Clicking 'OK' brings us back to the original batchmesh window where we can now have the option to run it. Before doing this, it must be ensured that the quality parameters and criteria have been entered. If they have already been taken care of, we can let ANSA run the batchmesh process.

The algorithm understandably doesn't take as much time as the casting process (since the casting process also involves midsurfacing). On completion, ANSA lets us know the status is complete. If there are element failures, the 'completed' status is coupled with an exclamatory mark.

3. Taking a look at the batchmesh results, it has done a decent job overall. Definitely better than the casting mesh. There are minimal element failures, they can be easily fixed. The flow is average but again, better than the mesh produced via casting.

After fixing:

4. The batchmesh process has definitely done a better job with regards to dealing with holes in the mesh flow. But it too has issues with trias.

NOTE:
After each meshing process, the 'draw shell as solid' presentation parameter is activated (Quality Criteria > Presentation Parameters) to portray the mesh elements' thickness assigned to them through their thickness property:



LEARNING OUTCOMES

1. The manual method of midsurfacing and meshing definitely takes the most time here but also provides a good quality mesh (which is also subject to the person meshing the component). Whereas the batchmesh and casting processes take way less time but sacrifice mesh quality for quick results.

To summarize, the casting process takes the least amount of time, followed by batchmesh and then the manual process. The quality of the mesh also improves in the same order.

2. Learnt to use the batchmeshing and casting processes.

FINAL MODEL IMAGES
CASE 1 - MANUAL MIDSURFACING AND MESHING



No off elements and good mesh flow. Feature capturing is good as well.

CASE 2 - CASTING

A lot of off elements. Mesh flow is decent but bad at some places. Feature capturing (especially holes) is below average.

Making use of the smooth tool and using the reconstruct algorithm in some places, the number of off elements can be reduced a lot:


Unfortunately, the feature capturing is the reason why there are some residual off elements.

CASE 3 - BATCHMESHING


Overall, I felt the batchmeshing process did a decent enough job. The mesh flow and feature capturing is above average. There were only 2 off elements and they were easily fixable.

RESULT

The given sheet metal component was midsurfaced and meshed using the three suggested processes - manual, casting and batchmeshing. The mesh results were compared. Care was taken to ensure both manual and batchmesh meshes did not have off elements and they had better mesh flows. Casting had an excessive number of off elements and a below-average mesh flow. But it took the least amount of time.