Week - 4 - 2D meshing for Plastic components

Aim: Mesh the given Bottle cap model with the given quality criteria and assign proper thickness to it

Tools used:

In Topo Mode

• Hot points - Insert, Project, Delete & Info tools.
• Cons - Paste, Release & Fill hole tools.
• Faces - Info, Cut, Delete, Undelete, Set PID, Midsurface, Offset, Orient, Extend, Convert, Intersect & Topo tools.
• Curves - Create, Middle & Delete. These are all the tools that have been used.

In Mesh Mode

• Hot points - Insert, Delete, Project, Info tools.
• Perimeters - Number, Num+/- & Length tools.
• Macros - Cut, Release, Orient, Join, Edge2Perimeter & SetPID tools.
• Grids - Move, Origin and Paste tools.
• Mesh Generation - Best Mesh, Spot Mesh & Erase tools.
• Shell Mesh - Reconstruct, Smooth
• Elements - Split, Join, Swap these are the tools that have been used.

Procedure:

• Firstly, open the Ansa software and then import the Bottle_cap model into the graphical area.

• Click on the model browser from the tab present at the top of the window or press F12 to display the database on the left side of the graphic area at the top to select the component to be worked on. Since the given model contains only one component it is ok to carry on.

• Click on the CHECKS tool from the dropdown list select the Geometry option. Upon entering into the Geometry window, check on the Active button and change the option for the Execute on option to Visible and click on the Execute button. The errors present in the model will be displayed.

• Now click on the errors one by one and right-click and select the option Fix which means the error will be automatically fixed by Ansa if possible and if it is not possible it needs to be fixed manually. In this way clear all the errors before taking the midsurface from the given model.

• There are two ways to extract the midsurface from the given component, extracting the midsurface manually i.e., using the Offset option and the other by using the automidsurface i.e., using the Midsurface option. Both tools Offset and Midsurface present in the Faces tools in the Topo mode.

• Use the Offset tool to extract the midsurface for a better experience of working on the component.

• Before using the Offset tool, measure the thickness of the Bottle_cap model. After measuring the thickness of the Bottle_cap component use the Offset option to extract the midsurface from the given component.After extracting the midsurface from the given component try to mesh the extracted midsurface.

• Use the Offset tool to extract the midsurface from the given component where it is possible.

• But there are some surfaces on the component like Ribs, Threads, Teeth etc where the Offset option cannot be used. So there is a way to extract the midsurface from these surfaces.

• If we look at Threads that are in Trapezoidal shapes it is impossible to extract the midsurface using the Offset option.

• So we use the Middle option in the Curves to create a curve in the middle of two selected CONS. Firstly, click on the Middle in the Curves, then select the first and second Cons on the Thread and then Middle-click to confirm the curve.

• The Fine option in the Auxiliaries can be used to click multiple times over purple coloured curves to increase the resolution on the curve. By doing this, the curve will come on the Top of the surface of the thread.

• The Middle curve then projected in the normal direction to the base Midsurface by using the Project option in the CONS by first selecting the Curve press the Middle-click and then selecting the Face or the Midsurface where it is to be attached and then Middle-click to confirm it.

• After projecting the Middle curve to the side Midsurface, create a surface by using COONS in the Surfaces tools.

• Click on the COONS option in the Surfaces tools and then select the Middle curve and then select the Double Cons projected onto the side Midsurface and Middle-click to confirm the surface.

• Do not worry about Triple Cons formation after the surface creation. It is formed due to the sharing of the three edges over there, which is common.

• The same procedure can be repeated for Ribs and all the other complicated surfaces where we cannot extract the midsurface normally.

• For the Teeth surface use the Middle option in the Faces tools to extract the midsurface. Click on the Middle option in that select the Single-Mode option and select the first face and click on the middle-click and then select the second face on the other side and click on the middle-click to confirm it.

• After extracting the Midsurface try to extend it by using the Extend option in the Faces tab.

• Select the Single CON and middle-click and select the face to which it needed to be extended and middle-click once after confirmation to finish it.

• A Triple CON will be formed after the extension of the Single CON to the surface because of the connection of the 3 surfaces.

THE TOTAL MIDSURFACE OF THE BOTTLE CAP MODEL

• After extracting the midsurface for all the surfaces, try to apply the given target element length on the midsurface.

• To apply the length, change to the Mesh mode from Topo mode, select the Length option in the Perimeters, select the whole midsurface, enter the given target element length value and click the middle-click on the mouse to confirm the task.

• After applying the target element length on the midsurface try to mesh the component. Keep the Mesh mode as it is and click on the Best mesh in the Mesh Generation.

• Select a face on the midsurface and middle-click to generate the mesh. The mesh generated on the selected face, if the mesh pattern was not good try to reconstruct the mesh by using the Reconstruct tool in the Shell Mesh tools.

• If there are any mesh elements failing for the given quality criteria, try to make them not fail by using the different tools.

• In the Mesh mode and at the bottom there are the Elements tools present. In these Elements tools, there are options like Split, Join, Swap etc are present use these tools to clear the mesh quality manually.

• For example, if any less number of elements failing for the Minimum Elements Size try to clear them manually by using the Split option in the Elements tools by splitting the elements and also to clear the Trias in the mesh generated by splitting them and also by joining them by using the Join tool.

• There might be some Failed elements near Triple CONS or at smaller regions that are bounded by two Triple CONS. Keep those OFF elements as it is if not possible to solve.

• After splitting the elements, the mesh pattern will be disturbed and then use the Smooth tool in the Shell Mesh tools to smoothen the disturbed mesh pattern. If there are a huge number of elements that are failing for the quality try to use the Reconstruct tool present in the Shell Mesh tools.

• There are a lot of surfaces present in the component and try to apply the Thickness for each of the surfaces individually because of the varying thickness of the different surfaces.

• To Assign thickness for the varying thickness ribs, Split the surface into multiple surfaces by using the “CUT” command and give different thickness values such that it captures varying thickness components in the best possible way.

• Use the Set PID tool to apply the Thickness by creating a Property ID. Click on the Set PID tool and select the whole surface because the total surface is of the same thickness, a pop-up window will be displayed in that enter the thickness value and select a proper colour in the Colour-edit and click on the OK button. If there is any varying thickness in the given model then the property applied should be different for different surfaces.

ALL THE PROPERTY ID'S APPLIED FOR DIFFERENT SURFACES ON THE MODEL

• In this way apply Property ID for different components based on their Thickness.

THE MIDSURFACES WITH THICKNESS APPLIED

• Switch on the PID mode which is at the bottom of the window in order to look if the property has been applied properly or not (displayed in an applied colour).

Conclusion:

The Midsurfaces have been extracted for different surfaces from the given model, the Geometry cleanup is done on the extracted surfaces and the Mesh has been generated on the extracted surfaces and the Quality has been checked within the given quality criteria values and the Thickness has been assigned to all the extracted Midsurfaces.