Week 12:Project 2-Meshing of Rear Wheel Holder challenge

AIM:

To mesh the given floor panel of a sheet metal using the following quality criteria and assign thickness.

Target Element Length= 5mm

S.N 1	Quality Criteria Aspect Ratio	Value 5
2	Skewness	45
3	Warping	15
4	Taper	0.5
5	Min. Length	2mm
6	Max. Length	8mm
7	Min angle Quad	45
8	Max angle Quad	135
9	Min angle Tria	20
10 11	Max angle Tria Tria %	120 10

Given model:

OBJECTIVE:

• To perform a geometry cleanup on the given surface for any errors.
• To extract the midsurface for the given comoponent.
• To perform a cleanup on the extracted midsurface for any minimum length errors.
• To perform a mesh with minimum number of trias and satisfying all the given quality criterias.
• To assign thickness to the model.

THEORY:

The model provided is a spare wheel floor panel for an automobile. This panel is manufactured using the stamping process where the raw material which is steel or aluminium sheet is introduced into the die and the hydraulic punch produces a punch so as to obtain a desired shape of the component.

PROCEDURE:

STEP 1: Component study

• The component is the floor panel of the car trunk, where we keep the spare tyre.
• Since it is a sheet metal component its is of a uniform thickness.
• This component has a uniform thickness of about 0.75mm
• Since this model is having a lot of complex converging areas and sharp edges, their might be an increase in the number of trias.

STEP 2: Opening the file

• Since the given file is in '.hm' format, we can directly open the file using the following steps.
• From the main bar, select FILE > click open > click model > select the file to open > click open.
• The file is opened. Click f from the keybord for the model to fit on the screen.

STEP 3: Geometry cleanup

• After importing the model we can find out that there are many empty components and also some components are spread out in different components.
• We can organise them.
• First move all the components to a single component using TOOLS>ORGANISE>COLLECTORS.
• Select surfaces and select all the surfaces to be moved.
• In destination component, choose the component to which we have to move all these surfaces.
• Click on 'move'.
• After that we can delete All the components using delete option.

• From the above showned option, choose components>preview empty.
• In the bottom left corner, we can see how many components are empty.
• Click on delete entity to delete those empty components.
• This model has no much of deformations.
• There are only some unnecassary surfaces and some missing surfaces.
• To find out theses errors easily, change the view to topo mode.

• We can use the mask option in order to check for the deformations in these areas.
• Select the mas tool visible on the side of the window or we can also use F5.
• Select the visible surfaces in order to mask them , so that the unnecassary inner surfaces can also be visible.
• Delete theses surfaces and toggle the edge again by using Geometry>quick edit>toggle.
• Also in some areas we can find some missing regions.
• These regions can be filled by using geometry>quick edit>filler surface and click on the edge of the surface to be filled.
• If it doesnt work, we can also go for the ruled otion.Geometry>surface>ruled.
• Then select he two lines that requires surface in between and then click on create.

• These holes can be removed using unsplit option since it is very small.

Step 4:Midsurface extraction and its geometry cleanup.

1. MANUAL MIDSURFACING:

• Since this is a sheet metal component, it is of uniform thickness. We can also confirm this by checking the thickness of various component.
• Checking thickness at the edges will be easy but checking thickness at area exept the sides is difficult. So we can do this using an another tool.
• Create temp nodes (Shift+F2) on both sides of the parent surface.
• Then use distantce (f4), 'Two nodes' option to measure, Thus we can measure the thickness of inside areas.
• After getting thickness we can start manual mid surfaceing. For manual mid surfaceing we will use the Offset in Surface edit option.
• Geometry>Surface Edit> Offset.

• In offset option choose continuous offset.
• Then choose the surface to be offset.
• Make duplicate of that surface. Then click on offset.
• While doing the manual mid-surface we can do the whole part in a single stretch because the thickness is same.
• Make sure that there are no deformations.

2. CLEANING UP THE MIDSURFACE.

• Small gaps and unnecasssary hole can be filled using Filler surface in Quick Edit tool.
• Small deformations can be cleared using Replace points option from Quick Edit tool.
• Lines failing for minimum length can be toggled using Toggle edge from Quick Edit tool.
• Proper connections have to be established between lines.

Step 5: Setting up quality criteria.

• For setting up the quality criterias, we have to go to criteria editor.
• This can be done from Preference> Criteria file settings.

• Tick mark the options that are required and assign the given values.
• Save the criteria file in order to avoid wastage of time.
• Click on Apply.
• Click on OK.

Step 6: Meshing.

• After setting up the criteria files, start meshing.
• 2D>Automesh.
• After clicking on the surface box, select the surfaces to ber meshed.
• Give the Element size as 5.
• Give the mesh type as Mixed.
• Element to surface component is chosen in order to add the mesh to the surface component.
• Keep connectivity is chosen in order for a proper connectivity between the mesh.
• Align and Size options are ticked in order to get a good mesh flow.
• If the mesh is not that satisfying, we can change the Surface to Elements and select the required elements and click on mesh option in order to remesh and get a more satisfying mesh.
• The mesh we get will have a lot of trias, fixed trias and rotational quads. Also the mesh flow wont be that good.
• In order to get a good mesh , we have to reduce the number of trias and also clear the rotational quads.
• This can be achieved by going to 2D>Quality index>Cleanup tools.
• We can reduce the trias and attain a good mesh flow by using the various cleanup tools.

Main points to keep in mind during tria management:

1.No trias in corner or edges.

2.No opposite trias.

3.No back to back trias.

4.No trias at hemmings or fillets or keep it minimal as lower as possible.

5.No rotational quads.

6.No trias should share a boundary with feature line.

7.Connectivity between elements.

8.Split and perform the mesh.

9.Use mixed type of mesh for irregular surfaces and use quad type mesh for rectangular and square surfaces.

The main tools used in Quality index>Cleanup tools.

• Place node: Used to manually move the node.
• Smooth: Used to smooth the elements to get a good mesh flow.
• Swap edge: To swap the sides of the element.
• Node optimize: Place the node in an optimize position which try to reduce the errors.
• Element optimize: optimize the element sides to eliminate errors.
• Split/Collapse edges: Used to split the elements.
• Drag tria elements: To move the trias in the mesh.
• Split quad elements: To split quad elements.
• Combine tria elements: Used to combine tria elements.

Other than this there are:

• smooth> Shift+f12: used to smooth the mesh to get a good mesh flow
• project> Shift + f7: to align the lines with features
• Translate> Shift+f4: to move nodes to eliminate errors.

• Also in some areas we can see that the surface is symmetry. In those region we can reflect the elements.
• Tools > Reflect

• Choose the elements option and select the elements to be reflected.
• Select the N1, N2, N3 in the direction to reflect.
• Click on Reflect.
• The reflected surface will not have any connections with the surface and lines. In order to make connections we can project it Using, Tools> Project.
• Connection with the lines are necassary for the connectivity with the adjacent mesh and also for easiness of selection.

Step 7: Checking for normals and free edges.

1. To check for normals,

• To check for normals, go to tool>Normals.
• Choose elements.
• Select displayed 2d elements for selecting the whole elements.
• Color display in order for color representation.
• Click on display.
• Then we can see all whole model in blue and red.
• If the whole positive side is in one color and the negative side is in another color, then its fine.
• If the one side is having both the colors, then its not satisfying the normals.
• By clicking on adjest, almost all of it will be corrected.
• But if not, we need to change that by Changing the 'Displayed 2D elements' to 'Elements' and select the elements which we want to change.
• Then click on Reverse to change the normals.

2. To check for free edges,

• To check for free edges we need to go to Tool>Edges.
• Choose Elements and then select the whole elements.
• Click on Find edges.
• Now Hide other parts and Make edges mesh only visible.
• Now check if there is red line on any area which is not a boundary.

Step 8: Assigning thickness

• After the whole meshing is done we can assigin thickness to the mesh inorder to make the 2d mesh exact as the real product.
• This is a sheat metal model so the whole part will be having uniform thickness so we make a property and assign it to the component
• To make property. Right click on Model view area > Create> Property.
• Rename the property with the thickness value.
• Also set the thickness of the property. By clicking on property we can see its details below.
• In that we can see a T which represents the thickness give the thickness value . Click on enter.
• To Apply the property to the Components. Right click on component
• Select assign. Choose the property of the component from the pop up dialogue box
• Click on Apply. Click on Ok.
• To see the mesh in 3D. Choose the 2D detailed element representsation.

FINAL MODEL:

RESULT:

Finished midsurfacing and meshing the car trunk floor panel component with no fail of criteria and minimised tria percentage. Also checked for the normals and free edges and also assigned thickness to the component.