# HM: 3110: Mesh Without Surfaces

Surfaceless meshing is defined as the creation of mesh using points, lines, and nodes rather than surfaces. Some parts may have missing surfaces and some parts may not have any surfaces at all and are instead defined by line data. Either way, a mesh still must be created. HyperMesh has a number of panels that you can use to create a mesh based on geometry rather than surfaces.

In this tutorial you will learn about:
• The basic concepts of surfaceless meshing and how to mesh a bracket
• Scale (Uniform scaling)
• 2D mesh by using spline, line drag, and skin
• Ruled mesh
This exercise uses the bracket.hm file, which can be found in the hm.zip file. Copy the file from this directory to your working directory. The model consists on only line data. No surfaces are present.

## Open the Model File

In this step you will open the model file, bracket.hm.

1. Start HyperMesh Desktop.
2. From the menu bar, click File > Open > Model.
3. In the Open Model dialog, open the bracket.hm model file.
4. Observe the model using the differnet visual options available in HyperMesh, such as rotation and zoom.

## Create a Concentric Circle Using the Scale Panel

In this step you will create a concentric circle around a hole on the top face using the Scale panel.

There are three circles on the upper region of the bracket, which represent three holes in the bracket. Two of the holes have concentric circles around them. This configuration allows you to create a radial mesh pattern around the holes. The following steps will show you how to create a concentric circle around the third hole.

1. To open the Scale panel, click Geometry > Scale > Lines from the menu bar, or select Scale from the Tool page.
2. Click uniform and type 2.0 in the scale= field.
3. To open the Distance panel, press F4.
4. Go to the three nodes subpanel.
5. Verify that the N1 node selector is active.
6. Press and hold your left mouse button, move it over the circle representing the hole as indicated in the following image, and then release it when the cursor changes to a square with a dot in the center .
HyperMesh highlights the circle.
7. Left-click on the highlighted circle.
A node is created for N1.
8. Left-click twice more at different locations on the circle to create nodes N2 and N3.
9. Click circle center.
A node is created at the circle's center.
Note: This node will be selected as the origin node when the circle is duplicated and scaled.
10. To go back to the Scale panel, click return.
11. Set the entity selector to lines.
12. Select the circle with the node in its center.
13. Click lines >> duplicate >> original comp.
14. Activate the origin: node selector.
15. Select the temporary node you created in the circle's center.
16. Click scale+.
A new circle is created, which is concentric with the original.
17. To exit the panel, click return.

## Create a Radial Mesh Using the Spline Panel

In this step you will create a radial mesh between each of the concentric circles using the Spline panel.

1. To open the Spline panel, click Mesh > Create > 2D Elements > Spline from the menu bar, or select Spline from the 2D page.
2. Verify that the entity selector is set to lines.
3. Select all six circular lines.
4. Switch from mesh, keep surf to mesh, delete surf.
Note: This option creates surfaces based on the selected entities, uses the surfaces to create a mesh, and then deletes the surfaces.
5. Clear the keep tangency checkbox.
6. Click create.
The meshing module opens and element edge density numbers appear on the selected lines.
Note: The numbers on a pair of concentric circular lines must be identical to achieve a radial mesh.
7. In the density subpanel, type 8 in the elem density= field.
8. Click set all to.
All circular line's element densities are changed to 8.
9. Click mesh.
The preview mesh is updated based on the change.
10. To accept the mesh and go back to the Spline panel, click return.

## Mesh Using the Spline Panel

In this step you will mesh the rest of the top face using the Spline panel.

1. With the entity type set to lines, select the four lines defining the perimeter of the top face and the three circular lines defining the outside perimeter of the three radial meshes.
2. Click create. The meshing module opens.
3. To accept the mesh and go back to the main menu, click return twice.

## Mesh Using the Line Drag Panel

In this step you will mesh the back face of the bracket using the Line Drag panel.

1. To open the Line Drag panel, click Mesh > Create > 2D Elements > Line Drag from the menu bar, or click Line Drag from the 2D page.
2. Go to the drag geoms subpanel.
3. Set the drag selector to line list.
4. Select the line that is on the perimeter of the existing mesh and adjacent to the bracket's back face as indicated in the following image.
5. Activate the along: line list selector.
6. Select one of the two lines defining the back face that are perpendicular to the selected line to drag as indicated in the following image.
7. Leave the toggle set to use default vector.
8. Leave the creation method set to mesh, w/o surf.
9. Click drag. The meshing module opens.

## Mesh Using the Ruled Panel

In this step you will mesh the bottom face of the bracket using the Ruled panel.

1. To open the Ruled panel, click Mesh > Create > 2D Elements > Ruled from the menu bar, or select Ruled from the 2D page.
2. Verify that the top entity selector is set to node list.
3. Click node list >> by path.
The entity selector changes to node path.
4. Select the end nodes located on the back face edge that borders the bottom face, as indicated in the following image.
All nodes between the two selected nodes are selected.
5. Click node path >> show node order.
HyperMesh highlights and numbers the nodes to show the order in which they have been selected.
6. Set the bottom entity selector to line list.
7. Select the line defining the opposite edge of the bottom face as indicated in the following image.
8. Switch the creation method from mesh, keep surf to mesh, w/o surf.
9. Select the auto reverse checkbox.
Note: When elements are generated, the edges used to create them can be ordered in different directions. The order of the edges is determined by the order in which the nodes are selected or the direction of the selected line(s). If the direction is different for each selection, then a mesh that crosses itself, similar to a bow tie, will be created. To prevent this, the auto reverse option ensures elements are generated with a similar order on each side of the mesh.
10. Click create. The meshing module opens.