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Advanced Solid Shapes

With the Solid block, you can specify the geometry of a solid. This block provides a set of standard shapes so that you can easily specify simple shapes, e.g., Cylinder. For more complex shapes, the block provides two shapes: General Extrusion and Revolution.

When to Use Extrusion and Revolution Shapes

Use General Extrusion and Revolution shapes to represent solids that are to complex for standard shapes. The choice of shape depends on the symmetry of the solid. If the solid has translational symmetry, use General Extrusion. If the solid has rotational symmetry, use Revolution.

The solid has translational symmetry if its cross-section is constant along its length axis. The solid has rotational symmetry if its cross-section is constant about its length axis. The figure shows two solids that you can represent using Revolution and General Extrusion shapes.

Both solids are too complex for standard shapes like Cylinder, Brick, or Sphere. The solid on the left possesses a constant cross-section about its length axis. You can represent it using shape Revolution. The solid on the right possesses a constant cross-section along its length axis. You can represent it using shape General Extrusion.

Specifying Extrusion and Revolution Shapes

To specify General Extrusion and Revolution shapes, you must provide the cross-section coordinates. Enter these coordinates as a matrix in the Geometry > Cross-Section parameter of the Solid block dialog box. SimMechanics™ connects the coordinate pairs with straight lines to generate the cross-section shape.

    Note:   To see the Cross-Section parameter, you must first select General Extrusion or Revolution from the Geometry > Shape drop-down list.

The figure shows the cross-sections that you must specify to represent the extrusion and solid of revolution introduced in this section. The coordinate matrices for these cross-sections must follow a set of rules to be valid as input. For more information, see Cross-Section Coordinates.

Use the Length parameter of the General Extrusion shape to specify the length to extrude the cross-section along. Use the Revolution Angle parameter of the Revolution shape to specify the angle to sweep the cross-section about.

    Note:   To see the Revolution Angle parameter, you must first select Custom from the Geometry > Extent of Revolution drop-down list.

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