Copyright Goodheart-Willcox Co., Inc. 136 AutoCAD and Its Applications—Advanced Extruding a Surface A planar surface can be extruded into a solid object in the same manner as a region. Nonplanar (curved) surfaces can be extruded, but only into extruded surfaces. A planar surface can be quickly converted to a solid using the EXTRUDE command. Simply select the surface when prompted to select objects. The surface can be extruded in a specifi c direction, along a path, or at a taper angle. Any closed object, such as a circle, rectangle, polygon, or polyline, can be converted into a surface with the Object option of the PLANESURF command. After accessing the PLANESURF command, enter the Object option and select the closed object. The resulting surface can then be extruded into a 3D solid. As previously discussed, the Mode option of the EXTRUDE command allows you to set the output type to solid or surface. Creating Revolved Models Creating Revolved Models The REVOLVE command allows you to create solids and surfaces by revolving a shape about an axis. Shapes that can be revolved include lines, arcs, circles, ellipses, polygons, 2D and 3D polylines, 2D and 3D splines, regions, planar surfaces, and donuts. The selected object can be revolved at any angle up to 360°. Open curves and line segments create revolved surfaces. Closed curves can be used to create either solids or surfaces. Surface revolutions have no mass properties. When the command is selected, you are prompted to pick the objects to revolve. Then, you must defi ne the axis of revolution. The default option is to pick the two endpoints of an axis of revolution. This is shown in Figure 6-7. You can also revolve about an object or the X, Y, or Z axis of the current UCS. Once the axis is defi ned, you are prompted to enter the angle through which the profi le will be revolved. When the angle is specifi ed by either moving the cursor or entering a value, the revolution is created. If the command is selected from the Solid tab in the ribbon, the mode is automatically set to solid. However, if an open profi le is selected, a surface is created instead of a solid. If the command is selected from the Surface tab in the ribbon, the mode is automatically set to surface. In either case, you can use the Mode option to change the output type. PROFESSIONAL TIP PROFESSIONAL TIP When creating solid models, it is important to consider that the fi nal part will most likely need to be manufactured. Be aware of manufacturing processes and methods as you design parts. It is easy to create a part in AutoCAD with internal features that may be impossible to manufacture, especially when revolving a profi le. PLANESURF Ribbon Surface Create Planar Surface Type PLANESURF REVOLVE Ribbon Home Modeling Solid Solid Revolve Surface Create Revolve Type REVOLVE REV P1 P2 Figure 6-7. Points P1 and P2 are selected as the axis of revolution for the profile.