Copyright Goodheart-Willcox Co., Inc. Chapter 6 Model Extrusions and Revolutions 141 Using Extrude and Revolve as Using Extrude and Revolve as Construction Tools Construction Tools It is unlikely that an extrusion or revolution will result in a fi nished object. Rather, these operations will be used with other model construction methods, such as Boolean operations in solid modeling, to create the fi nal composite 3D object. The next sections discuss how to use EXTRUDE and REVOLVE with other construction methods to create a fi nished solid object. Creating Features with Extrude You can create a wide variety of features with the EXTRUDE command. Study the shapes shown in Figure 6-15. These detailed solid objects were created by drawing a profi le and then using the EXTRUDE command. The objects in Figures 6-15C and 6-15D must be constructed as regions before they are extruded. For example, the fi ve holes (circles) in Figure 6-15D must be removed from the base region using the SUBTRACT command. Look at Figure 6-16. This is part of a clamping device used to hold parts on a mill table. There is a T-slot milled through the block to receive a T-bolt and one side is stair- stepped, under which parts are clamped. If you look closely at the end of the object, most of the detail can be drawn as a 2D region and then extruded. However, there are also two holes in the top of the block to allow for bolting the clamp to the mill table. These features must be added to the extruded solid. First, change the UCS to the front preset orthographic UCS. Display a plan view of the UCS. Then, draw the profi le shown in Figure 6-17 using the PLINE command. You can draw it in stages, if you like, and then use the PEDIT command to join all segments into a single polyline. Next, use the EXTRUDE command to create the 3D solid. Extrude the profi le a distance of –6 units with a 0° taper. This will extrude the object away from you. Display the object from the southeast isometric preset viewpoint or use the view cube to display a pictorial view. The object should look similar to Figure 6-16 without the holes in the top. Set the Conceptual visual style current, if you like. The two holes are ∅.5 units and evenly spaced on the surface through which they pass. Change to the WCS and draw a construction line from midpoint to midpoint, as shown in Figure 6-18. Then, set PDMODE to an appropriate value, such as 3, and use the DIVIDE command to divide the construction line into three parts. The two points created by the DIVIDE command are equally spaced on the surface and can be used to locate the two holes. Region Regions A B C D Figure 6-15. Detailed solids can be created by extruding the profile of an object. The profiles are shown here in color.