Copyright Goodheart-Willcox Co., Inc. 156 AutoCAD and Its Applications—Advanced PROFESSIONAL TIP PROFESSIONAL TIP If the location of the base point in relationship to the path is important, line up the shape with the path before starting the SWEEP command. Turn off the Alignment option in this situation. Scaling the Sweep Profi le By default, the size of the profi le remains uniform from the beginning of the path to the end. However, using the Scale option of the SWEEP command, you can change the scale of the profi le at the end of the path. This, in effect, tapers the sweep. Figure 7-5 shows a .25 scale applied to a sweep object. A 2D polyline with multiple segments must be edited using the Fit or Spline option in order to be used as a path. Sharp corners will not work with the Scale option. A 3D polyline path must be a spline. Once the SWEEP command is initiated, select the profi le and press [Enter]. Before selecting the path, enter the Scale option. You are prompted for the scale. Enter the scale value and press [Enter]. The scale value must be greater than zero. You can also enter the Reference option. With this option, pick two points for the fi rst reference line and then two points for the second reference line. The difference in scale between the two distances is the scale value. Once the scale is set, pick the path to create the sweep. The Expression option allows you to enter a mathematical expression to specify the scaling of the sweep. When used with a surface sweep, it creates a parametric relation- ship between a dimensional constraint and the swept surface. If the sweep results in a solid, the parametric relationship is not maintained. Twisting the Sweep The profi le can be rotated as it is swept along the length of the path by using the Twist option of the SWEEP command. The angle that you enter indicates the rotation of the shape along the path of the sweep. The higher the number, the more twists in the sweep. Figure 7-6 shows how a simple, closed profi le and a straight line can be used to create a milling tool. The profi le was swept with a 270° twist. Once the SWEEP command is initiated, select the profi le and press [Enter]. Then, before selecting the path, enter the Twist option. You are prompted for the twist angle or to enter the Bank option. Banking is the natural rotation of the profi le on a 3D sweep path, similar to a banked curve on a racetrack. See Figure 7-7. The path must be 3D (nonplanar) to set banking. The banking option is disabled for a 2D path, although you can go through the process of turning it on when creating the sweep. Once you use the Bank option to turn banking on, it is on by default the next time the SWEEP command is used. To turn it off, enter a twist angle of zero (or the twist angle you wish to use). The Expression option allows you to enter a mathematical expression to specify the number of rota- tions in the sweep. When used with a surface sweep, it creates a parametric relation- ship between a dimensional constraint and the swept surface. If the sweep results in a solid, the parametric relationship is not maintained. A B Figure 7-5. A—The profile and path for the sweep. B—The resulting sweep. Notice how the .25 scale results in a tapered sweep.