Spline Options. Student Web Site. Using Bowties

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1 Spline Options Splines are complex curves that can be adjusted and calculated using a variety of methods. After creating a spline, right-click on the spline to access options for refining the spline shape. Using Bowties The Bowtie option contains a cascading submenu with three tools that allow you to adjust the spline shape using bowties. Pick one, two, or all three selections, depending on the application. To better understand the concept of spline bowties, see Figure 3A-1, which shows a spline that appears to be constrained. The curves that define a spline can be manipulated and constrained in a number of ways using bowtie handlebars. To add a bowtie, right-click on a spline curve or point, and then choose Handle, Curvature, or Flat from the cascading submenu. Use the Handle option to add a handlebar. Drag the bowtie grips or constrain the handlebar using dimensions and geometric constraints. Choose the Curvature option to add both a handlebar and a curvature bar. The curvature bar adds control to the Handle option by allowing you to dimension the spline curve radius. Finally, when you pick the Flat option, all three bowtie tools become active, adding a handlebar and a flat curvature bar. The Flat option removes the radius from the specified spline curve. Inventor

2 Figure 3A 1 Effects of the bowtie options on splines created with the same dimensions. Inventor

3 Figure 3A 1 (continued) Inventor

4 Figure 3A 1 (continued) Inventor

5 Figure 3A 1 (continued) Inventor

6 Specifying Fit Method Pick the Fit Method option to access a cascading submenu with three options. The options are used to define how spline points are positioned in reference to the spline. The Standard option is active by default and displays smooth curves between spline points. Pick the Minimum Energy option to create a spline with smoother and more even curves than those provided with the Standard fit, or select the AutoCAD option to use AutoCAD s spline fit technique. Displaying Curvature Choose the Display Curvature option to add combs to the spline. See Figure 3A-2. If you select a fit method other than Standard from the Fit Method cascading submenu, you may want to pick the Display Curvature option to help visualize the fit. Once you select Display Curvature, the Setup Curvature Display option becomes available from the shortcut menu when you right-click on a spline. Pick Setup Curvature Display to access the Curvature Settings dialog box. The Curvature Settings dialog box contains sliders used to increase or decrease comb density and scale. When AutoCAD is configured to display a screen menu, the commands appear in a separate screen. NOTE The Display Curvature and Setup Curvature Display options are available when you right-click on any curve, not just a spline. Inventor

7 Figure 3A 2 Adjustable combs help illustrate and analyze the spline curvature. Combs Adjusting Spline Tension The Spline Tension option allows you to adjust the amount of arc, or arc radius, between spline points using the Spline Tension dialog box. Use the slider to adjust the spline curve tension from 0 to 100 and pick the check mark button. See Figure 3A-3. If you specify a spline fit method other than minimum energy and then increase spline tension, the fit method is automatically converted to minimum energy. Inventor

8 Figure 3A 3 These splines were identical until the tension was increased in the lower spline. Adding Control Points and Adjusting Close Pick the Insert Point option to add another control point to the spline. Pick a point on an existing spline to insert the additional spline joint. Select the Close Spline option to change an open spline into one in which the start and end points are connected, creating a closed spline. Inventor

9 When AutoCAD is configured to display a screen menu, the commands appear in a separate screen. NOTE Many of the spline bowtie, fit, curvature, and tension adjustments are unnecessary for basic spline sketching, but they can be used to analyze and fully control the display of a spline when needed. Activity 1. Launch Inventor, if it is not already open. 2. Begin a new part file using the Part-IN.ipt or Part-mm.ipt template from the New File dialog box. Do not open the actual template file. 3. Open a new sketch on the XZ plane and use the Look At tool to ensure that your line of sight is perpendicular to the XZ plane. 4. Sketch a spline with two points and another spline with seven points. 5. Right-click on the splines and explore the menu options described in this supplement. 6. Save the part file as SUPP3-1.ipt. 7. Exit Inventor or continue working with the program. Inventor