Alibre Design

Chapter 4 - SketchingMove Curve Points - Modify shape by moving a point on the B-spline curve to anew position.Insert Knots - Insert new knots on the curve knot vector without changing curveshape.Remove Redundant Knots - Remove existing knots that can be removed withoutchanging the curve shape. Alibre Design will automatically remove any possibleknots; then a dialog box will appear summarizing the results.DXF/DWG import/export of NURBS curvesNURBS geometry defined by control points present in DXF/DWG files can be read andprecisely represented by the same mathematical representation in Alibre Design.DWG files can also contain splines that are defined by interpolation points. AlibreDesign will read these and convert them into B-spline curves. While for most partsthese curves will appear very similar to what they look like in AutoCAD, their shapesmay not exactly match. Also, AutoCAD allows users to specify “tolerance” while definingsplines by interpolation. Alibre Design will assume this value is always zero.Using Offset on a spline curveThe offset tool can be used to select B-spline curves for creating an offset curve. Aswith other figures this offset will not be associative to the original B-spline curve.Reference section 4.5.5 for details on how to use the Offset tool.4.3.6 Ellipses‣ To sketch an ellipse:1. From the Sketch menu, select Figures > Ellipse.2. Click to select the ellipse center.3. Move the mouse pointer and click a second time to place the major axis of ellipse.4. Move the mouse pointer and click a third time to place the minor axis of the ellipse.63