第3章 倒圆技巧.doc

第3章 倒圆技巧【目的】本章将介绍在一些特殊设计情况下倒圆的技巧，以及如何最大限度地减少倒圆的更新故障。【目标】 变半径倒圆。 控制拐角回切的选项。 控制拐角突然停止的选项。 控制修剪的选项。 控制倒圆的溢出( Overflow)选项。 创建表面倒圆。【练习】练习3-1倒圆多个边缘。练习3-2相邻边缘的倒圆。练习3-3重新指定倒圆边缘练习。练习3-4创建变半径倒圆。练习3-5建立拐角停止的倒圆。练习3-6在相邻边缘上的倒圆。练习3-7溢出选项的控制。练习3-8面倒圆。练习3-9面倒圆相切控制。边缘倒圆可以理解成为一个圆球沿要倒圆的边缘滚动过程，球面维持与在边缘处遇到的表面接触。球滚动的轨迹就是倒圆面。球能在两个相交面的内侧或是外侧滚动，取决于是否要建立加材料的倒圆或是移去材料的倒圆。在心里形成这样的概念对构造倒圆有益，参见图3-1。图3-1 两类倒圆从菜单InsertDetail FeatureEdge Blend或工具条FeatureEdge Blend打开边倒圆对话框如图所示。练习3-1 倒圆多个边缘本练习学习按不同顺序选择边缘进行倒圆。第1步：打开部件文件apd_blend_rocker.prt，如图3-1所示。图3-1 apd_blend_rocker.prt部件第2步：倒圆前臂的底部边缘。 按下图3-2选择边缘。图3-2选择要倒圆的边缘 输入默认半径值为4，结果见图3-3。图3-3倒圆后的结果第3步：在臂的根部创建倒圆。 旋转部件，以便更好地选择臂的根部边。 采用同上一步骤相同的选项，选择臂的根部边，见图3-4所示。图3-4臂的根部边缘被倒圆第4步：倒圆除了位于加工面上的上部所有边缘。 回到三角轴侧视图，选择臂上部要倒圆的边缘，见图3-5。图3-5上部边缘倒圆第5步：在另一个臂上，按相反的次序创建倒圆。 首先，创建顶部边缘倒圆。 其次，创建底部边缘倒圆。 最后，倒圆臂的根部边缘，结果见图3-6。图3-6 在两个臂上按不同顺序倒圆注意：正如所看到的，不同的创建倒圆次序将产生不同的结果。第6步：关闭部件。练习3-2 相邻边缘的倒圆本练习学习和演示分别倒圆的原理以及边缘的建立次序的重要性，见图3-7。 图3-7本练习学习内容第1步：打开部件apd_blend_separate,prt。第2少：两个边缘一起倒圆。 选择InsertDetail FeatureEdge Blend. 将倒圆半径默认值改为.375。 选择如图3-8所示的两条边。图3-8选择两条边一起倒圆 选择Apply，倒圆不能被创建，错误提示见图3-9。图 3-9错误信息提示第3步：尝试分别倒圆。 按住Shift再选择一次长的边，这样可以将已选的边去掉。选择Apply。 再次执行边缘倒圆，选择长边，选择Apply创建倒圆，见图3-10。图3-10 对长边的倒圆这种倒圆一定不是所想要的，因为这种体无效。第4步：按不同次序创建倒圆。 选择EditUndo List。退回到进入Modeling处，或是打开部件。 选择InsertDetail FeatureEdge Blend. 仅选择长边，选择Apply。当倒圆此边时，相邻的平面被检测到是一个修剪的面，被自动延伸。延伸的表面有两条新边缘，一条是椭圆形的，一条是直边。新的直边代表了两条直边间的过渡，见图3-11。 再倒圆由第一个倒圆修剪产生的直边及原先的短边，见图3-12示意。选择Apply。 图3-11按长短的次序倒圆边缘 图3-12第二次操作例圆这两条边虽然所有的倒圃采用的是相同的倒圆半径，但必须倒圆会产生足够大的中间边的边。在中间边上倒圆成为在两个倒圆面间的过渡段。第5步：关闭部件。练习3-3：重新指定倒圆边缘练习修改后修改前 本练习修改了要倒圆的边缘1. Open blend_edit.prt. 2. In the graphics window, double-click the edge blend.The blend is opened for editing, and the edges that were blended are selected.3. On the Selection bar, from the Curve Rule list, select Single Curve. 4. Deselect the following three edges.You may get an alert, which will disappear when you finish deselecting edges.One edge is still selected.5. Select the following two edges to add to the blend.6. In the Edge Blend dialog box, click OK. 7.Close the part.3.1 创建变半径倒圆:练习3-4：创建变半径倒圆Step1: Open the part and select the edge to blend1) Open blend_frame.prt。 2) On the Feature toolbar, click Edge Blend . 3) Set the Curve Rule to Tangent Curves. 4) Select the edge shown.All the tangent edges are selected and are specified as Radius 1. 5） In the on-screen input box, ensure that Radius 1, type 0.5 and press Enter. Step2: Set the first variable radius value1) In the Edge Blend dialog box, in the Variable Radius Points group, click Specify New Location . 2) Select the left end point as shown.Note：A point and direction arrows appear at the selected location3) Drag the point back and forth, and observe how the on-screen input box updates the arc length percentage as you move the point.You could also type a specific value.4) Move the slider so the point is located on the left end point, where % Arc Length is set to 100. 5) Set the V Radius 1 to 1.12 and press Enter. The following alert appears, which will be corrected when you select the next point.Step3: Set variable radius values 2 and 31) Select the following edge at its center control point.Note：ou can set the snap point options on the Selection bar to limit the types of points you can select. 2) Ensure that the % Arc Length is 50. The blend can now be calculated over the entire edge string.3) In the Variable Radius Points group, expand the List box. TipYou can also access options for a point by right-clicking it or its handle in the graphics window.Right-clicking a point offers a choice between Arc Length and Through Point. You can remove a point by right-clicking a point or point handle and choosing Remove. 4) Select the left end point on the center edge and ensure that the % Arc Length is set to 0%. 5) Set the V Radius 3 to 0.5 and press Enter. Step4: Set variable radius values 4 through 61） Select the right end point on the same edge.The % Arc Length value should be 100. 2） Select the following edge at its center control point and ensure that the % Arc Length is set to 50. 3） Set the V Radius 5 to 1.12. 4） Select the endpoint as shown and set the V Radius 6 to 1.12. 5） Click OK. The blend appears symmetric about the part center.Step5: Edit one of the variable radii1) In the graphics window, select the new blend feature, right-click and select Edit with Rollback from the radial menu. 2) In the Variable Radius Points group, from the List box, select V Radius 3. The point is selected in the graphics window.3) In the on-screen input box, edit V Radius 3 from 0.5 to 1.75. 4) Change the % Arc Length value to 20 and press Enter. 5) Click OK. 6) Close the part.3.2 拐角突然停止The following example shows an edge blends stopped short at selected points.练习3-5：本练习建立拐角停止的倒圆 Create edge blends at the vertex of a model. Modify a blend to define a specified stop location.Step1: Open the part and create the first edge blend1) Open edge_blend_3. 2) On the Feature toolbar, click Edge Blend . 3) On the Selection bar, from the Curve Rule list, select Tangent Curves. 4) Select the following edge.The first set of tangent edges is selected.A preview of the blend appears, if your Preview check box is selected. 5) In the Radius 1 on-screen input box, type 8 and press Enter. Step2: Create the second edge blend1)In the Edge to Blend group, click Add New Set . In the List box, the first set Radius 1 appears. 2) Select the following edge.The second set of edges is selected.3) In the Radius 2 on-screen input box, type 10 and press Enter. Notice that the two sections of the blend do not merge smoothly at the corner. You want to modify the first section so it stops before the intersection.Step3: Create a stop short at the vertex1) In the Stop Short of Corner group, from the Stopping Location list, select At Intersection. 2) With Select End Point active, select the Radius 1 edge at the vertex. The blends should update as shown in the following figure.Step4: Change the stop short location by dragging1) In the List box, select Stopshort1. 2) From the Stopping Location list, select At Distance. You may receive an Alerts message during this or later steps. If so, close the message and continue. 3) From the Location list, select Arc Length. 4) Drag the right edge of Radius 1 to the left until the Arc Length on-screen input box is about 18 mm. Step5: Change the stop short location by specifying a point1) From the Location list, select Through Point. In the graphics window, the on-screen input box for arc length changes to the current point parameters.2) Click Point Dialog . 3) In the Point dialog box, from the Type list, select Arc/Ellipse/Sphere Center. 4) Select the arc center of the following hole.5) Click OK. The edge is aligned with the arc center of the hole.6) In the Edge Blend dialog box, click OK. The edge blend updates.7) Close the part.3.4 倒圆修剪The following image shows the before (left) and after (right) of using a faceto determine the blend trim.In some cases you can trim an edge blend to a selected face or face group,instead of relying on the default trim face.User Selected Objects allows you to select options with which you can trim the blend.Trim Object list lists two options in which to trim the blend.Plane lets you create a trim plane.Face lets you select an existing face.Use Trim Plane to Cap Blend available when Trim Object is set to Planeand caps the blend with the specified plane.练习3-6：控制倒圆修剪边界Step1:Open the part and create the edge blend1) Open edge_blend_2. 2) On the Feature toolbar, click Edge Blend . 3) Select the following two edges.4) In the Radius 1 on-screen input box, type 5 and press Enter. 5) Click OK. Notice how the upper ends of the blends are capped by the upper conical face. You want the blends to end at the planar face at the top of the cone.Step2: Modify the end caps of the blend1) Double-click the Edge Blend you just created. The blend opens for editing.2) In the Trimming group, select the User Selected Objects check box. 3) From the Trim Object list, select Face. 4) With Select Face active, select the face at the top of the cone. The trimming direction arrow should point up; click Reverse Direction if necessary. 5) Click OK. The upper end of the blend is now capped at the face.6) Close the part.3.5 倒圆溢出选项 Roll Over Smooth Edges：A blend that overflows the edge of an existing blend (1)produces a smooth, shared edge where the blends meet(2).Roll on Edges (Smooth or Sharp)：A blend that encounters an existing edge, foregoes tangency and leaves the existing edge unchanged (1).Maintain Blend Over Sharp Edges：A blend that encounters existing sharp edges,maintains tangency and moves the existing edges (1).For this edge blend, an encountered edge (1) is selected with Select Edge toProhibit Roll on, to not have the Roll On Edges (Smooth or Sharp) optionapplied to it. The edge of the other cylinder is not prohibited and is processedby the Roll On Edges (Smooth or Sharp) option.练习3-7：溢出选项的控制In the Variable Radius and Blend Overflow section, do the following activity:1）Open blend_overflow. 2) Under Allowed Overflow Resolutions, clear the check boxes for Roll on Edges (Smooth or Sharp) and Maintain Blend and Move Sharp Edges. 3) Select the edge shown.4) In the Radius 1 box, type 9 and press Enter, select ok.5） On the Feature toolbar, click Edge Blend . 设置如下选项。6） Select the following edge.7) In the on-screen input box for Radius 1, type 2.5 and press Enter. 8) Close part.3.6面 倒 圆面倒圆( Face Blend)功能可以创建倒圆相切于指定的面组。有选项可设定要不要修剪倒圆面。面倒圆对话框可选择InsertDetail FeatureFace Blend或FeatureFace Blend得到，见图。面倒圆对话框3.6.1 何时采用面倒圆面倒圆将在实体的表面之间和或片体的表面之间产生。表面可以是不相邻的或是在不同的体上。墙表面可自动修剪到新的倒圆边缘，可以与倒圆面附着。既然面倒圆并不要求遵循边缘，它可被成功地应用在边缘倒圆失败的情形下，例如整个面都被去掉的情况。在许多倒圆的情况下，可以既用边缘倒圆，也可用面倒圆实现。然而，面倒圆在特殊建模的情况下，提供某些独特的功能。在下列情况，将使用面倒圆： 已存表面必须在倒圆后被去掉。 可以指定特殊的倒圆半径，该倒圆半径是采用恒定的”或是“可变半径的”边 缘倒圆不能实现。 希望指定曲线作为相切控制。 要倒圆的表面属于多个体。练习3-8面倒圆Step1: Open the part and specify the Selection bar options1) Open face_blend_3. 2) On the Feature toolbar, click Face Blend . 3) On the Selection bar, set the following values:a) Face Rule = Tangent Facesb) Curve Rule = Tangent CurvesStep2: Select geometry for the face blend1) In the Face Blend dialog box, from the Type list, select Two Defining Face Chains. 2) While Select Face Chain 1 is active, select the conical face of the boss. The direction arrow should point away from the conical surface.3) Click Select Face Chain 2 . 4) Select the vertical face of the pad adjacent to the boss.The direction arrow should point away from the body.Step3: Define parameters and create the face blend1) In the Blend Cross Section group, set the following values: o Specify Orientation = Rolling Ballo Shape = Circularo Radius Method = Constanto Radius = 6.352) In the Trim and Sew Options group, from the Blend Faces list, select Trim to All Input Faces. 3) Ensure that the Trim Input Faces to Blend Faces and the Sew All Faces check boxes are selected. 4) In the Settings group, select the Add Tangent Faces as Encountered check box. 5) Click OK. You now want to add an edge blend on the top of the boss.Step4: Select geometry for the edge blend1) On the Feature toolbar, click Edge Blend . 2) On the Edge Blend dialog box title bar, click Reset . 3) From the Curve Rule list, select Vertex Tangent Edges. 4) Select the top edge of the boss.An Alerts message warns you that self intersecting blend surfaces have been repaired. 5) In the Radius 1 on-screen input box, type 4.8 and press Enter. Step5: Define the blend overflow and settings1) In the Overflow Resolutions group, clear the Roll on Edges (Smooth or Sharp) check box. 2) In the Settings group, clear the Special Blend At Convex/Concave Y check box. 3) Click OK. 4) Examine the completed blend.Although technically there does not appear to be anything wrong with the current blend, this is not the desired visual result. You want to de