Pro/ENGINEER TutorialLesson #6: Sweeps and BlendsOverview of this LessonThis lesson will introduce you to the last part design features covered in this series. These are:Sweepsa feature that sweeps an open or closed sketch along a specified trajectoryBlendsa feature that allows smooth transitions between specified cross sectionsThese are very advanced modelling features with many options. In this lesson, we will only look at the simplest versions. We will create several different parts that are totally independent of each other, so you can jump ahead to any one of these:1. Sweeps Sweeping a Closed Section - An S-Bracket Sweeping an Open Section - A Lawn Sprinkler2. Blends Straight Blends Smooth Blends

SweepsThere are a number of different sweep geometries available in Pro/E. We will look at just two of them: sweeping a closed section along an open trajectory, and sweeping an open section along a closed trajectory. A sweep can be used to create a protrusion, slot, or cut. In the following, we will just create protrusions.Closed Section, Open Trajectory - The S-BracketThe part we are going to create is shown in the figure below.

The part consists of two features: the solid protrusion block at the left, and the s-shaped sweep coming off to the right. The cross section of the sweep is like an I-beam.Start a new part calleds_brackand create the default datum planes. First create the block as a solid protrusion, one-sided, with a blind depth of60usingDTM2as the sketching plane andDTM1as the Right reference. The right edge of the sketch aligns withDTM1. The sketch of the base is shown in Figure 7.Figure 7Now we will create the sweep. This is done in two steps: creating the sweep trajectory, then creating the cross section. To start, selectCreate > Solid > Protrusion > Sweep | Solid | DoneIn the SWEEP TRAJ menu selectSketch Trajand useDTM3for the sketching plane, andDTM2as theTopreference plane. Sketch the S-shaped line shown in the following figure:Figure 8Don't forget to align the left end of the trajectory with the base block (top and side). Notice the arrow starting at the left end of the trajectory. This shows the starting point and direction of the sweep. When the trajectory regenerates successfully, selectDone.The next menu has to do with the end conditions of the sweep. SelectFree Ends | DoneNow you will move on to the second step - creating the cross section. The screen should show you a light blue cross hair. This is centered on the start point of the trajectory. You might like to rotate the view a bit to see the orientation of the sketch that is determined automatically by Pro/E. Use the Sketcher tools to create the following cross section (don't forget alignment):Figure 9When this successfully regenerates, you can selectDonefrom the Sketcher menu, and thenPreviewthe sweep. If everything is satisfactory, selectOK. The part should now look like this:Figure 10Use theModifycommand to experiment with changes you make make to the sweep.Before we leave this sweep, you should note that it is not strictly necessary for the cross section to lie exactly on the trajectory. If the section is offset, then the sweep will be offset. You have to be careful that during the sweep, the cross section doesn't pass through itself - this occurs when the radius of a trajectory corner is very small, and the section is on the inside of the curve. Also, note that you can also sweep a closed section around a closed trajectory. For advanced users, the trajectory can be formed as a three-dimensional spline.Open Section, Closed Trajectory - The Lawn SprinklerThis version of the sweep command will be used to create the part shown below:Figure 11This part has only three features: the sweep used to create the base with two arms, a revolved protrusion to create the hub, and a revolved cut to create the bore. A detailed view of the arm cross section is shown below. The part is shown on p.272 ofFundamentals of Graphics Communications(Irwin Graphics Series).Figure 12Start a new part calledsprinklerand create the default datums as usual. The first feature we will create is the base, with two extending arms. As before, we do this in two steps: first the sweep trajectory, then the cross section. We only need to create an open section showing the edge detail. We will use a special command to fill in the surfaces between the swept edge.Create > Solid > Protrusion > Sweep | Solid | Done > Sketch TrajUsingDTM2as the sketching plane, andDTM1as theRightreference plane, sketch the trajectory shown below. This trajectory is for the outer edge on the bottom surface of the part. The swept section will be inside and above this trajectory. Unless you are very good with Sketcher, don't try to sketch this all at once. Sketcher allows you to cycle through the draw - dimension - regenerate - modify - draw sequence as often as you wish. Creating the sketch all at once will probably lead you to regeneration errors. Doing it in small steps will make it easier to correct. For example, you can sketch half the trajectory and then use the mirror command, and you can use the fillet command. Notice how few dimensions are actually required to define the sketch:Figure 13After the final successful regeneration, selectDone. Since we are only going to sketch the edge detail, we will want Pro/E to completely fill in the top and bottom inner surfaces of the part from the free ends of the cross section sketch. Therefore, selectAdd Inn Fcs | DoneAgain, you are presented with an edge view of the trajectory, with the light blue cross hairs to show where you will create the swept section. You might have to rotate the view a little to get a better idea about the orientation of the part. Sketch (including alignment and dimensioning) the open line shown in Figure 14.Figure 14The purpose of the cross hair is to show you the relative position of your sketch and the trajectory. As stated above, the cross section does not necessarily have to touch the trajectory. The free ends of the cross section will be closed in by the inner faces of the sweep. When you get a successfull regeneration, selectDone. You can ignore theWARNINGabout the open ends. Finally, you can Preview the feature. SelectOKif it is satisfactory. The part should look like Figure 15.Figure 15Add the hub as a revolved protrusion using the sketch below for dimensioning details:Figure 16Finally, create a hole for the central shaft. This time, instead of a straight hole, we will specify a cross sectional shape for the hole, including the counterbore.Create > Hole > Sketch | Done > Linear | DoneThe only difference between this and a straight hole is that we have to provide the cross sectional shape of the hole using Sketcher. Pro/E will automatically revolve the section shape through 360 degrees prior to adding it to the model. In the small window that opens up, create the following sketch (don't forget the centerline):Figure 17The placement plane is the top surface of the hub, and the dimensioning references areDTM1andDTM3. Pro/E will take the top edge of the sketched hole and align it automatically with the placement plane, with the axis of the hole at the placement point.So, that's the end of sweeps! As you can see, these are quite complicated features, packing a lot of geometric information into a single feature. You might like to go back and modify any of the dimensions of the sweeps to see what happens. You can modify either the trajectory, or the section, or both! Be aware that arbitrary modifications might make the sweep illegal, so save your part before you try anything drastic.

BlendsA blend is like a sweep with a changing cross section. A blend can be used to create a protrusion, cut, or slot. Some restrictions apply: At least two sections are required. The sections must either be parallel to each other (aparallel blend), or they must all have a common axis (arotational blend) Each section must be created separately and constrained to either the existing geometry, or a previous blend section. Each section must have the same number of line (or arc) segments, and the same number of vertices Each section has a starting point - these must be placed properly on all the sections or else the resulting geometry will be twisted. For a rotational blend, the sections can be no more than 120 degrees apart.The sections of the blend can be connected either with straight (ie. ruled) surfaces, or with smooth surfaces.In the following, we will create two parts that illustrate the basic features of blends.Straight, Parallel BlendThis is the simplest form of a blend. We will create the part shown below.Figure 18This blend has three sections: a square, a rounded rectangle, and a final thin rectangle. These are shown best in the wire frame view of the part.Figure 19Start up a new part called blend1 and create the default datum planes. To create the blend:Create > Solid > Protrusion > Blend | Solid | DoneParallel | Regular Sec | Sketch Sec | DoneStraight | DoneSelectDTM3as the sketching plane, andDTM1as theRightreference plane.Each section will be sketched separately. This includes dimensioning, aligning, regenerating, and so on. When each section is completed, we will move on to the next section. The previous section will remain displayed on the screen in gray. The new sections can use the old ones for constraint references, or they can be defined with respect to other part features.The first section is a 10 X 10 square centered on the datum planes, as shown below.Figure 20Note the round dot and arrow on the upper left corner. This is called thestart pointand shows the direction that vertices will be traversed in the section. Since the square has four vertices, each section we produce must also have four, and their start points must correspond to each other. If your sketch's start pointis not in the position shown, select:Sec Tools > Start Pointand click on the desired vertex.When you have a successful regeneration, selectSec Tools > ToggleThis will take us to the next section. The previous one is grayed out, and Sketcher is now used to create the second section. When that one is regenerated successfully, toggle to the third section. The dimensions and placement of all the sections is shown in the figure below. Make sure all your start points at located correctly.Figure 21When the third section is complete, selectDone. Now you will be asked for the distance between each planar section. The distance from the first section (the square) to the middle section is15. The distance to the next section is20. This should complete the specification of the blend.Previewthe part, and selectOKwhen you are satisfied with the part.Shade the image. You might like to try toModifythe dimensions of the cross sections. When you select the feature, you will see all the section shapes with their dimensions displayed on the original sketching plane.Smooth, Rotational BlendA rotational blend is set up by specifying the cross sectional shape on a number of sketching planes that have been rotated around a common axis. The usual restrictions apply as to the number of segments and vertices in each section and the start point. The sections can be no more than 120 degrees apart.We are going to make the part shown in the two figures below.Figure 22 Front isometricFigure 23 Rear isometricNote that the surfaces on the blend are smooth. If we select straight surfaces, we will get the shape shown here:Figure 24Start a new part called blend2 and create the default datum planes. Also, create a default datum coordinate system (see Lesson #1). Then start the blend creation:Create > Solid > Protrusion > Blend | Solid | DoneRotational | Regular Sec | Sketch Sec | DoneThe attributes window will open. Click on theAttributesline and theDefinebutton, and selectSmooth | Open | DoneNow selectDTM3as the sketching plane (the view direction is okay), andDTM1as theRightreference plane. We are going to create four cross sections, with a separation of 30 degrees. Therefore, the total angle of rotation of the blend will be 90 degrees. Each section must include a coordinate system in the sketch (discussed below). The rotation will occur around the y-axis of this system.The first section will be sketched directly onDTM3. The dimensions of the section, and its position on the blend, are shown in the figure below.Figure 25 First SectionDraw and dimension the sketch. When you regenerate, you will get a message about a missing coordinate system. Select:Sketch > Adv Geom > Coord Sysand pick approximately at the origin of the default datum planes. Align this new coordinate system with the default coordinate system created earlier. Now a regeneration should be successful. Take note of the start point. When you selectDone, you will be asked for the angle to the next section. Enter30.A new sketcher window opens up. In this window, you need to sketch the second section and supply a coordinate system to allow alignment with the first section. Dimension the sketch to the coordinate system and make sure the start point is on the correct vertex. The second section has the following dimensions:Figure 26 Second SectionWhen you selectDone, proceed on to the next section. The separation angle is again 30 degrees. The third section has these dimensions:

Figure 27 Third SectionFinally, the last section has these dimensions:Figure 28 Fourth SectionWhen the fourth section is complete and you are asked to continue to the next section, type inn. The message window should indicate that all elements are complete, and you canPreviewthe part. SelectOKwhen you are satisfied.That completes our limited presentation of blends. As you can see, blends contain a lot of geometric information and are therefore a bit more difficult to set up. However, they offer considerable flexibility and can create very complex shapes not attainable with the simpler features.