Wiley SolidWorks 2009 Bible Part 4 doc

209 W henever I do a woodworking project, the most frustrating part of the job is to envision a result, but not be able to accomplish it because I do not have the tools to get it done; worse yet is to actually have the tools but either not understand how to use them or not even realize that I have them. Getting the job done is so much more satisfy- ing when you use the right tools and get the job done right — not just so that it looks right, but so that it really is right. I see users run into the same issues with SolidWorks. SolidWorks offers so many ”tools in the toolbox” that it is sometimes difficult to select the best one, especially if it is for a function that you do not use frequently. This chapter helps you to understand how each feature functions and offers situations when they are best applied or avoided. Identifying When to Use Which Tool I am always trying to think of alternate ways of doing things. It is important to have a backup plan, or sometimes multiple backup plans, in case a feature doesn’t perform exactly the way you want it to. As you progress into more complex features, you may find that the more complex features are not as well behaved as the simple features. You may not be able to get away with just doing blind extrudes and cuts with simple chamfers and fillets for the rest of your career. And even if you could, who would want to? IN THIS CHAPTER Identifying when to use which tool Creating curve features Filleting Selecting a specialty feature Tutorial: Bracket casting Tutorial: Creating a wire- formed part Selecting Features 210 Building Intelligence into Your Parts Part II As an exercise, I often try to see how many different ways a particular shape might be modeled, and how each modeling method relates to manufacturing methods, costs, editability, efficiency, and so on. You may also want to try this approach for fun or for education. This chapter helps you identify which features to use in which situations, and in some cases which features to avoid. As SolidWorks grows more and more complex, and the feature count increases with every release, understanding how the features work and how to select the best tool for the job becomes ever more important. If you are only familiar with the standard half-dozen or so features that most users use, your options are limited. Sometimes simple features truly are the correct ones to use, but using them because they are the only things you know is not always the best choice. Extrude Extruded features can be grouped into several categories, with extruded Boss and Cut features at the highest level. With the use of Instant3D, extruded bosses can be transformed into cuts. It is unclear what advantage this has in real world modeling, but options are options. As a result the names of newly created extrude features are simply Extrude1 where they used to be Extrude-Boss1 or Extrude-Cut1. The “Base” part of the Extruded Boss/Base is a holdover from when SolidWorks did not allow mul- tibody parts, and the first feature in a part had special significance that it no longer has. This is also seen in the menus at Insert ➪ Boss/Base. The Base feature was the first solid feature in the FeatureManager, and you could not change it without deleting the rest of the features. The intro- duction of multibody support in SolidWorks has removed this limitation. CROSS-REF CROSS-REF Multibody parts are covered in detail in Chapter 26. Solid Feature In this case, the term solid feature is used as an opposite of thin feature. This is the simple type of feature that you create by default when you extrude a closed loop sketch. A closed loop sketch fully encloses an area without gaps or overlaps at the sketch entity endpoints. Figure 7.1 shows a closed loop sketch creating an extruded solid feature. This is the default type of geometry for closed loop sketches. Thin Feature The Thin Feature option is available in several features, but is most commonly used with Extruded Boss features. Thin features are created by default when you use an open loop sketch, but you can also select the Thin Feature option for closed loop sketches. Thin features are commonly used for ribs, thin walls, hollow bosses, and many other types of features that are common to plastic parts, castings, or sheet metal. Even experienced users tend to forget that thin features are not just for bosses, but can also be used for cuts. For example, you can easily create grooves and slots with thin feature cuts. 211 Selecting Features 7 FIGURE 7.1 A closed loop sketch and an extruded solid feature Figure 7.2 shows the Thin Feature panel in the Extruded Boss PropertyManager. In addition to the default options that are available for the Extrude feature, the Thin feature adds a thickness dimension, as well as three options to direct the thickness relative to the sketch: One-Direction, Mid-Plane, and Two-Direction. The Two-Direction option requires two dimensions, as shown in Figure 7.2. FIGURE 7.2 The Thin Feature interface Thin feature sketches are typically simpler than closed loop sketches, which usually means that they are more robust through changes. You can create the simplest cube from a single sketch line and a thin feature extrude. However, because they are more specialized in some respects, they are not as flexible when the design intent changes. For example, if a part is going to change from a constant width to a tapered or stepped shape, thin features do not handle this kind of change. Figure 7.3 shows different types of geometry that are typically created from thin features. 212 Building Intelligence into Your Parts Part II FIGURE 7.3 Different types of geometry created from thin features Sketch types I have already mentioned several sketch types, including closed loop and open loop. Closed loop sketches make solid features by default, but you can also use them to make thin features. Open loop sketches make thin features by default, and you cannot use them to make solid features. Sketch contours Sketch Contour is an option that is used in other competing CAD packages and that SolidWorks has adopted, probably more to match features in the competing software than to create a better way of doing things. In my opinion, using sketch contours promotes sloppy work, although in some cases, they act as valid time savers. In general, sketch contours enable you to select enclosed areas where the sketch entities themselves actually cross or otherwise violate the usual sketch rules. One of these conditions is the self-inter- secting contour. 213 Selecting Features 7 BEST PRACTICE BEST PRACTICE SolidWorks works best with well-disciplined sketches that follow the rules. As a result, if you plan to use sketch contours, then you should make sure that it is not simply because you are unwilling to clean up a messy sketch. When you define features by selecting sketch contours, they are more likely to fail if the selec- tion changes when the selected contour’s bounded area changes in some way. It is best practice to use the normal closed loop sketch when you are defining features. Contour selection is best suited to “fast and dirty” conceptual models, which are used in very limited situations for pro- duction models. As shown in Figure 7.4, there are several types of contour selection. FIGURE 7.4 Types of contour selection 3D sketch You can make extrusions from 3D sketches, even 3D sketches that are not planar. While not neces- sarily the best way to do extrudes, this is a method that you can use when needed. You can estab- lish direction for an extrusion by selecting a plane (normal direction), axis, sketch line, or model edge. When you make an extrusion from a 3D sketch, the direction of extrusion cannot be assumed or inferred from anything — it must be explicitly identified. Extrusion direction from a 2D sketch is always perpendicular to the sketch plane unless otherwise specified. 214 Building Intelligence into Your Parts Part II Non-planar sketches become somewhat problematic when you are creating the final extruded fea- ture. The biggest problem is how you cap the ends. Figure 7.5 shows a non-planar 3D sketch that is being extruded. Notice that the end faces are, by necessity, not planar, and are capped by an unpredictable method, probably a simple Fill surface. This is a problem only if your part is going to use these faces in the end; if it does not, then there may be no issue with using this technique. If you would like to examine this part, it is included on the CD-ROM as Chapter 7 Extrude 3D Sketch.sldprt. FIGURE 7.5 Extruding a non-planar 3D sketch If you need to have ends with a specific shape, and you still want to extrude from a non-planar 3D sketch, then you should use an extruded surface feature rather than an extruded solid feature. One big advantage of using a 3D sketch to extrude from is that you can include profiles on many different levels, although they must all have the same end condition. So if you have several pockets in a plate, you can draw the profile for each pocket at the bottom of the pocket, and extrude all the profiles Through All, and they will all be cut to different depths. 3D sketches also have an advantage when all the profiles of a single loft or boundary are made in a single 3D sketch. This enables you to drag the profiles and watch the loft update in real time. CROSS-REF CROSS-REF Surfacing features are covered in detail in Chapter 27. Chapter 4 contains additional details on extrude end conditions, thin features, directions, and the From options. Chapter 31 also has more information on 3D sketches. 215 Selecting Features 7 Instant 3D Instant 3D is a function that was added in SolidWorks 2008, and largely replaces the Move/Size Features function. Instant 3D is not a complete replacement of Move/Size Features — it has some limitations that the older function does not have — but it also adds new functionality that did not exist before. This topic follows the Extrude feature because one of the functions of Instant 3D is to help you create extruded bosses and cuts quickly. Instant 3D also allows you to edit other types of features and sketches by simply dragging handles in the graphics window, instead of editing numbers in a dialog box. Creating extrudes with Instant 3D Instant 3D allows you to select a sketch or a sketch contour and drag the Instant 3D arrow to cre- ate either a blind extruded boss or cut. The workflow when using this function requires that the sketch must be closed. Instant 3D cannot create a thin feature, and any sketch or contour that it uses must be a closed loop. Sketches must also be shown (not hidden) in order to be used with Instant 3D. NOTE NOTE Even though the words “Instant 3D” suggest that you should be able to instantly create 3D geometry from a sketch that you may have just created, you do have to close the sketch first to get instant functionality. Figure 7.6 shows Instant 3D arrows for extruding a solid and the ruler to establish blind extrusion depth. These extrusions were done from a single sketch with three concentric circles, using con- tour selection. Even after you create an extruded boss, you can use Instant 3D to drag it in the other direction to make an extruded cut. When you do this, the symbol on the feature changes, but the name does not. Prior to SolidWorks 2008, SolidWorks automatically assigned the name Boss-Extrude1 to an extruded boss. In SolidWorks 2008 and later, the default is simply Extrude1. If your second fea- ture is a cut, SolidWorks names that feature Extrude2. So in the automatic naming conventions, SolidWorks no longer distinguishes between bosses and cuts. If you have a sketch that requires contour selection — for example, the three concentric circles used in Figure 7.6, after the first feature is created from the sketch — SolidWorks automatically hides the sketch, and to continue with Instant 3D functionality using additional contours selected from that sketch, you will have to show the sketch again. This interrupts the workflow and makes using this functionality less fluid than it might otherwise be. I only mention it here so that you are aware of what is happening when the sketch disappears and the Instant 3D functionality disap- pears with it. 216 Building Intelligence into Your Parts Part II FIGURE 7.6 Creating features with Instant 3D Notice the boss extrude symbol next to the hand in Figure 7.6. This enables you to switch the type of feature you are creating with Instant 3D. If geometry already exists in the part, and you drag a new feature into the existing solid, SolidWorks assumes you want to make a cut. But maybe what you are really trying to make is a boss that comes out the other side of the part. These heads-up display icons enable you to do this. Options include boss, cut, and draft. The draft option enables you to add draft to a feature created with Instant 3D. While Instant 3D can only create extruded bosses and cuts, it can edit revolves. If you create a revolved feature revolving the sketch say 270°, the face created at the angle can be edited by Instant 3D dragging. 217 Selecting Features 7 Editing geometry with Instant 3D Instant 3D enables you to edit 2D sketches and solid geometry. You can also edit some additional feature types using Instant 3D such as offset reference planes. It can neither create nor edit surface geometry or 3D sketches in some situations. To edit solid geometry, click on a face, and an arrow appears. Drag the arrow, and SolidWorks automatically changes either the sketch or the feature end condition used to create that face. If a dimensioned sketch was used to create that face, SolidWorks will not allow you to use the Instant 3D arrow to move or resize the face. An option exists that enables Instant 3D changes to override sketch dimensions at Tools ➪ Sketch Settings ➪ Override Dims On Drag. CAUTION CAUTION Be careful with the Override Dims On Drag option. If you accidentally drag a fully defined sketch, this setting enables SolidWorks to completely resize the sketch. For working conceptually, it can be a great aid, but for final production models, you may do better to turn this off. Instant 3D offers different editing options depending on how a sketch is selected. n A sketch is selected from the graphics window. The pull arrow appears, enabling you to create an extruded boss or cut. n A sketch is selected from the FeatureManager. If the sketch has relations to anything outside of the sketch, the sketch is highlighted with no special functionality available. If no external relations exist, a box with stretch handles enable scaling the sketch, and a set of axes with a wing enables you to move the sketch in X or Y or X and Y. Figure 7.7 shows this situation. FIGURE 7.7 Sketch scaling and moving options with Instant 3D When Instant 3D is activated, double-clicking a sketch in either the FeatureManager or on a sketch element in the graphics window opens that sketch. While you are in a sketch, if you double-click with the Select cursor in blank space in the graphics window, you close the sketch. This only works for 2D sketches; 3D sketches can be opened, but not closed this way. [...]... background, it is time to move forward and talk about a few of the major aspects of Loft features in SolidWorks It is probably possible to write a separate book that only discusses modeling lofts and other complex shapes This has in fact been done The SolidWorks Surfacing and Complex Shape Modeling Bible (Wiley, 2008) covers a wide range of surfacing topics with examples in far greater detail In this single... sketches that are used to make the part There are two sketches with points; you can use points as loft profiles The image in the middle shows the Loft feature without guide curves, and the one to the right is the part with guide curves If you would like to examine how this part is built, you can find it on the CD-ROM with the filename Chapter 7 Guide Curves.sldprt 2 24 Selecting Features FIGURE 7.12 A... envision features such as this when you are troubleshooting or setting up more complex sweeps If you open the part mentioned previously from the CD-ROM, you can edit the Sweep feature to examine the sections for yourself 229 7 Part II Building Intelligence into Your Parts In most other published SolidWorks materials that cover these topics, sweeps are covered before lofts because many people consider... This is like extruding the sketch and using 235 7 Part II Building Intelligence into Your Parts the Up To Surface end condition The sketch can be an open or closed loop, but it may not be multiple open or closed loops, nor can it be self-intersecting Figure 7. 24 shows an example of projecting a sketch onto a face to create a projected curve FIGURE 7. 24 A projected curve using the Sketch Onto Face option... from which solids are made, it would make sense to teach surfaces first, and then solids However, the majority of SolidWorks users never use surfacing, and do not see a need for it, and so surface functions are generally given a lower priority 221 7 Part II Building Intelligence into Your Parts CROSS-REF Refer to Chapter 27 for surfacing information Loft end constraints Loft end conditions control the... 3D curves I cover 3D curves toward the end of this chapter, and so you can refer ahead to these features to understand how this part is made FIGURE 7.18 A 3D sweep ON the CD-ROM The part shown in Figure 7.18 is on the CD-ROM with the filename Chapter 7 3D Sweep.sldprt This part is created by making a pair of tapered helices, with the profile sketch plane perpendicular to the end of one of the curves... diameter of the sweep 231 7 Part II Building Intelligence into Your Parts Cut Sweep with a solid profile The Cut Sweep feature has an option to use a solid sweep profile This kind of functionality has many uses, but is primarily intended for simulating complex cuts made by a mill or lathe Figure 7.19 shows a couple of examples of cuts you can make with this feature The part used for this screen shot... TIP The following types of curves can be defined in SolidWorks: n Helix/tapered helix/variable helix/spiral n Projected curve n Curve through XYZ points n Curve through reference points n Composite curve You can find all the curve functions on the Curves toolbar or through the menus at Insert ➪ Curve 233 7 Part II Building Intelligence into Your Parts Helix The Helix curve types are all based on a... the pitch and the diameter are variable The diameter number in the first row cannot be changed, but is driven by the sketch In the chart shown, the transition between 4 and 4. 5 revolutions is where the pitch and diameter both change 2 34 Selecting Features FIGURE 7.22 The tapered helix FIGURE 7.23 The variable pitch helix Spiral A spiral is a flattened (planar) tapered helix The pitch value on a spiral... panel enables you to specify how many intermediate sections to create between sketched profiles 225 7 Part II Building Intelligence into Your Parts SelectionManager The SelectionManager simplifies the selection of entities from complex sketches that are not necessarily the clean, closed loop sketches that SolidWorks works with most effectively The SelectionManager has been implemented in a limited number . casting Tutorial: Creating a wire- formed part Selecting Features 210 Building Intelligence into Your Parts Part II As an exercise, I often try to see how many different ways a particular shape might be modeled,. Extrude-Boss1 or Extrude-Cut1. The “Base” part of the Extruded Boss/Base is a holdover from when SolidWorks did not allow mul- tibody parts, and the first feature in a part had special significance that. is always perpendicular to the sketch plane unless otherwise specified. 2 14 Building Intelligence into Your Parts Part II Non-planar sketches become somewhat problematic when you are creating