Wiley SolidWorks 2009 Bible Part 13 potx

943 Using Plastic Features and Mold Tools 32 Figure 32.18 shows how this analysis produces some anomalous results, especially at the corners, and also in the middle. Again, this is a useful tool, if not completely accurate. You can use it to find problem areas that you may not have considered, but you should certainly examine the results critically. FIGURE 32.18 Results of the Thickness Analysis The Treat corners as zero thickness option should always be on. I have never seen a situation where turning it off improved the results; in fact, I have found that turning it off has always made corners and fillets behave worse. This feature can generate a report, which to some extent answers questions about how or why it classifies faces in the way it does. To get a complete picture of the situation, it may be useful to look at the report when you are using the results to make design or manufacturing decisions. A sample of the report is shown in Figure 32.19. 944 Working with Specialized Functionality Part VII FIGURE 32.19 A sample of a Thickness Analysis report Undercut Detection The Undercut Detection tool is found under the View menu, relocated from the Tools menu. It is also an on or off display tool, which changes dynamically as you change the model. Undercut Detection is conceptually flawed in that it gives incorrect results every time. However, if you think of the labels as being changed slightly, the results become partially usable. Even if you and your mold builder know that a part has absolutely no undercuts, the Undercut Detection tool will nonetheless always identify all of the faces to be undercut. In fact, the only faces that this tool will identify as not undercut are faces that have no draft on them. The only time it correctly identifies an undercut is when it classifies the undercut as Occluded Undercut. Faces that have no draft and are occluded undercut are improperly identified as simply No Undercut. You may want to avoid this tool because too much interpretation of incorrect results is necessary; however, if you still want to use it, then here is a translation guide that may help: n Direction 1 Undercut — should read Pull from Direction 2 n Direction 2 Undercut — should read Pull from Direction 1 n Straddle Undercut — should read Straddle faces 945 Using Plastic Features and Mold Tools 32 n No Undercut — should read No draft in the primary draft direction, but may be occluded undercut faces n Occluded Undercut — should read Occluded Undercut faces that have draft in the com- pletely irrelevant primary draft directions; does not include occluded undercut faces that have no draft in the primary direction Figure 32.20 shows the PropertyManager for this function and the results. If you would like to test it for yourself, the part is on the CD-ROM with the filename Chapter 32 Draft Analysis. sldpr t. FIGURE 32.20 The results of the Undercut Detection tool Working with the Mold Tools Process The SolidWorks Mold Tools are intended to help you create cavity and core blocks for injection molds. They do not provide libraries or functionality for building the entire mold or mold compo- nents. Mold Tools entail a semi-automatic process to follow, with the tools in order on the toolbar. Mold Tools rely heavily on surfacing tools, and require a fair amount of manual intervention for certain types of parts. The next section deals with the manual intervention techniques. This section deals with the idealized semi-automatic process. 946 Working with Specialized Functionality Part VII In order to fully understand the formalized Mold Tools process, it might be helpful to understand SolidWorks capabilities with mold geometry in general. First, understand that to create cavity and core geometry in SolidWorks, you are not required to use the Mold Tools. You can manually model surfaces or solid features to accomplish the same tasks. Surface features are widely used for mold modeling because they allow you far more control than solid features. You can also make mold geometry using an assembly of in-context parts or multi-body techniques. The formal Mold Tools functionality uses the multi-body approach. This has benefits and drawbacks. With the formal SolidWorks process, you start in part file with just the final plastic part in it, and then build both the cavity and core blocks around the plastic part. You also build any side actions or core pins within the part file, which seems a bit clumsy. To me, mold creation is better suited to assembly techniques, but that is not how SolidWorks built their functionality. Figure 32.21 shows the part of the Mold Tools toolbar that identifies the process. From the left to the right, the icons are: n Split Line n Draft n Move Face n Scale n Insert Mold Folders n Parting Lines n Shut-off surfaces n Parting Surfaces n Tooling Split n Core FIGURE 32.21 The Mold Tools Mold Tools are really meant for tooling engineers, but part designers often use the first part of the process to apply draft to parts. Tooling engineers often need to add or correct draft to plastic parts they receive from part designers without draft or not designed with any process in mind whatsoever. CROSS-REF CROSS-REF The Split Line feature was covered in Chapter 7, and is not covered again here. Draft was covered earlier in this chapter. 947 Using Plastic Features and Mold Tools 32 The general workflow for using Mold Tools to create cavity and core blocks for an injection mold is as follows: 1. Create split lines to add draft where needed. 2. Create draft as needed (Move Face can be used to angle faces much like the Draft feature). 3. Scale the part up to compensate for shrinkage during molding. 4. Identify the parting lines that separate cavity faces from core faces. 5. Create Shut-off faces, which are surfaces that close any through holes (windows or pass-throughs) in the part, and represent places where the steel from the cavity side of the mold directly touches steel from the core side of the mold. These openings in the part are capped by surface features. 6. Create Parting surfaces. These are the faces outside the part where the steel from oppo- site sides of the mold touch. 7. Create the Tooling Split. Tooling Split uses the faces of the Shut-offs, Parting Surfaces, and the faces of either the Cavity or the Core side to split a block into two sides. 8. Create any Core features. Core is an unfortunately named feature in SolidWorks. Even in mold lingo, the word has several meanings, and it doesn’t become any clearer when translated into SolidWorks terminology. In this case, the word “core” refers to the mate- rial used to make core pins, side action, slide, lifter, or pull in a mold. If you were to create a mold with manual modeling functions, you might go through roughly the same steps in the same order. The SolidWorks process often breaks down in the automated surface modeling areas, such as shut-offs and parting surfaces. You may need to manually intervene in the process for these steps. Fortunately, the SolidWorks process is flexible enough to allow for manual modeling as needed. Each one of these process steps may have several steps of their own. Cavity and core creation is far from a push-button operation, but when you understand the overall process, the detailed steps become clearer. Using the Scale feature The Scale feature is used to make the plastic part slightly larger to compensate for plastic shrinkage during molding. Scale is driven by a multiplier value, so a part that is twice as big gets a scale fac- tor of 2, half as big gets a scale factor of .5. Plastic materials have a shrink rate that is usually mea- sured in thousandths of an inch per inch of part. Five thousands inch per inch is equal to a 0.5 percent rate. If the part is four inches long, the mold cavity to produce it must be 4.020 inches with that material. The 0.5 percent rate is equal to a scale factor of 1.005. Some materials have anisotropic shrink rates, meaning they shrink different amounts in different directions. SolidWorks has a means to compensate for this, although it may not always be practical. 948 Working with Specialized Functionality Part VII Usually the shrink directions are identified as “in the direction of flow” and “across the direction of flow,” and the direction of flow of molten plastic inside a mold cavity is not always a straight line. Any anisotropic shrink applied to a part in SolidWorks is an approximation at best. If you turn off the Uniform Scaling option in the Scale feature, SolidWorks enables you to set different scale factors for X, Y, and Z directions. The Scale PropertyManager is shown in Figure 32.22. FIGURE 32.22 The Scale PropertyManager Insert Mold Folders Mold Folders are folders that the Mold Tools add underneath the Surface body folders. You can add these folders manually using the Insert Mold Folders button on the Mold Tools toolbar. They are used to organize the different groups of faces used in separating the cavity and core solid bod- ies. The folders that are added are: n Cavity surface folder n Core surface folder n Parting surface folder Parting Lines The Parting Lines feature identifies (automatically or manually) the edges that separate the cavity faces from the core faces. Figure 32.23 shows the PropertyManager as well as the preview for this feature. The edge selections for this feature were mostly manual. SolidWorks intends for you to use the red arrow shown after you select an edge to propagate the selection around the part by press- ing Y for yes if the red arrow indicates the correct next edge of the Parting Line or N for no if it does not. In this case SolidWorks gives me a message that says that the parting line is a complete loop around the part, but the part has some through holes, so it requires shut-off surfaces to close the holes. 949 Using Plastic Features and Mold Tools 32 FIGURE 32.23 The Parting Lines interface The Parting Lines feature can also split faces if need be. You might need to split a face that strad- dles the parting line. For example, a filleted face might bridge across the parting line and need to be split. Shut-off Surfaces The screw holes that go through this housing require shut-off faces in order to create the mold cav- ity and core. You can’t just seal off one end of the holes; you have to pay attention to which end of the hole is where the draft in opposite directions meet. In this case, the counterbored holes from the outside have to be drafted from the outside, so they must be sealed or shut off from the inside. When you initiate the Shut-off Surfaces feature, SolidWorks identifies some of the necessary shut- offs for you. Figure 32.24 shows this. 950 Working with Specialized Functionality Part VII FIGURE 32.24 Creating Shut-offs When all appropriate edges around all of the holes and slots are selected, the Shut-off Surfaces PropertyManager message window turns green and says “The mold is separable into core and cavity.” The tags on the loops in the graphics window will say either “No Fill,” “Contact,” or “Tangent.” No Fill means that you do not want SolidWorks to create the shut-off surfaces. You will do these man- ually. Sometimes shut-off surfaces require complex or multi-feature shut-offs, which you have to do manually. The Contact condition means that the shut-off surface just needs to touch the edges, usually at a right angle. Tangent should be obvious. Sometimes you need a combination of conditions in a single shut-off, in which case you will need to finish the feature manually. When the parting line and shut-off surfaces are complete, SolidWorks will automatically knit together all the surfaces in each Cavity and Core folder into a single surface body. Parting Surface The Parting Surface in SolidWorks works best on planar parting lines that are convex all the way around. That is to say that it will work okay on a part with a parting line that looks like an “O” from the direction of pull, but may not work optimally on a part that looks like a “C.” In fact, it 951 Using Plastic Features and Mold Tools 32 might be safe to say that the Parting Surface is in many cases unusable for any but the simplest parts. The part that I have been using as an example for this section is too much for the Parting Surface feature for two reasons: it is non-planar and the parting line has two concave areas (corners where handle intersects the housing). There are not enough options with this feature to make it work in most situations in which it doesn’t work by default, so I don’t think it is worth going into in any further detail here. What this boils down to is that for 70 percent or more of your Parting Surfaces, you will need to create your own manually, which I show you how to do in the next section. Just to show an example that does work, I have created a very simple part and brought it to this point using the Mold Tools process. When the process works as it should, and even when you have to create surfaces manually, you will wind up with one complete surface body in each of the Mold Tools Folders — Cavity, Core, and Parting surfaces. From this you can see that the Parting Surface and Cavity Surface define the top side of the Cavity block. Likewise, the Parting Surface and the Core Surface define the top side of the Core block. In Figure 32.25, the Parting Surface is transparent so you can see both the Cavity and Core surface bodies. The grayscale image may not show this distinctly, but if you open the part from the CD-ROM, it will become obvious. FIGURE 32.25 A completed Parting Surface [...]... sufficient The Parting Line of the front part of the device should probably face forward instead of up to prevent as much vertical steel in the mold as possible To send the cavity and core blocks to a shop for mold building, you will probably want to separate the multi-body part into individual part files Use the techniques from Chapter 26 for this (Save Bodies, Insert Into Part, Insert Into New Part) 952... difficult Non-planar Parting Surfaces Frankly, the method SolidWorks uses to create the Parting Surface is insufficient for most tasks It will work well if you are molding a range of Frisbees or dinner plates, but it will not work well 955 32 Part VII Working with Specialized Functionality for hand-held medical devices Figure 32.29 shows the part on the CD-ROM named Chapter 32 – frame parting surface.sldprt... FIGURE 32.29 An automatically created Parting Surface for the hand-held medical device From this you can learn that the SolidWorks Mold Tools are not reliable for concave parting lines or non-planar parting lines Flat parting line disks and boxes work well Beyond that, expect to need to do some manual surface modeling If you want software that will do automatic parting surfaces for you, consider MoldWorks... factor of 1.008 Scale about the Origin of the part 18 To initiate the Parting Line tool., use the Top plane as the Pull Direction, and set the draft angle to 1 degree Click the Draft Analysis button 19 Notice a purple parting line that goes all the way around the part, but a warning message at the top of the Parting Line PropertyManager The warning says that the parting line is complete, but you need to... simple part, running some plastics evaluations on it, and then making the cavity and core blocks for the mold using a couple of different techniques The goal of the tutorial is to make you familiar with the workflow of the tools rather than to teach every available option 957 32 Part VII Working with Specialized Functionality 1 To create a simple plastic part, start by opening a new SolidWorks part file.. .Part VII Working with Specialized Functionality Tooling Split Assuming you have completed the Parting Surface either manually or through the SolidWorks Mold Tools, the next step is the Tooling Split If you complete the Parting surface manually, make sure it is knit together as a single surface body, and then in the Surface Bodies folder, drag the knit surface into the Parting Surface... the original part, making sure to turn off the Merge Result option Then use the Combine tool to subtract the mold parts from the new block Then use the inverse scale to shrink it back down to the original scale factor NOTE Also note the Interlock surface option in Figure 32.26 Most if not all of the examples of molds that you see created with SolidWorks mold tools are going to employ parting line interlocks... model and document every aspect of mold hardware NOTE To manually create the parting surfaces for this part, I tackled the hard part first, which turns out to be easy once you know a couple of tricks The first thing I did was to create a sketch and use it to lay out directions that I could pull off the non-planar sections of the parting line Figure 32.30 shows three lines that identify the non-planar top,... rectangular notch The edges selected for the Parting Line should be a clean single loop of edges that always separate the red faces from the green or yellow faces Be careful that the Parting Line goes around the Step Draft faces correctly NOTE FIGURE 32.36 The Parting Line PropertyManager and the model up to Step 19 20 Click the green check to accept the Parting Line feature 21 To crate Shut-off faces,... Animation Wizard This chapter does not cover Motion Analysis, formerly COSMOSMotion, because it is beyond the scope of the base SolidWorks package Using animations to flex parts IN THIS CHAPTER Animating the view Animating with key points Animating with Basic Motion Overview SolidWorks 2009 uses two different types of motion studies: Animation and Basic Motion Animation uses key frames to drive the motion, . next edge of the Parting Line or N for no if it does not. In this case SolidWorks gives me a message that says that the parting line is a complete loop around the part, but the part has some through. body. Parting Surface The Parting Surface in SolidWorks works best on planar parting lines that are convex all the way around. That is to say that it will work okay on a part with a parting line that. created Parting Surface for the hand-held medical device From this you can learn that the SolidWorks Mold Tools are not reliable for concave parting lines or non-planar parting lines. Flat parting