How to Present the MBD Data of a Gear Box Assembly

We worked on defining several critical callouts in a gear box assembly in a previous article. However, is defining 3D callouts everything we need to do? Is model-based definition (MBD) all about calling out these 3D annotations? Let’s first take a look at Figure 1.

Figure 1. A messy MBD presentation.

Obviously, no one would enjoy having to deal with this messy presentation. It would result in unnecessary resistance in MBD implementations. Many engineers have been focused on defining 3D product and manufacturing information (PMI), but they haven’t paid enough attention to the 3D PMI presentations. In reality, we all know that people do judge a book by its cover. Presentable MBD data is vital to implementation success, especially for downstream consumers such as those in machining, inspection and purchasing. Therefore, this article will be centered on presenting MBD data in a consumable, actionable and professional way, especially as it applies complex models.

In this regard, Tim Benson with Waters Corporation shared his experiences in a SOLIDWORKS MBD forum discussion, “One point that should NOT be discounted is the capturing of organized, thoughtfully presented 3D views. Just recently, our core research team began using MBD and one of the first parts completed was not presented very well. The views and dimensions were scattered about in no logical order and it just looked bad. So bad, in fact, that the machinist ended up creating his own manual sketch on paper to create something he could work with! Not exactly a ringing endorsement of MBD. Fortunately, I was able to clean up the presentation and show the machinist how the data could and should be presented. He was much happier after that.”

Now, let’s solve the problems presented in Figure 1 together.

The first problem is the unclear internal structures and component relationships. For an enclosed assembly such as the gear box shown in Figure 1, the relationships between gears and shafts are at the heart of the design and must be communicated clearly. When compared to Figure 1, Figure 2 reveals the internal structures, relationships and section cap profiles of the housing components with much-needed clarity.

Figure 2. A quarter section view of the gear box.

The Zonal Section View tool shown in Figure 3 provides multiple control options to cut models in a wide variety of popular ways. For example, you may enable up to three cutting planes. Figure 3 illustrates a Top plane for the first section and a Right plane for the second section. These cutting planes divide the 3D space into multiple intersection zones and you can decide which ones to cut out. First, click on the blue list box on the Section View property manager on the left side. Now it’s ready to accept selections. Next, in the graphics area on the right side, click on the zones to remove them. Zones that are to be removed are highlighted in the transparent green boxes shown in Figure 3. Multiple intersection zones can be selected. What you see in the graphics area is what you will get in the final section view. So you don’t actually have to flip a cutting plane on the property manager to adjust the cutout portions.

Figure 3. The intersection zones in the graphics area.

Another key requirement is to exclude certain components in the quarter section view. According to the ASME Y14.3-2003 standard, “When the cutting plane lies along the longitudinal axis of items, such as shafts, bolts, nuts, rods, rivets, keys, pins, screws, ball or roller bearings, gear teeth, spokes, and the like, these parts are not sectioned except when internal construction is shown.”

Figure 4 shows that the blue output shaft, gear, bearings and rings are excluded and are therefore not sectioned. The output shaft is actually the target to be exposed by the section view, so it should remain. Additionally, the gear, bearings and rings are standard purchased components anyway. Sectioning them wouldn’t add any actionable value for manufacturing.

Figure 4. Excluding the output shaft, gear, bearings and rings in the quarter section view per ASME Y14.3-2003.

To further clarify the relationships between all the components, Figure 5 shows an exploded view with component balloons and a bill of materials (BOM) table.

Figure 5. An exploded view.

The second problem in the original MBD presentation is the overlapping annotations. When there is a large amount of 3D PMI as shown in Figure 1, categorizing it into annotation views can help control the annotation visibilities layer by layer. For instance, in Figure 1, the components, 3D dimensions and tolerances, 21 balloons and a BOM table were all piled up on top of each other. To clean up the display, let’s analyze them each case by case.

1. The assembly-level 3D dimensions and tolerances only make sense in an assembled gear box. The predefined orthogonal annotation views such as Right, Top and Front worked out well as shown in Figure 2. For example, the highlighted green callouts are on the Right annotation view facing us.
2. As shown in Figure 5, balloons are apparently better understood when they are attached to individual components in an exploded view where 3D dimensions and tolerances may not apply. So let’s organize the balloons into a separate annotation view called “Balloons” so that we can show them in an exploded state, but hide them in collapsed states. Similarly, we can show the Right, Top and Front annotation views in collapsed states but hide them in the exploded state. Although the balloons in Figure 5 and the highlighted callouts in Figure 2 are all from the same Right perspective, separating them into multiple layers enables a finer control over visibility.
3. The BOM table should always be displayed flat to screen for easier reading. You can assign it to a special annotation view called “Notes Area,” which is the first option in the annotation view folder on the left tree in Figure 5. Items with an extensive amount of text such as notes, tables and statements assigned here will always be displayed flat to screen.

The third problem in the original MBD presentation is the complicated display setting combinations. Now, with all the above control options, you may ask how you can quickly capture and retrieve specific setting combinations afterward. Obviously, an exploded state cannot be displayed at the same time as a collapsed state. Different types of 3D PMI need to be shown or hidden in certain views or states, in addition to the display orientations and zooming factors. The number of various combinations can be compounded pretty quickly. 3D Views is your tool to solve this problem. It can capture not only orientations, scales and section cuts, but also annotation views, configurations and display states as shown at the bottom of Figure 5. These visual bookmarks are self-explanatory. By glancing through the thumbnails, captions and pop-up bubbles on the 3D Views panel, you see exactly which elements capture what. Furthermore, a series of 3D Views forms a storyline that can help you articulate a design for downstream consumers.

Now it’s time to recap this article in Table 1. To learn more about how the software can help you with your MBD implementations, please visit its product page.

Table 1. MBD Presentation Problems, Tools and Use Cases.

About the Author

Oboe Wu is a SOLIDWORKS MBD product manager with 20 years of experience in engineering and software. He is an advocate of model-based enterprise (MBE) and smart manufacturing.