Proven 3D GD&T Advantages at Johnson Controls
The model-based definition (MBD) history and successes at Gulfstream are impressive and encouraging to many manufacturers worldwide. However, some people may be wondering about the MBD experiences at companies outside of the aerospace industry. In this article, let’s review an example at Johnson Controls, which is a global company offering products and services to optimize energy and operational efficiencies of buildings, automotive batteries and interior systems. Figure 1 shows an energy storage product by Johnson Controls.
Figure 1. An energy storage product by Johnson Controls. (Image courtesy of Johnson Controls.)
Johnson Controls first started the MBD implementation in 2011, with a mission to enable seamless sharing of product information within the extended enterprise and automotive industries. The company clearly saw the advantages of 3D models integrated with product and manufacturing information (PMI) over 2D drawings.
For example, Ram Pentakota, the engineering director with the Johnson Controls automotive seating division, shared several reasons why 3D geometric dimensioning and tolerancing (GD&T) are better than 2D drawings. Figure 2 shows a typical 2D drawing.
Figure 2. A typical 2D drawing. (Image courtesy of Johnson Controls.)
In order to make sense of a single GD&T feature control frame, a reader of this drawing must find the related datum symbols by manually scanning through the entire sheet and possibly many other sheets. Moreover, multiple datum references require multiple rounds of this type of manual searching. After locating a datum symbol, an engineer needs to interpret the datum feature identified by this symbol and remember the relationship between them to understand a feature control frame.
As you can see, the experience feels similar to looking for several needles in a haystack and weaving a thread through these needles. A simple question—such as, “Where is datum feature A?”—may be fairly challenging in the haystack.
As a comparison, with 3D GD&T defined in CATIA V5, you can easily select the datum symbol A in the feature tree list. Then the datum feature A is automatically highlighted in the orange color in the viewport, as shown in Figure 3. This case is especially tricky in 2D drawings because the datum feature A includes multiple surfaces identified by multiple datum target symbols: A1, A2 and A3. Now with 3D GD&T, the presentation is straightforward and intuitive.
Figure 3. Multiple datum feature surfaces are automatically highlighted with 3D GD&T. (Image courtesy of Johnson Controls.)
Another common question to ask is how many datum features there are in total. The answer can affect the machining and inspection fixtures and setups. With the 2D drawing as shown in Figure 2, you must manually scan and count all the datum symbols and features. But with the 3D GD&T, the datum symbols are well organized in the feature tree, as shown in Figure 4. In addition, all the views, datum reference frames and geometric tolerances are also listed. Of course, selecting them in the tree on the left will highlight the corresponding callouts and features in the viewport on the right. The cross highlighting provides an instant visual confirmation to reduce miscommunications.
Figure 4. Datum symbols, reference frames, geometric tolerances and views are well organized in the feature tree. (Image courtesy of Johnson Controls.)
One step further, with the 3D GD&T definitions (as shown in Figure 5), the software can intelligently help you flag GD&T errors. For example, the highlighted Simple Datum 6 in the tree is a conflicting duplicate to the previously created Simple Datum 1 constructed by three datum targets. Therefore, these datum callout icons along with the Datum Reference Frame 1 are all attached with yellow warning signs. Similarly, SOLIDWORKS MBD has built in hundreds of rules to verify your GD&T, as discussed in a previous article, “Check Your Grammar: Verification for GD&T and MBD.” This type of automatic GD&T verification can greatly improve the annotation quality and consequently, the manufacturing quality, but it isn’t available in 2D drawings.
Figure 5. The problematic datum callouts and reference frame are automatically flagged with warning signs. (Image courtesy of Johnson Controls.)
By the way, please notice that the three separate datum targets, A1, A2 and A3, are cohesively constructing one datum feature A. It’s nice to see that the software can automatically recognize separate targets collectively as one datum feature. This automatic construction isn’t available in 2D drawings either.
Besides flagging existing errors, 3D GD&T in CATIA V5 can also help you prevent errors. Depending on the feature you select, the software will provide you only the valid GD&T callout options. For instance, Figure 6 shows that a flat surface has been selected.
Figure 6. A flat surface is selected. (Image courtesy of Johnson Controls.)
Please notice that on the dialog box, as shown in Figure 7, only the valid callout types are provided for the selected flat surface feature, such as datum symbols, straightness, flatness, line profile and surface profile tolerances. Other irrelevant callouts are hidden automatically.
Figure 7. Only relevant callout types are provided for the selected flat surface feature. (Image courtesy of Johnson Controls.)
If you select a cylindrical surface, as shown in Figure 8, then the callout options are adjusted accordingly, as shown in Figure 9. For instance, the flatness tolerance doesn’t apply to a cylinder, so this option is hidden. Instead, the circularity and cylindricity tolerances are now presented.
Figure 8. A cylindrical surface is selected. (Image courtesy of Johnson Controls.)
Figure 9. The callout options are adjusted automatically according to the selected cylindrical surface. (Image courtesy of Johnson Controls.)
Figure 10 shows a more complex case in which a torus surface is selected.
Figure 10. A torus surface is selected. (Image courtesy of Johnson Controls.)
Now you can see that several dimensioning and tolerancing options specific to torus surfaces appear on the dialog box (as shown in Figure 11), including the torus body diameter and radius along with the revolving ring diameter and radius.
Figure 11. The callout options are adjusted automatically according to the selected torus surface. (Image courtesy of Johnson Controls.)
In summary, Johnson Controls is convinced of the advantages of 3D GD&T over 2D drawings, including:
- straightforward identification and organization of datum symbols and datum features,
- intelligent GD&T error flagging and
- automatic prevention of GD&T errors by providing only valid callout options according to the selected feature.
I hope that you are convinced of these advantages as well. Most importantly, I hope that you can enjoy similar benefits in your own MBD practices. To learn more about how SOLIDWORKS MBD can help you with your MBD implementations, please visit its product page.
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 and smart manufacturing.