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PMI Enhancements in SOLIDWORKS MBD 2016

CAD Concept Design

PMI Enhancements in SOLIDWORKS MBD 2016

SOLIDWORKS MBD 2016 was released almost a year ago, but many of us are still unaware of some handy product and manufacturing information (PMI) enhancements, even several long-awaited additions. In this article, let’s explore three examples and see how they can help.

DimXpert in Assemblies

DimXpert was first released in SOLIDWORKS 2007 to automate the 2D detailing of manufacturing features. Then in SOLIDWORKS 2008, it expanded to define 3D PMI on parts in response to the ASME Y14.41:2003 standard. In recent years, with the releases of the military-standard 31000A:2013 and the updated ASME Y14.41:2012 and ISO 16792:2015 standards, the model-based definition (MBD) adoption has grown significantly as explained in a previous article, “Top 5 Reasons to Use MBD.” As a result, the engineering community has shown an increasing demand of DimXpert in assemblies.

For example, we may need to install many self-clinching fasteners onto a sheet metal body. They are usually treated as inseparable parts in one piece and produced with one part number, but technically speaking, they are an assembly. We need to define the sheet metal hole spacing, interfaces and overall size dimensions and tolerances as shown in Figure 1.

Figure 1. DimXpert in an assembly to define inseparable parts.

Another typical use case is to define assembly features. For instance, in a window set, different parts are first glued onto one mounting frame to make sure all the components are accurately positioned. Then pin holes are drilled through multiple components so that they are aligned precisely for pins to go through. Therefore, these holes are typically modeled as assembly features and drilled at the assembly procedure, not at the part manufacturing steps. Figure 2 shows an assembly feature, Hole1, being defined.

Figure 2. DimXpert in an assembly to define assembly features.

By the way, DimXpert in assemblies is not just about adding dimensions. It also carries over all the powerful DimXpert tools from parts to assemblies, such as the GD&T syntax verification, Auto Dimension Scheme, Copy Scheme, PMI cross-highlighting and Show Tolerance Status.

Face Edge Selections

As introduced by a previous article, “Define Manufacturing Features Directly,” DimXpert focuses on defining comprehensive features, rather than simple geometries, to support downstream procedures better. The challenge here is the differences in selection behavior. In 2D drawings, we are used to picking a line or a circle, whereas in MBD, we need to pick features such as planes or hole inner faces. Sometimes, selecting faces could be tricky, especially for small details. We may have to zoom in to make a hole inner face big enough to click on accurately. Or rotate models back and forth to pick two parallel opposing faces.

In order to improve the ease of use and facilitate the transition from 2D drawings to MBD, the 2016 release can now recognize a face edge selection and automatically infer the most probable features to define. This way, we can enjoy the long-awaited benefits of both worlds: the easy selection of edges in 2D drawings and the intelligence of features in MBD.

The top example in Figure 3 shows a click on a hole edge. Then DimXpert interprets automatically that we may want to define the hole feature, so it highlights this hole and provides the callout. Similarly, in the bottom example, we just pick an edge and then the two parallel opposing planes are highlighted and the distance in between is provided. Otherwise, we would have to rotate the model to click on the lower hidden plane highlighted in green outlines. An added benefit is for PMI placements. Because we can now pick edges, DimXpert will try to place the callouts in the same plane as the selected edges. That is, they are not dropped deep down to the bottom of this hole or the bottom edges of the notch opening.

Figure 3. Select face edges to define features.

Automatic Coordinate Systems for Datum Reference Frames

In geometric dimensioning and tolerancing (GD&T), datum reference frames are the cornerstones. When we read a GD&T feature control frame, the first thing we need to know is its datum references. Where are datum features A, B or C? What are their relative priorities? What are the material boundaries? These determine how a part is set up for machining and inspection. Only when a setup is established or the part is placed in a certain way can we make sense of the rest, such as tolerance symbols, zone types, values and modifiers.

However, there are several problems. First, datum symbols may not be obvious at first glance. Some may be hidden on a certain view. Some may be buried in other PMI. There may be so many callouts that our eyes often have a hard time locating two or three key datum symbols as the starting points. To interpret a control frame, we often have to rotate, zoom or pan a model and comb through various views to find all the relevant datum symbols. Second, once we identify these datum features, we have to remember them and imagine a reference framework with its location and orientation in our mind. This short-term memory can easily be muddied in a busy product definition. Furthermore, these problems are compounded when there are multiple datum reference frames, for instance, ABC, CAB, BDE and so on, which are often used in production.

To solve these problems, the ASME Y14.5:2009 standard proposed using coordinate systems to indicate the locations and orientations of datum reference frames as shown in Figure 4.

Figure 4. Coordinate systems per datum reference frames in an NIST PMI test model.

To comply with the ASME standard, MBD 2016 added a new feature to create and display coordinate systems per datum reference frames. Just click on a feature control frame and the corresponding coordinate system is presented automatically as shown in Figure 5. Now that the datum features, locations and orientations are just one mouse click away, we don’t have to remember all of them by heart anymore. By the way, this display is on-demand only so that multiple coordinate systems won’t cloud the model viewport all together.

Figure 5. A coordinate system is presented automatically in MBD 2016.

We explored three long-awaited PMI enhancements in the MBD 2016 release: DimXpert in assemblies, face edge selections and automatic coordinate systems per datum reference frames. Many of us have been asking for them for years. Now they are available. I hope you find them relevant and helpful too. 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 (MBE) and smart manufacturing.  


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