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Reuse CAD Models with MBD

Most often, engineers waste productive design efforts in fixing the CAD models, so that they can be reused successfully in downstream applications. The roadblocks that prevent engineers from reusing their design however are the CAD models itself; and to avoid this, a more systematic approach for specifying complete product definition and design intent in CAD models called Model Based Definition (MBD) is gaining popularity.

MBD is the fundamental element of model-based enterprise (MBE), which aims to get more benefits out of complete and reusable CAD models for organization as well as the suppliers. To make the most out of your CAD models thus requires adopting proper modeling techniques, so that the ROI on adopting MBE is significant.

Learning from the Past

With increasing competition, improving the productivity is critical for manufacturers globally, and this requires that the product definitions are complete and reusable, whether in 2D or 3D. Since last many years, the process of improving the efficiency of 2D and 3D product definitions is underway. However, it is only now that manufacturers have started adopting rigorous standards for the development, authoring and publishing of 3D product information, including all dimensions and tolerances for complete description of the product or part being developed.

There are numerous standards that have evolved over time to ensure that product definitions remain consistent. Some of the widely known standards are:

  • ASME Y14.41 (Digital Product Definition Data Practices) developed using the drawing based standard ASME Y14.5 (Digital Product Definition) defines standards for dimensioning and tolerancing, symbols and definitions required from drawings in the CAD models
  • ASME Y14.47 (Model Organization Schema Practices) includes definitions for complete model and the need of integrating data geometry and tolerances.
  • QIF (Quality Information Framework) is all about the right ways to capture the data and exchange key characteristics along with safety items. QIF is an open source and free ANSI standard that supports digital product definition concept across different engineering applications like product design, manufacturing and quality inspection.

Thus, in order to develop a 3D model with complete product definition and avoid material wastage as well as rework due to human misinterpretation, following above standards is important.

Defining MBD

MBD is all about integrating product manufacturing information (PMI) with the 3D CAD models, to completely define the annotations and attributes. A complete production definition then is the one that meets key criteria of adhering to standards, design and modeling practices, setting up CAD files, creating CAD geometry as well as determining the level of details displayed in the PMI. While the standards discussed above can lead to lack of agreement on what a complete product definition is for MBD, the ASMEY14.47 is meant to assist organizations to define MBD properly for upstream as well as downstream users of MBD data sets.
As an example, it is not necessary to include full dimensions on the 3D model, since the geometry already defines the basic dimensions. Instead, it should include manufacturing tolerances to meet the inspection criteria.

Benefits of MBD

The prominent benefits of MBD are it facilitates clear, error-free and repeatable communication on a single 3D CAD model. Sharing information with stakeholders in design, review, approval, sourcing and manufacturing is better and hence improves the collaboration. Usable models also reduce the cost of material scrap and rework, since the level of knowledge on the design intent is much higher before actually manufacturing the product. It is also possible to search the model data for correct product information in less time, since the meta-data includes all the necessary details on part number, supplier information, material, etc. These benefits significantly interests C-level personnel, since it shortens the design cycle and promotes design reuse.

Thinking Ahead

To gain the benefits of MBD, it is important to think the organizational environment in the context of MBE. While shifting to this change will result in resistance from employees, it is important to chart out proper plan and critical activities to make the environment favorable for MBD. The benefits of MBD can only outweigh the costs, if implemented correctly and with an understanding of its long-term impacts. It is also crucial to define the roles properly to ensure accountability. With a continuous feedback, the required standards and schema can be developed successfully.