How MBD and MBE Can Fix Your CAD Models
Dick Bourke posted on September 07, 2016 | 5940 views

In a previous post, we introduced model-based design (MBD) for providing clear, repeatable and unambiguous communication to all stakeholders. However, the procedural capabilities of MBD as shown below need to be integrated with model-based enterprise (MBE) processes to generate the desired results. With the emergence of the “digital thread” concept, the process of communication becomes ever more critical.

The illustration shows the four elements of Model-Based Definition as a minimally annotated data set defining the product in a manner that can be used effectively without a drawing graphic sheet; interpreted definition from the proposed in ASME Y14.41.1draft. (Image courtesy of Action Engineering.)
The illustration shows the four elements of Model-Based Definition as a minimally annotated data set defining the product in a manner that can be used effectively without a drawing graphic sheet; interpreted definition from the proposed in ASME Y14.41.1 draft. (Image courtesy of Action Engineering.)

Now, we'll explore the core concept of creating the data package (DP) to enable a digital thread implementation in an MBE environment. As with the previous post, Jennifer Herron, CEO of Action Engineering, shares her expertise.

Jennifer Herron.(Image courtesy of Action Engineering.)
Jennifer Herron. (Image courtesy of Action Engineering.)

First, let's hear how Herron describes MBE: “The cultural environment needed for successful use of MBD is a proactive organization that approaches product development, manufacturing and lifecycle support by using MBD to drive all engineering and manufacturing activities. A critical element is an infrastructure—the people and technology resources required to support MBD and MBE.”

“As a key benefit, MBE is an enabler for bringing the culture of discrete manufacturing into a rapid deployment of innovative products through unambiguous definition of the product,” Herron continued. “The designer makes it in 3D; the analysis disciplines process the same data, the manufacturers and quality groups build to exactly the same data as the designer envisioned and the analysts analyzed.”

“The outcome is the manufactured product matches the designed product within allowable tolerances,” Herron concluded.


What Is the Digital Thread?

As an emerging concept, several definitions have arisen, including “Digital Twin,” from knowledgeable sources such as the Air Force's “Why Digital Thread.”

For our purposes, a simple definition is “the digital representation of the desired physical reality”—in simulation language, the essence without the reality. With a growing interest in simulation processes within an MBE product development environment, keep this context in mind.

One of the major proponents of the digital thread is General Electric as shown below.

(Image courtesy of General Electric.)
(Image courtesy of General Electric.)

To take advantage of the digital thread, a “digital bucket” is required to collect the data. For the DOD environment, it is identified as the technical data package (TDP) per MIL-STD-31000A; for the commercial entities, it’s known generically as a DP.


Defining the TDP:MIL-STD-31000A: 3.1.37

A TDP is a technical description of an item adequate for supporting acquisition, production, engineering and logistics (for example, engineering data for provisioning, training and technical manuals). It defines the required design configuration or performance requirements, as well as procedures required to ensure adequacy of item performance. It consists of applicable technical data such as models, drawings, associated lists, specifications, standards, performance requirements, QAP, software documentation and packaging details.

A TDP is defined by selections made by the contracting officer on the TDP OPTION SELECTION WORKSHEET.(Image courtesy of Action Engineering.)
A TDP is defined by selections made by the contracting officer on the TDP OPTION SELECTION WORKSHEET. (Image courtesy of Action Engineering.)

Herron continued to share her experiences: “First, let me remind you that ASME standard Y14.41.1 is replacing this MIL-STD-31000A Appendix B, a significant development as the value of MBD in commercial companies increasingly continues to be recognized. Presentations at a recent NIST conference validate this assertion.”

With broad interpretations of the digital bucket, you can transform the concept of the TDP into a DP with a variety of flavors as the illustration shows.

(Image courtesy of Action Engineering.)
(Image courtesy of Action Engineering.)

Examples of those flavors might be:

  1. Prototype data package of a machined part that will be prototyped in plastic for concept evaluation. It contains the native CAD file, a STEP file and no annotations. Because this communication is early in the product lifecycle, full-blown product definition is not needed, nor is it practical.
  2. Production data package of a sheet-metal part that is out for large quantity procurement and absolute, unambiguous definition is required to return repeatable parts. It would contain a gathering of data objects:

    • STEP file only to protect intellectual property (IP), yet still completely represent the geometry
    • Certification report that the STEP file was compared and verified against the source authority (typically native)
    • Material and process specifications (organization-specific standard operating procedures)
    • 2D DXF file for laser-cutting the flat pattern
    • Annotations that specify flat pattern cutting tolerances and manual bend instructions and tolerances


Supporting All Stakeholders with 3D PDFs

Steps to create a TDP/DP for the Digital Thread. (Image courtesy of Action Engineering.)
Steps to create a TDP/DP for the Digital Thread. (Image courtesy of Action Engineering.)

Finally, the result: communicating with all stakeholders via the medium of 3D PDFs.

Herron wrapped up with some observations: “Digital thread isn't just a marketing term. It's real. At a recent NIST conference, interest and implementations are increasing; the value of the digital thread is being recognized by both large companies such as Rockwell Collins and smaller companies.

It is neither trivial nor simple to undergo an MBD initiative, but if you never start, you certainly won't get there. Take action to enable your digital enterprise.

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