Clarifying the Confusing Terminology of Drawingless Initiatives
Chad Jackson posted on April 01, 2013 |

In this industry, terminology is a bear. There are special acronyms and terms with subtle differences that can actually have big implications. And unfortunately, there isn't a good place to get definitions for them all.

A few weeks ago, I launched survey that looks at design data interoperability, model-based enterprise initiatives and the use of 3D outside engineering. Statistics and findings from that survey will be used to publish The State of 3D Collaboration and Interoperability Market Report in May. You can take the survey here to get a complimentary copy of the report. But the exercise of carefully developing the survey made me tease apart the definitions of various terms related to drawingless efforts.

Given that, I thought it'd be valuable to put them here. So here they are.

Drawingless and Paperless

They're the same, right? Well, actually no. 

Drawingless refers to an organization's efforts to remove the engineering drawing as the authority document that is passed downstream during design release. Instead, a 3D Model is used instead.

Unlike Drawingless, Paperless actually has an entry in wikipedia. Here it is:

A paperless office is a work environment in which the use of paper is eliminated or greatly reduced. This is done by converting documents and other papers into digital form. Proponents claim that "going paperless" can save money, boost productivity, save space, make documentation and information sharing easier, keep personal information more secure, and help the environment. The concept can also be extended to communications outside the office.

In the engineering world, Paperless roughly means the same thing. It refers to the medium that used to consume engineering documentation that is passed downstream during design release. It could be an engineering drawing or a 3D Model. But with a paperless effort, the engineering documentation isn't printed or given hardcopy form. It is consumed digitally instead.

Product and Manufacturing Information

Product and Manufacturing Information, commonly referred to as PMI, is simply the non-geometric information of a part applied to a 3D model instead of an engineering drawing. Here's the well formed definition from its wikipedia entry.

Product and manufacturing information, also abbreviated PMI, conveys non-geometric attributes in 3D computer-aided design (CAD) and Collaborative Product Development systems necessary for manufacturing product components or subsystems. PMI may include geometric dimensions and tolerances, 3D annotation (text) and dimensions, surface finish, and material specifications. CAD application literature may also refer to PMI synonymously with Geometric Dimensions and Tolerances (GD&T) or Functional Tolerancing and Annotation (FT&A).

So what are all of these non-geometric attributes that are added? Let's take a look.

  • Geometric Dimensioning and Tolerancing (GD&T): This is simply a symbolic language that documents nominal geometry and its allowable variation. You can find much more on its definition in its wikipedia entry.
  • 3D Annotation: These are the equivalent of the notes you would see on a drawing. However, in this case, they are attached to geometric entities. When you rotate the 3D model, the leader terminates to a specific geometry item.
  • Dimensions: This is simply the equivalent of a measurement that appears on engineering drawings. However, in this case, the lead lines are connected to geometry.
  • Surface Finish: This is a specification that defines how smooth a particular surface needs to be. In turn, this property determines if and how a surface should be machined.
  • Material Specifications: This simply documents what material should be used to manufacture the part or component.

So basically, PMI adds non-geometric information to 3D models. Now, there's an important distinction here. 3D Models without PMI enable the enterprise to create deliverables and validate things that are reliant on the form and fit of the design. 3D Models with PMI, however, extend the uses of this asset into other scenarios, which we'll explore further in the next section.

The major point here, however, is that all of these non-geometric attributes used to documented in the engineering drawing. The idea behind the 3D Model with PMI concept is that they live together on the 3D geometry.

Model-Based Initiatives

This set of terminology is relatively new. Look this up in wikipedia and you'll come across many model-based terms, most of which refer to software architectures. In the engineering world, these terms refer to efforts that are similar to Drawingless. These terms, however, offer a little more specificity. Furthermore, they are championed by an organization called PDES Inc, whose goal is the following:

PDES, Inc. is an international industry/government/university consortium committed to accelerating the development and implementation of standards enabling enterprise integration and PLM interoperability for its member companies.

Model-Based Enterprise

The concept behind the Model-Based Enterprise is an overarching idea that many organizations within a manufacturer, or across product development, use the model as the product definition. This idea is broken down into a number of sub-initiaitves including: Model-Based Engineering (MBe), Model-Based Manufacturing (MBm) and Model-Based Sustainment (MBs). These definitions are actually reflected in their organizational structure of PDES Inc..

Model-Based Engineering

Per PDES, Model-Based Engineering (MBe) covers a wide range of engineering activities, including systems engineering, engineering analysis, requirements, routed systems and interoperability. This field isn't actually about creating engineering documentation. It focuses on embedding items, attributes and characteristics in the 3D model that help engineers in the design process. This includes things like variational analysis and Design for Six Sigma (DFSS) which relies on tolerancing.

Model-Based Manufacturing

Organizations have been using 3D models in digital manufacturing activities for a while. However MBm extends those use cases in some interesting ways.

The idea of using the 3D model to design tooling, jigs and fixtures has been around for a long time. The geometry of the 3D model determines the shapes of the mating surfaces of these items so they can fit together or be used for production.

Non-geometric information from 3D Models with PMI can be used for extended cases. Required surface finishes on the design part require certain surface finishes on tooling. Material specifications for the design part affect its shrinkage and, as a result, the negative cavity of tooling. So there is direct application of PMI here.

That's not the only case though. The concept of using 3D models to generate tool paths for numerically controlled (NC) machines like milling, turning and coordinate measuring machines (CMM) have be in practice for years. The geometry of the 3D model drives the NC moves in the tool paths so manufacturing engineers don't have to manually program such sequences.

As is the case with designing tooling, jigs and fixtures, non-geometric information from PMI serves a purpose here as well. Tighter tolerances documented as GD&T on design parts determine tool selection as well as NC speeds and feeds for machining. Likewise, GD&T embedded in design geometry determines touch points and tolerances for CMM machines.

Summary and Questions

OK. There you go. I hope that sheds some light on the terminology used in this field.

Don't forget: if these topics are important to you, then it might make sense to take the 3D Collaboration and Interoperability survey so you can get a complimentary version of the report.

Take care. Talk soon. And thanks for reading.

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