Engineering Drawings: Are they of any value today?

Engineering Drawings: Are they of any value today?

What are engineering drawings? 

The classic summary:   

  • Engineering drawings are a rich and specific outline that shows all the information and requirements needed to manufacture an item or product.  
  • It is a graphical language that communicates ideas and information 

Did you know….drafting methods date back thousands of years. The perspective drawing was invented in the 1300s, descriptive geometry was invented in 1765, orthographic projection was invented in 1770, and 2D CAD was invented in the 1980s. 

The art of drafting has evolved over time.  The ability to create and manufacture parts/assemblies has also progressed. 

Model based definitions

In developing a 2D drawing for a component, the engineer must envision the part shape, then record images of the Front, Top, Side views on a sheet of paper. 

With 3D Computer Aided Design (CAD), this thought process is reversed.  Creating of part shapes in three dimensions is where we start.   

The example at right was selected from an images search 

Can you find the missing dimension? (Hint, section view) 

From a modeling perspective, a typical creation process would look like this….

Note, sketches and all features are actual size. 

We then add material, finish, and other requirements to the model as we progress

And this is where things get interesting.

  • The 3D model is created at actual size.
  • We attach material and finish specifications using Product Manufacturing Information (PMI) to the model.
  • For specific tolerances required for a feature, this information may also be added to the model.
    • To learn more about PMI

Which are all attributes and requirements typically associated with an engineering drawing.

  • The model may also be used in an assembly, where interferences may be detected, and then resolved, before the part is ordered.
  • The model may be directly transferred to a machine shop, where CNC programming can begin
  • A free body diagram may be associated to an analysis assembly.The analysis assembly is comprised of finite element mesh, load / restraint conditions (the free body diagram), material properties and any other topics of interest.
    • The component may be validated in its working conditions before part manufacture, and if physical testing is required for final validation, previous iterations in simulation provide a much more focused effort.
  • And there is more…the model may be directly prototyped…..think 3D printing…
  • A free body diagram may be associated to an analysis assembly.The analysis assembly is comprised of finite element mesh, load / restraint conditions (the free body diagram), material properties and any other topics of interest.
    • The component may be validated in its working conditions before part manufacture, and if physical testing is required for final validation, previous iterations in simulation provide a much more focused effort.
  • And there is more…the model may be directly prototyped…..think 3D printing…

The theme of Model Based Definition is using 3D models to define, and provide specifications for, individual components and product assemblies.

  • The 3D data contains information to manufacture and inspect product without the need for an engineering drawing.

From a technology perspective, the repeating theme….question the need for an engineering drawing

In other disciplines, engineering drawings have been displaced by simulation.  Would you do a drawing for this design?  (Image from Electronic Design)

Integrated circuits have reached remarkable packing densities through use of simulation and modeling.

Code development, which formerly had produced printed documentation, no longer does so.  Value is in the files

Let’s look at the Engineering Drawing next…in terms of design time

In this image we have placed the 3D model onto a drawing template, and established the orthographic views

We MANUALLY select edges/radius/etc.  to show component dimensions.

These dimensions and attributes are already in the model. 

In terms of labor content, we are paying twice for the same information!

What value does the engineering drawing provide, in this context of model-based design?

Today, it provides an easily read format for others.  However, there are alternatives which provide the same information without the labor required to create a redundant engineering drawing

Communication within the organization, is our next topic.  

“I need a drawing…” 

Start to follow a quoting process, or any other function outside of engineering and you get this request.

Why? 

Because that’s what we know, what we understand and current practices all start with…“I need a drawing…”

The image at right is Teamcenter, with the Viewer tab selected. 

You don’t need a CAD application to work with CAD models.  Visualizers use the JT file derived from NX CAD model and allow anyone to find the same information that a manually created drawing has

We saw earlier in this blog that CAD models drive downstream processes.

Yet, what do we provide within our organizations?  A PDF of the drawing.

And then, who gets the phone call asking…”Could you send me the CAD model?”

We build physical prototypes to verify the design.  Often these “Engineering Models” go through several iterations at considerable expense to the organization.

  • Do we match test results to the pre-released simulations?
    • No, we update the drawings and make new parts, then re-test

And here is an interesting tidbit, if you are trying to interpret what a drawing view is showing, or if you are trying to trace the root cause of a problem…it takes less time overall if you utilize the models!

People, Processes and Technology

If you have conversations that go like this….

  • “That’s nice, but I need a drawing…”
    • Don’t you have Teamcenter and the viewers on your PC?
      • Yes I do, don’t use them….

You have found the beginnings of why your organization still uses engineering drawings.

If you do a Search for “Paperless Office” it doesn’t take long to determine that attempts to attain this goal has been a decades long process.

The root cause of why we are still using drawings is….The person in the mirror……

This is a culture change.

As Jason Albanese noted, “In the height of the Digital Era, we’re not lacking the means to eliminate paper from the workplace, but we are lacking the mindset.”

Or maybe hoping something magical will happen….

Source:  “Resistance to Change Can Be a Killer in the Business World”

Post by Craig Robillard

Hello, I'm Craig! With beginnings starting as an engineer/draftsman back in 1983, I was the first user of McAuto Unigraphics II Version 1.0. At that time, Teamcenter was not invented, however the need for file management was soon recognized. I am now an Application Engineer at Swoosh Technologies that specializes in Teamcenter, and has a background in new product development, working on a wide range of products such as the following: Copiers, Ink Jet Printers, Scanners, Satellites like Google Earth, Fusion Energy Research, and Industrial Compressor Design (HVAC).

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