Will MBD replace 2D drawings?

You have been hearing it for years:

“MBD will replace 2D drawings!”

“Drawings are dead!”

“Boeing has switched over completely!”

I thought it was strange that we keep hearing those words, yet I haven’t met a single engineer or a manufacturer that uses MBD.

So I decided to dive in and find out what the current state is. In this post, I am going to share what I have learned so far.

What is MBD anyway?

MBD stands for Model-Based Definition. It is being presented as the logical successor of 2D drawings. The idea is that the 3D model is leading in every step of the design and manufacturing process.

Detailing your design is done by adding annotations in the form of dimensions, tolerances and other remarks to your 3D model.

This annotated model is then exported as a native model, a 3D PDF or (using SOLIDWORKS) an eDrawings file. These files can be combined with other information that is required for manufacturing, support and life cycle management.

The goal is to go completely digital and ditch 2D drawings altogether. When all customers and suppliers work with these files, the need for translations between 3D and 2D and the usual paperwork should be gone. Of course, it should save you time and money.

Source: GoEngineer MBD webinar on YouTube

According to this image, even MBD is just a stepping stone towards MBE. Abbreviations are always confusing, so I think they should be avoided altogether. This is a list of abbreviations that I ran into while researching this post:

• MBD:
  • Model-Based Definition: “An annotated model and its associated data elements that define the product in a manner that can be used effectively without a drawing graphic sheet.” [ASME]
  • Model-Based Design: Overarching name for the concept of using the 3D model as the reference for all further activities
• MBE:
  • Model-Based Engineering: “An approach to product development, manufacturing, and lifecycle support that uses a digital model to drive all engineering activities.” [NIST]
  • Model-Based Enterprise: Enterprise that uses MBE and MBD in its engineering practices
• MBI:
  • Model-Based Inspection: Using the 3D model when doing quality control measurements

The standards behind MBD

The American Department of Defense issued MIL-STD-31000A to define Technical Data Packages or TDPs. This standard includes both drawing-based documentation as well as 3D model-based packages.

There is also ASME 14.41 by the American Society of Mechanical Engineers, which in turn was the basis for the international ISO 16792:2015 standard. The MIL specification focuses on the complete design package, of which drawings/models are only a tiny fraction. The ASME and ISO standards focus more on the representation of the 3D model, its geometry, its annotations and tolerances. They treat both drawing and 3D models.

 File types

The preferred way of sharing information with MBD is by sharing the native 3D model. Most companies are reluctant to share those with suppliers or even customers, so I think other formats will have a bigger chance of succeeding.

Since you want all CAD and CAM systems to read each other’s output, so you need a universal 3D file type. They chose STEP 242 for this, the latest and greatest version of STEP. It is ‘upward compatible’ with previous versions like STEP 203 and 214 and it is designed specifically with MBD in mind. STEP 242 can, therefore, contain many more types of information.

3D PDF is the second standard. You can create a company template and include not only the 3D model but multiple views and extra information as well. You can supply notes, part numbers, material, stuff like that. The result could be something like this:

3D PDFs only work in Adobe Reader, unfortunately. That piece of software has become so clunky and bloated that I use Sumatra PDF as my default PDF viewer. It’s a super-fast PDF reader with a clean interface. The site looks hideous, but the product’s awesome.

SOLIDWORKS can also export annotated 3D models to eDrawings files so you can share it with people that don’t have a full license to CAD software.

Cost of switching to MBD

SOLIDWORKS, Inventor, Catia and Creo have all added MBD capabilities to their software. Some include the features for every user, some sell MBD as a plugin.

MBD for SOLIDWORKS is not included in any version, it has to be bought separately. It doesn’t matter whether you have a Standard, Professional or Premium license, it works with all three versions.

• $2,000 per seat for the license
• $500 per seat per year for maintenance and support

I could only find prices at the time of the introduction in 2015, but SOLIDWORKS rarely changes their prices so I assume these are still valid.

The real cost of switching to a 3D-centric approach will probably be caused by the time it takes to learn new software and new ways of working. Your whole company has to switch over and it would be best if all of your suppliers can handle the files as well.

Those are some pretty big ifs.

The state of 2D drawings

Drawings have the following advantages:

• They use a universal language that is spoken across the globe.
• They are accepted by all suppliers and customers.
• When making drawings, engineers go through every line, hole and every point where two parts meet. Many errors are caught in this reviewing process.
• Printouts can be written on, copied and stored easily.
• They can be shared on paper or as a PDF and every PDF reader can open them.

Disadvantages

• Making drawings can take a lot of time:
  • When you make drawings of many simple parts like I used to do when designing one-off machines, most of your time is spent creating files, views and blocks.
  • When you are detailing complex parts, most of your time is spent making sure every feature is fully dimensioned and every view fits on the sheet.
• It is best if the engineer that designed the part creates the drawing as well. He knows which dimensions are important and where possible issues might occur.
• It can be hard to keep a consistent company style across all drawings that are made by many engineers.
• Making good drawings could be considered an art. It takes practice to create a drawing that tells the story you want to tell in a clear way. Sometimes it takes a few iterations to get there.
• The drawing can become disconnected from the 3D model:
  • This happens when the drawing is not updated together with the model. Some companies knowingly let this happen by having different revision numbers for the drawing and the model. Please don’t do this.

How drawings are evolving

Results from the 2016 CAD Trends worldwide survey also show that about 80% of companies use 3D modeling and this percentage grows by about two percentage points per year. The surprising thing is that about 70% of companies still rely heavily on 2D drafting and this percentage is actually increasing slightly. Apparently companies don’t ditch 2D for 3D, they just add another tool to their tool belt.

I see companies switching to minimal dimension drawings to save engineering time. This concept basically means they only add the most important dimensions to a drawing. The drawing and a STEP model are sent to the manufacturer. I think this approach can work for simple parts and known suppliers. There are a lot of underlying assumptions and if your assumptions don’t match the supplier’s, it’s easy to get into an argument. Manufacturers have also told me they just quote a higher price because it takes them more work to make the parts.

Trends in MBD

I have looked in a few places and found the following data points:

• Only 2% of companies rely on MBD only [2015, source]
• 108 hits in the last year when searching the SOLIDWORKS forum on the term ‘MBD’, versus hundreds of hits on the term ‘drawing’. The MBD section gets about a single question per week now, where the drawing section gets about ten a day.

I browsed through Google Trends to check search volumes. In these plots, 100 is the maximum amount of search volume that occurred once, so the data is only relative.

The term ‘MBD’ doesn’t work well here because it looks like there is a shopping mall in India with the same name. This looks kinda ok:

That is until you compare it with the results on drawings:

These plots confirm my suspicion that MBD isn’t really catching on.

Tentative conclusions

It seems that 2D drawings are here to stay. They are so ingrained in every engineering and manufacturing business. Everybody knows how to read them and you don’t need special tools to do so.

The data confirms that companies aren’t quick to change tools, probably because it’s a big change and everyone has to change at the same time.

I must add that I’m not against progress and innovation. I love the fact that we can design in 3D and that we are able to add projections of that model on a sheet. It’s hard to imagine how a draftsman would design complex machines and products by using just a drawing board and pencils. Hell, I even tip my hat to engineers that use only projections to design something in AutoCAD.

Maybe MBD just isn’t mature enough yet, it just doesn’t appeal to me as a simple alternative. The impact of switching is so large that it is hard to make that decision currently.

Drawings made easier

There are a few things that can be improved in the process of making drawings in SOLIDWORKS:

• Setting up a drawing should be quicker because both time and people are scarce at the end of any project
• It should be easier to maintain a consistent company style
• The program should know more of your preferences

We are currently finalizing our SOLIDWORKS plugin Drew. Drew lets you create advanced templates that contain drawing templates, sheet formats, default views, allowed sheet scales and (soon) tables and annotations. It literally takes me a single click to create the drawing below from the 3D model of this random part.

The drawing that is created uses the default company style to create a drawing, places 2D views and an isometric 3D view and fits all of them on the sheet.

When you create tens or hundreds of drawings of simple parts (like I used to do), you spend almost all of your time creating views and spacing them nicely across the sheet. I’d like to automate that. The next image shows the result after I change the orientation of the main view (one click) and add two views on the left (one click). Awesome 🙂

Finally, if you start working on a project for a different customer, it takes a single click to change the default company style. The drawing is updated accordingly and even the 3D view changes from an isometric view to a trimetric view according to your template.

Check out the Drew page for a free trial.

Further watching

• This webinar by GoEngineer gives you a nice introduction in (SOLIDWORKS) MBD in 28 minutes.
• Introduction to MBD by SOLIDWORKS

Further reading

• Results from Business Advantage 2016 CAD trends survey
• A recent topic on the SOLIDWORKS forum that has a collection of useful documents and presentations.
• The Wikipedia article on ISO 10303, the standard behind STEP files