Will Model-Based Definition Be the End of 2D Drawings?
By: Polly Britton
Project Engineer, Product Design
26th July 2017
Despite advancements in computer-aided design over recent decades, 2D technical drawings remain as the industry standard deliverable. This means that after designing a part for a customer or manufacturer in 3D, they will expect you to prepare drawings like these:
Click images to zoom
This way of representing a 3D object on a 2D page through using a number of different viewing angles is called “Multi-view orthographic projection“; it has been the standard for engineering design across most of the world for many decades now. The 3D model is just a tool to help create the drawing views and dimensions, which are what truly define the part.
But now there is another way…
A rotatable 3D model with dimensions, tolerances, and annotations all included. It’s called “Model-based definition (MBD)” and there are some who think it is the future of engineering design. A simpler version can be seen below, just click the play button to enable the 3D ability.
As computers become more powerful, more people than ever before can open a 3D model file, like this one pictured, on their PC, tablet, or even smartphone. People can also intuitively figure out how to navigate around the model to find and extract the information they want from it.
Is it better?
To overcome the 2D drawing’s legacy of over 200 years, any new system trying to take its place would have to be far superior to encourage engineers to make such a major change to how they work. So what are the advantages?
Seeing is understanding
Trying to imagine a solid object using information from “flat” 2D views sometimes results in errors, and unnecessary mental gymnastics that are done away with when using MBD. However, standard 2D drawings already have a solution to this, which is to include a 3D orientation view.
A view like this one on the right, or even a few of them, can go a long way to helping the reader understand your drawing. 3D orientation views can be easily generated from Computer Aided Design (CAD) models.
Dimensions
MBD does make it easier to find information about a particular feature all in one place. Just zoom-in and see every dimension you need to fully understand the feature. This replaces the need of having to inspect multiple 2D views to find the various dimensions for the width, height, and depth, which might be far apart on the page. These dimensions can even include geometric tolerances (the subject of my last blog).
File types
There is no universal or standard file type for MDB yet. Different CAD packages have different file type outputs that require a specific program to be installed on your device to open. Some PDF readers can display 3D PDFs, which allow you to examine 3D models and their annotations in a slightly cruder, less controlled way.
With 2D drawings, all you need to view them is paper, which can then be copied and carried into workshops and meeting rooms, and easily annotated by hand if necessary. And when the project is finished the designs can be physically archived in your company’s filing system of choice. These days, it is common to save drawings as PDFs, which can be opened on any device, and archived electronically. And that’s the way we like it, for now at least.
Conclusion
So, as the title of this blog asks, will model-based definition be the end of 2D drawings? I don’t think it will happen soon. The small conveniences allowed by MBD are not enough to encourage engineers to convert to a new format, especially one with its own set of difficult quirks. MBD may well become more popular in the future, but for now, I believe old-fashioned 2D drawings will still play a fundamental role in engineering and my career.
