# A Rose is a Rose: How to Choose the Best 3D CAD SoftwareA Rose is a Rose: How to Choose the Best 3D CAD Software

DN Staff

August 18, 2015

Several weeks ago on Design News, I wrote about the privilege of practicing engineering in this day and age with the design, simulation, prototyping, and manufacturability tools currrently available.

Now I would like to take a deeper dive into the design bucket. 3D CAD has definitely been decided upon as the tool of choice. But there are many solutions out there. And are they all the same?

When Gertrude Stein wrote, "A rose is a rose..." her intention was to express that things are what they are. Casual users of 3D CAD may agree, but the truth is more complex.

All 3D CAD programs can draw cubes and holes. But how do you draw the cube? How is the position of the hole constrained? What if the depth of the block doubles? What if base contour is now a circle instead of a square? Is the diameter of the hole proportional to the size of face it is located on? Such questions could go on for days.

There are several buzzwords that are thrown around in the industry that distinguish various 3D CAD products: parametric, direct, history-based, feature-based, Sub-D, solid, surface, and hybrid.

Parametric refers to the fact that every piece of data entered into the model is a variable that is stored and can be modified at any time. Direct means that geometry can be modified without having to access any data regardless of how the geometry was originally constructed. History-based modelers have a running list of all the actions taken within a file. The order of these operations is vital to what the geometry looks like. For example, a feature can only reference another feature that was created before it in time.

Feature-based modelers compartmentalize geometry creation into discrete features that usually stem from 2D profiles. Sub-D modeling subdivides a surface into many smaller surfaces that can be manipulated as simply as pushing and pulling. This approach is utilized more heavily by industrial designers that think more along the lines of molding clay rather than defining dimension after dimension.

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Solid modeling creates solid pieces of geometry. Surface modeling creates zero thickness boundaries. The nuance between solid and surface bodies in 3D modeling is that when a collection of surfaces is “watertight,” they can be knit together and thickened to form a solid volume. Hybrid modeling leverages the benefits of solid and surface modeling and allows them to be used concurrently as well as sequentially.

Now that you can talk the talk in the land of 3D CAD, it is time to get some work done!

So which software is the best fit for your application? I strongly recommend speaking to other folks in your industry. The preferred application in automotive is definitely going to have different characteristics than the gold standard in biomedical devices.

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For example, in automotive Catia dominates because it handles large assemblies (over 1,000 parts) with ease and has 100-plus workbenches with toolsets optimized for various engineering functions. In the biomedical device industry, SolidWorks is king. Its intuitive process flow and simple user interface make it quite powerful, yet friendly and forgiving. Typical projects can be a single part, such as a heart stent, or hundreds of components in an MRI machine.

Knowing all of this, why would anyone not want to use the most expansive tool for every application? Well, there is no such thing as a free lunch. A single license of Catia will run you four times that of SolidWorks (comparing the base packages). It is tempting to look at product matrices and compare everything that one tool has and the other does not.

Do not purchase on this criteria!

Just remember that it is more important to find a product that fits your needs rather than the one with the longest feature list or the cheapest price.

Adopting the right CAD tool is worth the extra couple bucks in the long run, both in terms of increased productivity and reduced head-banging. Hopefully now you are armed with the vocabulary and knowledge to have the right 3D CAD discussion.