What is the Difference Between CAD and CAE?

CAD vs. CAE snap fit

This article focuses on explaining the difference between CAD and CAE. But before we do that, let’s first understand what is CAD.

Not too long ago, before CAD was introduced, engineers made their drawings and calculations by hand, which today is considered a struggle. They only drew 3 different views on their sheet of paper and had to simplify their product in order to make calculations on the product behavior if external forces were applied. With the introduction of CAD software, it was possible to create accurate 3D models which most recently can be analyzed using CAE software.

From Manual to Automated Calculations

On the way to being a mechanical engineer, the first thing you learn in university is how to solve mechanical problems. In this example, our mechanical problem is the need to find out how wind affects the Olympic Tower in Munich.

The first thing we do is simplifying the model. Details and features of the tower that might not be needed for a rough mechanical calculation are going to be neglected. Actually, the Olympic Tower looks like a big pole, so the assumption that the tower is a pole without the restaurant and the antenna is being made in this case.

At the beginning  of the calculations, we make a rough drawing of the tower, which in our case is a simple line on the paper. The wind we estimate as a constant force at the tip of the tower with the goal of the calculation being to get the momentum at the bottom of the tower. The equation would simply be the force of the wind times the height of the tower.

This model is extremely simplified and everyone knows that in reality it is much more complicated than that. Especially the person that is responsible for the success of the project would want a more sophisticated calculation of the problem.

Counterarguments for the easy approximation we did are:

  • The Olympic Tower is not a two-dimensional line drawn on a paper, but a complex three-dimensional geometry
  • Second, the wind is not a single, constant force, but rather a dynamic force that causes turbulence and other effects

To calculate this, the power CAE comes in.

The Difference Between CAD and CAE

CAD model Olympic Tower MunichCAD is the abbreviation of computer-aided design, which refers to using a computer to visualize a product idea. CAE abbreviates computer-aided engineering — the analysis of the designed visualization. In short, the difference between CAD and CAE can be put this way: CAD designs a product and CAE simulates it.
The advantages of using the aid of computers for designing and analyzing a project in comparison to old-school methods are quite obvious. The main perks of 3D CAD software over 2D drawing include but are not limited to the following:

  • A 3D version of the object can be created. Engineers and production workers can more easily understand  the shape and the properties of the designed geometry. Furthermore, some geometries can be extremely complicated and very hard, if not impossible to properly understand without seeing them in 3 dimensions. 
  • Changes to the geometry can be made very easily as the software recalculates the product after every change. Moreover, the CAD program lets you know if you have some errors in your geometry that would, for example, cause a collision of moving parts.
  • Probably the most important advantage is that a CAD model can be transformed into a mesh and then simulated for analyzing and testing purposes. 

Using CAE tools is also connected to a lot of advantages:

  • Not needing as many prototypes and driving the overall development costs down
  • CAE reduces the errors in design
  • The user avoids over-engineering since he or she can see immediately if the changes to the product design affect the performance and decide early in the process if it’s worth it to continue developing or dropping the design version after the first simulations
  • The effect of altering a few parameters on the product can be studied.

All of this leads to CAE helping to reduce the costs and time to market for a product. 

The Difference between CAD and CAE: The Meshing Process

Olympic Tower Munich meshSo let’s get back to the key point: what is the difference between CAD and CAE? The models used by CAD and CAE software look almost the same from the distance. Taking a closer look reveals that they are fundamentally different, though. They both have the shape of the product but from a mathematical standpoint, they do not have a lot in common.

There are different ways of combining geometrical elements to form a 3D geometry. Most likely, CAD models are designed as an assembly of volumes or bodies with parameters like density of the actual material. The model widely used for CAD modeling is a parametric model with a construction history. This brings the advantage of being able to change features retrospectively. So 3D objects are built as a combination of geometrical shapes with parameters.

In a CAE environment, the CAD model is transformed into a mesh during pre-processing. The mesh either consists of cubes, cuboids or tetrahedrons, so generally polygon meshes. Therefore, it is legit to compare a CAD model to a vector graphic, whereas a CAE model could be described as a pixelated model.

Calculation and Post-Processing

This clearly shows that you cannot just transform a CAD model into a CAE model. Problems that you probably need to face are the modeling of spheres, for example. This is impossible to do with volumes that have corners, but if the single volumes of the mesh are small enough, it can be a good approximation.

After the pre-processing, the calculation starts. This differs according to the problem you need to solve and the type of simulation — finite element analysis, computational fluid dynamics, thermal, etc.

In the previous example, after having designed the tower with CAD, a finite element analysis would be used to calculate the forces of the wind affecting the Olympic Tower.

After this step, the post-processing has to be done to visualize the solution of the analysis. The visualization of the Olympic Tower looks like this:
Olympic Tower Munich - difference between CAD and CAE

The engineer will want to simplify his CAD model because he won’t be able to process a perfect one due to the lack of calculating power. In contrast, an engineer using a CAD model wants to create a perfect depiction of the model he has in mind. The approximations that are being made are highly accurate if you think about the fact that the concrete column of the Olympic Tower is also not perfectly round but has small edges where the planking of the concrete was placed. As soon as this is completed, creating the mesh and setting up the simulation are the next steps. You can take a look at this projects and see the results of the harmonic analysis and static analysis that were performed to identify the displacement and von Mises stresses produced in the Olympic Tower due to the wind pressure.

If you want to learn more about CAE, you can go to the dedicated Simulation Wiki and find more interesting articles and explanations.

How to learn to use CAE Simulations

After displaying the advantages and the difference between CAD and CAE, the question is how can a CAD user start using CAE for simulations.

There are several possibilities, including step-by-step tutorials, video tutorials, webinars, and workshops. Furthermore, professional trainings, documentations, blog articles, and help forums are also available

Why not start today? The 14-day free trial awaits.


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