How to differentiate between CAD and CAE.

This article explains the difference between CAD und CAE. But let`s first clarify what CAD is. CAD is very important in the creation process of a 3D configurator.

Not so long ago, before CAD was introduced, engineers did their drawings and calculations by hand. Today this would be far to expensive and not recommendable. The engineers drew only three different views on their sheet of paper and they had to simplify their project to calculate the behavior when external forces were applied. With the introduction of computer-aided-design (CAD) software, engineers were suddenly able to create accurate 3D models. With further technological advances, these 3D models can now be analyzed using Computer Aided Engineering (CAE) software.

From manual to automated calculations.

On the way to graduating as a mechanical engineer, students are the first to learn how to solve mechanical problems. In this example, our mechanical problem is to find out how the wind affects the Olympic Tower in Munich.

The first thing we do is to simplify the model. Details and features of the tower that are not needed for a rough mechanical calculation are eliminated. Actually, the Olympic tower looks like a large mast, so in this case it is assumed that the tower is a mast without a restaurant and antenna.

At the beginning of the calulations we make a rough drawing of the tower, which in our case is a simple line on paper. We estimate the wind as a constant force at the top of the tower with the aim of maintaining the momentum at the bottom of the tower. The equation would be simply the force of the wind times the height of the tower.

This model is extremely simplified. Everyone – including the person responsible for the success of the project – knows that in reality it is much more complicated and he wants a differentiated calculation of the problem.

Counterarguments for the simple approach we have made are:

• The Olympic Tower is not a two-dimensional line on paper, but a complex three-dimensional geometry.
• The wind is not a singlem constant force, but a dynamic force that causes turbulence and other effects.
• To calculate this, we use the power of CAE.

The difference between CAD and CAE.

CAD is the abbreviation for Computer Aided Design, which means that a product idea is visualized on the computer. CAE is the abbreviation for Computer Aided Engineering, i.e. the analysis of the designed visualization. In short, the difference between CAD und CAE can be expressed in this way: CAD constructs a product and CAE simulates it.

The advantages of using computers in design over old school methods are obvious. The main advantages of 3D CAD software over 2D drawings include the following:

• A 3D version of the object can be created. Engineers and production staff can better understand the shape and properties of the designed geometry. In addition, some geometries can be extremely complicated and difficult, if not impossible, to understand without seeing them in three dimensions.
• Changes to geometry can be made very easily because the software recalculates the product after each change. In addition, the CAD program recognizes and warns you of errors in your geometry that would lead to a collision of moving parts, for example.
• Probably the most important advantage is that a CAD model can be transformed into a mesh and simulated for analysis and testing purposes.

CAE tools also have many advantages such as:

• CAE reduces the potential for design errors.
• Users avoid over-engineering because they can immediately see whether changes to the product design affect performance, so they can decide early on whether it is worth continuing development or whether they should drop the design version after the first simulations.
• The effect of changing some parameters on the product can be investigated.
• All this leads to CAE helping to reduce a product`s cost and time-to-market.

The difference between CAD und CAE is the meshing process.

So let`s get back to the key point: What is the difference between CAD und CAE? At first glance, the models of CAD und CAE software look almost the same. On closer inspection, however, it becomes apparent that they are fundamentally different. Both have the shape of the product, but mathematically they don`t have much in common.

There are several ways to combine geometric elements into a 3D geometry. Most likely, CAD models are designed as a collection of volumes or bodies with parameters such as the density of the actual material. The model widely used for CAD modeling is a parametric model with a deign history. This has the advantage that the features can be changed afterwards, so that 3D objects can be created as a combination of geometric shapes with parameters.

In a CAE environment, the CAD model is transformed into a mesh during post-processing. The mesh consists of either cubes, cuboids or tetrahedra, usually polygon meshes. Therefore it is legitimate to compare a CAD model with a vector graphic, while a CAE model can be called a pixelated model.

Calculation and post-processing.

This clearly shows that a CAD model cannot simply be converted into a CAE model. Modeling Spheres, for example, will be a problem for you. This is not possible for volumes with corners, but if the individual volumes of the mesh are small enough, it can be a good approximation.

After the post-processing is complete, the calculation starts. This varies depending on the problem to be solved and the type of simulation, such as finite element analysis, numerical fluid mechanics, of thermal analysis.

The engineer will want to simplify the CAD model because it will not be possible to achieve a perfect result due to the lack of computing power. In contrast, an engineer using a CAD model will want to create a perfect representation of the model he has in mind. The approximations that are made are very accurate.

Just remember that even the concrete column of the Olympic Tower is not perfectly round, but has small edges to which the concrete planking is attached. Once this is complete, the next steps are to create the mesh and set up the simulation.

How to learn how to use simulation software.

Now that we`ve discussed the difference between CAD und CAE and their benefits, the question is: How can a CAD user start engineering simulation?

We will discuss this question in more detail in upcoming articles.