Computer Aided Design: An Introduction

By Fatima Mubeen Butt

CAD: What Exactly is it?

No, it’s not an abbreviation for “Canadian Dollar”. In the realm of engineering, CAD stands for computer-aided design, which is exactly what the name suggests- the use of computers to aid in the creation, modification, analysis, or optimization of a design. CAD is an important industrial art extensively used in many applications, including automotive, shipbuilding, and aerospace industries, industrial and architectural design, prosthetics, and the like. Basically, it is a means of visualizing and accordingly producing functioning devices. CAD is also widely used to produce computer animation, as some might be aware.

There are multiple types of CAD, each suited to different purposes. For example, 2-D CAD is used to generate models from 2-D sketches, and is relatively easier to use, leading to less headaches in the user. 3-D CAD, however, tends to be on the more complicated side. Where in 2-D modelling the system inserts the lines into the model, in 3-D, the user must insert them themselves, and manipulation of the resulting model is limited. In order to counter-act this, multiple types of 3-D CAD have been developed, with some examples being the following:

·       Parametric Modelling: If you liken your “design intent”- the design you intend to develop- to a parameter and treat it as such, you can create a modifiable model. For example, if you intend for a feature to be located from the center of the part, the operator should locate it from the center of the model. The feature could be located using any geometric object already available in the part, but this random placement would defeat the design intent. If the operator designs the part as it functions, the parametric modeler is able to make changes to the part while maintaining the functional and geometric relationships that are instrumental in maintaining the integrity of the model.

·       Direct or Explicit Modelling: Usually, when making changes and adding features to a design, you name and record them, leading to the formation of a “history tree”. When using direct modeling, a sketch is utilized to build geometry and then integrated into the new geometry, eliminating the need for the original sketch when modifying the geometry later on.

·       Assembly Modelling: It is the process of combining the outcomes of earlier single-part modeling into a multi-part final output. Depending on the particular CAD software provider, assemblies may be hierarchical, and fairly complicated models may be produced.

Additionally, there is also free-form CAD, which provides the designer with the freedom to produce whatever they want without having to worry about compatibility and geometry or any algorithmic constraints, except for device compatibility.

The Technology and Software Associated with CAD

CAD typically does not require any special hardware. Most contemporary parametric feature-based modelers and freeform surface systems are constructed using several essential C modules, each having its own set of APIs. A graphical user interface (GUI) and NURBS geometry or boundary representation (B-rep) data interact through a geometric modeling kernel to form a computer-aided design (CAD) system. The associative relationships between geometry, such as wireframe geometry in a sketch or components in an assembly, can also be managed by a geometry constraint engine.

CAD software experienced an unprecedented popularity boom during the industrial conquests of the late 20th century, and have only grown in relevance since then. The vast variety of computer-aided design software packages available today includes 3D solid and surface modelers and 2D vector-based drafting programs. Additionally, many modern CAD programs include three-dimensional rotations, which enable the viewing of a planned object from any desired aspect, including an inside-out perspective. Dynamic mathematical modelling is now possible with certain CAD programs.

But What is it Used For?

The human mind, when picturing something to make, be it your favorite cookies or a large hadron collider, always visualizes what it aspires to create. However, it can be rather complicated to visualize the intricacies of any complicated device and keep a record of them. This is where CAD comes in. A new form of prototyping has emerged in recent times- digital prototyping- which has eliminated the need to create physical prototypes. While the practice has not been entirely discarded, it has been modernized to a great extent. Physical prototypes can be scanned and a CAD model can then be generated which can be subjected to further modification, reducing labor and conserving precious time.

As mentioned earlier, the use of CAD is also extensively employed in order to create industrial models, especially in aviation industries. Furthermore, research in computer graphics (hardware and software), discrete differential geometry, and computational geometry has all benefited greatly from CAD.

All in all, CAD remains one of humanity’s greatest advancements in the field of computation and has proven to be crucial in engineering.