CAD – Computer Aided Design

The abbreviation CAD (Computer Aided Design) refers to computer-aided design. In concrete terms, this means that technical drawings are not made by hand, but are constructed with the help of a hardware and software system. Objects designed using CAD include components, cars and buildings. Two-dimensional designs such as the creation of a city map can also be realized on the computer, as can projects in 3D. 

History of CAD

Dr. Patrick Hanratty, American scientist and known as the "father of CAD", created the basic recipe for computer aided design in 1957 with the numerical control system. In 1962, Ivan Sutherland developed Sketchpad, the first software with a graphical user interface and input pen. The program set the first building block for graphical interfaces and CAD. However, a lot of time passed before the program was widely used. Pen, paper and drawing board continued to be the number one tool for technical draftsmen over the next few decades.

The first freely available CAD systems came onto the market in the 1980s. With ADAM (Automated Drafting and Machining), Hanratty succeeded in developing the basis on which around 80% of current CAD software is based. In 1981, the multinational software development company Dassault Systèmes developed CATIA on this basis, which is still an important tool for 3D surface modeling today. A year later, AutoCAD was developed, one of the most successful CAD programs that works on various operating systems. After Missler Software started the distribution of a CAD software that also worked on personal computers in 1984, a real boom of the software began.

As early as the mid-1970s, the US government introduced the IGES standard. Until then, the data formats of the various commercial CAD programs were not compatible with each other. The IGES data format was supposed to solve the problem. However, 3D modeling was not possible with IGES. Starting in 1989, the British company Shape Data introduced the CAD kernel Parasolid to the market. The parametric system made the creation process of a model traceable, so that the software could merge 2D surfaces into 3D geometry. Parasolid is still the most powerful core system today.

Due to more powerful hardware, CAD software became affordable for smaller companies in the 1980s. Thanks to the STEP data exchange format developed in 1994, it was now possible to save and transfer 3D models.

Application areas of CAD programs

CAD programs are nowadays an integral part of the industry. There are different programs on the market that are tailored to the corresponding area of application. The following areas work with CAD software:

Architecture: with the help of CAD programs, buildings are designed in 2D or 3D. The architecture software ArchiCAD makes it possible to model objects with certain properties such as windows and doors and thus calculate the amount of costs and raw materials. Both houses and entire housing complexes can be visualized and realized.

Mechanical engineering: Whether it's a screw, motor, wind turbine, electrical circuit diagram or machine tool - CAD programs are indispensable for designs in mechanical engineering. In order to meet the requirements of the diverse and complex projects, CAD systems for this sector are programmed to respond flexibly.

Craftsmen: A professional CAD system for craftsmen enables precise planning and production of individual components. Customer requirements and own ideas can be realized quickly and cost-efficiently with the help of the program.

Automotive industry: Just like the aviation industry, the automotive industry also recognized the advantages of computer-aided design at an early stage. By using 3D CAD systems, several work steps can be carried out simultaneously, so that less time is needed from planning to production.

The CAD software

A CAD software carries all the information that a hardware needs to be usable for the defined task area. With the help of CAD software, the design process can be carried out directly on the computer, from concept development to production. Overall, this makes the entire design process much more efficient and significantly less prone to errors.

Advantages and disadvantages of CAD software

The use of computer aided design software improves and accelerates the process chain in production. The computer-aided design of machines or buildings runs much more efficiently and involves fewer errors. The advantages of CAD include:

• Time savings: Both the actual design and the making of changes to a drawing can be realized more quickly with CAD software.
• Error prevention: Gross errors are avoided and the general susceptibility to errors is reduced to a minimum.
• Cost reduction: The use of CAD software speeds up the entire process and reduces costs.
• Simplified documentation: Dimensions, design data and lists for the required individual parts are documented in a bundled form on the PC.
• Reproducibility: Successful designs can be saved in the CAD system and reused, adapted and optimized as required.

Although the use have positive effects on the whole manufacturing process, one should also consider possible disadvantages of CAD software. These are:

• High acquisition and maintenance costs: The hardware and the full version of CAD software are expensive to purchase. The more employees a team has, the more suitable CAD workstations are needed. After the initial introduction of the CAD system, the costs drop noticeably - but regular updates and maintenance continue to incur costs.
  
  
• Intensive training: Employees need extensive training to work with CAD. Software updates also ensure that new functions are added and existing ones are revised at regular intervals. Each update therefore entails a new training effort.
  
  
• Training costs: Familiarization with the software entails certain costs. These software updates also require that employees receive ongoing training in the use of the software. Appropriate training and an appropriate period of familiarization with new functions and interfaces is necessary.

CAD programs

Nowadays, there is a wide range of CAD programs that differ in terms of the scope of their functions. Some basic functions can be found in most programs. These include functions for plastic and mold design and solid modeling. Frequently used programs are:

• CATIA
• SolidWorks
• Autodesk Inventor
• AutoCAD
• SpaceClaim
• SketchUp

The CAD software CATIA

CATIA (Computer-Aided Three Dimensional Interactive Application) is the world's leading cross-platform software for computer-aided product design and development. Developed in the 1970s initially for internal use by Dassault Systèmes, CATIA was later used primarily in the automotive and aerospace industries. CATIA is suitable for creating solids, surfaces, drawings, assemblies and for manufacturing and analysis. The software has powerful parametric modeling tools and can render photorealistically. Dassault Systèmes continues to develop CATIA today, making it one of the most widely used CAD software. Learn more about the CAD software CATIA in our dictionary article.

This is how the practical use of CAD software works

After installation, the CAD software is immediately ready for use. Any project can now be designed and temporarily saved. With the help of intermediate CAM programs, the data is forwarded to the production machine or 3D printer for manufacturing. If the CAM program is missing, the data can be sent to an external provider who realizes the model.

CAM

CAM (Computer Aided Manufacturing) refers to the use of software and computer-aided CNC machine tools for automated production. Computer-aided production is usually preceded by computer-aided design (CAD). 

CAD drawings

A CAD drawing is any drawing that has been created using CAD software. You can make CAD drawings in 2D as well as in 3D.

CAD drawing in 2D

Engineering drawings are created using CAD software for the entire design process; starting from design to completion. In the early days of CAD, there were no 3D applications. Today, a CAD program basically states how many dimensions it can work in. Pure 2D CAD programs are suitable for displaying bodies in different views and sections. This allows a closer look at the object from above and below as well as from the sides. Isometric views are also possible.

CAD drawing in 3D

Three-dimensional objects have the advantage that they can be viewed from any angle during the design process. Another advantage is that a wide range of information is calculated in 3D designs - for example, the weight and volume of an object. 3D constructions enable a vivid representation of objects that even a layman can understand. 3D objects fall into three basic categories:

• Wireframe model: A wireframe model is a three-dimensional geometric model whose body consists only of a framework.
• Surface model: These models consist of one-dimensional surfaces that together form a two-dimensional body.
• Solid model: In a solid model, the volume is defined. Three-dimensional solids are used to obtain properties of mass.

The term 3D CAD often appears in connection with 3D. This term generally stands for all 3D models developed with CAD software. The term is also used synonymously for such CAD programs that are capable of creating 3D models. A 3D CAD drawing is also called a CAD model.

CAD Modeling Methods

To obtain a 3D model, a design object is transformed into a geometry model using formal elements such as volumes, lines, surfaces and points. The next step is to start refining the model using slopes and curves, and the working techniques differ depending on the CAD system. Basic modeling methods include direct modeling and parametric modeling.

Direct modeling

Direct modeling has only recently become known, although it has been around for decades. This modeling method allows designers to act directly on 3D geometry. Individual geometry elements are changed and surfaces are manipulated by dragging, moving, pushing and rotating. With direct modeling, the process is not saved. Due to the fact that there is no history, it is only possible to undo the most recent steps. Direct modeling is more functional than parametric modeling and less costly in the initial stages of design.

Parametric modeling

In parametric modeling, the 3D model is controlled by various parameters. Parametric modeling is the most commonly used method by designers and engineers. The 3D object contains all the parameters that a real object has. These include weight, size, physical and optical parameters. Parametric modeling allows individual CAD models to be assembled and modified into an assembly. This type of modeling is primarily advantageous for design objects that are heavily influenced by dimensions, such as office furniture or tools. With the help of the parametric approach, the design objects can be created easily and quickly in different designs and configurations.

The CAD file

A CAD file is created to store a CAD model or a CAD drawing. A single file contains all the data of the design. Once the design data is imported or exported for further processing, one can either use native CAD files or resort to exchange formats. Just as there are different CAD systems, there are different data formats for CAD files. Common types of CAD file formats are:

• .eps
• .dxf
• .dwg

Often the systems of the technical draftsmen do not match those of the manufacturers, so that the file formats differ. In such a case, the file is converted via an interface into a so-called neutral format. This means that most machines can recognize and read the format. Exchange formats such as STEP, IGES or STL are primarily used in additive manufacturing, in which the object is created layer by layer. With the additive process, even the most complex structures can be realized.

The STEP data format

STEP (Standard for the Exchange of Product model data) is an international and manufacturer-independent file exchange format that is used in all application areas such as mechanical engineering, architecture or engineering. With the interface, an object consists of a holistic element including volume, which is why the amount of data for STEP data formats is small. STEP is the most widely used format in the world for converting CAD files and achieves the best results when exchanged. STEP files end in .stp or .step.

The IGES data format

IGES (Initial Grafics Exchange Specification) is another neutral data format for the exchange of CAD files. IGES was developed in the 1980s, when three-dimensionally represented bodies were composed only of surfaces. Each surface of an object forms its own element. As a result, IGES formats have a high data volume compared to STEP. In addition, the conversion is error-prone. The surfaces are often incorrectly recognized by the software and consequently displayed incorrectly. IGES files end in .iges or .igs.

The STL data format

The neutral data exchange format STL (Surface Tessellation Language) from the company 3D-Systems is mainly used in the field of model making. In contrast to the other two neutral file formats, STL describes only the surface of a volume. The data does not contain any geometric elements and can only be modified with the help of special systems. STL files end with .stl.

Summary

By definition, CAD (Computer Aided Design) is a software application for sketching and designing engineering drawings in 2D and 3D models. As early as the 1950s, the first numerical control system laid the foundation for CAD. In the meantime, CAD programs have replaced the manual drawing of technical designs and are an integral part of a wide variety of industries, such as architecture and the automotive industry. The various CAD programs are geared to the needs of the individual industries and have the advantage of significantly reducing production times. Since there are a considerable number of CAD programs available today, the respective data formats also differ. In order for CAD designs to go into production, they must be adapted to the file format of the respective system for production. This is usually done with the help of so-called "neutral" data formats such as STEP or IGES.

FAQs

What is CAD?

CAD stands for Computer Aided Design and is a software application for sketching and designing engineering drawings. These digital construction drawings can be 2D as well as 3D models. 

What is a CAD program or CAD software?

With the help of CAD software, the design of objects can be done directly on the computer, from concept development to production. Overall, this makes the entire design process much more efficient and much less prone to errors. Today, there is a wide range of CAD programs available. Frequently used programs include CATIA, SolidWorks, Autodesk Inventor and AutoCAD.

Which CAD system should I use?

Anyone who wants to use CAD software should first consider the purposes for which they need it. Private users have the option of downloading free trial versions and trying them out at their leisure. However, trial versions have the disadvantage that many functions can only be used to a limited extent. Companies should opt for a paid full version and make sure that the software contains the appropriate tools for their area of application. CAD systems for architects, for example, have different tools than comparable systems for mechanical engineers. The selection of the CAD system therefore depends on the respective area of application and the desired modeling (2D or 3D).

Who makes CAD drawings?

Technical draftsmen and system planners already learn how to convert ideas into 2D and 3D CAD drawings during their training. Various institutes, such as TOP CAD Schule or the distance learning school AKAD, offer fee-based training in the use of CAD software. After graduation, it is possible to apply for a vacancy as a CAD draftsman as a career changer. In addition, the training courses are also interesting for private individuals who want to develop their own ideas with the help of a CAD program and, if necessary, produce them with a 3D printer.