CAD is used to design, develop and optimize products, which can be goods used by end consumers or intermediate goods used in other products. CAD is also extensively used in the design of tools and machinery used in the manufacture of components, and in the drafting and design of all types of buildings, from small residential types (houses) to the largest commercial and industrial structures (hospitals and factories).
CAD is mainly used for detailed engineering of 3D models and/or 2D drawings of physical components, but it is also used throughout the engineering process from conceptual design and layout of products, through strength and dynamic analysis of assemblies to definition of manufacturing methods of components.
CAD has become an especially important technology, within CAx, with benefits, such as lower product development costs and a greatly shortened design cycle, because CAD enables designers to lay out and develop their work on screen, print it out and save it for future editing, saving a lot of time on their drawings.
This is an ever-changing industry with many well-known products and companies being taken over and merged with others. There are many CAD software products currently on the market. More than half of the market is however covered by the four main PLM corporations Autodesk, Dassault Systemes, PTC, and UGS Corp., but there are many other CAD packages with smaller user bases or covering niche user areas. See also list of free and open-source CAD software.
Packages can be classified into three types: 2D drafting systems (e.g. AutoCAD, MicroStation); mid-range 3D solid feature modelers (e.g. Inventor, TopSolid, SolidWorks, SolidEdge, Alibre Design, VariCAD); and high-end 3D hybrid systems (e.g. Pro/ENGINEER, CATIA, NX (Unigraphics)). However these classifications cannot be applied too strictly as many 2D systems have 3D modules, the mid-range systems are increasing their surface functionality, and the high-end systems have developed their user interface in the direction of interactive Windows systems.
Simulation
Simulation is an important feature in engineering systems or any system that involves many processes. For example in electrical engineering, delay lines may be used to simulate propagation delay and phase shift caused by an actual transmission line. Similarly, dummy loads may be used to simulate impedance without simulating propagation, and is used in situations where propagation is unwanted. A simulator may imitate only a few of the operations and functions of the unit it simulates.
Most engineering simulations entail mathematical modeling and computer assisted investigation. There are many cases, however, where mathematical modeling is not reliable. Simulation of fluid dynamics problems often require both mathematical and physical simulations. In these cases the physical models require dynamic similitude. Physical and chemical simulations have also direct realistic uses, rather than research uses; in chemical engineering, for example, process simulations are used to give the process parameters immediately used for operating chemical plants, such as oil refineries.
For example, discrete event simulation is often used in industrial engineering, operations management and operational research to model many systems (commerce, health, defence, manufacturing, logistics, etc.) for example, the value-adding transformation processes in businesses, and optimize business performance. Imagine a business, where each person could do 30 tasks, where thousands of products or services involved dozens of tasks in a sequence, where customer demand varied seasonally and forecasting was inaccurate- this is the domain where such simulation helps with business decisions across all functions. Related topics include Theory of Constraints, bottlenecks, and management consulting.
