Computer-aided design (
CAD) is the use of
computerA computer is a machine that manipulates data according to a set of instructions.Although mechanical examples of computers have existed through much of recorded human history, the first electronic computers were developed in the mid-20th century . These were the size of a large room, consuming as...
technology for the design of objects, real or virtual. CAD often involves more than just shapes. As in the manual
draftingDrafting may be:* Technical drawing, or a subset of the technical drawing discipline, such as:** Architectural drawing** Electrical drawing** Engineering drawing** Plumbing drawing** Structural drawing* Drafting * Campdrafting...
of
technicalTechnical drawing, also known as drafting, is the academic discipline of creating standardized technical drawings by architects, interior designers, drafters, design engineers, and related professionals...
and
engineering drawingAn engineering drawing, a type of technical drawing, is created within the technical drawing discipline, and used to fully and clearly define requirements for engineered items....
s, the output of CAD often must convey also symbolic information such as materials, processes, dimensions, and tolerances, according to application-specific conventions.
CAD may be used to design curves and figures in
two-dimensional2D computer graphics is the computer-based generation of digital images—mostly from two-dimensional models and by techniques specific to them...
("2D") space; or curves, surfaces, or solids in
three-dimensional3D computer graphics are graphics that use a three-dimensional representation of geometric data that is stored in the computer for the purposes of performing calculations and rendering 2D images...
("3D") objects.
CAD is an important
industrial artIndustrial Arts is an umbrella term originally conceived in the late 19th century to describe educational programs which featured fabrication of objects in wood and/or metal using a variety of hand, power, or machine tools...
extensively used in many applications, including automotive, shipbuilding, and aerospace industries, industrial and architectural design,
prostheticsIn medicine, a prosthesis is an artificial extension that replaces a missing body part. It is part of the field of biomechatronics, the science of fusing mechanical devices with human muscle, skeleton, and nervous systems to assist or enhance motor control lost by trauma, disease, or defect...
, and many more. CAD is also widely used to produce
computer animationComputer animation is the art of creating moving images with the use of computers. It is a subfield of computer graphics and animation. Increasingly it is created by means of 3D computer graphics, though 2D computer graphics are still widely used for stylistic, low bandwidth, and faster real-time...
for
special effectThe illusions used in the film, television, theater, or entertainment industries to simulate the imagined events in a story are traditionally called special effects ....
s in movies,
advertisingAdvertising is a form of communication used to influence individuals to purchase products or services or support political candidates or ideas. Frequently it communicates a message that includes the name of the product or service and how that product or service could potentially benefit the consumer...
and technical manuals. The modern ubiquity and power of computers means that even perfume bottles and shampoo dispensers are designed using techniques unheard of by shipbuilders of the 1960s. Because of its enormous economic importance, CAD has been a major driving force for research in
computational geometryComputational geometry is a branch of computer science devoted to the study of algorithms which can be stated in terms of geometry. Some purely geometrical problems arise out of the study of computational geometric algorithms, and such problems are also considered to be part of computational...
,
computer graphicsComputer graphics are graphics created using computers and, more generally, the representation and manipulation of pictorial data by a computer....
(both hardware and software), and discrete differential geometry.
The design of geometric models for object shapes, in particular, is often called
computer-aided geometric design (
CAGD).
Overview
Current Computer-Aided Design software packages range from 2D
vectorVector graphics is the use of geometrical primitives such as points, lines, curves, and shapes or polygon, which are all based on mathematical equations, to represent images in computer graphics....
-based drafting systems to 3D
solidSolid modeling is a technique for representing solid objects suitable for computer processing. Other modeling methods include surface models and wire frame models .Primary uses of solid modeling are for CAD, engineering...
and
surfaceFreeform surface modelling is the art of engineering Freeform Surfaces with a CAD or CAID system.- Introduction :The technology encompasses two main fields...
modellers. Modern CAD packages can also frequently allow rotations in three dimensions, allowing viewing of a designed object from any desired angle, even from the inside looking out. Some CAD software is capable of dynamic mathematic modeling, in which case it may be marketed as
CADD —
computer-aided design and drafting.
CAD is used in the design of tools and machinery 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 the scope of
computer-aided technologiesComputer-aided technologies is a broad term describing the use of computer technology to aid in the design, analysis, and manufacture of products....
, with benefits such as lower product development costs and a greatly shortened design cycle. CAD enables designers to lay out and develop work on screen, print it out and save it for future editing, saving time on their drawings.
The people that work in this field are called: Designers, CAD Monkeys, Automotive Design Engineers and Digital Innovation Engineers. Computer-aided design is also a common work activity for the traditional engineering professions.
Software technologies
Originally software for Computer-Aided Design systems was developed with computer languages such as
FortranFortran is a general-purpose, procedural, imperative programming language that is especially suited to numeric computation and scientific computing...
, but with the advancement of
object-oriented programmingObject-oriented programming is a programming paradigm that uses "objects" – data structures consisting of datafields and methods together with their interactions – to design applications and computer programs. Programming techniques may include features such as information hiding, data...
methods this has radically changed. Typical modern parametric feature based modeler and freeform surface systems are built around a number of key
C (programming language)C is a general-purpose computer programming language developed in 1972 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
modules with their own
APIAn application programming interface is an interface in computer science that defines the ways by which an application program may request services from libraries and/or operating systems. An API determines the vocabulary and calling conventions the programmer should employ to use the services...
s. A CAD system can be seen as built up from the interaction of a
graphical user interfaceA graphical user interface is a type of user interface item that allows people to interact with programs in more ways than typing such as computers; hand-held devices such as MP3 Players, Portable Media Players or Gaming devices; household appliances and office equipment with images rather than...
(GUI) with NURBS geometry and/or
boundary representationIn solid modeling and computer-aided design, boundary representation—often abbreviated as B-rep or BREP—is a method for representing shapes using the limits. A solid is represented as a collection of connected surface elements, the boundary between solid and non-solid...
(B-rep) data via a
geometric modeling kernelA geometric modeling kernel is a 3D solid modeling software component used in computer-aided design packages. Examples include Romulus, Parasolid, ACIS, and Open CASCADE....
. A geometry constraint engine may also be employed to manage the associative relationships between geometry, such as wireframe geometry in a sketch or components in an assembly.
Unexpected capabilities of these associative relationships have led to a new form of prototyping called
digital prototypingDigital Prototyping gives conceptual design, engineering, manufacturing, and sales and marketing departments the ability to virtually explore a complete product before it’s built. Industrial designers, manufacturers, and engineers use Digital Prototyping to design, iterate, optimize, validate, and...
. In contrast to physical prototypes, which entail manufacturing time and material costs, digital prototypes allow for design verification and testing on screen, speeding time-to-market and decreasing costs. As technology evolves in this way, CAD has moved beyond a documentation tool (representing designs in graphical format) into a more robust designing tool that assists in the design process.
Hardware and OS technologies
Today, CAD systems exist for all the major platforms - CAD systems like
QCadQCad is a computer-aided design software package for 2D design and drafting. It is available for Linux, Mac OS X, Unix and Microsoft Windows. The QCad Community Edition, which lacks functionality present in the full version, is released under the GNU General Public License and is not available...
, NX provide multiplatform support including
WindowsMicrosoft Windows is a series of software operating systems and graphical user interfaces produced by Microsoft. Microsoft first introduced an operating environment named Windows in November 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces...
,
LinuxLinux is a generic term referring to Unix-like computer operating systems based on the Linux kernel. Their development is one of the most prominent examples of free and open source software collaboration; typically all the underlying source code can be used, freely modified, and redistributed,...
,
UNIXUnix is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
and
Mac OS XMac OS X is a line of computer operating systems developed, marketed, and sold by Apple Inc., and since 2002 has been included with all new Macintosh computer systems...
;
ArchiCADArchiCAD is an architectural BIM CAD software for Macintosh and Windows developed by the Hungarian company Graphisoft.Development started in 1982 for the original Apple Macintosh. ArchiCAD is recognized as the first CAD product on a personal computer able to create both 2D and 3D drawings...
works on both Windows and Mac OS X, but not on Linux; and, for example,
AutoCADAutoCAD is a CAD software application for 2D and 3D design and drafting, developed and sold by Autodesk, Inc. Initially released in late 1982, AutoCAD was one of the first CAD programs to run on personal computers, and notably the IBM PC...
works on Windows only. For more information on OS compatibility, see Comparison of CAD editors for AEC,
Comparison of CAD editors for CAMThis is a comparison of CAD software for the field of Computer-aided manufacturing . This is an overview about credible aspects of flexibility of CAD software, not a judgement about their power, ease of work, and other quality-related aspects....
and
Comparison of CAD editors for CAE- Comparison of CAD Editors for Computer Aided Engineering :...
. Catia V5 is supported on Sparc Solaris but not x86 Solaris, HPUX, and AIX, but not Linux. It has been announced that Catia V6 will only be supported on one proprietary operating system.
Right now, no special hardware is required for most CAD software. However, some CAD systems can do graphically and computationally expensive tasks, so good graphics card, high speed (and possibly multiple)
CPUThe Central Processing Unit or processor is the portion of a computer system that carries out the instructions of a computer program, and is the primary element carrying out the computer's functions. This term has been in use in the computer industry at least since the early 1960s...
s and large amounts of
RAM-Ram, ram, or RAM as a non-acronymic word:As a non-acronymic word Ram, ram, or RAM may refer to:-Animals:*Bighorn Sheep, A North American mountain sheep species*Sheep, an uncastrated male of which is called a ram...
are recommended.
The human-machine interface is generally via a computer mouse but can also be via a pen and digitizing
graphics tabletA graphics tablet is a computer input device that allows one to hand-draw images and graphics, similar to the way one draws images with a pencil and paper...
. Manipulation of the view of the model on the screen is also sometimes done with the use of a spacemouse/
SpaceBallSpaceball may refer to:* Spaceballs, a 1987 science fiction spoof film directed by and starring Mel Brooks* Spaceballs: The Animated Series, an animated television spin-off of the film* Spaceballs , a Norwegian demoscene group...
. Some systems also support stereoscopic glasses for viewing the 3D model.
Using CAD
Computer-Aided Design is one of the many tools used by engineers and designers and is used in many ways depending on the profession of the user and the type of software in question. There are several different types of CAD. Each of these different types of CAD systems require the operator to think differently about how he or she will use them and he or she must design their virtual components in a different manner for each.
There are many producers of the lower-end 2D systems, including a number of free and open source programs. These provide an approach to the drawing process without all the fuss over scale and placement on the drawing sheet that accompanied hand drafting, since these can be adjusted as required during the creation of the final draft.
3D wireframe is basically an extension of 2D drafting. Each line has to be manually inserted into the drawing. The final product has no mass properties associated with it and cannot have features directly added to it, such as holes. The operator approaches these in a similar fashion to the 2D systems, although many 3D systems allow using the wireframe model to make the final engineering drawing views.
3D "dumb" solids (programs incorporating this technology include AutoCAD and Cadkey 19) are created in a way analogous to manipulations of real world objects. Basic three-dimensional geometric forms (prisms, cylinders, spheres, and so on) have solid volumes added or subtracted from them, as if assembling or cutting real-world objects. Two-dimensional projected views can easily be generated from the models. Basic 3D solids don't usually include tools to easily allow motion of components, set limits to their motion, or identify interference between components.
3D parametric
solid modelingSolid modeling is a technique for representing solid objects suitable for computer processing. Other modeling methods include surface models and wire frame models .Primary uses of solid modeling are for CAD, engineering...
require the operator to use what is referred to as "design intent". The objects and features created are adjustable. Any future modifications will be simple, difficult, or nearly impossible, depending on how the original part was created. One must think of this as being a "perfect world" representation of the component. If a feature was intended to be located from the center of the part, the operator needs to locate it from the center of the model, not, perhaps, from a more convenient edge or an arbitrary point, as he could when using "dumb" solids. Parametric solids require the operator to consider the consequences of his actions carefully.
Some software packages provide the ability to edit parametric and non-parametric geometry without the need to understand or undo the design intent history of the geometry by use of direct modeling functionality. This ability may also include the additional ability to infer the correct relationships between selected geometry (e.g., tangency, concentricity) which makes the editing process less time and labor intensive while still freeing the engineer from the burden of understanding the model’s design intent history. These kind of non history based systems are called Explicit Modellers. The first Explicit Modeling system was introduced to the world at the end of 80's by Hewlett-Packard under the name SolidDesigner. This CAD solution, which released many later versions, is now sold by PTC as "CoCreate Modeling"
Draft views are able to be generated easily from the models. Assemblies usually incorporate tools to represent the motions of components, set their limits, and identify interference. The tool kits available for these systems are ever increasing; including 3D piping and injection mold designing packages.
Mid range software are integrating parametric solids more easily to the end user: integrating more intuitive functions (
SketchUpSketchUp is a 3D modeling program designed for architects, civil engineers, filmmakers, game developers, and related professions. It also includes features to facilitate the placement of models in Google Earth...
), using the best of both 3D dumb solids and parametric characteristics (
VectorWorksVectorworks is a computer-aided design software program developed by Nemetschek North America that is used for drafting, technical drawing and 3D modeling.-Description:...
), making very real-view scenes in relative few steps (Cinema4D) or offering all-in-one (
form•Zform·Z is a computer-aided design tool developed by AutoDesSys for all design fields that deal with the articulation of 3D spaces and forms and which is used for 3D modeling, drafting, animation and rendering.-Overview:...
).
Top end systems offer the capabilities to incorporate more organic, aesthetics and ergonomic features into designs (
CatiaCATIA is a multi-platform CAD/CAM/CAE commercial software suite developed by the French company Dassault Systemes and marketed worldwide by IBM...
,
GenerativeComponentsGenerativeComponents is parametric CAD software developed by Bentley Systems, was first introduced in 2003, became increasingly used in practice by early 2005, and was commercially released in November 2007. GenerativeComponents has a strong traditional base of users in academia and at...
).
Freeform surface modellingFreeform surface modelling is the art of engineering Freeform Surfaces with a CAD or CAID system.- Introduction :The technology encompasses two main fields...
is often combined with solids to allow the designer to create products that fit the human form and visual requirements as well as they interface with the machine.
The Effects of CAD
Starting in the late 1980s, the development of readily affordable Computer-Aided Design programs that could be run on personal computers began a trend of massive downsizing in drafting departments in many small to mid-size companies. As a general rule, one CAD operator could readily replace at least three to five drafters using traditional methods. Additionally, many engineers began to do their own drafting work, further eliminating the need for traditional drafting departments. This trend mirrored that of the elimination of many office jobs traditionally performed by a
secretaryA secretary is an administrative assistant in business office administration.The executive secretary has a myriad of administrative duties. Traditionally, these duties were mostly related to correspondence, such as the typing out of letters...
as word processors, spreadsheets, databases, etc. became standard software packages that "everyone" was expected to learn.
Another consequence had been that since the latest advances were often quite expensive, small and even mid-size firms often could not compete against large firms who could use their computational edge for competitive purposes.
Today, however, hardware and software costs have come down. Even high-end packages work on less expensive platforms and some even support multiple platforms. The costs associated with CAD implementation now are more heavily weighted to the costs of training in the use of these high level tools, the cost of integrating a CAD/CAM/CAE PLM using enterprise across multi-CAD and multi-platform environments and the costs of modifying design work flows to exploit the full advantage of CAD tools.
CAD vendors have effectively lowered these training costs. These methods can be split into three categories:
- Improved and simplified user interfaces. This includes the availability of “role” specific tailorable user interfaces through which commands are presented to users in a form appropriate to their function and expertise.
- Enhancements to application software. One such example is improved design-in-context, through the ability to model/edit a design component from within the context of a large, even multi-CAD, active digital mockup.
- User oriented modeling options. This includes the ability to free the user from the need to understand the design intent history of a complex intelligent model.
Product lifecycle
Computer-Aided Design is one part of the whole Digital Product Development (DPD) activity within the
Product Lifecycle ManagementProduct lifecycle management is the process of managing the entire lifecycle of a product from its conception, through design and manufacture, to service and disposal...
(PLM) process, and as such is used together with other tools, which are either integrated modules or stand-alone products, such as:
- Computer-aided engineering
Computer-aided engineering is the use of information technology to support engineers in tasks such as analysis, simulation, design, manufacture, planning, diagnosis, and repair.- Overview :...
(CAE) and Finite element analysis (FEA)
- Computer-aided manufacturing
Computer-aided manufacturing is the use of computer-based software tools that assist engineers and machinists in manufacturing or prototyping product components...
(CAM) including instructions to Computer Numerical Control (CNC) machines
- Photo realistic rendering
Rendering is the process of generating an image from a model, by means of computer programs. The model is a description of three-dimensional objects in a strictly defined language or data structure. It would contain geometry, viewpoint, texture, lighting, and shading information. The image is a...
- Document management and revision control
Revision control is the management of changes to documents, programs, and other information stored as computer files. It is most commonly used in software development, where a team of people may be changing the same files...
using Product Data ManagementProduct data management is the business function often within product lifecycle management that is responsible for the creation, management and publication of product data.- Introduction :...
(PDM).
See also
- 3D computer graphics software
3D computer graphics software refers to programs used to create 3D computer-generated imagery. This article only covers some of the software used.-Uses:...
- CAD standards
CAD Standards have been created to improve productivity and interchange of Computer-aided design documents between different offices and CAD programs, especially in architecture and engineering.- CAD Layer Standards :Most common:...
- Comparison of CAD editors for AEC
- Comparison of CAD editors for CAM
This is a comparison of CAD software for the field of Computer-aided manufacturing . This is an overview about credible aspects of flexibility of CAD software, not a judgement about their power, ease of work, and other quality-related aspects....
- Comparison of CAD editors for CAE
- Comparison of CAD Editors for Computer Aided Engineering :...
- Comparison of Free EDA software
Also worth mentioning is SPICE, a general purpose analog circuit simulator.Free or Open EDA enables end users with programming skills to add features and fix bugs and works as a safeguard to ensure designs are readable in the future.- See also :...
- Comparison of 3D computer graphics software
3D computer graphics software refers to programs used to create 3D computer-generated imagery.-General information:This is a chart on basic comparative elements that is based on the raw software without the inclusion of additional plugins....
- Electronic design automation
Electronic Design Automation is the category of tools for designing and producing electronic systems ranging from printed circuit boards to integrated circuits. This is sometimes referred to as ECAD or just CAD...
- ISO 128
ISO 128 is an international standard , about the general principles of presentation in technical drawings, more specific the graphical representation of objects on technical drawings.- Overview :...
- List of CAD companies
- Molecular design software
Molecular design software is a software for molecular modeling, distinctive property of which is the presence of the special support for developing the molecular models....
External links