View source for Engineering:Computer-aided design

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{{Short description|Constructing a product by means of computer}}
[[File:Schneckengetriebe.png|thumb|A 2D CAD drawing]]
[[File:Cad crank.jpg|thumb|A 3D CAD model]]

'''Computer-aided design''' ('''CAD''') is the use of [[Computer|computer]]s (or {{vanchor|[[Workstation|workstation]]s|WORKSTATION}}) to aid in the creation, modification, analysis, or optimization of a [[Design|design]].<ref name="Narayan 2008">{{cite book |last=Narayan |first=K. Lalit |title=Computer Aided Design and Manufacturing |date=2008 |publisher=Prentice Hall of India |location=New Delhi |url=https://books.google.com/books?id=zXdivq93WIUC |isbn=978-8120333420 }}</ref>{{Rp|3}} This software is used to increase the productivity of the designer, improve the quality of design, improve communications through documentation, and to create a database for manufacturing.<ref name="Narayan 2008" />{{Rp|4}} Designs made through CAD software help protect products and inventions when used in [[Social:Patent|patent]] applications. CAD output is often in the form of electronic files for print, machining, or other manufacturing operations. The terms '''computer-aided drafting''' ('''CAD''') and '''computer-aided design and drafting''' ('''CADD''') are also used.<ref>{{cite book|last=Duggal |first=Vijay |date=2000 |title=Cadd Primer: A General Guide to Computer Aided Design and Drafting-Cadd, CAD |isbn=978-0962916595 |publisher=Mailmax Pub}}</ref>

Its use in designing electronic systems is known as ''[[Engineering:Electronic design automation|electronic design automation]]'' (''EDA''). In mechanical design it is known as ''mechanical design automation'' (''MDA''), which includes the process of creating a [[Engineering:Technical drawing|technical drawing]] with the use of computer software.<ref>{{cite book |last=Madsen |first=David A. |title=Engineering Drawing & Design |date=2012 |publisher=Delmar |location=Clifton Park, New York |page=10 |url=https://books.google.com/books?id=qdtJDEPZrrkC&pg=PA2 |isbn=978-1111309572 }}</ref>

CAD software for mechanical design uses either [[Vector graphics|vector-based graphics]] to depict the objects of traditional drafting, or may also produce [[Raster graphics|raster graphics]] showing the overall appearance of designed objects. However, it involves more than just shapes. As in the manual drafting of [[Engineering:Technical drawing|technical]] and [[Engineering:Engineering drawing|engineering drawing]]s, the output of CAD must convey information, such as [[Physics:Material|material]]s, processes, [[Physics:Dimension|dimension]]s, and [[Engineering:Engineering tolerance|tolerances]], according to application-specific conventions.

CAD may be used to design curves and figures in [[2D computer graphics|two-dimensional]] (2D) space; or curves, [[Computer representation of surfaces|surfaces]], and solids in [[3D computer graphics|three-dimensional]] (3D) space.<ref>{{cite book|author1=Farin, Gerald |author2=Hoschek, Josef |author3=Kim, Myung-Soo |title=Handbook of computer aided geometric design [electronic resource]|url=https://books.google.com/books?id=0SV5G8fgxLoC|date=2002|publisher=Elsevier|isbn=978-0-444-51104-1}}</ref>{{r|Schoonmaker2003|p=|pages=71,106}}

CAD is an important [[Industrial arts|industrial art]] extensively used in many applications, including automotive, [[Engineering:Shipbuilding|shipbuilding]], and [[Earth:Aerospace|aerospace]] industries, industrial and architectural design ([[Building information modeling|building information modeling]]), [[Biology:Prosthesis|prosthetics]], and many more. CAD is also widely used to produce [[Computer animation|computer animation]] for [[Special effect|special effect]]s in movies, [[Finance:Advertising|advertising]] and technical manuals, often called DCC digital content creation. The modern ubiquity and power of computers means that even perfume bottles and shampoo dispensers are designed using techniques unheard of by engineers of the 1960s. Because of its enormous economic importance, CAD has been a major driving force for research in [[Computational geometry|computational geometry]], [[Computer graphics|computer graphics]] (both hardware and software), and [[Discrete differential geometry|discrete differential geometry]].<ref>Pottmann, H.; Brell-Cokcan, S. and Wallner, J. (2007) [http://www.geometrie.tuwien.ac.at/ig/sn/2007/pbw_surfaces_07/pbw_surfaces_07.html "Discrete surfaces for architectural design"] {{webarchive|url=https://web.archive.org/web/20090812113324/http://www.geometrie.tuwien.ac.at/ig/sn/2007/pbw_surfaces_07/pbw_surfaces_07.html |date=2009-08-12 }}, pp. 213–234 in ''Curve and Surface Design'', Patrick Chenin, Tom Lyche and Larry L. Schumaker (eds.), Nashboro Press, {{ISBN|978-0-9728482-7-5}}.</ref>

The design of geometric models for object shapes, in particular, is occasionally called '''computer-aided geometric design''' ('''CAGD''').<ref>Farin, Gerald (2002) [http://www.farinhansford.com/books/cagd/ ''Curves and Surfaces for CAGD: A Practical Guide''], Morgan-Kaufmann, {{ISBN|1-55860-737-4}}.</ref>

==Overview==
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.

CAD is one part of the whole digital product development (DPD) activity within the product lifecycle management (PLM) processes, and as such is used together with other tools, which are either integrated modules or stand-alone products, such as:

* [[Computer-aided engineering]] (CAE) and finite element analysis (FEA, FEM)
* [[Computer-aided manufacturing]] (CAM) including instructions to computer numerical control (CNC) machines
* Photorealistic rendering and motion simulation
* Document management and revision control using [[Software:Product data management|product data management]] (PDM)

CAD is also used for the accurate creation of photo simulations that are often required in the preparation of environmental impact reports, in which computer-aided designs of intended buildings are superimposed into photographs of existing environments to represent what that locale will be like, where the proposed facilities are allowed to be built. Potential blockage of view corridors and shadow studies are also frequently analyzed through the use of CAD.<ref>{{Cite web |url=https://www.inc.com/encyclopedia/computer-aided-design-cad-and-computer-aided-cam.html |title=Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) |website=Inc.com |access-date=2020-04-30 }}</ref>

==Types==
[[File:CAD Modeling.gif|thumb|A simple procedure of recreating a solid model out of 2D sketches]]

There are several different types of CAD,<ref>{{cite web |title=3D Feature-based, Parametric Solid Modeling |website=EngineersHandbook.com |url=http://engineershandbook.com/Software/cad2.htm#3dp |access-date=2012-03-01 |archive-url=https://web.archive.org/web/20121118110426/http://www.engineershandbook.com/Software/cad2.htm#3dp |archive-date=2012-11-18 }}</ref> each requiring the operator to think differently about how to use them and design their virtual components in a different manner. Virtually all of CAD tools rely on [[Engineering:Constraint (computer-aided design)|constraint]] concepts that are used to define geometric or non-geometric elements of a model. 

=== 2D CAD ===
There are many producers of the lower-end 2D sketching systems, including a number of free and open-source programs. These provide an approach to the drawing process where scale and placement on the drawing sheet can easily be adjusted in the final draft as required, unlike in hand drafting.

=== 3D CAD ===
''3D [[Wire-frame model|wireframe]]'' is an extension of 2D drafting into a [[Three-dimensional space|three-dimensional space]]. 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 add 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'' are created in a way analogous to manipulations of real-world objects. Basic three-dimensional geometric forms (e.g., prisms, cylinders, spheres, or rectangles) 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 do not usually include tools to easily allow the motion of the components, set their limits to their motion, or identify interference between components.

There are several types of ''3D [[Solid modeling|solid modeling]]''

* ''Parametric modeling'' allows the operator to use what is referred to as "design intent". The objects and features are created modifiable. Any future modifications can be made by changing on how the original part was created. If a feature was intended 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 geometric and functional relationships.
* ''[[Explicit modeling|Direct or explicit modeling]]'' provide the ability to edit geometry without a history tree. With direct modeling, once a sketch is used to create geometry it is incorporated into the new geometry, and the designer only has to modify the geometry afterward without needing the original sketch. As with parametric modeling, direct modeling has the ability to include the relationships between selected geometry (e.g., tangency, concentricity).
* ''[[Engineering:Assembly modelling|Assembly modelling]]'' is a process which incorporates results of the previous single-part modelling into a final product containing several parts. Assemblies can be hierarchical, depending on the specific CAD software vendor, and highly complex models can be achieved (e.g. in building engineering by using [[Software:Computer-aided architectural design|computer-aided architectural design]] software)<ref>{{Cite book |last=Stroud |first=Ian |title=Solid modelling and CAD systems: how to survive a CAD system |last2=Nagy |first2=Hildegarde |date=2011 |publisher=Springer |isbn=978-0-85729-259-9 |location=London New York}}</ref>{{Rp|page=539}}

==== Freeform CAD ====
{{Further|Surface-to-surface intersection problem}}
Top-end CAD systems offer the capability to incorporate more organic, aesthetic and ergonomic features into the designs. [[Freeform surface modelling|Freeform surface modeling]] 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.

==Technology==
[[File:cad mouse 1.svg|thumb|A CAD model of a computer mouse]]

Originally software for CAD systems was developed with computer languages such as [[Fortran]], [[ALGOL]] but with the advancement of [[Object-oriented programming|object-oriented programming]] 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]] modules with their own [[Application programming interface|API]]s. A CAD system can be seen as built up from the interaction of a [[Graphical user interface|graphical user interface]] (GUI) with NURBS geometry or [[Engineering:Boundary representation|boundary representation]] (B-rep) data via a [[Engineering:Geometric modeling kernel|geometric modeling kernel]]. 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 prototyping. In contrast to physical prototypes, which entail manufacturing time in the design. That said, CAD models can be generated by a computer after the physical prototype has been scanned using an industrial CT scanning machine. Depending on the nature of the business, digital or physical prototypes can be initially chosen according to specific needs.

Today, CAD systems exist for all the major platforms ([[Software:Microsoft Windows|Windows]], [[Software:Linux|Linux]], UNIX and [[Software:Mac OS X|Mac OS X]]); some packages support multiple platforms.<ref>{{Cite web|url=https://www.computertechreviews.com/definition/cad-workstation/|title=What is a CAD Workstation? Definition, Uses and More|date=2019-11-21|website=Computer Tech Reviews |access-date=2020-04-30}}</ref>

Currently, no special hardware is required for most CAD software. However, some CAD systems can do graphically and computationally intensive tasks, so a modern [[Engineering:Graphics card|graphics card]], high speed (and possibly multiple) [[Central processing unit|CPU]]s and large amounts of [[Random-access memory|RAM]] may be recommended.

The human-machine interface is generally via a [[Computer mouse|computer mouse]] but can also be via a pen and digitizing [[Graphics tablet|graphics tablet]]. Manipulation of the view of the model on the screen is also sometimes done with the use of a [[Company:3Dconnexion|Spacemouse/SpaceBall]]. Some systems also support stereoscopic glasses for [[Scientific visualization|viewing the 3D model]]. Technologies that in the past were limited to larger installations or specialist applications have become available to a wide group of users. These include the [[Cave automatic virtual environment|CAVE]] or [[Virtual reality|HMDs]] and interactive [[Company:Leap Motion|devices]] like motion-sensing [[Engineering:Kinect|technology]]

==Software==

Starting with the IBM Drafting System in the mid-1960s, computer-aided design systems began to provide more capabilitties than just an ability to reproduce manual drafting with electronic drafting, and the [[Cost–benefit analysis|cost-benefit]] for companies to switch to CAD became apparent. The software automated many tasks that are taken for granted from computer systems today, such as automated generation of [[Bill of materials|bills of materials]], auto layout in integrated circuits, interference checking, and many others. Eventually, CAD provided the designer with the ability to perform engineering calculations.<ref name="Schoonmaker2003">{{Cite book|last=Schoonmaker|first=Stephen J.|url=https://www.worldcat.org/oclc/50868192|title=The CAD guidebook : a basic manual for understanding and improving computer-aided design|date=2003|publisher=Marcel Dekker|isbn=0-8247-0871-7|location=New York|oclc=50868192}}</ref> During this transition, calculations were still performed either by hand or by those individuals who could run computer programs. CAD was a revolutionary change in the engineering industry, where draftsman, designer, and engineer roles that had previously been separate began to merge. CAD is an example of the pervasive effect computers were beginning to have on the industry.
Current computer-aided design software packages range from 2D [[Vector graphics|vector]]-based drafting systems to 3D [[Solid modeling|solid]] and [[Freeform surface modelling|surface modelers]]. 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.<ref name="Schoonmaker2003" /> Some CAD software is capable of dynamic mathematical modeling.<ref name="Schoonmaker2003" />

CAD technology 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).<ref>{{cite web
 | title = 3D Model-Based Design: Setting the Definitions Straight
 | author = Jennifer Herron
 | publisher = MCADCafe
 |date= 2010
 | url = http://www10.mcadcafe.com/nbc/articles/2/867959/3D-Model-Based-Design-Setting-Definitions-Straight
}}</ref>

CAD is mainly used for detailed design of 3D models 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. It can also be used to design objects such as jewelry, furniture, appliances, etc. Furthermore, many CAD applications now offer advanced rendering and animation capabilities so engineers can better visualize their product designs. [[4D BIM|4D BIM]] is a type of virtual construction engineering simulation incorporating time or schedule-related information for project management.

CAD has become an especially important technology within the scope of computer-aided technologies, with benefits such as lower product development costs and a greatly shortened [[Systems development life cycle#Design|design cycle]]. CAD enables designers to layout and develop work on screen, print it out and save it for future editing, saving time on their drawings.

=== License management software ===
In the 2000s, some CAD system software vendors shipped their distributions with a dedicated license manager software that controlled how often or how many users can utilize the CAD system.{{r|Schoonmaker2003|p=166}} It could run either on a local machine (by loading from a local storage device) or a local [[File server|network fileserver]] and was usually tied to a specific IP address in latter case.{{r|Schoonmaker2003|p=166}}

==List of software packages==
CAD software enables engineers and architects to design, inspect and manage engineering projects within an integrated [[Graphical user interface|graphical user interface]] (GUI) on a [[Engineering:Personal computer|personal computer]] system. Most applications support [[Solid modeling|solid modeling]] with [[Engineering:Boundary representation|boundary representation]] (B-Rep) and NURBS geometry, and enable the same to be published in a variety of formats.{{Citation needed|date=May 2023}}

Based on market statistics, [[Commercial software|commercial software]] from Autodesk, Dassault Systems, Siemens PLM Software, and PTC dominate the CAD industry.<ref>[http://caewatch.com/the-big-6-in-cadcaeplm-software-industry-2011/ The Big 6 in CAD/CAE/PLM software industry (2011)], CAEWatch, September 12, 2011</ref><ref>{{cite web|url=http://www.softwaretop100.org/global-software-top-100-edition-2011|title=GLOBAL SOFTWARE TOP 100 – EDITION 2011|website=Software Top 100|date=2011-08-23|first=Michel|last=van Kooten}}</ref> The following is a list of major CAD applications, grouped by usage statistics.<ref name="bm">[http://www.beyondmech.com/pro-e/cad-topic-33.html List of mechanical CAD softwares] {{Webarchive|url=https://web.archive.org/web/20200728192806/http://www.beyondmech.com/pro-e/cad-topic-33.html |date=2020-07-28 }}, BeyondMech</ref>

===Commercial software===
* [[Software:AC3D|AC3D]]
* [[Software:Alibre Design|Alibre Design]]
* [[Software:ArchiCAD|ArchiCAD]] (Graphisoft)
* [[Software:AutoCAD|AutoCAD]] ([[Company:Autodesk|Autodesk]])
* [[Software:Autodesk Inventor|Autodesk Inventor]]
* [[AxSTREAM]]
* [[Software:BricsCAD|BricsCAD]]
* [[Software:CATIA|CATIA]] (Dassault Systèmes)
* [[Software:Cobalt (CAD program)|Cobalt]]
* [[Software:CorelCAD|CorelCAD]]
* [[Software:Fusion 360|Fusion 360]] (Autodesk)
* [[Software:IntelliCAD|IntelliCAD]]
* [[Software:IRONCAD|IRONCAD]]
* [[Software:KeyCreator|KeyCreator]] (Kubotek)
* [[Software:Landscape Express|Landscape Express]]
* [[Software:MEDUSA|MEDUSA]]
* [[Software:MicroStation|MicroStation]] (Bentley Systems)
* [[Software:Modelur|Modelur]] (AgiliCity)
* [[Software:Onshape|Onshape]]
* [[Software:PTC Creo|PTC Creo]] (successor to Pro/ENGINEER)
* [[Software:PunchCAD|PunchCAD]]
* [[Software:Remo 3D|Remo 3D]]
* Revit (Autodesk)
* [[Software:Rhinoceros 3D|Rhinoceros 3D]]
* [[Software:Siemens NX|Siemens NX]]
* [[Software:SketchUp|SketchUp]]
* [[Software:Solid Edge|Solid Edge]] (Siemens)
* [[Software:SolidWorks|SolidWorks]] (Dassault Systèmes)
* [[Software:SpaceClaim|SpaceClaim]]
* [[Software:T-FLEX CAD|T-FLEX CAD]]
* [[Software:TranslateCAD|TranslateCAD]]
* [[Software:TurboCAD|TurboCAD]]
* [[Company:Vectorworks|Vectorworks]] (Nemetschek)

===Open-source software===
* [[Software:BRL-CAD|BRL-CAD]]
* [[Software:FreeCAD|FreeCAD]]
* [[Software:LibreCAD|LibreCAD]]
* [[Software:LeoCAD|LeoCAD]]
* [[Software:OpenSCAD|OpenSCAD]]
* [[Software:QCAD|QCAD]]
* [[Software:Salome|Salome]]
* [[Software:SolveSpace|SolveSpace]]

===Freeware===
* [[Software:BricsCAD#BricsCAD Shape|BricsCAD Shape]]
* [[Engineering:TiffinCAD|TiffinCAD]]
* [[Software:Tinkercad|Tinkercad]] (successor to [[Software:Autodesk 123D|Autodesk 123D]])

===CAD kernels===
* [[Software:ACIS|ACIS]] by Spatial
* [[Software:C3D Toolkit|C3D Toolkit]] by C3D Labs
* Open CASCADE Open Source
* [[Parasolid]] by Siemens
* [[Engineering:ShapeManager|ShapeManager]] by Autodesk

==See also==
{{Div col}}
* {{annotated link|3D computer graphics}}
* {{annotated link|3D printing}}
* {{annotated link|Algorithmic art}}
* {{annotated link|CAD standards}}
* {{annotated link|Coarse space (numerical analysis)}}
* {{annotated link|Software:Comparison of 3D computer graphics software}}
* {{annotated link|Software:Comparison of computer-aided design software}}
* {{annotated link|Software:Comparison of EDA software}} (electronic design automation)
* {{annotated link|Engineering:Computer-aided industrial design}}
* {{annotated link|Engineering:Electronic design automation}}
* {{annotated link|Engineering:Engineering optimization}}
* {{annotated link|Finite element method}}
* {{annotated link|ISO 128}}
* {{annotated link|ISO 10303}} (STEP)
* {{annotated link|Model-based definition}}
* {{annotated link|Software:Molecular design software}}
* {{annotated link|Open-source hardware}}
* {{annotated link|Social:Rapid prototyping}}
* {{annotated link|Responsive computer-aided design}}
* {{annotated link|Space mapping}}
* {{annotated link|Surrogate model}}
* {{annotated link|System integration}}
* {{annotated link|Engineering:Virtual prototyping}}
* {{annotated link|Virtual reality}}
{{Div col end}}

==References==
{{Reflist|refs=}}

==External links==
* [https://www.youtube.com/watch?v=RgUSsXdLjvc MIT 1982 CAD lab]

{{CAD software}}
{{Building information modeling}}
{{Design}}

[[Category:Computer-aided design| ]]
[[Category:Computer-aided design software| ]]
[[Category:Design engineering]]
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