Computer Aided Design
|of these articles describes CAD, to computers the Aided Design; for other meanings see CAD (term clarifying).|
WithOne does not only provide technical designs to CAD programs. With the aufwändigeren programs first of all three-dimensional volume models are provided. From this two or three-dimensional designs and visualizations of the objects even moved can be derived. CAD software comes in all specialist areas, in those constructionsare developed, for application: for example in the equipment construction, mechanical engineering, shipbuilding and also in architecture and in the building industry.
With the volume models one can accomplish most diverse Simulationen with the help of special software, for example Belastungssimulationen (finite element method) Construction units, Lichtsimulationen or Simulationen of the interior climate with buildings, Strömungssimulationen (wind or waves), Crashsimulationen in the construction of vehicles and Simulationen of different manufacturing methods (z. B. Injection moulding).
One knows the volume models still for many other things such as strength calculations, generativer manufacturing methods andnaturally also in the CNC - manufacturing with machines use. CAD is also a component of the computer-integrated production (CIM), with which the draft the manufacturing follows.
Modern programs are based on object-oriented data bases. Each component of the Design existsfrom one or more objects by programming. Changes and specifications are the parameters of the objects. Parameters can be based on relations with other Design aspects and make versions and variations of the same Design available. Object-oriented data bases permit optimal reusability of Design components, the optimumRecording of the intention of the designer as well as the possibility of fast adaptation. Together these advantages result in object-oriented parametric modelling “State OF the kind”.
Table of contents
2D and3D applications of constructions
mechanical CAD solutions are particularly within the following ranges:
- space planning
- historical reconstruction
- equipment construction
- textile industry
- product Design
- wood technology
- mechanical engineering
- construction of vehicles
- mechanical simulation, see also to finite element method (FEM/FEA)
- packing development and building of punching forms (DIECAD V.10.5)
a further area of application is the draft of electronic circuits. Appropriate programs are summarized often also under the term ECAD, in particular with applications in the board design and the building services engineering (see below).
In the trial process of an electrotechnical development for printed circuit boards standin the center:
- the draft of the circuit in form of a connection diagram,
- the verification of the function,
- the simulation under different tolerance - conditions, e.g. with the software SPICE,
- the production of housing and construction unit libraries,
- the transfer of the connection diagram into a layout (Printed circuit board),
- the production of exposure masks for production,
- the derivative of production-important data as for instance parts lists and inspection schemes.
Because of the special requirements special ranges with partly strongly different development methods formed, particularly for the computer-based chip draft, i.e.draft automation (EDA) for similar or digital integrated circuits, e.g. ASICs. The Design of programmable components is related for this such as gate array, GALs, FPGA and other types of programmable logic (PLDs) using e.g. VHDL, Abel.
Also in the classical building services engineering are numerous ranges of application for computer often commodity. Whether large house installations for industry or public buildings, or the draft and the conversion of SPS were based control devices for the respective purposes - even inthis sector today the individual Design of the respective plant is supported strongly by the computer.
In the range of the micro system engineering a special challenge consists in it to unite circuit data with the mechanical product statements (CAD) and to manufacture with such data directly Mikrosysteme.
simple one 2D of CAD systems are vector-oriented indication programs. Design elements are points, lines, Linienzüge, circular arcs, Splines. Tools make a producing, a positioning, a changing and deletion possible of design elements. The function differs little from thatclassical work on the board. Substantial progress becomes by the use of levels (Layertechnik) and the work also pre-defined symbols (approximately for standard and repeat parts) reaches. Far ones developed CAD systems support semi or fully automatic production of dimensionings and shadings. A further capability characteristics of modern 2D CAD of systems is the use of Assoziativität between design elements, for example between lines and dimensionings. Efficient CAD systems make programming interfaces available to the extension of functionality or to the user specific adjustment.
2 1/2 D
this is not “genuine” 3 D - that means that with surfaces and straight lines in the area one works. This method is less computer-bound than 3D and of architect programs is often used, because similar results are possible as with volume models.
a 3D CAD system processes a volume model of the construction object. Are the following modelling procedures spreads
- edge model - the body edges are illustrated by a mathematical description. An accurate description betweenis given the edges lying surfaces in this case however only with planar surfaces.
- Surface model - the body limiting surfaces become by a mathematical description, for example by NURBS - surfaces described. Usually still those becomes additionalTopology of the surfaces, i.e., which surface borders on which other surface, with stored.
- Construction history - the construction object is deduced by a set of construction steps (like for example associations, cuts) made of basic geometry such as right parallelepiped , cylinder , cone. ThoseSequence of the construction steps as well as the geometrical parameters of the bases are stored. A substantial advantage history are based of modelling is the high flexibility. Geometry can be changed by changes at the individual construction steps also afterwards variously.
Moderne 3D CAD-Systeme unterstützenall 3 modelling procedures.
A further characteristic of modern CAD systems is particularly the large Assoziativität between different geometry elements and between the 3D-Objekt and the design derived from it. For example the 3D-Modell of the part can by change of the diameter measure of the design of a drillingthe building group, in which the part is blocked, to be modified - beyond that at the same time in addition, the tool necessary for the manufacturing.
most programs set on their own file format. Makes more difficult data exchange betweendifferent CAD programs, why there are beginnings for standardisation. As data exchange format the DXF has itself - format as standard for designs establishes to a large extent. The predominant number of the CAD systems can read and write DXF files, however thereby frequently CAD system-specific characteristics are lost. It is to differentiate between CAD Systemneutralen and system-specific data formats. Substantial CAD Systemneutrale of data formats is VDAFS, IGES, SOWS and STEPS as well as for special applications the STL interface. The data formats in detail:
- VDAFS - Data exchange format for surfaces, develops from the federation German automobile farmer (VDA),in the past quasi standard for this range;
- IGES - Data exchange format for 2D-Zeichnungen and 3D-Daten (surfaces), in nearly all CAD applications as exchange format usually and possible. Replaces due to the better applicableness VDAFS more and more, is more extensive and more system-independent than DXFapplicable;
- STEP - a standardized file exchange format, which was internationally developed with the requirement to be able to transmit also parametric data. Only data format, which solvent and/or. Volume nearly loss-free and with Parametrik (with Solids) transfers. Likewise to the transmission of design data usable (therebut not as powerfully as in the 3D-Bereich);
- Vrml 97 ISO/International Electronical Commission 14772, was originally developed as 3D-Standard for Internet. Most 3D-Modellierungswerkzeuge makes in and export of vrml for files possible, whereby itself the file format also as an exchange formatfrom 3D-Modellen established.
With these formats usually only the transmission of edging, surface and volume models succeeds. Construction history is lost usually, thus is the transferred data usually for a subsequent treatment only conditionally suitable.CAD system-specific data formats make the transmission possible of the complete CAD models, it are available however only for few systems.
the beginnings of the CAD programs lie into the 1960er year.
To ALSO in bad clay/tone Ivan Suez ago country showed 1962 with its Sketchpad - development that it is possible, at a computer-controlled radar display screen interactively (light pen, keyboard) simple designs (English Sketch)to provide and change.
1965 was started with Lockheed (aircraft construction, the USA) the first approaches for a commercial CAD system for the production of technical designs (2D). This system, CADAM (computer Augmented Design and Manufacturing), based on IBM large computers, special screens, and with highCosts connected, by IBM and was, at least in the aircraft construction, market leader into the 1980er was marketed later years. It is partial in CATIA (S. down) come up, however practically from the market disappeared.
At the university in Cambridge, England, end becamethe 1960er years the first research work taken up, which should examine, whether it is possible, 3D-Grundkörper to use and this to the illustration of more complex compositions (z. B. To use pipings in the construction of chemical plants). From these work the system PDMS developed (Design management plansSystem), that today of the company Aveva under the name VPD is marketed.
Likewise end of the 1960er years began to program the French airplane manufacturer Avions Marcel Dassault ( today Dassault aviation) a diagram program for the production from designs to. From this that developedProgram CATIA. The Mirage was the first airplane, which was developed thereby. At that time such a program needed still the achievement of a large computer.
After years the first home computers were located to at the beginning of the 1980er in companies and households, came alsoCAD programs for it on the market.1982 appeared AutoCAD for the operating system DOS. The procedure with the construction remained the same however almost as before it at the paper. The 2D-CAD brought however as advantage very clean designs, which are simply again changedcould. It was faster possible to draw different versions of a construction unit.
Already in the middle of the 1980er years came with the German 3D-CAD-System PYTHA a first color Renderer on the market.
Into the 1980er years began because of the sinking job costs and thatbetter becoming software a CAD boom. In the industry hope was preserved to be able to loosen with a system all lining up design and tasks of construction. This beginning failed however. Today a special system with very efficient becomes for each special task of planningSpecial functions uses. For his criticism and his practical commitment against the employment from CAD with Lucas Aerospace and for its suggestions production to civilian and useful goods to change over, received Mike Cooley 1981 to the alternative Nobelpreis.
The step tothird dimension became by the ever higher efficiency of the hardware then toward end of the 1980er years even for smaller companies affordable. Thus knew virtual bodies from all sides will examine. Likewise it became possible to simulate loads and production programmes forto derive computer-controlled machine tools (CNC).
Since beginning of the 2000er years are there first beginnings to let the up to then still compellingly necessary design disappear. Into the ever more frequently existing 3D-Modellen become from the dimensioning over color and materialall necessary data for the manufacturing brought in. If the 3D-Modell is extended geometry-strange characteristics by these additional, it becomes the product model. The individual uniform volume objects become instances of different classes. Thus construction rules and references between individual objects (z can. B.Window embodied in wall) to be realized.