[attachment=14675]
Computer-aided design
Computer-aided design (CAD), also known as computer-aided drafting and design (CADD), is the use of computer technology for the process of design and design-documentation.
Computer Aided Design describes the way in which technology is folded into a design process.
Computer Aided Drafting describes the process of drafting with a computer.
CADD output is often in the form of electronic files for print or machining operations.
The output of CAD must convey information, such as materials, processes, dimensions, and tolerances, according to application-specific conventions.
CAD may be used to design curves and figures in two-dimensional (2D) space; or curves, surfaces, and solids in three-dimensional (3D) objects.
CAD is also widely used to produce computer animation for special effects in movies, advertising and technical manuals .
Overview
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).
It can also be used to design objects.
CAD has become an especially important technology within the scope of computer-aided technologies
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
Uses
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) process, and as such is used together with other tools, which are either integrated modules or stand-alone products, such as:
1.Computer-aided engineering (CAE) and Finite element analysis (FEA)
2.Computer-aided manufacturing (CAM) including instructions to Computer Numerical Control (CNC) machines
3.Photo realistic rendering
4.Document management and revision control using Product Data Management (PDM).
Potential blockage of view corridors and shadow studies are also frequently analyzed through the use of CAD.
Capabilities
There are several different types of CAD. Each of these different types of CAD systems require the operator to think differently about how we will use them and we must design their virtual components in a different manner for each.
The capabilities of modern CAD systems include:
1.Wireframe geometry creation
2.3D parametric feature based modelling, Solid modelling
3.Freeform surface modelling
4.Automated design of assemblies, which are collections of parts and/or other assemblies
5.Create Engineering drawings from the solid models
6.Reuse of design components
7.Maintain libraries of parts and assemblies .
Fields of use
Fashion Design
AEC Architecture Engineering and Construction
MCAD Mechanical
1.Automotive
2.Aerospace
3.Consumer Goods
4.Machinery
5.Ship Building
Manufacturing process planning
Coordinator
Face Mapping
Survey Draughting
SSMON, Stability Monitoring database
Generalized co-ordinate and database connectivity
DBDS Drill and Blast database system
Software providers today
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 Systems, PTC, and UGS Corp., but there are many other CAD packages with smaller user bases or covering niche user areas.
Packages can be classified into 3 types:
1.2D drafting systems (e.g. AutoCAD, Microstation)
2. Mid-range 3D solid feature modellers (e.g. SolidWorks, SolidEdge, Alibre)
3.High-end 3D hybrid systems (e.g. CATIA, NX (Unigraphics))
Software Technologies
Originally software for CAD systems were developed with computer language such as Fortran, but with the advancement of Object-oriented programming methods this has over the last decade or so radically changed.
The development of a typical modern Parametric feature based modeler and freeform surface systems are built around a number of key, C programming language, modules with their own APIs.
A CAD system can be seen as built up from the interaction a GUI with an Associative engine and Geometry constraint engine controlling BREP, CSG and NURBS geometry via a Geometric modeling kernel.
Hardware and OS technologies
Today, CAD systems exist for all the major platforms (Windows, Linux, UNIX and Mac OS X); some packages even support multiple platforms.
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) CPUs and large amounts of RAM are recommended .
The human-machine interface is generally via a computer mouse but can also be via a pen and digitizing graphics tablet. Manipulation of the view of the model on the screen is also sometimes done with the use of a spacemouse/spaceball.
Some systems also support stereoscopic glasses for viewing the 3D model.
Features of CAD
Computer-aided design (CAD) involves creating computer models defined by geometrical parameters.
These models typically appear on a computer monitor as a three-dimensional representation of a part or a system of parts, which can be readily altered by changing relevant parameters.
CAD systems enable designers to view objects under a wide variety of representations and to test these objects by simulating real-world conditions
Why we go for CAD services
Increased productivity
Less errors using 3D Modeling
Improved collaboration
Quicker Turn-around time
Lower overhead costs
Effects of CAD
Today,hardware and software costs have come down.
Even high-end packages work on less expensive platforms and some even support multiple platforms .
There are three categories.
1.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.
2.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.
3.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 .
Advantages of CAD
Can be easily erased and changed
Can be zoomed in for more detailed sections
Can be copied and pasted many times
Depending on skill, can be neater
Can be quicker
Can be sent to elsewhere quickly
Can be stored in a safe place
Can be checked for measurements by the computer
Disadvantages of CAD
If computer problem, all data will be lost
If not checked properly, the object created can go very wrong
Can be very expensive
Can be hard to do and handling needs training
Since not manual, can be slightly irritating because if not familiar with technology, it is very hard to insure exactly what is wanted by the designer.
Ex: If wanted something engraved instead of cut, the line colour has to be changed into black instead of red.
Compare with 2D CAD
A few advantages of 2D CAD: 1.Reduced design timescales. 2.Reuse of designs. 3.Drawing errors can be corrected easily. 4.Drawings can be sent/received via email in seconds.
Disadvantages: 1.Time & cost of implementing the CAD system 2.Time & cost of training people to use the CAD. 3.Time & cost of migrating legacy drawings into CAD format
Compare with 3D CAD
Advantages of 3D CAD: 1.More stylish /complex products can be designed using 3D surfacing. 2.Parametric modelling allows many design iterations to be generated & evaluated quickly. 3.Designs can be analyzed and optimized virtually using finite element analysis. 4.Clearance/interference checks can be mase easily 5.3D CAD data can be imported directly in to CAM software, further reducing timescales and mistakes from interpretation of 2D drawings
Conclusion
Computer-aided design (CAD) is the use of a wide range of computer-based tools that assist engineers, architects and other design professionals in their design activities.
CAD is also extensively used in the design of tools and machinery used in the manufacture of components.
CAD is used throughout the engineering process from conceptual design and layout, through detailed engineering and analysis of components to definition of manufacturing methods.