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In todays world computer are used to perform many tasks which were done by human being previously. Some common examples are accounting, Typing communication, data base management, etc. computer were used different software to perform these tasks.
computer-aided design (CAD) or computer-aided design and drafting (CADD), form of automation that helps designers prepare drawings, specifications, parts lists, and other design-related elements using special graphics- and calculations-intensive computer programs. The technology is used for a wide variety of products in such fields as architecture, electronics, and aerospace, naval, and automotive engineering. Although CAD systems originally merely automated drafting, they now usually include three-dimensional modeling and computer-simulated operation of the model. Rather than having to build prototypes and change components to determine the effects of tolerance ranges, engineers can use computers to simulate operation to determine loads and stresses. For example, an automobile manufacturer might use CAD to calculate the wind drag on several new car-body designs without having to build physical models of each one. In microelectronics, as devices have become smaller and more complex, CAD has become an especially important technology. Among the benefits of such systems are lower product-development costs and a greatly shortened design cycle. While less expensive CAD systems running on personal computers have become available for do-it-yourself home remodeling and simple drafting, state-of-the-art CAD systems running on workstations and mainframe computers are increasingly integrated with computer-aided manufacturing systems.
The process of constructing of drawing on the computer screen with the help of specially Developed software and hardware is called computer aided designing and drafting. [CAD]
The computer system is based on what is called interactive computer graphics [ICG]. ICG helps to convert the data entered by the user in the form of graphics. The user enters the data in the form of command by using hardware which is converted into graphics by the software.
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 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.
CAD software, also referred to as Computer Aided Design software and in the past as computer aided drafting software, refers to software programs that assist engineers and designers in a wide variety of industries to design and manufacture physical products ranging from buildings, bridges, roads, aircraft, ships and cars to digital cameras, mobile phones, TVs, clothes and of course computers! CAD software is often referred to as CAD CAM software ('CAM' is the acronym for Computer Aided Machining).
The clocks ticked into 2000 and the IT industry, CAD software vendors included, breathed a sigh of relief as it became evident that fears of Y2K problems were not to materialize.
In the CAD software industry, attention swung back to Web enabled CAD as Alibre released Alibre Design, based on Spatial Technology's ACIS, which was the first 3D CAD software able to perform client-server 3D modeling over the Internet (although in Japan, Toyota Caelum's TeamCAD had been capable of 3D modeling across LANs since the mid 1990s, even before the term 'client-server' became popular!).
Using "virtual product development" with a digital master 3D assembly of 3D component models replacing clay prototypes, Boeing had succeeded in reducing product development times in the aerospace industry and now Ford had done the same in the automotive industry. At least at the enterprise manufacturing level, the competition had shifted away from the function to function comparisons typical of the major 3D CAD software deals of the late 1980s and early 1990s and had now become a test of how well the vendor could manage the flow of design and engineering data; of which the 3D CAD model was an increasingly smaller percentage.
Picking up on the term PLM "Product Life-cycle Management", which had started as university research into manufacturing databases in the early 1990s and had begun to gain popularity in the industry in the late 1990s, the leading CAD software companies were quick to redefine themselves to the emerging market trend. Suddenly "3D CAD software vendor" was out and "PLM solution provider" was in. The four leading vendors (Dassault Systemes, Parametric Technology, Unigraphics Solutions and SDRC) began the task of realigning their corporate images, marketing and sales processes; "blistering 3D modeling speed", "faster than lightening rendering" and "graphics so real you can feel it" were out and "value propositions", "portfolio management" and "life cycle analysis" were in.
Ford was using SDRC's Metaphase PDM software in its C3P platform and in late 2000 SDRC acquired Metaphase's long-time PDM competitor, Sherpa, to consolidate its PLM image. In addition to strong database and network management, the ability to rapidly view large assemblies of 3D data is a key component of modern PLM solutions and in late 2000 Unigraphics Solutions acquired the leading 3D viewer vendor EAI.
One of the few 3D CAD software events (other than mostly routine upgrades, updates and extensions to the leading vendors traditional 3D software products) was Dassault Systemes' acquisition of Spatial Technology's ACIS 3D solid modeling kernel in late 2000. Despite its 1996 IPO, which proved that a component technology vendor could achieve commercial success, Spatial had lost its way; partly because it had never managed to license ACIS to a leading 3D CAD software vendor and partly because like many other vendors it had over-invested in non-essential Internet ASP development. To this date neither Dassault Systemes nor its SolidWorks subsidiary use ACIS and the reasons for the acquisition remain obscure.
Early in 2001, Unigraphics Solutions changed its name to UGS and acquired SDRC. At the same time EDS bought back the 14% of UGS stock that it had publicly sold in the late 1990s (UGS was recently acquired from EDS by a consortium of venture capital funds). Ford were relying on SDRC for the core of the C3P platform but were prompted to consider a multi-vendor strategy for their future PLM software needs. That strategy began to be implemented in early 2003 when Ford announced that they were implementing IBM-Dassault Systemes' CATIA and ENOVIA software.
While there have been no fundamental technology breakthroughs (what Professor Clayton Christensen would term "disruptive technological changes") since Pro/Engineer's release in 1987, the early part of this decade did see one or two interesting developments in making it simpler and more intuitive to create 3D CAD models. In late 2001 think3 introduced its GSM "Global Shape Modeling" into its thinkDesign software to make it possible to "push and pull" NURBS surfaces. Early in 2003, PTC (which is how Parametric Technology now likes to be known) released its new WildFire 3D CAD software which also attempted to make it simpler to create 3D geometry.
The only new 3D CAD software vendor (at least that I am legally allowed to mention) that emerged to upset the industry's status quo was ImpactXoft, which in 1999-2000 jointly developed the IX/Speed and XXen CAD software with Japan's Toyota Caelum. Initial releases of IX/Speed and XXen were made early in 2001. Dassault Systemes made a substantial investment in ImpactXoft at the end of 2002 and IX, having now broken away from the joint development agreement with Toyota Caelum, has joined a long list of companies that have become partners of Dassault Systemes developing on the CATIA Component Application Architecture.
So today, in July 2004, the CAD software industry is dominated by 3 PLM solution vendors (IBM-Dassault Systemes with CATIA & ENOVIA, UGS with Unigraphics & iMAN, and PTC with Pro/Engineer & WindChill) and Autodesk, whose market value is typically slightly below Dassault Systemes' and more than 3x that of PTC. SolidWorks and SolidEdge (owned by Dassault Systemes and UGS respectively) continue to battle with Autodesk's Inventor in the mid-price CAD software market and there are many small CAD software vendors, some of which are listed on CADAZZ's free CAD software pages who survive by being excellent in niche markets and by being data compatible with the CAD software programs offered by the four leading vendors.
True innovation of the kind that drove the industry forward in the 70s and 80s seems to have died though, if only temporarily, and as Clayton Christensen might say, "This is one market just waiting for a big bang to happen!".
CAD IN THE FUTURE
3D CAD software is today dominated by 3 vendors, Dassault, PTC and UGS.
Their 3D CAD software products are very similar - in fact so functionally similar that they now almost always avoid competing on 3D CAD functionality but instead focus almost exclusively on their PLM capabilities and "business process innovation".
Technical innovation in 3D CAD software seems to have flown out of the window as PLM stomped in through the door.
What is PLM? What is "business process innovation"? Do they really help ordinary CAD software users (designers and engineers) get their job done? Or do they more likely help large CAD software companies make their quarterly revenue targets?
Clayton M. Christensen, author of "The Innovator's Dilemma" shows that sustained innovation, even funded by billion dollar research budgets, only enables leading companies to survive so long as no disruptive technology suddenly appears to upset the corporate apple-cart. In the 1980s Digital and Computervision were leading companies in their markets; today neither exists. Both were the victims of disruptive technologies.
Just as propeller powered aircraft could not compete with jets; neither will today's CAD software be able to compete with new products on the imminent horizon.
Types of CAD Programs
When it comes to computer-aided design and drafting (CAD), one size does not fit all. The type of design and drafting your company does will determine what kind of software package is best for you. CAD programs vary by how the drawing is plotted as well as what type of drawing--mechanical, architectural, civil or other--you are engaged in. Knowing your options is the first step toward making the right decision for your company.
Two-dimensional computer-aided drafting is the most basic type of CAD program. The designer creates drawings by plotting along the X- and Y-axes. Designs have no depth to them, being displayed by their outlines only. This type of drafting relies upon the skill of the designer to express himself using only basic geometric figures. Drawings in two dimensions have a very flat quality about them. These types of programs are useful for architects and other professionals who do not require any depth to provide a representation of their creations.
Two-and-a-half dimensional CAD drafting allows the user to create psuedo-three-dimensional drawings. This is typically done through isometric projection to create a false sense of depth. Designs will still have a wire-frame quality to them (that is, made up entirely of lines), with no solid modeling figures or true surfaces.
Three-dimensional computer-aided drawing programs are some of the more expensive CAD programs. They may use nurbs, wire frames or solids to create truly three-dimensional drawing architecture. The design has true depth to it, allowing the designer to rotate her design 360 degrees around three different axes. This is one of the most accurate representations of how a design will look when actually produced.
In addition to differences between computer-aided drafting and design programs according to how they represent drawings, companies make programs specifically for use by drafters working in certain trades. For example, Autodesk, the creator of AutoCAD, makes a special AutoCAD for both architecture and civil engineering.
These programs allow for drafting professionals to do their jobs more easily by incorporating and streamlining functions that would be irrelevant or cumbersome in a more general package. For example, architectural CAD programs include functions for laying out walls and civil engineering programs include tools for surveying and plotting highway cloverleafs.
REASONS FOR IMPLEMENTING A CAD SYSTEM
INCREASE THE PRODUCTIVITY OF THE DESIGNER:
CAD improves the productivity of the designer to visualize the product and its component, parts and reduces required time
IMPROVE THE QUALITY OF THE DESIGN:
CAD system improves the quality of design. A CAD system permits a more detailed Engineering Analysis and a large number of design alternatives can be investigated.
Improve the communication in design .The use of CAD system provides better engineering drawings.
IMPROVE THE EFFICIENCY OF DESIGN :
It provides the efficiency of the design process and the wastage at the design stage can be reduced.
BENEFITS OF CAD
The implementation of cad system provides variety of benefits to industries in design and production .they are shown below:
Improved productivity of drafting.
Shorter preparation time for drawing.
Reduced manpower requirements
customer modifications in drawing are easier.
More efficient operation in drafting .
Low wastage in drawing .
minimize transcription errors in drawing.
Improved accuracy of drawing.
Better design can be evolved..
Revisions are possible.
Preparation of part list
printing can be done at any stage .
COMPUTER AIDED DRAWING TOOLS
Conventional tools can be useful for sketching and rough layout. The use of computers in every phase of engineering, design, drawing, analysis is well known. The integration of computers into the manufacturing industry from design to marketing, is changing the methods used in the technical education and training of technicians, designers and engineers. A computer system consists of hardware and software. The various pieces of physical equipment that comprises a computer system are known as hardware. The programs, instructions that permit computer system to operate are classified as software. Computer software is categorized as either application programs or operating system (OS) programs. Operating system programs are set of instructions that control the operation of computer and peripheral devices. This type of program may also provide support for activities and programs such as input/output (I/O) control, editing, storage, assigning drives for I/O, in addition to providing support for standard system commands and networking. Some typically used hardware is explained below.
Central Processing Unit
Most of the central processing units (CPU) use Pentium chips. They are available with random access memory (RAM) ranging from 512 mega bytes (MB) to a few giga bytes (GB). A byte consists of eight bits. Bit is acronym for binary digit which can have on or off. Clock speed plays an important role in the computational speed. Higher the clock speed higher the computational and processing speed.
Hard disk is an internal storage device. It stores the programs, drawings, documents and other data inside the computer. Hard disks up to 120 GB capacity are available with PC based CAD systems.
The most obvious component of a CAD system is the video display screen or monitor. It is familiar piece of equipment because it looks like a TV screen. The most common forms of monitors are vector stroke and raster scan displays. The resolution of the display depends upon the picture (pix) and elements (el). The greater the number of pixel on the screen provides higher the resolution. Low resolution screens may produce lines that have a jagged look which can be seen predominantly in inclined lines or curves.
Color and Monochrome
The color monitor is similar to a color TV set. A pixel on color screen is actually composed of three primary colors, red, green, and blue (RGB). In monochrome monitors grey level can be controlled by the intensity of pixel values. Monochrome screens are available in a variety of single display colors such as green, amber, blue, black on white, and red. The size of the viewing area or screen (14" 15", 17", 19", or 21") is measured diagonally across the screen. For CAD systems large size monitors with high resolutions are recommended.
The alphanumeric keyboard is a well known input device. A CAD system may use one or a combination of input devices to create images on the display screen. The main function of the input devices is to specify points and line, usually done by controlling the position of a set of cursor cross hairs on the screen. The input devices are also used for the selection of menu items and manipulate parts of the constructed image on the screen. The some main input devices are:
(a) Tablet or Digitizer: The tablet is a flat surface over which 'a stylus' or 'hand cursor' is moved. The position of the hand cursor or stylus is available to the computer.
(b) Mouse: Mouse is a hand held device with rollers on its base. Mouse has several push buttons
which can be used to input commands or other information. Mouse requires only a small table area to use and is inexpensive to manufacture. Hence, it became a very popular input device.
(c) Scanners: A scanner is an input device used for converting an existing paper drawing made by traditional tools to CAD drawing.
(d) Keyboard: The keyboard is a device used to input alphanumeric data. It can also be used to select CAD menu and control the cursor movement with arrow keys on a key board. It is more cumbersome to use keyboard as an input device.
Printers and plotters are main output devices in a CAD system. Printers usually provide hard copies of text as well as graphics. Laser or inkjet printers are used for printing of drawings up to A0 size. Pen plotters are two types, viz. flat-bed and drum. In the flat-bed plotter, the paper is stationary and the pen holding mechanism can move in two axes.
A computer program that provides specific instructions to enable a computer to do a certain task is called software. When CADD software is purchased from a manufacturer, it is known as application program or application software. This specialized software provides service for a specific endeavor such as mechanical drawing, piping layout, solid modeling, structural, and architectural drawing.
Data Storage Devices
All the data is kept in random access memory (RAM) when a job is processed in a computer. This data will be lost when the computer is turned off, hence it should be saved or stored, before the power is ssoff. Data storage devices provide a place to save information permanently for later use. When the drawing is completed or the operator wanted to stop the work, the drawing and all the associated data must be saved before the program is exited or computer is shut off. Otherwise all accumulated data from that work session will be lost. The storage medium for the computer drafting system is hard disk. Another form of disk is compact disk (CD) drive. The CDs are removable and store the data up to 700 MB. Rewritable compact disks CD-RW permit to over write the data on an already recorded disk. The third form is floppy disk drive. It is simple, and removable flexible plastic disks (floppies) are used in this device. Existing data can be erased and new data copied or new data over written on existing data any number of times. The other form is Memory stick (pen drive) and external Hard Disk can also be used.
The computer programs designed for specific tasks in response to user's requirements are called application software. It is time consuming, tedious, and expensive to develop application programs and hence it is considered advantageous to buy existing software. Some of the CAD software used for drafting and design are:
LIMITATION OF CAD
There are some limitation in CAD system :
32-bit word computer is necessary because of large amount of computer memory and time .
the size of the software package is large.
skill and judgment are required to prepare the drawing .
APPLICATION OF CAD:
There are various way which can be performed by use of computer in the drafting process.
AUTOMATED DRAFTING ;
This involves the creation of hard copy engineering drawing directly from CAD data base . it has ability to do transformation of image and prepare 3 D drawing like isometric view perspective view etc.
GEOMETRIC MODELLING :
Geometric modeling is concerned with computer compatible mathematical description of the geometry of an object . there are three form of representing the object in geometric mode through wire frame models.
2D- two dimentional representation is used for a flat object.
2.5D- It is better than 2D capability by permitting a 3D object be represented as long as it has no side wall details allows for full 3D modeling of a mere complex geometry.
3D- it is 3D picture of the real object.
The computer-aided drawing system of individualized ideal arch can help to draw a matching individualized ideal arch accurately and quickly. This system eliminates the complex and cockamamie process of manual drawing.