Moving from manual drafting to computer-aided design and drafting was an important step in terms of the potential of today's technology. CAD originally meant computer-aided drafting because of its original use as a replacement for traditional drafting. Now it usually refers to computer-aided design to reflect the fact that modern CAD tools do more than just drafting (Figures 2.5A, B, and C). Related acronyms are CADD, which stands for computer-aided design and drafting; CAID, for computer-aided industrial design; and CAAD, for computer-aided architectural design. All of these terms are essentially synonymous, but there are a few subtle differences in meaning and application. CAM (computer-aided manufacturing) is also often used in a similar way or as a combination (CAD/CAM).
When we use computer-aided design and drafting (CADD), certain questions arise that we never think of when working on the drawing board. Although with CAD or CADD we do not use the typical drawing-board tools, we are still required to design or make a drawing.
CADD is an electronic tool that enables you to rapidly create accurate drawings with the use of a computer. In fact, an experienced computer drafter can normally produce a construction drawing in less time than it would take if it was done manually. Moreover, unlike the traditional methods of making drawings on a drawing board, with CADD systems you can create professional drawings just by using a mouse and clicking buttons on the keyboard. Furthermore, drawings created with CADD have many advantages over traditionally produced drawings. In addition to the fact that they are neat, accurate, and highly presentable, they can be easily modified and converted to a variety of formats. In addition, CADD-generated drawings can be saved on the computer, a flash, a CD, or an external hard drive in lieu of vellum or Mylar sheets that require the use of large storage cabinets for filing.
A decade ago CADD was largely used for specific engineering applications that required high precision, and because of CADD's high production costs, not many professionals could afford it. In recent years, however, computer prices have dropped significantly, and professionals are increasingly taking advantage of this by adopting CADD programs.
There is a wealth of CADD programs available on the market today. Some are intended for general drawing work, while others are designed for specific engineering applications. There are programs that enable you to do 2D drawings, 3D drawings, renderings, shadings, punch lists, space planning, structural design, piping layouts, HVAC, plant design, project management, and other applications. Today we can find a CADD program for almost every engineering discipline that comes to mind.
Although CADD is primarily intended for single-line drafting and has very limited capabilities to create artistic impressions, CADD's 3D and rendering features are quite impressive. A 3D model of an object can be created and viewed from various angles and, with correct shading and rendering, can be made to look very realistic. With CADD you can create fine drawings with hundreds of colors, line types, hatch patterns, presentation symbols, text styles, and other features. Even if you don't like something about your presentation after you have finished it, you can instantly change it (Figure 2.6).
Most CADD programs have a number of ready-made presentation symbols and hatch patterns available that can be used to enhance the look of drawings. When drawing a site plan, for example, a draftsperson can instantly add tree symbols, shrubs, pathways, human figures, and other landscape elements to create a professional-looking site plan. Similarly, an architect can use ready-made symbols
of doors, windows, and furniture to make a presentation. Architects and designers also sometimes design their own symbols when working with CADD.
In addition to preparing impressive presentations on paper, CADD can be used to make on-screen presentations. Ideas can be presented on-screen by merely plugging the computer to a projector. Advanced CADD programs also allow you to created animated images. You can show how a building would appear while walking through it or how a machine assembly will operate as different machine parts move.
One of the main advantages of CADD is that it allows quick alterations to drawings. Modifications can be made with pinpoint accuracy. It takes only seconds to do a job that would otherwise take hours on a drawing board to produce. In many cases you may not even have to erase a section to make the change.
You can often rearrange the existing components of the drawing to fit the new shape. This enables the designer to compare various options with minimal effort.
The following are some of the main editing capabilities of most CADD systems:
• Move, copy, mirror, or rotate drawing elements with ease
• Enlarge or reduce elements of a drawing
• Make multiple copies of a drawing element
• Add one or more drawings to another drawing
• Change font style and size
• Change units of measure of dimensions
• Stretch drawings to fit new dimensions
• Convert CADD drawings to other formats
CADD allows you to work with greater accuracy. If you need to create highly accurate geometrical shapes, while avoiding time-consuming mathematical calculations, CADD is the answer. Computer-software programs like CADD allow the designer to work with different units of measure, such as architec tural units, engineering units, scientific units, and surveyor's units. These units can be represented in various formats commonly used by professionals.
When working with engineering units, the designer or drafter can specify whether all the dimensions should be represented in inches, feet-inches, centimeters, or meters. Angular units of measurement such as decimal degrees, minutes, seconds, or radians can also be chosen.
In general, when there is a need to work on a large-scale drawing such as a plan of a township, a high degree of accuracy may not be warranted, and it may be decided to set a lesser degree of accuracy—say ,1 foot, 0 inches. The computer will then round off all the measurements to the next foot, which avoids the use of any fractions less than a foot. Where minute detail is required, a higher degree of accuracy such as 1/8 or 1/64 inch may be set.
As previously mentioned, it is simple, quick, and convenient to generate or organize a CADD drawing on a computer. Most computer hard drives have the capacity to store thousands of drawings (and this storage capacity is continuously increasing with advancing technology), and they can be opened within seconds.
Some of the advantages of a computer's electronic filing system over traditional filing include:
• It enables and encourages the creation of a highly organized and efficient environment.
• It contributes to large reductions in general working space.
• An electronic drawing does not age or become faded. Whenever a new drawing is required, it can be printed from disks. (It is important that the program used to store the CADD files be regularly updated to avoid becoming obsolete. With continuously advancing technology, some storage methods have already become outdated, such as zip drives and some types of disks.)
Through networking electronic drawings can be shared by several users, allowing them to coordinate their tasks and work as a team. Different professionals such as architects, engineers, and construction managers can use the same electronic drawings to coordinate building services. When a modification is made to a drawing, this information becomes instantly available to all the team members. It has thus become far easier to share information. Professionals located in different cities or countries can now instantly transmit electronic drawings to one another. They can also publish these drawings on the Internet for anyone to access. Most CADD programs incorporate special functions designed to allow you to export drawings in a format (such as .gif or .jpeg) that can be viewed on the Internet.
The computer is an ideal instrument for generating project reports, cost estimates, and other business documents. CADD's database capabilities include the ability to link specific nongraphic information (such as text or financials) with the graphic elements of the drawing. The nongraphic information is stored in a database and can be used to prepare reports.
An architect, for example, can attach text attributes associated with the door and window symbols in a drawing. These attributes include the door's size, material, hardware, cost, and so forth. Equipped with this information, the computer can then automatically generate a door schedule listing all the doors and windows in the drawing!
Nongraphic information is directly linked with the graphics on the screen so that, when a change is made to the drawing, the values in the reports are automatically updated. This provides a useful means to manage large projects from design through project completion.
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