cadd

This condensed version of CADD PRIMER is intended to give you an overview of CADD. It includes only important topics from CADD PRIMER. It does not include any diagrams. CADD PRIMER includes more than 100 diagrams that illustrate the working of CADD. For complete understanding of CADD refer to CADD PRIMER. This complete book is available for download for $9.95 at http://www.caddprimer.com or you can order printed copies through the publisher listed at the end of this chapter.

Key Terms in this Chapter  

Term	Description
Attributes	Descriptions of electronic drawing elements.
CAD CADD	An acronym for Computer Aided Design. It synonymously used for Computer Aided Drafting. An acronym for Computer Aided Design & Drafting.
CADD system	A computer system that enables you to perform drawing and design tasks.
CAFM	An acronym for Computer Aided Facility Management
CAE	An acronym for Computer Aided Engineering
CAM	An acronym for Computer Aided Manufacturing
Command	A single instruction issued by the user to complete a task on the computer.
Database	A stored collection of data that can be retrieved and organized in different ways.
Function	A task in a program that can be completed by issuing a set of commands through the program.
Menu	A collection of functions or commands that are displayed on the screen. You can make selections from the menu with a pointing device such as a mouse.
Parametric design	A computer capability that links graphics on the screen with automated calculations and vice versa.

 

What is CADD?

 

When we think of Computer Aided Design and Drafting (CADD), certain questions arise that we never think of while working on the drawing board. We do not use the essential drawing board tools: paper, pencil, T-square, compass, eraser or scale, yet still have to design or make a drawing. When even one of these tools is missing we know how aggravating it can be. With CADD we don’t need even one of them!

CADD is an electronic tool that enables you to make quick and accurate drawings with the use of a computer. Unlike the traditional methods of making drawings on a drawing board, with CADD you can sit back in an easy chair and create wonderful drawings just by clicking the buttons of a keyboard. Moreover, drawings created with CADD have a number of advantages over drawings created on a drawing board. CADD drawings are neat, clean and highly presentable. Electronic drawings can be modified quite easily and can be presented in a variety of formats.

A decade ago, CADD was used only for specific engineering applications that required high precision. Due to CADD�s high price, only a few professionals could afford it. In recent years, however, computer prices have decreased significantly and more and more professionals are taking advantage of CADD.

There are hundreds of CADD programs available in the CADD industry today. Some are intended for general drawing work while others are focused on specific engineering applications. There are programs that enable you to do 2D drawings, 3D drawings, renderings, shadings, engineering calculations, space planning, structural design, piping layouts, plant design, project management, etc. There is a CADD program for virtually every engineering discipline you can think of.

CADD is primarily intended for single-line drafting. It has very limited capabilities to create artistic impressions. However, CADD�s 3D and rendering features are fascinating. You can create a 3D model of an object and view it from any angle. With proper shading and rendering, it can be made to look picture perfect!

What to Expect from CADD

You can do amazing things with CADD that you never thought possible while creating drawings with a pen or pencil. The following are some of the important capabilities that make CADD a powerful tool:

                Presentations

                Flexibility in editing

                Units & accuracy levels

                Storage and access for drawings

                Sharing CADD drawings

                Project reporting

             Engineering analysis

                Computer Aided Manufacturing (CAM)

                Design

                Add-on programs

 

Presentations

You can create fine drawings with hundreds of colors, line types, hatch patterns, presentation symbols and text styles. Even if you don�t like something about your presentation after you have finished it, you can quickly change it. It takes only a few simple steps to change the text style, color or line type and you can print a fresh copy of the drawing.

There are a number of ready-made presentation symbols and hatch patterns available in CADD that can be used to enhance the look of drawings. For example, a site planner can add tree symbols, shrubs, pathways, human figures, and other landscape elements to create a site plan. Similarly, an architect can use ready-made symbols of doors, windows, furniture, etc., to make a presentation.

In addition to preparing impressive presentations on paper, you can use CADD to make on-screen presentations. You can plug your computer into a projector and present your ideas on-screen. Advanced CADD programs even allow you to created animated images. You can illustrate how a building would appear while walking through it, or how a machine would function when different machine assembly parts operate.

Flexibility in Editing

CADD provides the flexibility to make quick alterations to drawings. You can erase any portion of a drawing with pinpoint accuracy. It takes only seconds to do a job that could take hours on a drawing board. In many cases, you won’t even have to erase the drawing to make the change. You can rearrange the existing components of the drawing to fit new shape. This enables you to analyze design options with minimal effort.

The following are some of the editing capabilities of CADD:

                Move or copy drawing elements

                Enlarge or reduce parts of a drawing

                Add one drawing to another

                Stretch a drawing to fit new dimensions

                Make multiple copies of a drawing element

                Change the size and style of text

                Change units of measure, accuracy and style of dimensions

 

Units & Accuracy Levels

CADD allows you to work with great accuracy. If you need to create highly accurate geometrical shapes, CADD is the answer. It can help avoid time-consuming mathematical calculations.

You can work with different units of measure, such as architectural units, engineering units, scientific units and surveyor’s units. These units are represented in standard formats commonly used by professionals.

Example:    When working with engineering units, you can specify whether all the dimensions should be represented in inches, feet-inches, centimeters or meters. Similarly, you can choose angular units of measurement such as decimal degrees, minutes, seconds or radians.

You can set an extremely high accuracy for the units of measurement. You can work with as high precision as 1/1000^th of an inch! However, such accuracy is seldom required. You will often need to set the CADD program to a lesser accuracy to avoid unnecessary fractions.

In general, when you need to work on a large scale drawing such as a plan of a township, you may want to set a lesser degree of accuracy, say 1’-0″. The computer will round off all the measurements to the next foot and you won’t see any fractions less than a foot. When you need to work on a minute detail, you can set a higher degree of accuracy such as 1/8^th or 1/64^th of an inch.

Storage and Access of Drawings

It is quick and convenient to organize CADD drawings in a computer. You can have thousands of drawings on a computer�s hard disk and can open any one of them within seconds.

A computer�s electronic filing system has the following advantages over the traditional filing system:

                It enables you to create a highly organized environment

                It contributes to savings in working space

                An electronic drawing never gets old and faded. Any time you need a drawing, you can print a new copy from the disks.

 

Sharing CADD Drawings

The electronic drawings can be shared by a number of users, allowing them to coordinate projects and work as a team. This is accomplished by connecting different computers via a network.

Example:   In a building project, different professionals such as architects, engineers and construction managers can use the same set of electronic drawings to coordinate building services. If a change is made to the drawings, this information becomes available to all the team members automatically.

With the use of modems and the Internet, it has become far easier to share information. Most architects and engineers these days share drawings electronically.

You can also publish your drawings on the Internet and collaborate CADD projects using a web site. Many CADD programs include special functions that allow you to export drawings in a format that can be viewed on the Internet. Refer to Chapter 9 “Maximizing CADD” for more information on collaborating CADD projects on the Internet.

Project Reporting

The computer can be used to prepare project reports such as records of areas, quantities and cost estimates. Using the database capabilities of CADD, you can link non-graphic information (such as text or value) with the graphic elements of the drawing. The non-graphic information is stored in a database, which can be used to prepare reports.

Example:   An architect can link text attributes associated with the symbols of doors and windows in a drawing. The attributes can describe the size of the door, material, hardware, cost, etc. Later on the computer can automatically prepare a door schedule listing all the doors and windows in the drawing.

The non-graphic information is directly linked with the drawing objects. When a change is made to the drawing, the values in the reports are updated automatically. This provides a useful means to manage large projects.

There is a special category of software called Computer Aided Facility Management (CAFM) designed for building management. These programs allow you to import drawings from CADD programs and link attributes to them to form a database. The database can be used to keep track of spaces, areas, costs, people, equipment, furniture, building maintenance schedule, etc..

See Chapter 10 “CADD Industry Resources” for a list of CAFM software.

Engineering Analysis

There is a separate category of programs called Computer Aided Engineering (CAE) that can use CADD drawings for engineering analysis. The CAE programs have a number of applications in structural design, civil engineering, mechanical engineering and electrical engineering.

Example: A structural engineer can use a CAE program to test the design of structural components in a building. The engineer can instantly analyze the impact on structural members when a different load is applied to the structure or the spacing between the members is changed. Similarly, there are programs for mechanical engineers to test machine assemblies. The mechanical engineer can create a prototype electronic model and test it without building a physical model.

The advanced engineering programs even provide the ability to link calculations with the CADD drawings. This capability is known as �parametric design” that allows the computer to automatically update the drawings when the associated calculations are changed and vice versa.