What is CAD?

CAD means Computer Aided Design. It also sometimes refers to Computer-Aided-Drafting, the use of computers to produce drawings that would normally be prepared manually.
CAD therefore stands for Computer Aided Design and Drafting. The major difference between the two systems is in the software. A Computer Aided Design system is primarily used to create 3D geometric models of objects, structures or assemblies. It can also perform automated drafting and assist in the analysis or optimization of a design through the use of application programs such as stress-strain analysis of components, dynamic response of mechanisms, heat-transfer calculations etc. A Computer Aided Drafting system is used to produce 2D pictures of objects, not true 3D models.

Graphical Representation: Traditional v Modern

Gasped Monger (1746-1818) is considered the "inventor" of descriptive geometry. During the time he was a professor at the Polytechnic School in France, Monger developed the principles of projection that are now the basis of our technical drawings. He worked out the theory of descriptive geometry as an easy, graphic means of working problems in the design of fortifications - tedious problems involving long mathematical calculations. The principles were recognized to be of such military importance that they were kept secret until 1795. "La Geometries Descriptive", Mange's first book, is regarded as the first text on the basics of projection drawing.

In 1816 Claude Crozet, an alumnus from the Polytechnic school, introduced Descriptive Geometry into the Engineering Design Graphics curriculum at the Military Academy at West Point which provided a strong foundation to the subject of drawing.

Since then engineering graphics has been greatly influenced by the needs of industry to produce engineering drawings for production. So far the graphic language which had been more or less an art characterized by fine ornate lines gave way to a relatively more exact method of representation. Standards became more prominent and were incorporated into engineering graphics. The emphasis in engineering graphics instruction was now on drafting practices and skills.

The next stage in the development in the history of engineering graphics was dominated by computer technology. Through the use of the computers some of the more formal phases of engineering graphics were slowly being eliminated. However the hardware and software, created by different vendors, used operating systems, storage devices and protocols that were essentially incompatible. This greatly increased the need for establishing graphics and computing standards.

Different countries had their own established standards imposed by development organizations, for example the British Standards Institution (BSI) and the American National Standards Institute (ANSI) in America. The constant exchange of information worldwide prompted the need for common standards which resulted in the development of the International Standards Organization (ISO). Today, many countries have adopted ISO standards but America continues to use the ANSI standards.

The first application of computers to design representation only resulted in a change of tools. Drawing boards were replaced by Computer-Aided Design and Drafting tools which although digital in character still emulated the approach laid down by Mange's descriptive geometry. The development of Computer-Aided Design systems capable of rapidly creating, modifying and manipulating 3D solid models have brought about significant changes in the way design information is represented, recorded and communicated. The use of solid geometry integrated conceptual design, analysis and manufacture with minimal human intervention.

With the advent of CAD packages, traditional tools such as the compass, ruler, T-squares, paper, pencils and erasers have become near obsolete. Some of the advantages that CAD packages have over manual drafting means are outlined below:

Discovering the Benefits of CAD

November 1991 -- Process Engineering By: Brian Fuser and Sam Peters

Rapid advances in food processing technology and the omni-present push for new products tend to tighten developmental timetables. This is noticeable in all areas of product design, including the design of new equipment and manufacturing lines. For this reason, automated drafting systems are making a big impact in the processing and packaging areas of the food industry. In fact, companies that have converted to CAD (computer-aided design and drafting) have found that it yields tremendous savings in time and money while improving the quality of facility and machine design.

Using CAD software, a designer or engineer inputs design information for a new machine or line electronically rather than committing a drawing to paper. In effect, CAD is to drafting what word processing software is to typing. As such, it offers many advantages through the computer's speed and flexibility in manipulating the inputted data.

For example, ideas can be explored on the computer instead of manually on the drawing board or -- as is sometimes the case -- on the plant floor. A food company can produce more drawings with greater speed and accuracy. It also is easier to create, revise, update, store and distribute these drawings and other engineering documents. Exchanging information with contractors or regulatory agencies is particularly simplified since complete, up-to-date drawing information can be conveyed on a computer tape, disk or via modem. (A standardized document conversion format allows files from one CAD system to be used on another.)

In addition to generating documents in a fraction of the time required by hand drafting, document quality is more consistent with CAD because using the software requires CAD operators to develop uniform standards and procedures that are applied automatically to every operation. Users can integrate graphic data with text to create a wide range of labeled reference drawings and even illustrated guides for product manuals.

CAD software can be run on high-performance workstations that offer communication links to mainframes and to other workstations in a distributed network.

The electronic frontier

For mechanical design and manufacturing, more advanced CAD software enables users to design complete 3-D product models. This capability is useful when industrial or manufacturing engineers set up an assembly or packaging line. For this they need to know the interaction between adjacent machinery or production operations and how much free space must be allowed for moving parts or conveyors. CAD programs that incorporate solids modeling enable the designer to see the layout in 3-D on the computer screen instead of relying on a conventional engineering drawing. Likewise, 3-D modeling can be used for package design. The designer can design the package on the computer screen, incorporate any requirements that are unique to the product or process, and subsequently determine the workability of various packaging materials.

These models are exact mathematical representations, suitable for precise manufacturing analysis. The models can be duplicated, rotated, grouped, segmented by level, manipulated or edited to enhance the design process. Despite their powerful capabilities, these software systems often are easy to learn, providing on-screen menus, special function keys and user-definable icon buttons.

With so many advantages to offer, it's not surprising that the food industry is applying CAD to processing and packaging line design. The technology is used to make facilities more productive in their initial design and when redesign is required by new production processes. CAD also speeds and improves machine design by allowing engineers to look at several alternative designs and to spot potential problems in the computer prototype.

Bringing the line to life

Designing a processing line is a much easier proposition with CAD. By putting a wealth of accurate, detailed information at the CAD operator's fingertips, the software makes it simple to perform throughput analyses. This can be particularly helpful for companies that incorporate just-in-time (JET) technology into their manufacturing or processing operations. By eliminating the need to stockpile excess inventory at each workstation, this increasingly popular management practice can reduce production costs by making raw materials reach the proper locations just as they are needed. Add-on software modules can actually "bring the design to life" electronically to ensure the design will maximize Jet's benefits.

For instance, the FLOWS software developed by Auto-troll Technology can show how a proposed layout will perform. It represents electronically what will happen as the product moves from workstation to workstation; what the uptime will be and where bottlenecks may occur. The facilities designer can then add a machine or rearrange equipment locations and then rerun the program to evaluate the effect of the changes.

Without CAD, designers may not know if the layout will work until it's actually in place; if it doesn't, machinery must physically be moved around the plant floor. This trial-and-error process can take hours or even days instead of the minutes it takes with CAD.

 Since drafting errors are basically eliminated, CAD also cuts down on construction delays and cost overruns. Rework and costly changes during construction also can be greatly reduced. This is particularly helpful when dealing with last minute changes in the design. What might take three or four days to redraw manually -- while construction crews are being paid to sit idly -- often can be accomplished in a matter of a few hours on the computer.

CAD can also expedite the installation process. Once you know where you want to place machinery, CAD will show where existing water, gas, electric and plumbing lines are located and calculate the distances from machinery. This makes it much easier for the facilities people to do their job. Moreover, since placement scenarios do not have to be tried out on the factory floor, production interruptions are minimized.

Maintaining reality

The value of CAD doesn't end at the design stage. It lends a hand with daily operations and maintenance. It can be used for something as simple as determining whether a new forklift can negotiate an aisle between machinery.

Routine maintenance also can be tracked with CAD by linking the graphic layouts to a relational database of essential information. For example, you can ask the computer to show all the machines that need maintenance on a given day. Other tracked information, such as the manufacturer, price and life expectancy of machinery can help in making long-term maintenance and replacement plans.

Large companies within the food industry are even applying Cad's clout to interior office design, laboratory layout and pilot plant setup. A company with 5,000 employees and a 5% turnover rate may have to accommodate 200 new employees per quarter. CAD applications can be used as a facilities management tool to track furniture and supplies, create effective spacing between furniture and to make space utilization as efficient as possible. Lab and pilot plant arrangements often must change according to project requirements. By showing available equipment, the location of utility sources and the available floor space, the computer makes these modifications less daunting, allowing staff to focus more on the project itself.

Given all of the benefits, it is easy to see why many companies are moving to adopt state-of-the-art CAD technology. More efficient plant floors and office space, better machinery design and improved maintenance are the rewards waiting for those willing to switch to automated design systems.