Computer-aided Design

System Acquisition

Given the cost of modern CAD/CAM systems, it is imperative that sufficient preliminary work be done before considering any purchase. If the task is upgrading an existing system, a lot of the work took place at the time the original system was purchased. Hopefully that work was done well and can be useful during the current evaluation. Another possibility is that the initial investment was not well considered, and the reason for upgrading is to correct previous oversights. Finally there may be people and organizations that are just starting down the path of CAD/CAM. In each case the same basic questions need to be applied to the decision process. The only differences are the degree to which past experience can shorten the process.

CAD Training

The old wisdom that says, "A CAD system won’t make a good designer or drafter out of a poor one!" is absolutely correct. Except where the newness of the system is a stimulus, the quality of thinking that makes a good designer will not be improved by using CAD techniques. CAD is a tool, The effect of its use is similar to moving from a slide rule to a calculator. Whatever you do can be done faster, and that includes making mistakes. So CAD training, in itself, cannot be viewed as the identifier of a competent designer or drafter. And yet good training and well-practiced skills are the keys to success in the growing world of CAD/CAM/CAE.

Probably the most overlooked and problematical part of a new CAD system startup are the implications and costs of training the system users. More than one expensive system has failed due to inadequate or inappropriate training. Although training requires a considerable investment in both time and money, the consequences of poorly trained users, versus the benefits of a fully capable user community can be measured in terms of productivity. This can be the number of drawings produced, the time to complete a design model from its concept stage, the quality of a finished design using ECO activity as a metric, or the robustness of a design based on rates of customer returns or field failures in parts per million. Without getting into a discussion of productivity measurement, whatever the measure of productivity, proper training will have a dramatic affect in the positive direction. The converse is equally true!

The most credible CAD systems on the market today have a command set of several thousand commands, mostly modifiers to the initial command. The command INSERT LINE is of little use without further qualification, and the effective use of those qualifiers is what CAD training is all about. More typically the command line may be INSERT LINE of LENGTH 3 and PERPENDICULAR TO LINE dld2 with an END at d2 and in the +Z direction. Every system has its own way of constructing such a command, and these syntax differences are what make the CAD training industry viable. When you consider the number of basic commands, times the number of available modifiers and specifiers, it is easy to see why the command set gets into the thousands.

On the other hand a system survey of the commands being employed in a large mechanical design department that worked totally with 3-D wire frame models showed that 85% of the work was being done with only seventeen commands! Linguists have probably noted that fewer than one hundred words are the basis for 90% of our day-to-day word usage. That doesn’t mean that effective communications can take place with such a limited vocabulary. Similarly, knowledge of those seventeen commands will not make a useful CAD designer. However it strongly suggests where initial training should be focused.

Organizing for CAD

The organizational structures of CAD drafting and design functions can be as varied as the organizations they support. In the simplest form the engineering/design/drafting function is a stand-alone unit whose people continue to provide their services to the rest of the organization just as they did when they were paper- and pencil-based. Unless the quality or timeliness of those engineering services has decreased since the conversion to electronic tools the rest of the company probably does not care either functionally or organizationally how these services are provided. Hopefully they realize and appreciate the improvements made by a well-equipped and well-trained CAD function.

In more complex organizations the implications of a CAD function can be very significant. If these implications are recognized and dealt with in the early stages of the organization, the growth of the function can be much smoother than if it is left to the casual whims of a parent or would be parent organization. It may be that the biggest difference between a conventional design/drafting organization and a CAD-based function is the latter’s relative newness. Pencil and paper engineering organizations have been around for decades and for that reason there isn’t anything (organizationally speaking) that hasn’t been tried before, and the organizational process has reduced itself to somewhat of a cookbook approach: "SO you want an engineering and design department. To do exactly what? How big? Fine. Let’s set up this structure, it’s worked for years."

The opportunities for organizational experimentation in CAD-based structures are far greater because of the newness of the entity and the lack of "pat" answers. In addition the logistical, financial and structural implications of such groups makes organizational design gurus drool at the thoughts of getting into the bowels of such an organizational entity. Are they really an engineering organization or are they somehow related to the MIS world? After all they both depend almost totally on computers. Shouldn’t they be grouped with birds of a similar feather? Maybe the people should belong to engineering, but shouldn’t the equipment be owned and managed by "computer professionals?"

And from within engineering itself there are pressures to mold the design process to fit local needs since well-defined operational procedures were not developed before the arrival of the new systems. So we hear, "We’re all grownups and know how to act responsibly. Everyone will have root access so that system and data refinements can be done locally and quickly." and, "We’ll protect ourselves by backing up on our own server. Besides, I can’t trust the network to be up and working every time I need a drawing." and, "Forget what the vendor recommends, they only want to sell us more equipment. They don’t even know what were trying to do. Their approach might be fine for most people, but we're much more sophisticated than that!" Anarchy reigns while everyone plays their favorite power games.

The results of such processes can go on for several years before these informal structures and seat-of-the-pants techniques create such chaos that only the most gut-wrenching measures can bring the system into some sort of order. All this in the name of progress.

The only way to avoid these traps is by developing a very detailed and widely accepted plan for the organization. That means involving all the people or organizations that will come into contact with the system. The list must include but is certainly not limited to, engineering management, MIS or computer systems operations, manufacturing, and representation from the eventual users and their supervisors.

Computer-aided Design/Drafting

Computer-aided design/drafting, or CAD, is a phenomenon that has been evolving since the 1960s. Its basic purpose is primarily to provide a mathematically accurate description of parts. Secondarily its value is in accelerating the preparation and production of engineering drawings. As microcomputer costs have decreased dramatically, the proliferation of CAD systems has increased just as dramatically. Today CAD systems are common even in the smallest organizations.

Any work activity that employs a computer for technical problem-solving requires a corollary standardization effort. The computer cannot think as a human being does; therefore, drafting practices, especially standardized dimensioning, tolerancing, and graphical representation such as line work, symbology, and other information, must be highly organized and standardized for computerization. A truism among CAD professionals is that CAD will not make better drawers; it will only make poor drawers faster. Technique and standards adherence still matter, even in a CAD environment.

CAD System Procedures

Whenever a computer-aided design system (CAD) is installed in a networked environment, procedures must be developed to ensure free-flowing access to the individual systems and centralized servers. The procedures described in this section are not inclusive. Rather, they are considered to be illustrative of those that may need to be developed for the orderly functioning of the system. They cover access, problem identification and reporting, access to system-related documentation, and other administrative matters.

Glossary of CAD Technology

Computer-aided design (CAD) has become almost commonplace with the proliferation of microcomputer-based CAD systems. However, with multiple choices have come a seemingly endless set of terminology and conflicting terms crossing the more than forty different CAD systems available. No standards exist for CAD file format, likewise, none exist for CAD vocabularies and terminology. This section attempts to define in a generic fashion, terminology used among several popular CAD systems. Periodically as the Drafting Manual is updated, this glossary will be expanded and updated as newer systems gain market share.

Contracting for CAD Files

This section presents a methodology that can be used to improve cost efficiency between customers of computer-aided drafting services and contractors for these services. CAD service providers (“contractors”) include drafting services by freelance drafting consulting firms and internal CAD operations within the enterprise. The “customer” who contracts for CAD work may be the engineering department within the same firm (an internal customer) or a separate firm altogether (an external contractor). If the customer and the contractor are separate organizations, the process is more formal and will involve written contracts. If the customer and the contractor are within the same organization, the understanding between the two parties must still be thorough and detailed to avoid mistakes and misunderstandings. Misunderstandings and mistakes cause delays and raise costs. The section that follows discusses the issues that must be clarified in order to protect both customer and contractor. Also included in this section is a description of typical contract terminology, sample contract language and sample response language for internal customer requests, or externally via a request for proposal (RFP).

CAD Layering

This section describes guidelines for layer naming, organization and use. It is intended to be a basic framework to be expanded and customized as needed by subscribers. These guidelines are adopted from common industrial practice and in part from the ISO 13567 standard for architectural trades. Eventually ANSI and/or ISO standards will be developed for the needs of mechanical CAD systems users. Until that time the only option will likely be cannibalization from other disciplines.

As such, this section suggests a methodology for organizing layer content and differentiating it from the way content is represented, the coding. It represents general purpose guidelines that are open-ended and adaptable by users.

Graphics Data Exchange

The exchange of graphic data is a key component of a paperless design and manufacturing enterprise. A paperless system has broad appeal as a global economy becomes more of a reality and many companies are beginning to invest in the technology. The appeal, however, is not only from an improved cost-benefit ratio, but also from decreased time-to-market introduction of new and enhanced products and services.

Central to many such strategies is the exchange of graphics data. This is because graphics data is often the communications tool among design, manufacturing, quality assurance, packaging, materials handling, marketing, sales and after-sale service. With a totally electronic system many of these tasks could occur simultaneously. This section discusses the exchange of CAD and other graphic data among a variety of applications used in a manufacturing enterprise.