Turning your PC into a CAD workstation by JUDITH BIRD

T he arrival of computer-aided de- sign (CAD) was a major step forward for the drawing office -

albeit expensive. It required powerful mainframe computers to handle the complex layouts and users had to be trained to understand programming languages and techniques.

In recent years, the CAD package has been restructured to run on per- sonal computers. How easy is this transformation into a CAD work- station? Also, the choice of systems on offer begs the question of how much should a drawing office pay for an entry level system. Data Processing analyses the pros and cons of convert- ing the PC into a CAD workstation.

Simplicity

A drawing office considering CAD for the first time should aim for a general purpose 2D draughting system. The software manufacturers offering this low cost solution usually include the graphics capabilities most often used in the drawing office, for example PCB, mechanical and electrical engin- eering layouts which involve the

Abstract: Computer-aided design (CAD) packages are now available on some personal computers, and can make a good entry system for design ofjices. However, it is important to take into account the additional costs that might be incurred e.g. more memory, a graphics monitor, a lightpen etc.

Keywork: data processing, compum-aided &sign, microcomputers.

Judith Bird is assistant editor of Data Pro- cessing.

drawing of lines, curves and arcs. Other features include the ability to find intersection points or object snap. Parametric drawing and geo- metric properties are also featured in many packages. Software in the low cost entry system range includes Autocad, Cascade 1, Drawing Office Graphics Systems (DOGS), Microcad and Superdraft.

One advantage of running CAD on a personal computer is that it makes programming much easier. Many architects and engineers do not have the time to learn complicated pro- gramming techniques and the per- sonal computer simplifies the whole process. Another consideration is the improved response time. Mainframe access is notoriously slow and having

a micro on the desk puts the response control into the hands of the user.

A personal computer can bring CAD applications to even the smallest drawing office because it is cheaper and easier to program. But, not all personal computers can run CAD packages. Since CAD is a powerful application, it demands a large mem- ory store and a high resolution screen. The software manufacturers tend to prefer the IBM PC, AT or XT for the hardware. These machines are inher- ently powerful, especially the AT, and have fairly high resolution screens. Other compatible micros suggested by vendors include the Apricot, Apple II series and the Sirius. If you have another make of micro then it is worth checking how

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much extra memory is required and if extra boards are needed to convert it. Some vendors include the hardware in the bundle price but, before choosing the system, check the power of the micro and the graphics resolution capacity. Roboco 1500, for example, only runs on the Apple II, while DOGS runs on Apollo, Data General and Hewlett Packard machines.

Price

The price of CAD systems has been radically reduced over the years, but a worthwhile system i.e. one which is used regularly and produces good quality drawings, still needs wise investment. If the drawing office al- ready has an IBM PC, then the major expense has already been overcome. The next stage is to consider the extras to complete the package.

Software alone may be as cheap as 52 000 but extra memory boards, plot- ters, digitizers, coprocessors and monitors add substantially to the final bill. An average price for a low cost entry package is around &lOOOO.

Since CAD systems require a large memory store, the IBM. PC AT is the choice for many software vendors. A

basic memory for a CAD package is 512 kbyte RAM. Vendors also em- phasize the need for a floating point system such as the 8087 coprocessor. This will enhance output and increase response time which would otherwise be significantly slow.

It is possible to reconfigure the micro’s keyboard for graphics pro- gramming, but punching in numeric reference points can be confusing. The utility manufacturers have over-

come this problem by introducing the digitizer tablet. Used with a four button cursor or pen, the digitizer has an overlay created by the user to his/her requirements.

For optimum output, a good qual- ity plotter should also be purchased. A drawing office may want to replace the manual equipment but the end result should remain the same or

better. Prices for plotter start from about &500.

Screen resolution

The final addition to the CAD work- station may seem incongruous, a large screen monitor - preferably 20 in. Many would argue that this is defeat- ing the whole exercise of using a personal computer. Yet most micro screens are too small for detailed graphics use. As the plan or layout becomes more detailed, so the dia- gram will become ill-defined and the wording will be a series of dotted lines. Small may be beautiful but not if it is indecipherable! General pur-

pose 2D draughting systems usually include a monitor in the bundle price,

but not necessarily one with a large enough screen.

Micro Aided Engineering (MAE), for example, offers a Frontier 15 in monitor in its total price package of El0635 (including an Apricot micro). Mountford and Laxon offers com- plete systems from &4940 but the monitor is only 12 in. It is only by spending a substantial amount that a 20 in screen is included.

Viability - is it worth it?

The extra utilities required for a complete CAD workstation may make some drawing offices reconsider. The personal computer, though, is still an excellent entry point for CAD, if the drawing office carefully plans its re- quirements and investments. The micro is faster in response time than the mainframe and can run more than one program. For example, the user can exit from Autocad into Dbase II

with the minimum of programming and delay. Once the architect or engineer has mastered CAD on a personal computer, the system can be upgraded and networked as required. The more powerful the micro at the start, the easier the upgrading will be. Simulation, for example, cannot be performed on some micros, but can on the IBM PC AT.

MAE attaches a higher resolution screen to a personal computer to run its CAD softu~are .

CAD has made an important con- tribution to the drawing office and in order to allow more people access to the application, the PC offers one simple solution. It is the choice of input and output peripherals where the difference in quality will be noticed and if chosen wisely even the drawing office on a low budget can benefit.

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