Quality assurance in AEC design CAD is changing how we handle this essential building design phase.

31 May, 2003 By: Michael Dakan

CAD automation in the AEC drawing production process is changing some of the fundamental processes and aspects of professional practice, and not necessarily for the better. One such area is quality assurance checking and coordinating of drawings among the various professional disciplines involved in a building project. Here change is perhaps slower than some of us think it should be, but in many respects it's probably as quick as is appropriate.

Quality assurance as a fully integrated process in architectural design seems somewhat neglected. That may be partially attributable to an overreliance on computers for certain things. We've all heard the joke cliché, "It must be right, it's on the computer." That attitude can develop in a design office when people go on autopilot and don't always think carefully about what they are drawing.

CAD managers know that the cliché isn't true at all, because we've all seen users inappropriately override associative dimensions. We know how easy it is to move or stretch objects to make one set of elements fit and work together without giving enough consideration to critical clearances or the design criteria of adjacent items.

Dimension checking

CAD has mitigated what used to be the very tedious and time-consuming process of dimension checking—adding up strings of dimensions to make sure they agree. As a young intern architect, I spent many hours and days adding up dimension strings with a hand-held Add-Feet Jr. mechanical calculator and using trigonometry tables to figure out angled and curved wall dimensions. (I'm old enough to remember architectural practice before electronic calculators were readily available, let alone desktop computers.)

CAD lets you eliminate most of that manual checking labor, as long as you're certain that all your users follow proper procedures for drawing accurately and using things like object snaps.

Because you can't be fully assured that all your users always follow proper CAD procedures, you still need to do some manual dimensional checking and look at the CAD file to make sure associative dimensions are used appropriately. The use of CAD doesn't eliminate the need for some old-fashioned calculator use for spot-checking, but it sure makes it a lot easier than it used to be.

CAD Quality assurance

Automating CAD standards within your CAD program remains the best way to ensure standards compliance. Automated standards let users draw according to the standards without having to enter all the settings manually. In addition, tools for checking CAD-specific drafting elements, such as layer names and layer properties, have made tremendous advances in the past couple of years. The CAD Standards commands available in AutoCAD Release 2002 are wonderful tools for quickly finding and fixing CAD elements that don't comply with your office's standards.

With this tool, you set up a reference CAD file that contains all the elements that make up your office CAD standard, such as layers, linetypes, and dimension and text styles. You can create multiple reference files for different CAD standards in use in your office, such as client-specific standards you are obligated to comply with.

You can associate a reference file with each drawing file in a set, and AutoCAD then uses that reference file each time you run the commands. The program searches through a drawing and flags noncomplying elements, such as mismatched layer names or layer properties of a standard layer name. You choose from different options about what to do about the noncompliance—for example, you can have AutoCAD automatically correct obvious errors such as misspelled layer names or wrong colors applied to a layer.

Of course, AutoCAD is not smart enough to make assumptions and automatic decisions about how to correct something. It tells you only that a problem exists. Standards checking is therefore a highly interactive process, and it may take some time to go through a complete set of drawings and make all the necessary corrections. One of the keys to success with a tool like this is to use it early in the production process, before a lot of work has been done, to find and correct problem areas or users who are working with an inappropriate set of standards.

Interference detection

With interference detection tools, you can check a complete 3D CAD model that contains architectural and building engineering objects such as structural beams and ductwork to see where they collide. This is another area where quality checking used to consume a lot of time. Someone had to go back and forth between multiple printed sheets from all the professional disciplines involved in a drawing set to try to identify where such conditions might occur.

In my experience, the collision detection tools available in the AEC disciplines are still relatively immature. You can't rely on them totally to find all conditions that may require correction. But interference conditions that aren't corrected before construction begins are a common source of construction dispute and litigation.

With the widespread use and ongoing refinement of object-based CAD for AEC drawing, interference detection will probably be the impetus that finally convinces all members of the design team that it is worthwhile to work in 3D. An accurate and complete CAD model of a building will then become a commonplace part of the design and documentation process.

Quality assurance in the professional practice

CAD should allow the traditional quality assurance phase of professional services to be accomplished faster and easier than ever, but it seems like that hasn't happened yet.

The ability to temporarily xreference and overlay CAD files on a computer screen should be quicker and easier than paging back and forth among multiple printed drawing sheets laid out on a desk.

The ability to use a hyperlink to jump instantly to a detail from where it is referenced on a plan or elevation is almost totally automated in some CAD programs and readily accomplished in most others.

Unfortunately, many design offices fail to use these time-saving tools efficiently, if at all.

Change comes slowly

Part of the problem is that using these CAD tools requires a pretty fundamental shift in an important traditional working process. It will take some time for people to try new methods and then get used to doing them as a matter of course.

Another issue is that the most senior members of a firm traditionally perform quality assurance tasks because they are best able to spot potential problems. Unfortunately, these are often the people who are least comfortable with computers and accomplishing drawing-related tasks on a monitor. This is the main reason behind the failure of computer-based checking, and redlining tools in general, to gain widespread acceptance and use: the people who do checking and redlining are not yet comfortable with doing this work on a computer screen, regardless of how efficient it may be.

Help from hardware?

The availability of large LCD monitors, the growing use of pen-tablet interface tools, and the functional integration of these two technologies point toward a future where drawing-size monitors are embedded in desktops and everyone draws directly on a flat monitor screen with a more natural pen-type tool.

The mouse and tablet puck have never been good or intuitive interfaces to use for drawing tasks. It may take the long-awaited full-size flat monitor and pen input tool to get everyone in the office comfortable with CAD and computer-based graphics. That day is approaching faster than many of us thought would be possible. Though it's still prohibitively expensive to consider large LCD screens and pen-tablet interfaces for everyone in an office, soon it will become a functional necessity. See "AEC Tools" on p. 56 for more on the latest PC tablets.

You still need quality

CAD automation has the potential to make many traditional AEC processes easier and less expensive, and it is doing just that in many areas of professional practice. But quality assurance review hasn't benefited much from these new technologies, though the potential for improvement is there.

The fundamental issue is that people are not capable of changing their working methods as rapidly as the technology allows changes to occur.

In an area of practice as important as quality assurance, human limitation is an appropriate governor. CAD managers must be sensitive to this limitation when introducing anything new. You should look for technologies that ease and reinforce traditional practice procedures as much as they force changes to them.

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