Cad Guidebook: A Basic Manual for Understanding and Improving Computer-Aided Design (37 page)

Macro programs generally are computer programs that capture the user’s actions
as if it is recording the user. The user tells the software to start recording, the user
performs the functions that need to be captured, and then the user tells the soft-
ware to stop recording. The user is usually prompted to give a name to this macro
as a file. After this process is complete, the user can then run this macro when-
ever the set of steps is needed. This allows the user to automate some complex
functions of the software. The most important aspect of macro programs is that it
is assumed that users (not professional programmers) are going to create and use
them. CAD systems may offer this capability.

Once the CAD macro file is created, it may be possible to edit this file to
augment or alter the automated function. Considering the complexity of func-
tions and commands within a CAD system, this can be a very significant advan-
tage to using a CAD system. For instance, if a company makes a standard
component (such as a pressure vessel), and there are formulae or parameters that
can indicate the overall geometry of the component, it may be possible to use
macro programs to automate the creation of a drawing.

Another important potential source of increased productivity with the CAD
system is the use of the operating system via the macro program. Using this capa-
bility, the macro program may be able to create and manipulate files, plot or print
files, or start other programs or applications running on the computer. For in-
stance, if users need to e-mail electronic copies of a CAD drawing, and this func-

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tion is not found in the standard CAD system’s interface, then a macro program
could be created that uses the operating system’s mail function to send the file. In
this case, the user may click on a customized icon or type in a single command on
the keyboard that runs an entire series of commands automatically.

Keep in mind however that a macro program needs to be executed by a
command processor that is built into the system. This is a separate function in the
CAD system that must read each line of the macro program and then execute the
commands found in each line. This is transparent to the user, but from a computer
programming point of view it is the slowest possible approach. Macro programs
should execute faster than a user can enter the commands or click the mouse, but
it will be far slower than a real computer program that uses the API approach.

6.6.5 API Programming

A more advanced approach to automation is the API (Application Programming
Interface). In this case, the CAD system vendor makes available the object code,
libraries, foundation classes, objects, components, routines, or source code, etc.
This programming data can then be used by programmers to create new software
that uses the CAD systems capabilities but solves problems or performs functions
that are beyond the core capability of the original CAD system. It is important to
note that this option is generally done by programmers that have been trained for
this activity (unlike the macro programs mentioned above).

There are many advantages to this approach. First of all, the new programs
created are not using the command processor in the CAD system (as was the
macro program). Instead, the API-type of program can be considered compiled.
This means that the new program may be able to run as fast and as efficiently as
the CAD system itself. This is very important with programs that are going to
automate a large amount of geometry creation or manipulation. For instance, in
the previous example of creating an entire drawing of a pressure vessel, if the
drawing has 1000s of lines, arcs, and dimensions to be created, it could take quite
a while to complete if a macro program is used. The same operation for an API-
type of program could be finished in just seconds. If a customer is running this
program via a Web page to get a standardized drawing, this time difference can
be quite important.

Another advantage of the API-type of program is program sophistication.
Most macro programming languages are going to be limited to the functions that
the command processor can handle. The command processor may not handle
even basic computer programming techniques such as subroutines. This means
that the macro programs can be quite limited in their scope and readability. The
API-type of program, on the other hand, is only going to be limited by the com-
puter language being used. An API-type of program would use languages such as
FORTRAN, Lisp, ADA, C, C++, or Java.

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6.6.6 Utilizing “Metadata”

An important consideration in the standardization and optimization of a CAD
system is the metadata. This would be information such as part numbers, who
created the drawing, what revision level it is at, where it is filed on the computer
system, the release information, etc.

The metadata is vital to significant automation of functions and optimiza-
tion of the CAD system. A CAD system is simply not going to come initially
configured to search for and then sort all the drawings created by a certain user
using a certain ECO number for a part that is purchased instead of manufactured
in house. This information is simply too specific to the company that uses the
CAD system. Some companies will use numbers for the ECO, others will use
letters, or some other technique. Thus, it is going to be left to the automation pro-
grams (either macro program or API-type) to provide this functionality.

However, providing such sophisticated automation is not going to be possi-
ble unless all the drawings are created consistently and given metadata consis-
tently. The information such as ECO number and purchased/manufactured
indicator also may need to be extracted or exported from the drawings. Since this
information will need to be found by the automation programs, the drawings
must have the data in the correct location in some manner. For best results, the
metadata or Title Block information should not be created as a standard note in
the drawing, but rather as an attribute or tag operation. The use of templates is
also valuable in this regard. The template drawing file can have these tags ready
for use.

6.7 SYSTEM ADMINISTRATION ISSUES

There are some issues that must be addressed by the system administration or IT
group within a company. These issues are generally standard procedures for IT
departments, but some procedures may have unique aspects due to the nature of
the CAD systems.

6.7.1 File System Organization

Probably the most important system administration issue to consider carefully
and with a clear understanding of the nature of the CAD system software is the
file system organization. In particular, CAD system software tends to be quite
demanding of computational resources in comparison to common office soft-
ware. CAD software uses a large amount of RAM, floating point processing, and
graphics processing. The CAD software executables and runtime libraries are
also pretty enormous for 3-D CAD (1 to 2 GB). Therefore, it is usually consid-
ered a requirement that the CAD system software be loaded on a user’s individual

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computer system (i.e. loaded locally or on the client). It is not a good application
for access via a file server.

However, CAD users are going to be creating CAD data files that are going
to generally be shared. These files will be shared among users during the devel-
opment of a product design. And, once the project is finished, these files are usu-
ally going to be carefully maintained and revised over a fairly long period of time
(perhaps decades). This aspect of the CAD system naturally leads to the use of a
network and file server for these files. This allows the CAD data files (at least the
completed ones) to be controlled, managed, and shared from a central location.

The network architecture, however, needs to consider the size of the files
being accessed via the network. Some CAD data files will be 10 or 20 MB, so the
system needs to be able to reliably handle this amount of data in as short of a time
as possible.

When the CAD user decides to work on a CAD data file, some systems
may be configured to copy the file from the file server to a local disk. This means
that the network traffic is only generated
at the beginning of the process of revis-
ing the drawing. While the user is changing the drawing, the file is only stored
locally, and performance may improve. Then, when the user is finished, the draw-
ing may be copied back from the local disk to the file server again. In some cases,
this sort of process must be created and controlled by the user by simply manipu-
lating files with the operating system. However, some CAD systems will make
this process totally automated, and the CAD system may institute a data manage-
ment scheme that locks out other users from revising a drawing when one user
checks out the drawing. If this process is available, it must be exploited if at all
possible. It is often very difficult to rely on users to “manually” handle all the
aspects of file management.

Figure 2.5 shows a typical configuration of the local and file server data for
a large CAD system (2-D or 3-D).

6.7.2 Backup/Restore

Clearly a backup and restore system must be instituted for all CAD system data.
The dollar value invested in drawings is rather significant (perhaps 10 or 20 times
the annual engineering department budget), and these drawings represent an in-
valuable repository of intellectual property. Since property needs to be protected
from disaster, hardware failure, intentional corruption, etc., it becomes essential
to have backup copies of all the drawings, data files, and/or metadata for the
CAD system.

Beyond the need to restore data to the CAD system for disaster recovery or
accidental deletion problems (which involves restoring files of recent use), some
companies may want to permanently archive all drawings or data files. This in-
volves keeping copies and permitting restoration of files that have been super-

166 Chapter 6

ceded by newer revisions. The most important task, in this case, is to have proper
listings and databases that allow future users (particularly for field service issues)
to find and restore drawings that have not been used for a long time.

For the CAD systems that use metadata or complex data management
schemes, one has to consider whether certain files can be restored at all. If the
CAD system database information at one point considers a particular drawing to
be at a certain revision level, and a user checks out that revision to make a new
revision, but then this drawing is accidentally deleted from the database (and this
deletion is not noticed for some time), then it won’t matter if the drawing data file
(DWG) is restored from tape. The CAD database (like a DBF file) already re-
corded that the drawing revision was removed, and unless there is a way to reset
or synchronize the entire database with the operating system file, the revision to
the drawing will have to be started over again (using the last version properly
recorded in the database). The only way to recover from this situation might be to
restore a dummy image of the entire network from the older date and then export
a new copy of the drawing with its attributes or relational data intact. This copy
would then be imported into the production CAD system.

6.7.3 Licensing

In addition to monitoring the CAD system software, the CAD data files, and cus-
tomization files, there may also be a need for configuring a license manager. This
is a special program that runs on the local system or on a network file server that
controls how many times or how many users can be using the CAD system. The
license manager is usually provided by the CAD system vendor. License files or
password files are often tied to the ethernet address of the computer hardware
that is going to run the license daemon.