Cadtales
Encountering BIG Files
File
size is one of those
parameters that we tend to take for granted. Every file has
a size and, with the advent of cheap memory and
hard-drives, weve pushed this and other associated
parameters to the back of our minds. After all, were being
paid to put lines on paper not to worry about the size of
a file. Being recently and rudely reminded that even the
"boundless" Internet sometimes imposes limits on us
usually when we are not paying attention and/or facing a
looming deadline its worthwhile to take look for BIG file
causes and solutions. On that reminder occasion, a floor
plan file and a half-dozen XREFs, totaling about 9 Mb, was
zipped up and emailed to a client. An hour or so later a
message from the email demon (pun intended) told me in
computerese that my message was
too big. In other
similar cases the attachment was simply dropped and the text
message sent on to the recipient. But, NO! Not in this case.
My 9 Mb un-compressed file set had turned into a giant 20.5
Mb ZIP file and my client was waiting.
Well spare you the details of
everyone denying responsibility for the "refusal to
transmit" and move on to develop a procedure for early
discovery and workarounds to fix or avoid the problem in the
future.
Some of the known causes for
enlarged files are:
- Corrupted files
- Image files
- AEC Objects
- 3D Objects, views
- Exporting to AutoCAD by Autodesks vertical
applications
- Save to DWG by other CAD programs
- Scan & Convert
- Round Trips up and down the AutoCAD revision list
Corrupted files fall into two
categories: 1) Those that crash AutoCAD and, 2) those that
dont. In the first case, options are few: a) Find a backup
file, b) Run Recovery. If neither of those works you may be
out of luck. On one occasion a file would crash AutoCAD when
using certain edit commands. Workaround: With the file open,
copy the visible contents to the clipboard and paste into a
new drawing. This, and the Wblock operation, is also a
convenient way to capture just the stuff you want and
discard anything extraneous or not useful.
Image files are not "embedded"
when inserted into AutoCAD. They remain an external
reference file. Large image files can impact Load, Save,
Zoom, Pan and Regen operations. DWG files compress about 50%
with a commonly used ZIP program. Image files, on the
contrary, compress little or not at all. Workaround: Delete
or Freeze layers with image files when no longer in use or
needed. Convert logo and similar image files to AutoCAD
entities.
AEC Objects are generally 3D,
Multi-view, and sometimes known as "intelligent," objects.
Like an iceberg, however, an AEC object usually containing
multiple views and parametric data - may have 90% of its
content hidden from view. AEC Objects are generally created
and used in vertical applications (MEP, ARCH, Revit, etc.)
AutoCAD will display AEC entities by substituting a "proxy"
object with limited editable features as an accommodation.
AutoCAD can move, erase and copy certain AEC objects but
cannot purge or remove the hidden views and data features.
Workaround: Use the original CAD application to generate an
"Export to AutoCAD" file. Edit the file with the originating
CAD program. Use AutoCADs Flatten command to set all Z
coordinate values to Zero. (Takes a long time for large
files and creates an even larger DWG file). Try the Explode
command (sometimes yields unexpected results).
Exporting to AutoCAD is a
program feature
of Autodesks vertical CAD
applications, i.e. MEP, ARCH, Revit, etc. In my experience,
exporting to AutoCAD always generates a large DWG file,
because all objects, blocks, etc. are exploded into basic
line, arc & circle objects. For a large floor plan, for
example, this explodes all doors, windows, furniture and
other blocks into lines generating a huge file.
Workaround: Not many options here. Re-blocking repetitive
items is labor intensive but may facilitate easier editing
and re-use in other drawings. This feature does preserve
text in the original font and style.
Save as DWG is a feature of
many CAD programs (other than AutoCAD) and produces a "DWG"
file that is their programmers idea of what a DWG file
should look like. (Some work well, some work poorly, most
are not supported by the authors.) Most of these operations
take a sophisticated 3D file and export a flat file of
lines, arcs and circles. Some export text as text and others
export text as line entities which cannot be edited by
AutoCAD. Some also export long lines as a quantity of
smaller lines often to the point of absurdity. Such was
the case in the 9 Mb example in the opening paragraph. In
another example, a 15 Mb floor plan contained no blocks and
Audit reported 465,000 entities, an unwieldy file and a pain
to edit. Workaround: Using the Wblock-to-a-new file
operation cited in the Corrupted topic above, this
file was reduced to a manageable 7.5 Mb.
Scan & Convert has been around
for many years and there have been some notable improvements
in conversion routines. Shop around & test and chances are
good you will find something useful. The limitations,
however, are often similar to what you get with Exporting to
AutoCAD and Save as DWG operations: Broken lines, lines that
look like text, no blocks and lots of basic line
entities.
Round-Trips are the repeating
cycles of creating and editing a file in one version of
AutoCAD, saving down to an earlier version, than opening
again in a later version. This may cause some file integrity
problems but its difficult to know because the history of
these "open up" and "save down" operations is non-existent.
(For more on Drawing Integrity see our Cadtales article on
the subject). Some users, for economic and limited use
reasons, have not upgraded to the current version of
AutoCAD. Workaround: For almost all 2D applications AutoCAD
LT is an economical substitute with most of the features of
AutoCAD and complete file cross-version support. Avoid round
trips internally by hosting your entire drawing library on
your current version of AutoCAD and using Etransmit to
save-down to earlier versions.
In general a process to test and
validate incoming files will discover file problems and
offer an early opportunity to find a solution:
- Virus-scan all incoming files.
- Run File Recovery on all incoming root and XREF
files.
- Repair errors before starting the design/edit
process.
- Open project/sheet files in their native
application.
- Export to AutoCAD if necessary (larger file
size).
Do you see a benefit in educating
your operators, designing and integrating a drawing quality
& validation process into your CAD operation? Contact your
Hagerman sales representative for training, custom
programming and software upgrades.
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