Seeking a price breakthrough in features-based 3-D modeling, Autodesk makes a promising start with AutoCAD Designer 1.0
Evan Yares
Autodesk, the developer of AutoCAD, has been at the top of the PC CAD market for about 12 years. By any standard, the company has had quite a run, managing to make so much money that it must have had a hard time spending it all. Still, not all is well with Autodesk. Lurking behind its success has been a big question: Where does the world's sixth-largest software company go from here?
At one time, Autodesk won business due to the mistakes of its competitors, but that's happening less often. AutoCAD, which still accounts for the vast majority of Autodesk's sales, is not the technical leader it once was. A program that in 1982 offered 80 percent of the featu
res of high-end CAD systems for 20 percent of the price could in 1994 perhaps lay claim to providing a quarter of the technology at a quarter of the price.
The solution seems to be in developing advanced add-in products, such as AutoCAD Designer 1.0. Designer is a $1500 parametric feature-based modeler that works with AutoCAD Release 12. It is based on the ACIS (American Committee for Interoperable Systems) solid-modeling kernel from Spatial Technology (Boulder, CO) and DCM-2D constraint management technology from D-Cubed Ltd. (Cambridge, U.K.). Designer gives AutoCAD some of the solid-modeling capabilities found in such workstation-based CAD programs as Pro/Engineer from Parametric Technology Corp.
Getting the Parameters
Designer plows no new technological ground, but it represents a price/performance breakthrough. Although Pro/Engineer, the competitive product most often mentioned in the same breath as Designer, sells for about $18,000 in standard trim, the combined pric
e of Designer and AutoCAD is $5250.
To understand what Designer brings to AutoCAD, you first have to understand the vernacular used to describe it. The term parametric has a specific meaning in the context of CAD. It implies that the models created in the CAD system are not dimensionally fixed, but rather are defined by a set of dimensions and geometric constraints. If any of the defining dimensions are changed, the rest of the model is affected.
Consider a rectangle. Its dimensions are length and width. Its geometric constraints are that its top and bottom sides are horizontal, its left and right sides are vertical, and all its sides are connected end to end. In most CAD systems, you can draw a rectangle as a series of lines, but the software will not keep track of the relationships between the lines. Move a line, and you no longer have a rectangle. A parametric program, by comparison, keeps track of and preserves such relationships between objects.
An Awareness of Limitations
The term feature describes a 3-D object created by extruding, sweeping, or revolving a closed profile. In Designer, all objects are created by starting with a base feature and then joining, intersecting, or subtracting other features from it. I've outlined the process in the text box "A 3-D Feature Presentation: Anatomy of a Model," which describes how I built a 3-D test model of an automotive
connecting rod
.
In practice, however, Designer can be annoying to use. In the real world, you'd never find a connecting rod as simple as the example I used. Most connecting rods use split caps and have subtle machining details that are hard to represent in Designer. It's not surprising, then, that when I tried to draw a real-world connecting rod, I ran headlong into a few of Designer's limitations.
First, when I was constraining a profile, Designer turned some fillets (i.e., arcs that are tangential to two lines) into loops. The way to work around this was to constr
ain the profile in a different order. An alternative would have been to draw the initial sketch more accurately.
I ran into more constraint problems when I accidentally over-constrained several profiles. Frankly, it takes a good geometric eye to tell how a profile should be constrained; it shouldn't be so difficult. An Autodesk spokesperson claimed that over-constraining is a problem with CAD programs in general, and that the next version of Designer will make it easier to remove constraints individually at any point in the constraining process.
Furthermore, after creating the major features in one of my rod designs, I found that Designer could not apply the fillets I wanted because it has certain design limitations that you don't find in high-end CAD programs. I wanted to apply a variable radius fillet, but Designer makes no provision for it. Other problems I had with filleting are less explainable: Designer simply gave up on some fillets that it should have been able to do.
Still anothe
r problem cropped up when I tried to change the creation order of some of the features. No facility exists for doing this, so the only recourse is to delete some features and then recreate them--not an appealing option, considering it involves redrawing and reconstraining each affected profile. It is possible, however, to make a copy of a profile manually before turning it into a feature. You can retrieve this copy later, if needed.
One Point Oh
AutoCAD Designer is in its first release, and it shows. The program lacks certain refinements that come with maturity. For instance, it has no way of exporting surface data (at least not without going through Autodesk's $1500 AutoSurf program), it lacks the ability to sweep profiles in 3-D or create sculpted surfaces, and it cannot conveniently do sheet-metal or thin-shell design. Even Designer's documentation seems to suffer from first-release problems: It's a bit skimpy and has more than its share of errors.
Despite its warts, De
signer is an impressive program overall. Although I encountered difficulties in creating some of my test models, in the end, with the exception of a few complex fillets, Designer was able to create them. No other CAD program in its price range would have been able to do that.
Time will likely be Designer's salvation. Autodesk has issued two updates since the program's initial release, and the company plans to continue updating Designer on a regular basis. Now that AutoCAD Release 13 is shipping, Designer is slated to become more closely integrated with it, so its seams will be less obvious. Autodesk planned to release Designer 1.1 by the time you read this. Its new features include the ability to change constraints at any point in the design process, a set of on-line tutorials on 3-D modeling, and optimized performance (Autodesk claims to have reduced the time required to save some multimegabyte files from roughly 2 hours to 15 minutes).
For mechanical engineers and designers who are already usi
ng AutoCAD, buying Designer is almost a no-brainer. It gets them into feature-based modeling for a relatively small investment, and it doesn't require that they learn a new CAD system. Even if Designer proves useful in only a few applications, its cost can easily be justified.
For designers and engineers who don't use AutoCAD, however, the buying decision is more complicated. The investment in hardware and training for AutoCAD is not all that different from what you get into with high-end CAD systems. In some cases, paying an extra $12,000 for a high-end CAD system may be good economy, particularly if you're designing products that may produce a few million dollars in revenue to your company. On the other hand, it may be better economy to buy four times as many AutoCAD Designer seats and let four times as many engineers and designers have access to parametric feature-based modeling technology.
Chances are, future versions of Designer will evolve to be more like the high-end solid modelers. For n
ow, it occupies a unique price/performance niche that should appeal to a wide range of users.
ABOUT THE PRODUCT
AutoCAD Designer 1.0 $1500
Autodesk, Inc.
2320 Marinship Way
Sausalito, CA 94965
(800) 964-6432
(415) 332-2344
fax (415) 491-8311
photo_link (17 Kbytes)
A fully rendered test design created in AutoCAD Designer 1.0. The steps in the design process are illustrated on the next page.
Evan Yares is the principal consultant at Design Automation Systems in Phoenix, Arizona. You can reach him on the Internet at
5300.1771@compuserve.com
or on BIX c/o "editors."
Bringing 3-D Modeling to PCs
