One engineer's view on ease of useOne engineer's view on ease of use

CAD is not just for the engineer. The whole infrastructure of a company-manufacturing, marketing, management, purchasing, sales, suppliers, and vendors-should be able to use it. To do so, they need a CAD program that's feature rich yet easy to use so they can communicate product development ideas easily.

There are mid-range ($3,000 to $5,000) and premium-priced systems ($12,000 to $15,000) available to engineers. All vendors of premium-priced systems have introduced mid-range-priced versions of their products, offering about 75% of the functionality of their flagship products. Regardless of whether you choose a mid-range or premium-priced CAD package, here are some general benchmarks for judging ease of use. I have organized them according to the various considerations engineers take into account when thinking about CAD programs. This is by no means a complete list, but it does reflect my own experience after using CAD throughout my career. And they reflect my own opinions, not those of my employer.

1. The solid modeling kernel.

The kernel is the underlying math behind the software. The two major kernels are ACIS from Spatial Inc. and Parasolid from Unigraphics Solutions. Some CAD developers have their own proprietary kernels. CAD packages based on different kernels can't easily communicate, which is a problem for engineers who import files from different packages. IronCAD 3.1 uses both ACIS and Parasolids at the same time on the same part.

2. Creation of the solid model from individual parts

This is one of the main areas-if not the only one-where ease of use is key in the design progress.

CATIA 5 is the champion in minimum mouse clicks and redundant interactions. The interaction with other dimensions outside the sketching plane makes it easier to establish 3D relationships. As a premium-priced package, CATIA also uses knowledgeware technology for parametric product tables. It enables users to create generic shapes. Rules create different versions of the shapes. Surface Definition is also excellent since the user gets continuous feedback during the manipulation of the surface parameters.

Since in the solid modeling market the use of standards is non-existent, Autodesk's Inventor utilizes the Notebook for saving comments and notes for the designer and others to use and document the approach. In Inventor, the ability to load the model in segments-graphic information first, numerical information later (on demand), presents an increase in access speed that is good for assembly loading. On the other hand, the I-DEAS Artisan Series allows you to compare parts between versions and different parts.

Think3 simultaneously uses wireframe, surfaces, solids, and 2D geometry in a parametrically driven featured-based environment. With 20 options to create surfaces and 16 methods for curve definition, Think3 is one of the best in this area.

SolidWorks' Rapid Draft Drawings allow you to open a large drawing without opening the assembly. You can also send the drawing to someone without the overhead of the solid model.

The Design Assistant in Solid Edge is the only tool that can identify and preserve critical dimensions that drive the form of the assembly. The user gets feedback anytime these critical dimensions are violated in the assembly. Also, rib modeling and editing are more powerful and intuitive than any other software.

3. Create the assembly by mating the individual parts

Inventor's Exploded Views remember placement history. Users can create an AVI for video clips. Inventor will easily restructure an assembly to create subassemblies.

The fact that the assembly is fully integrated with its components in the same file is a key in Think3's CAD strategy.

SmartMates in SolidWorks Assembly, with its Snap-to Fit feature, automatically captures the assembly relationships for part placement. Parts can be dropped from the feature palette or even Windows Explorer.

Solid Edge's new Cognitive Assembly allows the creation of views with configurations that will load only the parts that are associated with the particular view. The Cognitive Assembly also introduces inter-part associativity to assemblies so that changes on one part will automatically update the features driven by the associativity on the other part. Solid Edge probably has the best sheet design in the mid-range category and is equivalent to CATIA's premium-priced version. Piping design and assembly is the easiest in Solid Edge with the XpressRoute. You select the starting and ending point and Solid Edge will figure out the rest, including options for layout.

4. Create the drawings from the assembly or the individual parts

Inventor has an excellent idea in collaborative design in the use of NetMeeting to share drawings or parts with other users who don't have Inventor. At one point, Inventor can turn control to the other users and let them use it while you watch.

SolidWorks has also embraced the concept of sharing drawings with its eDrawings, which can be used to mail the SolidWorks drawings to non SolidWorks users. eDrawings establishes an automatic link from view to view. All the views can be manipulated to produce animations for better visualization of the design.

5. Import/export solid parts or drawings for use by vendors/contractors

SolidWorks users will find it easy to recreate solid models from other vendors with Feature-Works, which can create all the solid features from Pro/ENGINEER parts. The associativity is preserved when importing files from IGES, VRML, STEP, SAT, or Pro/ENGINEER so that any modifications will recognize and use all the existing features.

Pro/ENGINEER's behavioral modeling techniques represent a new strategy in solid modeling. It is the adoption of procedural modeling that goes beyond feature-based technology and parametric definitions. A new player in this type of modeling is Paralogix, which claims significant reductions in mouse clicks and exclusive usage of procedures in capturing product and design intent.

And the winner is.....

Anyone on the users side will say that ease of use is definitely the name of the game in selecting a 3D CAD system. From my standpoint, I would like to have a system that has the open architecture of Think3, the flexibility in kernel selection of IronCAD, the assembly features of SolidWorks, the collaborative options of Inventor, and the surface capabilities of CATIA.

If I had to choose one package, it would be Think3's Thinkdesign. Despite its shortcomings in some areas, I like the openminded approach it enables in design, with little or no modeling restrictions. Just the fact that it gives you more than one method for approaching certain modeling tasks makes Thinkdesign an overall easy-to-use CAD package.

Altidis, a mechanical engineer, is in charge of structural analysis in the automotive transmission systems division of Borg Warner Automotive (Bellwood, IL). His views are not necessarily those of Borg Warner.