One 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

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