Issue: Volume: 24 Issue: 6 (June 2001)

Inventor 4

By David Cohn

Autodesk continues its aggressive release schedule with Inventor 4, the latest version of its mechanical modeling software. In this release, Autodesk has added more than 150 enhancements, aimed largely at helping users make the transition from 2D to 3D mechanical design, including complete compatibility with Auto CAD's DWG drawing file format.

Parts, assemblies, drawings, presentation views, and design elements are saved as separate files. To keep everything straight, the program organizes related files into projects. Unlike the previous release, however, whenever you start a new file or open an existing one, Inventor displays a well-designed Quick Start window with tools to select the appropriate project (or create a new one), edit an existing project, and locate or create the desired file. It's a welcome addition to what is already perhaps the best-designed user interface among all mid-range MCAD programs.

As in most parametric modeling programs, you begin a part in Inventor by sketching 2D geometry, and here Release 4 offers several improvements. You can now create chamfers as you sketch, something that's often easier than adding them later in the model, and dimensions and constraints are automatically created as you work. Another new feature lets you selectively project edges of existing parts onto the sketch plane, then use the projected geometry to build a new sketch. After you have created a sketch, a new Auto Dimension dialog box enables you to automatically add dimensions and constraints to your sketch, and indicates how many dimensions and constraints are required to fully constrain your sketch.
Assemblies, as well as parts, drawings, presentations, and design elements, are now saved as separate files in Inventor 4.

Inventor 4 also adds several improvements to part modeling. When creating fillets, the program provides more control over corner fillet shape by allowing adjustment of the setback of each edge fillet independently. And when a fillet runs over an edge, you can adjust the fillet radius and maintain the edge, or maintain the fillet radius and adjust the edge.

Until now, Inventor has lagged behind its competitors (such as SolidWorks) and even Autodesk's own Mechanical Desktop when it came to modeling surfaces. Inventor 4 makes some progress in this area. You can now use extrude, sweep, loft, and revolve to construct surfaces that can then be used to terminate or split other 3D solids. You also can fillet and chamfer composite surfaces and shell surfaces into solids. Although this is far from a complete set of surfacing tools, it's a good first step.

Inventor's sheet-metal capabilities are improved in the new version with the ability to create punched shapes across bends, flanges with setback, and ripped corners. You can now group sheet-metal settings so that if you change the material type and thickness, you don't have to worry about changes to other settings.

One especially useful new aspect of Inventor is iParts, a family-of-parts publishing capability that enables libraries of intelligent parts to be created and reused. When creating a part, you define its basic design as well as parameters that should be changeable later, with those parameters saved in an underlying Excel spreadsheet. When you use an iPart, you can select a standard part from a family of parts, or modify parameters to create a custom part.

Another new feature, iMates, lets you de fine how a part should connect to other parts by specifying key assembly constraints. For example, you can specify that a bolt always aligns with the axis of its mating hole with one face flush with its mating face.

Inventor 4 also includes many drawing enhancements, including a Dimension Style Manager, similar to AutoCAD's, to help ensure that drawings conform to company standards. You can also define and choose line styles, add associative hatch patterns and color fills to closed regions, and create custom symbols to annotate drawings.

Inventor 4 is rounded out with such features as a Pack-and-Go utility that pack ages models and their associated files to ship to someone else, the ability to import SAT and STEP files, and the ability to import AutoCAD drawing files as the basis of a 3D model and export 2D drawings for use in AutoCAD.

Although Inventor continues to improve, it's still not for everyone. For example, people doing sculpted surfaces, complex metal forming, or industrial design will be better served by other products-at least for now. But with each new release, Inventor continues to attract new users and challenge other popular MCAD programs that came before it.

David Cohn is a computer consultant and technical writer in Bellingham, Washington. He can be contacted at

Price: $4995
Minimum System Requirements: Windows 2000/98/NT; 450MHz Pentium II compatible; 256MB of RAM; 360MB of hard-disk space; OpenGL video card; 4MB of VRAM