September 1999

Autodesk Inventor:
A New Look at MCAD

Steven S. Ross

In this nozzle assembly, the components are interdependent and the cross handle is shown as an adaptive component. Inventor's Adaptive Assemblies functionality allows users to make changes anywhere in the model, not just in the order in which they created the constraint system.

Autodesk is taking fresh aim at MCAD, the mechanical design CAD market, with an entirely new software package, Autodesk Inventor. Unlike the popular AutoCAD Mechanical Desktop, Inventor is not based on AutoCAD itself. In fact, files created with the two packages are not completely compatible. Autodesk started development on Inventor in February 1996, two months before Mechanical Desktop first shipped.

The existing Mechanical Desktop is certainly a successful product. In fact, with a half-million copies sold, Autodesk claims market leadership in MCAD. But Autodesk has never claimed it is as robust as many of its competitors, especially for big assemblies of 300 to 3,000 components or more. Inventor, known to insiders by its code name "Rubicon" during its three-year development cycle, is aimed squarely at that market.

In a round of private press briefings and demonstrations earlier this summer, Autodesk emphasized three key features of Inventor:

  • Ease of use. The interface is clean, there's an awesome sketch-into-entity facility (much better than the one in other Autodesk products), and a great help system that includes tutorial videos. Autodesk claims designers can get used to it in a day or come back to it infrequently and still be productive.
  • The ability to design from the top down (starting with the design's overall function, and plugging in parts to fit), or the way most other packages work -- designing from the bottom up, one part at a time. Designers can mix finished parts with schematic links, in 3D, to see how everything might work before designing the final version of the link part or parts.
  • A new internal segmented database (it is a bit of an oversimplification, but a CAD program can be considered nothing more than clever interface to create database records, each record being a design entity) that arranges things so you load only the detail and functionality of each entity you need at the moment. Assemblies of 3,000 components load in a matter of seconds instead of many minutes. Other programs might appear to load views quickly, but this usually is done with lightweight images of parts and assemblies. These images do not contain all the information about the parts and may not reflect the latest version of the assembly.

There are other goodies as well:

  • An integrated "engineering notebook" that can record the reasons you chose certain design solutions. The notebook can accept data files, specification tables from a vendor catalog, or images and even videos and sound.
  • The ability to "associate" parts and subassemblies to one another without a one-way dependency. This sidesteps the annoyance of parametrically basing one part's dimensions on another that you've designed previously. In that case, modifying a later part does not have any effect on the earlier one; the modification destroys the parametric relationship. In Inventor, modifying the later part will indeed have an effect upon earlier ones.
  • Collaboration tools. Multiple team members can each work on a part or subassembly. Inventor keeps track of who has what piece. Even those without Inventor can track the design process.
  • Super-fast pans and zooms. Inventor is the first 3D mechanical design package to use the Fahrenheit 3D graphics technology being developed by Microsoft and SGI. This adds detail as the drawing scale changes, and also manages the on-screen drawing, avoiding time wasted drawing areas that can't be seen on the screen.

Shown here is a six-stage transfer machine for machining the cylinder heads for an automobile engine. Inventor allows users to work in the context of their entire design, however large the assembly is, without sacrificing power or performance. Inventor can effectively handle assemblies of 10,000+ components, and opens files two to ten times faster than other competitive best-performing solutions.

In general, files from AutoCAD Mechanical Desktop can be read directly into Inventor. Inventor is both an OLE server and client, so its 2D and 3D data can be embedded into Desktop files. But Inventor files cannot be read into Desktop while keeping their full intelligence. To put it another way, 2D data moves in both directions, but 3D data moves cleanly only from Desktop to Inventor. Desktop 4.0, early next year, will be better at that.

The first release of Inventor, due this month, will lack some polish. There are only limited tools for surface texture, for instance, and no easy way to show exploded assemblies without reading the Inventor file back into Desktop and handling the task there.

Autodesk claims to have spent $25 million developing Inventor. It has filed for 17 patents on new technology created along the way. The database technology itself is clearly a major advance in CAD -- probably the biggest since object technology became truly useful a few years ago.

When you think Inventor, think SolidWorks on steroids. You simply have to play with it, especially if you are involved in large projects with thousands of parts. Also think about using it in conjunction with Mechanical Desktop -- the products will co-exist for at least the next two or three years. And think about digging deep into your wallet. The price will be around $5,000.

Steven S. Ross is an associate professor of journalism at Columbia University. He has written several major design texts.

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