Last week Autodesk delivered release 8 of its Inventor CAD software to customers with update subscriptions. Like Pro/Engineer, SolidWorks, Solid Edge, CATIA version five, and Unigraphics, Inventor is Autodesk’s entry into the market for feature-based solid-modeling software for designing manufactured products.
Inventor release 8 contains 39 minor improvements. Most of these add capabilities that Solid Edge and SolidWorks users have enjoyed for some time.
The most significant change in the new Inventor software is that it completes certain tasks faster than previous versions. For example, when editing a model of a grill, we found that Inventor 7 takes 52 seconds to update the model after a change is made to its base feature. (Tests were run on a 3.0-gigahertz Pentium 4 workstation.) The update took only 33 seconds with Inventor 8. While this is a significant improvement, it should be noted that SolidWorks can make the same change to an identical part in about five seconds.
Inventor 8 was able to process a change to the base feature of this thin-walled grill in 33 seconds, 37 percent less time than Inventor 7. (Click image for a larger view.)
After updating the part with Inventor 8, we found that the two halves created by a mirror feature no longer fit together properly. A small ledge developed on the top surface, which would make the part unsuitable for manufacturing. Our test part was originally modeled with Inventor version six. We have made similar changes to it using Inventor versions six and seven without encountering such difficulties.
Following the rebuilding of the grill in Inventor 8, this unsightly ledge appeared between the left and right halves of the symmetrical part. (Click image for a larger view.)
Upon examining the original Inventor 6 model, we discovered errors in several of the feature sketches. These errors apparently had no effect on Inventor 7, but bothered Inventor 8 sufficiently to produce error messages and distort the geometry when we updated the part. Autodesk said in an e-mail that the defect is caused by a programming error that the development team is “working to fix...as quickly as possible.”
Nobody knows if fixing one bug will eliminate all incompatibilities between Inventor 8 and previous releases. Inventor 8 employs a new version of the Autodesk’s Shape Manager, a derivative of Spatial Incorporated’s ACIS solid-modeling toolkit that is currently being developed by D-Cubed of Cambridge, England.
Error messages like this one accompanied the change to the Inventor 8 grill model. Inventor 7 had no such problems with this model.
If Inventor 8 proves to be less tolerant of sloppy sketching than prior releases, it could force customers to produce better quality models. However, reworking sketches of existing models to eliminate all errors could require considerable extra work on the part of Inventor users.
Even though Inventor provides a Sketch Doctor to help users diagnose problems with feature profiles, the tool doesn’t always fix the problem. For example, when Inventor 8 told us that “multiple sketch points exist at the same location,” we followed the doctor’s suggestion to “combine sketch points.” Inventor responded with “Failed to add coincident constraint. Points lie on the same curve.”
The only certain way to eliminate errors from sketches is to redraw them. This task can be hard if another designer originally modeled the part and the sketch is complex. If your firm’s engineers use sophisticated sketches to make complex part cutouts, managers should be braced for the workload that upgrading to Inventor 8 might require.
In fairness to Autodesk, users of other CAD software, including SolidWorks and CATIA version five, have complained that geometry sometimes changes when parts are upgraded from past software releases. We have not actually seen such problems, and we understand that they generally occur with highly styled parts that combine lofts, sweeps, and surfaces. The features used in our Inventor 8 test part were straightforward extrusions, cuts, rounds, one mirrored feature group, and one shell. These sorts of features shouldn’t cause incompatibilities between releases.