For a gear to perform properly, the contact pattern is critical. Typically, the ideal tooth contact pattern under load should encompass the bulk of the tooth surface, but not touch the edge. It isn't easy. The design usually begins with guesswork, and errors are ironed out after physical testing. Arrow Gear Company (www.arrowgear.com) says it has a better idea. Using software and hardware from Gleason Corp. (www.gleason.com), the company now builds virtual models to predict how the gear will perform in actual operation. Computer analysis generates settings for machine tools, saving setup time. Arrow engineers say that the computer modeling yields the ideal tooth pattern on the first or second attempt on the manufacturer's floor.