Over the past decade, the wire electrical discharge machine (EDM) has become an increasingly important tool for machining non-standard shapes. It has even been used to cut gears and gear cavities for plastic molds. While generally accepted as a quick and versatile method for cutting spur gears, the EDM gear has lacked the precision of a mechanically machined or ground gear. We suspected that many of the errors associated with these gears were caused by inexact setup procedures, poor tool path control and improper cutting parameters. We decided to test the potential for the wire EDM to make the most accurate gear possible.
Earlier this year, a relative of mine, Sidney Mandell, tragically passed away. I had the good fortune to serve with Sidney on the Board of Directors and the Executive Committee of the Machinery Dealers National Association (MDNA). Though he started before me, his MDNA career and mine overlapped for about 2 years. As I think back on the many things I learned form him, one of his favorite phrases keeps come to mind: "We walk in the footsteps of those who have gone before us."
The word gear, in various forms, has been in use since around A.D. 1200, according to the Oxford English Dictionary. Last issue we brought you Shakespearean gears. Now we'd like to show you some of the uses Americans have given our favorite word (from the Random House Dictionary of American Slang).
Several trends in mechanical engineering are leading to greater surface stress on components and thus to unacceptable wear. These trends include greater stresses due to increased power densities; the need to maintain high precision of components throughout their service life; and the environmental imperative to reduce use of lubricants and additives.
The American Society of Mechanical Engineers (ASME) announced at Gear Expo '95 that a national service for the calibration of involute artifacts is now available at the Department of Energy's Y-12 Plant in Oak Ridge, TN.
Information is the name of the game in the 90s. We need more of it; we need it faster; and we need it in infinitely manipulatable and user-friendly form. In many cases, getting it that way is still something of a Holy Grail, somewhere off on the distant horizon. But thanks to computer technology, bit by byte, we're getting there.
In recent years, gear inspection requirements have changed considerably, but inspection methods have barely kept pace. The gap is especially noticeable in bevel gears, whose geometry has always made testing them a complicated, expensive and time-consuming process. Present roll test methods for determining flank form and quality of gear sets are hardly applicable to bevel gears at all, and the time, expense and sophistication required for coordinate measurement has limited its use to gear development, with only sampling occurring during production.
In the process of developing gear trains, it occasionally occurs that the tip of one gear will drag in the fillet of the mating gear. The first reaction may be to assume that the outside diameter of the gear is too large. This article is intended to show that although the gear dimensions follow AGMA guidelines, if the gear is cut with a shaper, the cutting process may not provide sufficient relief in the fillet area and be the cause of the interference.
Indianapolis is a nice city. No. It's a great city for a convention. The facilities and the city are modern, clean and bright. The Convention Center is easy to get to by either car or plane, and its central location in the heart of town and the enclosed skyway system between it and major hotels put visitors close to amenities like restaurants, shopping and entertainment. The people are friendly and go out of their way to make visitors feel welcome.
Gears are manufactured with thin rims for several reasons. Steel gears are manufactured with thin rims and webs where low weight is important. Nonmetallic gears, manufactured by injection molding, are designed with thin rims as part of the general design rule to maintain uniform thickness to ensure even post-mold cooling. When a thin-rimmed gear fails, the fracture is thought the root of the gear, as shown in Fig. 1a, rather than the usual fillet failure shown in Fig. 1b.