In order to improve load-carrying capacity and noise behavior, gears usually have profile and lead modifications. Furthermore, in gears where a specified tooth-flank load application direction (for drive and coast flanks) is a design enhancement, or even compulsory, the asymmetric tooth profile is a further solution. Nowadays, many gears need to be hard finished. Continuous generating grinding offers a very high process efficiency, but is this process able to grind all modifications, especially asymmetric gears? Yes, it is!

Grinding of bevel and hypoid gears creates on the surface a roughness structure with lines that are parallel to the root. Imperfections of those lines often repeat on preceding teeth, leading to a magnification of the amplitudes above the tooth mesh frequency and their higher harmonics. This phenomenon is known in grinding and has led in many cylindrical gear applications to an additional finishing operation (honing). Until now, in bevel and hypoid gear grinding, a short time lapping of pinion and gear after the grinding operation, is the only possibility to change the surface structure from the strongly root line oriented roughness lines to a diffuse structure.

Ground bevel and hypoid gears have a designed motion error that defines parts of their NVH behavior. The surface structure is defined by the hard finishing process.

This paper introduces the latest process developments for the hard-finishing of gears, specifically in regard to controlling the so-called flank twist.

A reader wants to know: Are profile ground and hobbed globoidal worm sets better than multi-axis CNC generated globoidal worm gear sets for reduction of noise and vibration?

New divisions, open houses and the continued rise of the Industrial Internet of Things - There's been a lot going on in gear grinding in the past year.

Excessive machine tool vibration during a precision grinding operation can result in poor workpiece quality in the form of chatter, rough finishes, burn, etc. One possible reason for excessive vibration is directly associated with the relationship between natural frequencies of a machine tool system and the operating speed of the grinding wheel spindle.

Gear Technology interviews Scott Yoders of Liebherr about the latest gear machining technologies of relevance to automotive manufacturers.

THE FINAL CHAPTER This is the last in the series of chapters excerpted from Dr. Hermann J. Stadtfeld's Gleason Bevel Gear Technology - a book written for specialists in planning, engineering, gear design and manufacturing. The work also addresses the technical information needs of researchers, scientists and students who deal with the theory and practice of bevel gears and other angular gear systems. While all of the above groups are of course of invaluable importance to the gear industry, it is surely the students who hold the key to its future. And with that knowledge it is reassuring to hear from Dr. Stadtfeld of the enthusiastic response he has received from younger readers of these chapter installments.

In comparison to the visionary Industry 4.0 - or the Fourth Industrial Revolution - the machine tool industry can appear rather down-to-earth.