The objective, according to Dr.- Ing. Hansjörg Geiser, head of development and design for gear machines at Liebherr, was to develop and design a combined turning and hobbing machine in which turning, drilling and hobbing work could be carried out in the same clamping arrangement as the hobbing of the gearings and the subsequent chamfering and deburring processes.

New material technology allows for more efficient and flexible hobbing.

Q&A with Liebherr's Dr. Alois Mundt.

It is well known that hobs with straight-sided teeth do not cut true involutes. In this paper, the difference between the straight side of a hob tooth and the axial profile of an involute worm is evaluated. It is shown that the difference increases as the diametral pitch increases, to the extent that for fine-pitch gearing, the difference is insignificant.

In this paper, the potential for geometrical cutting simulations - via penetration calculation to analyze and predict tool wear as well as to prolong tool life - is shown by means of gear finish hobbing. Typical profile angle deviations that occur with increasing tool wear are discussed. Finally, an approach is presented here to attain improved profile accuracy over the whole tool life of the finishing hob.

Several innovations have been introduced to the gear manufacturing industry in recent years. In the case of gear hobbing—the dry cutting technology and the ability to do it with powder-metallurgical HSS—might be two of the most impressive ones. And the technology is still moving forward. The aim of this article is to present recent developments in the field of gear hobbing in conjunction with the latest improvements regarding tool materials, process technology and process integration.

Fred Young, CEO of Forest City Gear, talks about sophisticated gear manufacturing methods and how they can help solve common gear-related problems.

This article examines the dry hobbing capabilities of two cutting tool materials—powder metallurgical high-speed steel (PM-HSS) and cemented carbide. Cutting trials were carried out to analyze applicable cutting parameters and possible tool lives as well as the process reliability. To consider the influences of the machinability of different workpiece materials, a case hardening steel and a tempered steel were examined.

The complete Product News section from the May 2009 issue of Gear Technology.

The method of cutting teeth on a cylindrical gear by the hobbing process has been in existence since the late 1800s. Advances have been made over the years in both the machines and the cutting tools used in the process. This paper will examine hob tool life and the many variables that affect it. The paper will cover the state-of-the-art cutting tool materials and coatings, hob tool design characteristics, process speeds and feeds, hob shifting strategies, wear characteristics, etc. The paper will also discuss the use of a common denominator method for evaluating hob tool life in terms of meters (or inches) per hob tooth as an alternative to tool life expressed in parts per sharpening.