As Gear Technology moves toward its third anniversary, we feel that we have reached a point in our development where it is time to pause, reflect on our accomplishments and plan for the future.
Noisy gear trains have been a common problem for gear designers for a long time. With the demands for smaller gear boxes transmitting more power at higher
rpms and incumbent demands for greater efficiency, gear engineers are always searching for new ways to reduce vibration and limit noise without increasing costs.
Today it is common practice when
climb hobbing to keep the direction of
the hob thread the same as that of the
helical gear. The same generalization
holds true for the mass production of
gears for automobiles. It is the authors' opinion, however, that conventional hobbing with a reverse-handed hob is more effective for the high-speed manufacture of comparatively small module gears for automobiles. The authors have proven both experimentally and theoretically that reverse-handed conventional hobbing, using a multi-thread hob with a smaller diameter is very effective for lengthening the life of the hob and for increasing cutting efficiency at high speeds.
Gear manufacturing schedules that provide both quality and economy are dependent on efficient quality control
techniques with reliable measuring equipment. Given the multitude of possible gear deviations, which can be found only by systematic and detailed measuring of the gear teeth, adequate quality control systems are needed. This is especially true for large gears, on which remachining or rejected
workpieces create very high costs. First, observation of the gears allows adjustment of the settings on the equipment right at the beginning of the process and helps to avoid unproductive
working cycles. Second, the knowledge of deviations produced on the workpiece helps disclose chance inadequacies on the production side: e.g., faults in the machines and tools used, and provides an opportunity to remedy them.
The load capacity rating of gears had its beginning in the 18th century at Leiden University when Prof. Pieter van
Musschenbroek systematically tested the wooden teeth of windmill gears, applying the bending strength formula published by Galilei one century earlier. In the next centuries several scientists improved or extended the formula, and recently a Draft International Standard could be presented.
NC and CNC metal cutting machines are among the most popular machine tools in the business today, There is also a strong trend toward using flexible
machining centers and flexible manufacturing systems. The same trend is apparent in gear cutting. Currently the trend toward CNC tools has increased, and sophisticated controls and peripheral equipment for gear cutting machines are now available; however, the investment in a CNC gear machine has to be justified on the basis of economic facts as well as technical advantages.