Gear honing, because of its economical feasibility, has become an essential part in the production of high-speed transmissions. This is especially true in the automotive and truck industry as honed gears, in comparison to ground gears, are extremely quiet and have excellent wear characteristics due to their typical surface finish. Recently, Fässler has taken the gear honing process a step further and has enhanced the economic feasibility and increased the process capability. Of special interest are the tool developments, machine developments and new process strategies which were adapted specifically to the customers' needs due to results of computer simulations in conjunction with the know-how over many years.

The new Fässler HMX-400 Gear Honing Machine was brought on the market incorporating all these developments and know-how. With this machine, our customers are able to finish high quality gears directly after hobbing and heat-treating very rapidly and economically. The costs per part are close to green shaving - but with the quality advantages of a hard finishing process!

Special kinematics of the gear honing process

Honed gears produce less noise and have a longer use life than other gears due to their typical surface structure. The structure of the surface of a honed gear, which resembles a fish skeleton, facilitates the formation of a lubrication film surface from the tip of the flanks to the pitch diameter and thereby positively influences the noise behavior in the gearbox. The special process kinematics cause this surface structure by which the honing tooling makes rolling contact on opposed axes of the work piece. The resulting speed division on the gear flanks results in having a cutting speed component in the axial direction so that the cutting grain comes into contact with the entire flank.

The cutting velocities at gear honing are very slow in comparison to gear grinding and lie between 0.5 – 10 m/s. Because of these low cutting velocities, there is no thermal load at the gear honing process. In fact, there are no micro structural changes in the gear material. The much feared “grinding burn” does not appear! Even when increasing the cutting speeds up to 10 m/s, which are reached with the new machine generation, there is still no thermal loading during the gear honing!

A further important advantage as a result of these low cutting velocities is the induction of high residual compressive stresses on the flank surface. These residual compressive stresses are minimum 1,000 N/mm2 up to 1,600 N/mm2. Increasing the residual compressive stresses benefits the wear behavior of the gears, which results in greater wear resistance and a longer gear lifetime than gears, which have been hard finished by using other processes.

Using the combination of the Fässler’s HMX-400 rigid direct drives and the ceramic bonded honing stones, we reach very short honing time and a very high process capability. As a result of using such rigid direct drives, we are able to almost eliminate the pitch error of gears, not to mention the excellent profile and flank quality.

Example: Spur Gear

before honing:

after honing:

Today the Fässler Gear Honing Process with the HMX-400 is the most economic way for hard finishing gears in mass production for the automotive, truck, motorcycle and aerospace industry. In recent time, the gear honing process has become popular in the whole gear industry because its technical and economical advantages.

Check out our gear honing machine HMX-400