Improving Bevel Gears through “Surface Structure Shift”

The only possibility to change the surface structure created in bevel gear grinding from roughness lines to a diffuse structure is the short time lapping of pinion and gear. Both accuracy and texture potentially enhance the rolling performance of bevel gears. It is the grinding wheel that represents the tooth of the generating gear while the work rolls on the gear to finish desired profile.

 

Surface Structure Shift in Bevel Gears

 

Noise excitations are produced by the regularities in the generating flats and roughness lines. Those generating flats are very small but it is still the grinding grain tracks that dominate the resulting surface roughness. The inaccuracies of wheel dressing cycle, the texture of the grinding wheel and its imbalance cause the generating marks. 

 

Apart from the effects of the grinding wheel, the movement of the machine can also contribute to the creation of generating marks. As it moves from one axis line position to another, the controller software will attempt to connect the positions using a smoothing function. In doing this, there are some milliseconds when the machine may pause in every position. This can generate what is called as microflats. Each microflat can be modified in different ways. However, despite the fact that microflats are shown to be consistent with the timing of each tooth mesh of bevel gears, no attention has been given to further explain this phenomenon.

 

In addition, the idea of the surface structure shift is fairly new that needs more investigation and studies, which can include testing of gear sets on the test rig, end-of-line tests, and vehicle testing. This process is very important to improve the excitation behavior of ground bevel gears by changing the surface structure of a generated member through the following cases.

 

• Shift the roll-positions to vary the position of each facet (waviness) on each flank, either together with a MicroPulse motion or without it.
• Change the position of each facet on each flank by just applying the MicroPulse motion.
• Change the distance of the roll angle increments in axis position table, from start-roll to end-roll position, from slot to slot.

 

Shifting the position for every facet or waviness for every flank using roll-position, with or without MicroPulse motion, is done to counteract the dynamic events during the grinding process. This leaves a surface structure without significant effects, avoiding higher harmonic excitations of bevel gears.