AGMA 04FTM2

Modern gear calculation programs give us the possibility todetermine the load carrying capacity and the noise behavior of agear transmission considering the shaft and bearing system, thetooth modifications and the production deviations.While load andstress optimized tooth modifications are quite insensible to thenormal production deviations; noise and vibration optimized toothmodifications need a much higher production accuracy because of thelow values of the transmission errors caused by the changes of themesh stiffness.

The numerical simulation leads often to more complexmodifications which can not be realized with normal standardmodifications like crowning and root or tip relief. Topologicalmodifications are required and have to be realized in the grindingprocess. Differences between the common profile grinding method andthe generating grinding method based on the different contactsituations between grinding wheel and gear gap will be shown.

More and more companies discover the high improvement potentialof topological modifications with which gears can be modified whereit is required – the generating engagement relief of a helicalgear corresponds to the normal tip and root relief of a spur gear.The teeth are modified in the area of highest pressure (at thebeginning and the end of the mesh). A contact area with a lowerHerzian pressure can transmit more load.

The topological modifications show big advantages for the noiseand vibration behavior also due to the much higher variability indirection of contact pattern. Gears with even overlap ratio shouldfor instance be modified as less as possible, otherwise the basicadvantages of the constant contact line is not given anymore.Unfortunately, a load optimized tooth flank modification is notalways a noise optimized modification also – a compromisebetween optimized load distribution and low noise has to befound.

The basic of the modern gear calculation programs is the exactdetermination of the mesh stiffness. All the secondary influenceslike shaft bending and deflection in the bearings should also to beconsidered. For the load distribution calculation a static view isoften sufficient. The basic of the dynamic analysis is the loadover the time in form of a FFT analysis. The running speed and thebehavior of the oscillating system have also to be considered. In apractical example the calculation possibilitieswill be shown.Itwill be demonstrated how an optimized tooth modification can befound. In the calculation possible production deviations have to beconsidered – the feedback from the production to the designdepartment is essential.

To satisfy the new requirements the gear grinders manufactureshad and have to improve their machines every year. Today, a serialproduction of gears in quality Q=1 according DIN 3962 (AGMA >15)is possible, if requested. This improvement was basically beenpossible with the substitution of the mechanical transmissions inthe grinder with themodern CNC controls. By introducing the torquemotor as the main table drive of a grinder the last geartransmission disappeared in the gear grinder field.

The accuracy of a gear grinder depends basically from theaccuracy of the table drive. The modern torque motor shows togetherwith the direct mounted encoder high advantages in comparison tothe mechanical worm/worm gear drive. Problems like worm gear wear,backlash and deviations are not known in a torque motor anymore.Without excitation, it realizes an incredible constant movement ofthe table axis. Machine frequencies – the main reason for thealmost disappearing of the generating grinders in thenineties – are not transmitted to the gear anymore. This andthe possibility to realize topologicalmodifications could now leadto a Renaissance of the generating grinders. They can be built insuch a way that also form grinding is possible on the samemachine.

Edition:

04

Published:

10/01/2004

Number of Pages:

9

File Size:

1 file , 2.5 MB