A new feature for ensuring optimum tooth flank contact is now available on the new release 08/2014 of the MESYS shaft system calculation.The teeth geometry of gear pairs can accordingly undergo either symmetric or unsymmetrical flank corrections based on three different approaches according to the standard (ISO 21771:2007), i.e. Flank line crowning, Flank line slope modification and Flank line end relief.

  • Flank line crowning:

It consist of a relief based on a circular arc which is tangent to the mid-point of the tooth width. The relief amount, which is measured from the corresponding end of the tooth, must be specified.

  • Flank line slope modification:

It consist of an increasing linear relief over the whole tooth width. So the slope of the relief line starting from one end to the other must be specified.

  • Flank line end relief:

It consist of an increasing linear relief starting from a certain point until the end of the flank line. The relief amount and length, which are measured from both ends of the tooth, must be specified.

All in all, the user can make use of the existing ‘Line load’ and ‘Gap width’ graphics as guidance to establish a flank correction proposal which leads to an homogeneous line load on the tooth. For instance, having a look at the original teeth mesh condition of the first stage of a two-stage helical gear pair as shown in the picture, it can be noticed that the flank contact needs to be corrected as the teeth are being improperly loaded.


By carrying out a combined symmetrical correction based on a major flank line slope modification of -29 µm and a light flank line crowning of 3 µm, the tooth flank contact end up being optimized as it can be deduced from the resulting line load on the flank:

Note that the flank corrections are only optimal for one load case. Using a load spectrum, the flank corrections can be evaluated for multiple load conditions simultaneously as shown in the following picture: