Modern Bevel Gear Grinding

Where is the real advantage of bevel gear grinding? The initial investment in a grinding installation is in fact higher than the investment in lapping machines for the same production volume.
The following qualitative diagrams compare the older cut and lapped methods (Five Cut and Face Milling Completing) with the current methods (Face Hob Lapped and Face Mill Ground).  The different aspects of the comparison are physical properties, quality and the capability for closed loop manufacturing. 
 
Figure 1 shows a modern Waguri ring gear grinding setup. Grinding allows the gear engineer to apply a completely different strategy when designing the ease-off in ground gears versus lapped gears.  The Gleason development of blended Toprem®, blended Flankrem and Universal Motions (UMC) with three flank sections results in quite different ease-off topographies, the so called "selective crowning". Selective crowning uses a conjugate flank center area and crowned top, root, heel and toe sections.  Selective crowning also defines in the path of contact section a flat center and progressively increased crowning on toe and heel.  This results in low motion error and high effective contact ratio with optimized load sharing.  Also in the contact line section the crowning is very low in the center and increases only near the top and root.  This provides low flank surface stress but still provides excellent protection against top and root edge contact.  Only bevel gear grinding using the above mentioned flank optimization features will result in strength advantages