gearcutter
Industrial
I found this on another forum and am interested in this forums views as we are seeing more of this type of finishing process. I've posted the original question along with my reply.
Ivan D.s question:
From Time to time we see unexplained tooth surface failure on large cyclo-palloid spiral bevel gears that we use on marine transmissions. The gears are case hardened and hard cut. The hard cutting is common for finishing of small hypoid and spiral bevel gears for automotive drive axles. But on large gears, hard cutting looks to be resulting in subsurface damage because of the very high cutting forces. Some of the large hard cut gears fail due to tooth surface damage much sooner than they should. We know that hard turning is not recommended for critical parts because an alternative grinding can be used. But how to avoid damage from hard cutting on large spiral bevel gears? We deal with AGMA class Q12 spiral bevel gears 1000mm – 2150mm in diameter. Would somebody know an alternative tooth finishing process that would not damage the hardened case as much as hard cutting.
Ron V.s reply:
I don't know about the cyclo-palloid system but I do know that the Gleason system can be finish ground.
The only other thing I can think of would be to lap them after heat treatment. I've had this done on spiral gears up to 800mm diameter with good results............I'm not sure about gears as large as you are quoting.
The reduction in resistance to surface fatigue, due to the hard cutting process, that you are seeing is a cause for concern as the process seems to be picking up in popularity.
From your results; do you think that these gear sets should be de-rated?
Ron Volmershausen
Brunkerville Engineering
Newcastle Australia
Ivan D.s question:
From Time to time we see unexplained tooth surface failure on large cyclo-palloid spiral bevel gears that we use on marine transmissions. The gears are case hardened and hard cut. The hard cutting is common for finishing of small hypoid and spiral bevel gears for automotive drive axles. But on large gears, hard cutting looks to be resulting in subsurface damage because of the very high cutting forces. Some of the large hard cut gears fail due to tooth surface damage much sooner than they should. We know that hard turning is not recommended for critical parts because an alternative grinding can be used. But how to avoid damage from hard cutting on large spiral bevel gears? We deal with AGMA class Q12 spiral bevel gears 1000mm – 2150mm in diameter. Would somebody know an alternative tooth finishing process that would not damage the hardened case as much as hard cutting.
Ron V.s reply:
I don't know about the cyclo-palloid system but I do know that the Gleason system can be finish ground.
The only other thing I can think of would be to lap them after heat treatment. I've had this done on spiral gears up to 800mm diameter with good results............I'm not sure about gears as large as you are quoting.
The reduction in resistance to surface fatigue, due to the hard cutting process, that you are seeing is a cause for concern as the process seems to be picking up in popularity.
From your results; do you think that these gear sets should be de-rated?
Ron Volmershausen
Brunkerville Engineering
Newcastle Australia