spur gear center to center distance

[GREIF]

Hi
Designing a rotary cutting die where the cutting edge rotates against a rotary anvil and they are driven by gears. When resharpening the dies and anvils it changes the dia. so then the center to center distance of the gears change. Question is how much deviation from correct center distance is ok? Would like to start with dia of dies larger so we can get more sharpening's out of it but how far can we go and still get good engagement?
thanks

 

[Compositepro]

The gears will work as long as the gear teeth engage each other and do not interfere with each other. The gear ratio (generally 1:1) will not change. But the surface speeds of the anvil and cutter depend on their diameters. A speed mismatch will result in scuffing between the contact points and, thus, faster wear.

 

[hendersdc]

Any chance you can switch to a timing belt and a tensioner to take up any slack?

 

[handleman]

I have zero expertise in designing rotary dies. However, my image would be that the alignment from roll to roll is pretty critical. Any deviation from the ideal gear spacing will, as Compositepro said, not change the gear ratio. However, the further apart the gear centers are, the more backlash. That means your rolls are not aligned anymore. It would seem to me that if it's expected that the dies change diameter, the machine should have been designed such that the drive mechanism properly accounts for that rather than varying the distance between spur gear centers.

 

[TheTick]

Part of the beauty of involute gear teeth is that they work just fine if center distance varies. What will happen is more backlash as the space between teeth increases.