Kashifuji centerless gear lapping machine

Parts requiring reduced vibration & noise, and increased transmission efficiency during motion transfer.

A lapping gear is made of commercially available MC (Monocast) Nylon, and it can be easily made by the hobbing process. The wear of MC Nylon is much less when the material of the mating gear is steel. And the shift/traverse function prolongs the life of the lapping gears.

With a simple machine structure, a low-cost gear finishing process has been developed as compared to conventional gear finishing processes such as, shaving, grinding and honing etc. in terms of both machines and tooling. Improvements to the tooth flank roughness is achievable by lapping after any of processes such as green hobbing, hardening, shot peening and gear grinding when the gear is made of steel.

The center-less gear lapping machine (Japanese patent No. 4957985) allows easy part loading/unloading, and doesn't require a part clamping device or part orientation device. A part can be loaded between two lapping gears (left and right) from above, and is supported by a guide gear from below. Additional support comes from two nylon pads separated by a small gap. This machine design allows center-less lapping with free motion relative to the part's radial orientation.

A small amount of lapping compound containing White Alundum Granules is supplied to the meshing area of the part and lapping gears from above. While the right lapping gear rotates as drive gear, and left lapping gear brakes, allowing simultaneous (dual flank) lapping. Several traverse feeds with a stroke slightly greater than the part face width are applied to part. The "crossed axis" (meshing angle) of lapping gears and part is set to as much as 30 degrees creating favorable stock removal and a short cycle using a high rotational speed.

It is possible to get a smooth mirror-like surface with a roughness of Rz 0.3~1 μm that cannot be achieved by conventional finish processes such as shaving, grinding and honing etc. A gear with mirrored flanks has a large amount of contact surface area delivering improved flanks, and has advantages of reduced wear and increased pitting resistance. Also, it turns out that a mirror finish lowers vibration and noise during the transfer of motion, and increases the transmission efficiency during the transfer of motion.

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