Hi,
We have a regular requirement for instrument gears of stainless steel, which are produced in-house by hobbing.
In spite of using a freshly re-sharpened hob, a burr is obtained at the leaving end of the job, which is very difficult and time consuming to remove. Can anyone suggest a process to avoid this. The gears are of 0.4M to o.8M with 10 - 30 teeth.

 

Have a look at this paper http://escholarship.org/uc/item/2239m1ns#page-14. Maybe adjusting your depth of cut and feed per tooth (at least for your finishing pass) could help. There are systems for automatic deburring (vibratory finishing) but if your gears are very tight tolerance you might not want to risk affecting the mating surfaces. Vendors of vibratory finishing machines will often run trials for you.

 

Thanks for the reply AndrewNew, and you have guessed it correct. The gears have a tolerance of 0.01mm, r/o on the PCD and 0.01mm on the BTL ( base tangent length). In the current process, the gear is finished by two final passes of 0.02mm each. We tried vibratory finishing, but by the time burrs are removed, the tip gets rounded. Well I am on the lookout for an old hand in hobbing, who might have a good practical way of tackling this. He would have faced this problem as well.

 

Gear Shaving could be an option. Since the module is small, you may even try Electrochemical machining, though I am not sure about the accuracy that one can attain.