Gear cutting

[davebaldwin]

I am trying to mill a gear using a cylindrical end mill. I have done this successfully cutting around the profile but in this case the gear is too thick to allow this. Over at homeshopmachinist.net there was a long discussion (Gears, gears and more gears - The Home Shop Machinist & Machinist's Workshop Magazine's BBS) about a program from Gearotic Motion that used a 4 axis milling machine to cut any tooth profile providing the end mill fitted between the teeth and was long enough to reach the root. As example of how this was done is show in http://www.youtube.com/v/qZJ95I3ZWro&

I have tried to reproduce this in Sprutcam7 but have not had much success. Rotary Machining seems the obvious choice but no matter what combinations of parameters I use it just seems to step down the tooth curve rather than cutting tangentially to it. I am using Trajectory Form as Linear, Rotary Transformation as Polar with Radial as Z, axial as X and rotary as A. The Contact Tool Type is to Axis.

Any help or guidance would be appreciated. I have attached a zipped version of the Sprutcam file if anyone wants to play.

Dave.