Page 340 - Gear Technology Solutions

24 Vector Feed

24.1 Why is Vector Feed Required?

Generated gears are often cut with a plunging first and a generating roll after-
wards. Formate ring gears only require a plunging to finish the slots with the flank
geometry. Older mechanical cradle style machines use the sliding base to feed a
tilted cutter into the steel. Depending on the blade angles and gear geometry, the
plunge with a tilted cutter head could cause mutilations in certain areas which
wouldn’t clean up and deliver damaged flank surfaces. In other cases, it was found
that feeding with a tilted cutter resulted in better tool life and a nicer sounding cut-
ting process, as if the cutter had no tilt. At the time of the cradle style machines,
there was no alternative plunging possible. The only mechanical slide on these
machines for advancing the cutter head towards the work piece was the sliding
base. The sliding base movement in all mechanical machines was collinear to the
cradle axis (which is equal to the generating gear axis). If the cutting summary in-
cluded a cutter tilt angle, then it was not possible to plunge without tilt.

®
When the free-form Phoenix machines were invented and introduced by Gleason
in 1989, any plunge direction became possible. The plunge direction could be
chosen along a Phoenix machine axis or in a direction which requires a combina-
tion of different machine axes.

At first, machine operators believed that now, when cutters can be fed in the direc-
tion of their axis into the material, the optimal condition for plunging exists. It was
expected that tool life and machine performance would improve. However, the
reality was different, especially for non-generated gears cut with the completing
process. The tilted cutter in the mechanical machines was always putting more
chip load on the outside blades for the face milling process. Now, when the plung-
ing was possible for all gear designs without any cutter tilt, the blades were fed
symmetrically with identical chip load on outside and inside blade. The result was
that the inside blades showed twice the wear compared to the outside blades. The
chip removing kinematic rotated the outside blade away from the material and the
inside blade towards the material. This effect pulls the inside blade deeper into the
cut but pushes the outside blade away from the cut. This unbalanced behavior led
to the difference in tool life.

This triggered the development of vector feed. The first vector feed was emulating
the tilted cutter of the mechanical cradle style machines on Phoenix machines and
the result was a great success. Tool life improved and a smoother running cutting
process was the result.

325