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Figure 11
Figure 12
Pre- and post-MMP surface roughness of TTO bevel pinion
A518–00011.
TTO Bevel Pinion A518–00011 flank form analysis after initial
MMP treatment.
tion, relative to any original finishing (grinding) features which
tended to be longitudinally oriented (heal-to-toe) in nature. The
longitudinal grinding features can be seen in the surface topography
of the as-received C518–00159 (Fig. 8). The root measurements
were taken longitudinally or parallel to the lay of the
grinding features.
The TTO bevel pinion A518–00011 proved to be more challenging
for the MMP treatment as the surface damage was
much more pronounced. This was the first time that MicroTek
had attempted to reclaim a part of this particular material and
geometry, so MMP method was conducted in two stages. The
initial processing was deliberately light to assess the material
removal rate versus time. Figure 11 shows the results obtained
after both initial and final processing. The remnants of the original
pitting damage (Fig. 7) can clearly be seen on the tooth surface
after the initial MMP treatment. The second (final) treatment
essentially removed evidence of the damage, providing a
very smooth surface finish.
Topographical Inspection
Both candidate gears were subject to a topological inspection
to assess the total amount of material removed, and to assess
gear conformance to the drawing specifications. The TTO bevel
pinion A518–00011 was sent to Gleason Works for inspection
at three different points in the process; i.e.—1) prior to the initial
MMP treatment, 2) after the initial and 3) final MMP treatments.
The TTO bevel pinion C518–00159 was inspected post-
MMP treatment by Sikorsky Aircraft against their digital master
gear.
Figure 12 shows the effect of the initial MMP treatment on
the tooth topography of bevel pinion A518–00011. As expected,
the changes were minimal with a maximum of 0.00009
inches being removed from the top land on the concave (driving)
side of the tooth. It should be noted that Gleason’s analysis
selected a center point on the tooth as a zero point. The positive
values indicated in the root must be added to the negative
values shown on the tip to arrive at the total amount of mate-
Figure 13
TTO bevel pinion A518–00011 flank form analysis after final
MMP treatment.
Figure 14
Flank Form Analysis of TTO Bevel Pinion C518-00159 after MMP
treatment.
54 GEAR TECHNOLOGY | October 2012
[www.geartechnology.com]