Cam indexing units are designed
to perform one output index with a partial rotation
of the input shaft. The partial rotation of the cam
with the output turret rotating is referred as the index
period. Rotation of the input shaft without the output
turret rotation is referred as the dwell period. The
ratio between the index and dwell periods is usually
related to time. Index verses dwell periods can vary
but the most common for continuous duty cycles are 1:3
ratio or one part index to 3 parts dwell periods. This
is typically used for continuous duty cycles when the
index drive runs nonstop and the output turret needs
to supply a long time for process work.
Indexing units that are driven
by machinery may need to match velocity with other equipment.
Custom index periods are available to synchronize motions
of the equipment to avoid crashing into the rotating
dial. Cycle on demand applications do not require long
dwell times because the index drive motor is turned
off to supply the dwell period time. If the index period
is long, the motor drive torque requirement is less.
For this reason, it is typical for Sankyo to use a 3:1
ratio or 270° index period with a 90° dwell
period with cycle on demand applications.
Timing sensor packages are
used to notify the machine controller to stop the index
drive motor when the indexing dial is in the correct
position. The timing cam(s) are mounted on the index
input shaft to interface with a sensor switch. When
the sensor detects the notched edge in the timing cam,
a signal is sent to the motor controller device.