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One of the most common applications of synchronization is to accomplish synchronization a
repetitive number of times based on a programmable number of pulses/counts from an external
lead axis (encoder or digital drive). For these applications, with the PCM-5 properly
programmed, the encoder can provide both synchronization control and the PCM-5 can be
programmed to cause automatic cycle initiations at the completion of a programmable number of
external axis counts. This is accomplished in the program set up mode with PCX. There are
three additional codes that allow for this.
A (T) code allows you to insert (in front of an INDEX, PROGRAM, or DWELL), a choice for a
time base. T = Time Base (TMBAS) and your choice is internal, being normal, or external,
meaning the external encoder.
A (S) code allows you to start counting the external encoder pulses. The SCS-2 with 2 (1000
line) channels produces 4000 counts/steps per revolution. S = Start Counter (ST CT).
An (R) code allows you to wait for the desired number of counts before starting again. R = Wait
for counter (WT CNT). When programming the (R) code you must program the desired number
of counts in the data field and counting is determined by CW (+) rotation of the sync encoder as
viewed from the shaft end of the sync encoder and CCW (-) counting is the opposite. The count
is based from the last start external counter (S) or wait for counter (R) code.
A specific application of this is a flying shear cut where a ball screw is connected to an EMC
motor and a drive with a PCM-15. The lead encoder is connected to a shaft that rotates pinch
rolls. Material is fed through the pinch rolls at varying line feed speeds. The drive must start
from a HOME position (a Positioning Drive feature), accelerate to the same linear velocity as the
material (a PCM-5 feature), perform a machine operation such as cut, punch, print, etc., at line
speed, then decelerate to zero velocity and return to the starting place by either homing or
indexing back. Once back, it must wait for re-initiation from a programmed count (a PCM-5
feature).
The motion cycle would appear as follows:
Figure 68
Motion Cycle Graph
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