PCM-22 Rotary Knife Controller
82
© EMERSON Motion Control
Issues Maintaining Phase
Phase issues may be caused by a number of different reasons:
1)
Master / Product control issues.
2)
Master phase variations are primarily a combination of product
slippage, encoder slippage, material stretch and sensor latency. This
will become worse as the system speed increases if not compensated
for by the Follower and/or mechanical adjustments. This would also
be seen if the Master distance per revolution does not match the
distance traveled. The Master sensor position should be at least the
computed minimum
Master Sensor Distance
from the center of the
Working Segment
so that the effects of material stretch are
minimized.
3)
Follower phase variations are primarily
Following Error
and will
become worse as the system speed increases if not compensated for.
4)
Follower length variations are primarily differences between the
individual Follower lengths which can be controlled by adjusting the
Follower Length Correction Limit
or
Follower Sensor Averaging
. If
the Follower distance per revolution does not match the gear ratio
then it will first be perceived as length variation and then as phase
variation once the
Follower Upper/Lower Length Limit
is reached.
5)
If the Master phase variation / Follower phase variation is positive
due to a late sensor from a short length or potential noise, a positive
phase variation is added to the of the next
Cycle Point
. Inversely, the
Master phase variation / Follower phase variation may be negative
due to an early sensor and is subtracted from the Follower/Master
position on the next cycle.
6)
A Master axis that is running too fast for the profile. Too narrow or
wide of
Master
or
Follower Length Upper/Lower Limits
.
7)
Too narrow or wide of a
Follower Sensor Valid Zone.
8)
Extra or missing sensors.
See
Maximizing Profile Performance
,
Master Cycles
and
Follower Cycles
screens.
