Each of the main axes of the machine, jaw,
film and infeed, are directly coupled to individual motors with
integrated encoders. The motors replace all the mechanical variable
speed gearboxes, 'slow-down' dwell units, two speed infeed gearboxes,
print registration systems and much of the chains and conventional
drive components.
Each motor is directly controlled by a high performance computer or
motion controller. The motor output shaft is both controlled and
monitored to a
resolution of one in four thousandth of a turn. Up to five thousand
times a second the computer monitors this angular position and
re-calculates the required motor demand speed. It does this
simultaneously for each
motor. A basic flowrapper usually has three axes, but a complex packing
line may include automatic positioning belts, collators, turning
systems, etc and extend to ten or twenty axes.
Software converts the required pack settings into positional 'maps' for
each of the motors and can effectively mimic a multi-output gearbox
with superimposed cams and any manner of continuous or intermittent,
simple or complex, motion profiles. For synhronised motion
it simultaneously operates each axes but can, at any time,
de-synchronise or re-synchronise a given axis or multiple axes in a
fully controlled manner. Motion profiles
and modes of synchronisation can be modfied and
re-calculated almost instantly - at the touch of a button!
Only motion computers of sufficient power and performance can achieve this effectively.
The functions that are obvious to the human operator - actioning
start and stop buttons, displaying images on the screen, changing product
parameters, monitoring sensors, controlling heaters, etc - are simply peripheral
functions handled after the core motion control actions have been
achieved.
