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Winding calculators are used when endless
material is unwound for further processing or rewound after processing.
This may be necessary in the paper, plastics, textile or sheet metal
industries. It is very important that the speed of the material
transport remains constant. The speed of the material roll is changed
in inverse proportion to its radius. To prevent the material from
tearing, it is wound smoothly and the tension must be kept constant.
The following description of the drive solution is based on two
unwinders.
- Endless, as in a paper
machine. The roll is unwound without interruption at a constant
circumferential velocity. The radius is calculated by the IPOSplus® program in MOVIDRIVE®. The speeds n1 and n2 and the diameter
d0 of the pull-off roller are known.
- Clocked, as in a trimmer. The unwinder has to start
and stop cyclically. Clocked further processing requires special
precautions to ensure jerk-free material transport. One precautionary
measure is to guide the material over a jockey roll, which acts
as a buffer to compensate for the tensile force fluctuations and
load shocks of clocked operation.
The MOVIDRIVE® solution
assumes that each unwinder and pull-off roller is driven by its own
motor. Both MOVIDRIVE® drive
inverters are connected with the standard system bus (SBus). External
encoders on the line can be avoided through the data exchange between
the inverters. The inverter can recognize possible band tearing.
An automatic threader ensures that the process continues as soon
as possible.
In the case of clocked further processing,
the guide around the jockey roll is extended. The jockey roll acts
as a buffer to compensate for the tensile force fluctuations and
load shocks arising from clocked operation. The position of the
jockey roll is entered with a potentiometer and the signal is forwarded
to the MOVIDRIVE® of the winder.
A significant feature of the MOVIDRIVE® drive inverter, the IPOSplus® positioning and sequence control
system, now comes into play. It turns the MOVIDRIVE® into a real winding calculator. An
IPOSplus® program in MOVIDRIVE® calculates the setpoint of the torque
or the setpoint of the unwinder speed based on the speed of the
unwinder and pull-off rollers and the specified valid tensile force
(for example, via the fieldbus of a PLC).
- The MOVIDRIVE® units
exchange the data for torque control or speed control via the system
bus.
- The roll radius is calculated independently in MOVIDRIVE®. No additional measuring equipment
is required.
- In the application without jockey roll, integrated torque
control, also for standard AC motors with encoder.
- In the application with jockey roll, integrated PI controller
for speed control for the unwinder.
- All movement control is carried out by the IPOSplus® program in MOVIDRIVE®.
- Safe operation of asynchronous AC motors even in the
field weakening range.
- Band tearing is recognized and threading help is started
automatically.
- Simple integration into higher-level machine control
systems is possible via fieldbus.
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