Drive application: Winding calculator
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.
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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.