Variable Speed Unwind Control for Out-of-Round Parent Rolls
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Solution Overview
Problem
Out-of-round parent rolls cause variations in web feed rate and tension during unwinding, leading to process disturbances and reduced manufacturing efficiency, as existing tension control systems fail to account for shape changes and resulting in web tension spikes and slackening.
Innovation Solution
A method involving the selection of a reference objective, choice of feedback devices, data collection, error calculation, and generation of correction signals to adjust the unwinding process, allowing for real-time adjustments to maintain consistent web feed rate and tension, utilizing actuators and feedback devices like force transducers and web speed sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the rotational speed of the parent roll remains substantially constant, then the ease of operation is maintained, but the web velocity and tension vary during rotation causing process disturbances
Solution Approach 1:
The patent applies dynamics by transitioning from constant rotational speed to variable rotational speed operation. The parent roll speed is dynamically adjusted based on the instantaneous radius at the web takeoff point, allowing the system to adapt to the out-of-round shape variations and maintain consistent web velocity and tension throughout the rotation cycle.
Solution Approach 2:
The patent changes the operational parameters by varying the rotational speed of the parent roll according to the measured out-of-round variations. The speed parameter is modified in real-time based on the position-dependent radius measurements, transforming the speed profile from constant to variable to compensate for geometric irregularities.
2Productivity
If faster unwind speeds are used to accommodate faster production output, then productivity increases, but web tension spikes and slackening are exacerbated
Solution Approach 1:
The system enables high-speed operation by implementing dynamic speed modulation that compensates for out-of-round effects. At higher unwind speeds, the variable speed control becomes even more critical to maintain tension stability, allowing the system to achieve high productivity without sacrificing web tension reliability.
Solution Approach 2:
The patent employs feedback mechanisms where web velocity and tension are continuously monitored, and the parent roll speed is adjusted based on these measurements. This closed-loop control allows the system to maintain stable web tension even at high unwind speeds by real-time compensation for radius variations.
3Device complexity
If typical tension control systems are used, then the device complexity remains standard, but they fail to account for radius changes at different rotational positions
Solution Approach 1:
The system performs preliminary measurement of the out-of-round shape characteristics before the unwinding process begins. By characterizing the radius variations at different rotational positions in advance, the control system can pre-calculate the required speed adjustments, enabling precise web feed rate control without adding excessive complexity to the tension control system.
Data Source
AI summary
A method for reducing the effects of variations in an unwinding, convolutely wound roll of web material is disclosed. The method utilizes the steps of: a. selecting a reference objective relating to a downstream operation, b. choosing at least one feedback device correlated to the reference objective, c. collecting process data from the at least one feedback device at different positions within a time-varying operation cycle for at least one operation cycle at a learning speed, d. calculating an error as the difference between the collected process data from step (c) and a reference signal related to the selected reference objective, e. generating a correction signal based upon the calculated error from step (d) and, f. applying the correction signal to the actuator during a succeeding time-varying operation cycle.