Moving Web Defect Positioning Using Local Stretch Compensation
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Solution Overview
Problem
Existing systems fail to accurately compensate for differences in web stretching during different processing stages, leading to incorrect positioning of web defects and inefficient defect correction due to changes in web tension and direction.
Innovation Solution
A method and system for calculating additional local stretching of a web in real-time by comparing actual web length measurements with coded position markers, allowing for precise estimation of defect positions during rewinding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If coded position markers are applied during winding at a first web speed and tension, then the markers are positioned at predetermined distances from the origin, but during rewinding at a second web speed and tension the web stretches differently causing the distance between markers to change, resulting in incorrect defect positioning
Solution Approach 1:
The system measures the actual distance between coded position markers during rewinding and calculates the stretching factor based on changes in web tension and speed parameters. This allows the system to compensate for parameter changes between winding and rewinding operations, maintaining accurate defect positioning despite web stretching variations.
Solution Approach 2:
The system uses feedback from the measured actual distances between coded position markers to calculate and apply stretching corrections. By continuously monitoring the web behavior during rewinding and comparing it with the original winding conditions, the system adjusts defect position calculations in real-time to maintain measurement precision.
2Productivity
If the web is stopped too early or too late due to incorrect stretching compensation, then the defect positioning is inaccurate, but if the web is stopped at the correct position, then defect repair efficiency is maximized
Solution Approach 1:
The system calculates the defect position and determines the optimal stopping point before the web actually reaches the repair station. By performing preliminary calculations of the defect location based on measured stretching, the system prepares the correct stopping position in advance, eliminating the need for time-consuming search operations and maximizing repair efficiency.
3Measurement precision
If real-time calculation of local stretching is implemented, then defect positioning accuracy is improved, but system complexity increases
Solution Approach 1:
The system uses coded position markers as intermediaries to indirectly measure web stretching. Instead of directly measuring web tension or length changes with complex sensors, the system tracks the positions of these markers during rewinding to calculate stretching, simplifying the measurement approach while maintaining high precision.
Data Source
AI summary
The present invention relates to systems and methods for calculating the additional local stretching of a moving web through a converting process in order, during rewinding, to find the position of defects in the web that were identified during winding and stopping the web with the web defect close to or at a defect correcting station. The method comprises, during rewinding of the web, the steps of detecting position markers (PM(n)) applied during winding of the web (5), measuring the distance between the position markers, calculating the additional local stretching between the position markers occurring during rewinding, applying the calculated additional local stretching to the known position of a following web defect to determine an estimated position of that web defect in the rewinding web. A method for correcting a web defect comprises the step of subsequently stopping the web with the web defect at, or close to, a defect repairing station (38).