Double Reflex Printing Web Velocity Equalization
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Solution Overview
Problem
In moving web printing systems using a double reflex system, variations in linear web velocities at different rollers can lead to misregistration of images due to inaccuracies in angular velocity measurements, causing visual noise and errors that accumulate over time.
Innovation Solution
A method and system that equalize linear web velocities by identifying low and high frequency components of angular velocity signals from encoders at different rollers, using low and high pass filters to compute a common baseline velocity, which is then used to generate firing signals for printheads, thereby reducing misregistration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If angular velocity measurements from encoders at different rollers are used to calculate linear web velocities, then the web velocity can be measured at multiple points, but measurement inaccuracies and variations accumulate causing misregistration
Solution Approach 1:
The patent segments the velocity measurement problem by separating low frequency components (from the first roller encoder) and high frequency components (from the second roller encoder). This segmentation allows each component to be processed independently through appropriate filtering, preventing error accumulation while maintaining measurement precision at multiple points.
Solution Approach 2:
The patent introduces frequency domain filtering as an intermediary processing step between raw encoder measurements and final velocity calculation. Low pass filtering extracts steady-state velocity trends while high pass filtering captures dynamic variations, acting as intermediaries that prevent direct error propagation and improve registration reliability.
2Measurement precision
If multiple encoders are used to measure web velocity at different rollers, then more velocity data is available for control, but the complexity of the system increases
Solution Approach 1:
The patent extracts only the essential frequency components needed for accurate velocity measurement - low frequency trends from the first encoder and high frequency variations from the second encoder. This extraction approach maintains comprehensive velocity coverage while removing redundant measurement paths that would increase system complexity.
Solution Approach 2:
The patent applies dynamic filtering strategies where low pass and high pass filters are selectively applied to different encoder signals based on their frequency characteristics. This dynamic processing approach optimizes the use of multiple encoders by assigning each to capture specific velocity characteristics, maintaining measurement precision without requiring all encoders to operate at full complexity.
3Measurement precision
If low pass and high pass filters are applied to separate frequency components, then velocity accuracy is improved, but the processing complexity increases
Solution Approach 1:
The patent applies different filtering qualities to different frequency components locally - low pass filtering for steady-state velocity components and high pass filtering for dynamic variations. This localized filtering approach improves velocity calculation accuracy for each component type while keeping the overall processing complexity manageable through targeted rather than universal filtering.
Data Source
AI summary
A method enables linear web velocities generated with reference to angular velocity signals generated by encoders at different rollers in a double reflex printing registration system to be equalized. The method includes identifying a low frequency component of a first linear velocity of a moving web, identifying a high frequency component of a second linear velocity of the moving web, and computing a linear velocity for the moving web at a roller in a print zone with reference to the identified high frequency component of the second linear velocity and the identified low frequency component of the first linear velocity.