Printing System Registration Mark Positioning for Web Alignment
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Solution Overview
Problem
High-speed printing systems face challenges in accurately tracking the position of paper webs due to high speeds and dimensional changes, leading to difficulties in aligning printed images and controlling printheads, especially when using multiple imaging units and complex registration marks.
Innovation Solution
A printing system that includes a first imaging unit for printing an image and a single registration mark, with a sensor detecting the mark within a second imaging unit to calculate an offset and shift the second image accordingly, ensuring alignment across the substrate width without requiring additional paper web width for the registration mark.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a first printhead on a first imaging unit prints the sense mark on the paper web, then the sense mark indicates a top of the page and enables position tracking, but the sense mark is located along a side margin of the paper web where subsequent images are not printed, requiring a larger paper web width to produce a printed image of a particular size
Solution Approach 1:
The patent moves the sense mark from the lateral dimension (side margin) to the longitudinal dimension (within the image area), allowing the sense mark to be detected without consuming additional paper web width. The sense mark is positioned within the printable area where subsequent images are printed, enabling position tracking while maintaining efficient use of paper width.
2Measurement precision
If complex registration marks and algorithms are used to correct for shrinkage, expansion, drift, and skew of the paper web, then detection of paper web problems is enabled, but the systems do not adequately prevent or minimize such problems before they occur and the device complexity increases
Solution Approach 1:
The patent performs preliminary detection of paper web position and dimensional changes by detecting the sense mark before subsequent imaging units print their images. This early detection allows the system to adjust printhead positions and printing parameters in advance, preventing misalignment issues before they occur rather than requiring complex correction algorithms after the fact.
Solution Approach 2:
The system uses the detected sense mark position as feedback to continuously adjust printhead positioning and printing parameters. This real-time feedback mechanism enables dynamic compensation for paper web shrinkage, expansion, drift, and skew, simplifying the overall system by replacing complex post-processing correction algorithms with proactive, feedback-driven adjustment.
3Productivity
If the paper web moves at high speeds along the paper path, then productivity increases, but it becomes difficult to accurately track the position of the paper web and provide accurate control of the printheads
Solution Approach 1:
The system uses rapid sense mark detection as feedback to continuously update printhead positioning at high speeds. The sense mark provides a reference point that enables the control system to track paper web position in real-time, allowing accurate printhead control even during high-speed operation.
Solution Approach 2:
The sense mark printed on the paper web itself serves as a self-service reference that automatically provides position information without requiring external measurement systems. This self-contained reference enables high-speed tracking by providing continuous position feedback inherent to the moving paper web.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for accurate alignment and registration of images across multiple imaging units, minimizing paper deformation and skew, and enabling efficient duplex printing without increasing paper web width, thus improving printing precision and efficiency.
Implementation Method 1
a sensor configured to detect the registration mark at a point where the registration mark is within a second imaging unit
Data Source
AI summary
A printing system includes a first imaging unit configured to print a first image and a registration mark associated with the first image on a web contemporaneously during a production run, and a sensor configured to detect the registration mark at a point where the registration mark is within a second imaging unit. The printing system further includes a controller configured to calculate an offset along a width direction of the web based on the registration mark and to instruct the second imaging unit to print the second image on the web. The second image is shifted in its entirety in accordance with the calculated offset and is printed on the same side of the web as the first image.