Register Correction in Converting Machines via Cylinder and Vacuum Transfer
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Solution Overview
Problem
Existing register control systems in converting machines, such as rotary die-cutter machines, face challenges in maintaining the alignment of printed motifs due to variations in sheet transportation, leading to misaligned colors and increased wear on drive mechanisms like belts and rollers.
Innovation Solution
A method and system that utilize sensors to detect the passage of the sheet's leading edge, calculate displacement errors, and apply corrections by adjusting the angular position of the printing cylinder and modifying the transportation speed of vacuum transfer units, thereby reducing the need for large accelerations and decelerations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the conveying system constantly changes the speed of vacuum transfer units to make displacement corrections to each sheet, then the alignment of printed motifs is improved, but the wear on drive mechanisms such as belts and rollers increases
Solution Approach 1:
The correction of sheet position is segmented into two independent parts: (1) angular position correction of the printing cylinder, and (2) speed correction of the vacuum transfer unit. This segmentation allows each component to handle only the correction portion for which it is best suited, reducing the overall correction burden on the vacuum transfer unit's drive mechanisms and thereby reducing wear while maintaining alignment precision.
Solution Approach 2:
The system dynamically adjusts the angular position of the printing cylinder independently from the linear speed of the vacuum transfer unit. By making the printing cylinder's angular position dynamic and adjustable, the system can compensate for sheet position errors without requiring large speed changes from the vacuum transfer unit, thus reducing mechanical wear while maintaining alignment.
2Manufacturing precision
If large accelerations and decelerations are applied to vacuum transfer units for displacement corrections, then the alignment of printed motifs is improved, but the mechanical stress on drive mechanisms increases
Solution Approach 1:
The total displacement correction is segmented into an angular component (handled by printing cylinder rotation) and a linear speed component (handled by vacuum transfer unit). This segmentation eliminates the need for large accelerations and decelerations in the vacuum transfer unit, as only the residual linear correction is applied, significantly reducing mechanical stress on drive mechanisms.
Solution Approach 2:
The system changes the parameter being corrected from purely linear sheet position to a combination of angular printing cylinder position and linear vacuum transfer position. By introducing angular position as a correctable parameter, the system reduces the linear correction burden, thereby reducing accelerations, decelerations, and mechanical stress on the vacuum transfer drive mechanisms.
Data Source
AI summary
The invention relates to a method of aligning a plurality of printed motifs on a sheet (3) in a converting machine (10). An actual position (Pa_1) at a first sensor is defined as an initial reference position (P_ref1) for the sheet, and at least one displacement error (Δd2) is calculated and compared to a first threshold (T1). If the displacement error is lower than the first threshold, then the angular position (α) of a printing cylinder (42) in the second flexographic printing unit (16b) is adjusted. However, if the error is higher than the first threshold, then at least part of the of the displacement error (Δd_2) is corrected by modifying the speed (V) of a vacuum transfer unit located between the first printing unit and the second printing unit.