Inkjet Print Quality Control for Long Web Printing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Inkjet printing on long web materials faces challenges in maintaining print quality due to changes in external factors like temperature and ink viscosity, leading to issues such as color position shifts, dot gain, and printhead misalignment and clogging, which degrade image quality over the print length.
Innovation Solution
A method involving the use of a test chart to capture image data, perform error corrections for defective nozzles and printhead alignment, and apply color space corrections based on Delta E calculations in the Lab color space to maintain consistent print quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If inkjet printing is performed on long web materials, then productivity is improved, but print quality deteriorates due to external factor changes
Solution Approach 1:
The system performs preliminary characterization by printing test charts at the beginning and during print jobs to capture baseline image data before actual printing. This preliminary action allows the control unit to establish reference values for color positions, dot gain, and nozzle performance, which are then used to correct subsequent print images throughout the long print job.
Solution Approach 2:
The system implements continuous feedback by capturing actual print image data during the print job, comparing it with target image data, and using the differences to dynamically correct control information for the printhead. This feedback loop compensates for changes in external factors like temperature and ink viscosity that occur during long printing operations.
2Productivity
If print length is increased, then productivity is improved, but color position stability deteriorates
Solution Approach 1:
The control unit continuously monitors color position by comparing actual print image data with target image data and dynamically adjusts control information to compensate for color shifts caused by temperature changes and ink viscosity variations during long print jobs.
Solution Approach 2:
The system changes control parameters based on captured image data, adjusting ink deposition amounts and timing to compensate for environmental factor changes. This allows color positions to remain stable despite variations in temperature and ink properties throughout the print job.
3Productivity
If print length is increased, then productivity is improved, but dot gain control deteriorates
Solution Approach 1:
The system measures actual dot gain by comparing captured print image data with target image data and uses this feedback to adjust control information, ensuring consistent dot gain compensation throughout the entire print job even as environmental conditions change.
Solution Approach 2:
The system performs preliminary dot gain characterization using test charts printed at the beginning and during the print job, establishing baseline dot gain values that are used to pre-correct control information for subsequent printing, maintaining consistent dot gain across long print lengths.
4Manufacturing precision
If automated error detection and correction is implemented, then print quality is improved, but device complexity increases
Solution Approach 1:
The system performs self-diagnosis and self-correction by automatically capturing print image data, comparing it with target data, and adjusting its own control information without external intervention. The control unit autonomously identifies nozzle errors, alignment issues, and color deviations, and applies corrections independently.
Solution Approach 2:
The system uses feedback from captured image data to automatically adjust control parameters, eliminating the need for manual calibration and complex external measurement equipment. The feedback loop enables the system to self-correct various print quality issues including nozzle clogging, misalignment, and color deviations.
Data Source
Figure 1
AI summary
The invention relates to a method for increasing the quality of a printed image of a digital printing machine, which printed image is printed onto a material web in the inkjet printing process, the digital printing machine comprising: a printing head having inkjet nozzles; an image-capturing unit for capturing at least part of the printed image; and a control unit for controlling the printing head. In order to keep the quality of the printed image constant over the entire printing length during the print job, the solution according to the invention is based on a method in which: a test chart is printed at the beginning of and/or during a print job, the first image data of which test chart are captured by the image-capturing unit and are transferred to the control unit, an error correction of defective inkjet nozzles and/or an alignment of the misadjusted printing head being carried out in dependence on the first image data; after the error correction and/or alignment has ended, a target printed image is printed, the target image data of which are captured by the image-capturing unit, are transferred to the control unit and are stored there; after the target printed image has been printed, additional actual printed images are printed, the actual image data of which are captured by the image-capturing unit, are compared in the control unit with the target image data and are stored as target-actual comparison image data, a color space correction being carried out in dependence on the target-actual comparison image data.