Offset Printing Toning Detection via Paper White Density Quotients
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Solution Overview
Problem
Current offset printing machines face difficulties in reliably detecting toning during the printing process, which impairs print quality due to imprecise dosing of printing ink and dampening solution.
Innovation Solution
A method involving the measurement of full-tone and white fields in color zones using sensors to record density values, with polynomial regression to determine paper white values, and quotients to detect toning, allowing for automatic adjustment of dampening solution supply to counteract toning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If precise ink and dampening solution dosing is implemented, then print quality is improved, but measurement and detection complexity increases
Solution Approach 1:
The patent segments the substrate surface into multiple color zones (cyan, magenta, yellow, black) with dedicated measurement fields for each zone. This segmentation allows independent measurement and control of each color channel, improving print quality while keeping the measurement system manageable through modular organization rather than requiring a single complex omnibus measurement system
Solution Approach 2:
The patent introduces sensor-measured density values as intermediary parameters between the printing process and quality assessment. Instead of directly measuring complex print quality attributes, the system uses density measurements of solid color and white fields as intermediaries to detect toning and control dampening solution dosing, simplifying the measurement task while maintaining precision
2Manufacturing precision
If automatic detection of toning is implemented, then print quality is improved, but measurement precision requirements increase
Solution Approach 1:
The patent performs preliminary measurements of paper whiteness in each color zone before assessing toning. By first establishing the baseline paper whiteness and then comparing it with the whiteness of white measurement fields printed with each process color, the system creates a reference framework that enhances detection precision. This preliminary action allows the system to automatically detect toning through quotient calculation while maintaining manageable measurement precision requirements
Solution Approach 2:
The patent transforms the detection task by changing the measurement parameter from direct toning detection to whiteness comparison. Instead of attempting to directly measure toning (which would require extremely high precision), the system measures paper whiteness and printed white field whiteness, then uses the quotient of these measurements to detect toning. This parameter change reduces the precision burden on individual measurements while achieving reliable automatic detection
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
Enables reliable detection and mitigation of toning, thereby improving print quality by ensuring precise ink and dampening solution dosing during the printing process.
Implementation Method 1
measuring with a sensor in each color zone of the substrate a solid color measurement field for the respective printed process printing color, wherein in each color zone of the substrate a solid color measurement field for the respective printed process printing color is measured with the sensor in such a way that a principal density measurement value and several secondary density measurement values are recorded
Data Source
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AI summary
A method for operating an offset printing press printing at least one of the process printing colors cyan, magenta, yellow, and black, comprising the following steps: Solid color measurement patches (19) of the respective process printing color, printed onto the substrate in color zones of the substrate, are measured with a sensor (30) such that a primary density measurement value and secondary density measurements are recorded for each solid color measurement patch (29) in a measurement color space. White color measurement patches (31) arranged adjacent to the solid color measurement patches (29) in the color zones are measured with the sensor, whereby paper white density measurements are recorded for each white color measurement patch (31) in the measurement color space.For each color zone, the white white density measurement field with the highest paper white density value is determined from all paper white density measurements of all white density measurement fields (31) within the respective color zone. The paper white density measurements of the white density measurement field with the highest paper white density value are stored for each color zone. Using polynomial regression for the colors of the measurement color space, a paper white density profile across all color zones is calculated from the stored paper white density measurements. For each color zone, the paper white density measurements of the respective white density measurement field with the highest paper white density value are corrected by the respective paper white density value. For each color zone, a quotient of the minimum and maximum paper white density measurements is calculated for the corrected paper white density measurements with the highest paper white density value.Depending on the quotient, a conclusion is drawn as to whether there is an undesirable tint in the color zone.