Inkjet Printhead Voltage Calibration for Uniform Tonal Density
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Solution Overview
Problem
Inkjet printing devices often produce non-uniform printing results due to differences in printing density among individual printing heads, caused by factors like wear, nozzle clogging, and ink characteristics, which compromise image quality.
Innovation Solution
A method involving printing test supports at varying electrical voltages, analyzing the results, and adjusting the electrical voltage for each head to achieve uniform tonal index across all heads, ensuring consistent ink application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the same printing density is selected for all printing heads, then the device complexity is reduced, but the printing uniformity deteriorates due to wear, clogging, and ink characteristics variations
Solution Approach 1:
The patent applies local quality by assigning individualized printing density values to each printing head based on its specific performance characteristics. Instead of using a uniform printing density for all heads, the system measures and analyzes the actual ink delivery of each head and tailors the printing density parameter locally to compensate for variations in nozzle performance, wear, and clogging, thereby achieving uniform printing output across all heads
Solution Approach 2:
The patent utilizes parameter changes by dynamically adjusting the printing density parameter for each printing head based on measured performance data. The system modifies the printing density value as a control parameter to compensate for deviations in ink delivery, transforming a static uniform parameter into a dynamic head-specific parameter that optimizes printing uniformity
2Manufacturing precision
If individual adjustment of printing density for each printing head is implemented, then the printing uniformity is improved, but the device complexity and operation difficulty increase
Solution Approach 1:
The patent implements self-service by enabling the printing system to automatically measure, analyze, and adjust the printing density of each head without requiring manual intervention. The system performs self-diagnosis through test pattern printing and optical measurement, then automatically calculates and applies the corrected printing density values, making the complex adjustment process transparent and easy to operate
Solution Approach 2:
The patent applies feedback by creating a closed-loop control system where the actual printing output of each head is measured and fed back to the control unit. Based on this feedback information, the system automatically adjusts the printing density parameter for each head to achieve the desired uniformity, eliminating the need for manual trial-and-error adjustments
3Measurement precision
If test printing and analysis is performed for each printing head, then the measurement precision is improved, but the time consumption and productivity are reduced
Solution Approach 1:
The patent applies segmentation by dividing the measurement and adjustment process into efficient discrete steps: test pattern printing, optical measurement of individual heads, data analysis, and parameter adjustment. This segmented approach allows for precise measurement of each head's ink delivery while streamlining the overall process to minimize time consumption
Solution Approach 2:
The patent implements preliminary action by performing the measurement and adjustment process proactively during maintenance cycles or before production runs. By conducting test printing and analysis in advance, the system prepares the optimal printing density values for each head before actual production, ensuring high measurement precision without interrupting production flow
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
The method ensures uniform printing results by compensating for differences in ink delivery among heads, enhancing image quality and providing a diagnostic tool for identifying and addressing uneven performance.
Implementation Method 1
Each printing head in turn comprises several dozen, or even hundreds, of nozzles... Each print bar is configured to apply an ink of a predefined colour to a print support... selecting a desired value of the tonal index for the printing heads; determining, based on said function, an electrical voltage to be applied to the printing heads
Data Source
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AI summary
A method for adjusting a plurality of printing heads of an inkjet printing device, wherein the printing heads are arranged in groups each of which prints an ink, comprises the steps of: • - printing at least two test supports (4) respectively for a first electrical voltage (Vmin) and for a second electrical voltage (Vmax) applied to the printing heads; • - analysing the printed test supports (4); • - defining a function which expresses how a tonal index varies as the electrical voltage applied to the corresponding printing heads varies, the tonal index being indicative of the amount of an ink applied by each group of printing heads, the step of defining a function being carried out using measurements of the printed supports (4) performed during the step of analysing; • - selecting a desired value of the tonal index for the printing heads; • - determining, based on said function, an electrical voltage to be applied to the printing heads in order that said printing heads work with said desired value of the tonal index.