Dynamic Printhead Timing for Inkjet Registration Errors
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Solution Overview
Problem
Inkjet printing systems with moving belts experience registration errors due to changes in frictional forces and belt stretch as media sheets pass through the print zone, affecting image formation accuracy.
Innovation Solution
A method and system that adjust the operation of printheads based on drag force measurements and belt displacements to synchronize ink ejection, using a controller to identify and compensate for changes in drag forces and belt stretch, ensuring accurate image registration across multiple printheads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the belt carries media sheets through the print zone, then printing productivity is improved, but registration accuracy deteriorates due to belt stretch from friction and drag forces
Solution Approach 1:
The system dynamically adjusts printhead operation timing based on real-time drag force measurements and belt displacement calculations. The controller modifies printhead activation times to compensate for belt stretch that occurs as media sheets enter and exit the print zone, maintaining registration accuracy while allowing continuous high-speed printing operations
Solution Approach 2:
The system uses drag force sensors to measure frictional forces on the belt, feeds this information to the controller, which then calculates belt displacement and adjusts printhead timing accordingly. This closed-loop feedback mechanism compensates for registration errors caused by belt stretch without interrupting the printing process
2Stability of the object's composition
If vacuum force is applied to hold media sheets against the belt, then media stability is improved, but drag force on the belt increases causing more belt stretch
Solution Approach 1:
The system dynamically compensates for the additional belt stretch caused by vacuum forces by adjusting printhead operation timing. The controller calculates the extra displacement resulting from vacuum-induced drag and modifies printhead activation to maintain accurate registration despite the increased belt elongation
Solution Approach 2:
Drag force measurements provide feedback about the total force acting on the belt, including the component from vacuum application. The controller uses this information to calculate and compensate for the resulting belt stretch, allowing the vacuum system to maintain media stability while the printing system adapts to the induced belt length changes
3Productivity
If multiple media sheets pass through the print zone simultaneously, then productivity is improved, but drag force variation increases causing greater registration errors
Solution Approach 1:
The system dynamically adjusts printhead timing based on the number of media sheets currently in the print zone. By monitoring drag force variations that indicate sheet presence and quantity, the controller calculates corresponding belt displacement changes and modifies printhead activation times to maintain registration accuracy during high-speed multi-sheet printing
Solution Approach 2:
Drag force measurements provide real-time feedback about the number of sheets in the print zone and the resulting frictional forces. The controller uses this feedback to calculate belt stretch variations and adjust printhead operation timing, enabling accurate registration even when multiple sheets are printed simultaneously at high productivity rates
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 solution effectively reduces registration errors by precisely timing ink ejection from multiple printheads, maintaining image accuracy despite variations in belt tension and media sheet presence, thereby improving overall print quality.
Implementation Method 1
friction between the belt and other structural members of the printer in the print zone generates drag on the belt
Implementation Method 2
The belt is formed from a material having a predetermined modulus of elasticity and the belt stretches under application of a drag or tension force to the belt
Data Source
AI summary
A method of adjusting the operation of printheads in a printing system with a moving sheet carrying device has been developed. The method includes identifying a first amount of sheet carrying device displacement and second amount of sheet carrying device displacement as the sheet carrying device carries a media sheet past first and second printheads, respectively, for imaging of a predetermined location of the media sheet. A time for operating the second printhead is adjusted based on a difference between the first sheet carrying device offset and the second sheet carrying device offset to provide color registration between ink drops of the first printhead and second printhead on the media sheet.