Printhead-to-platen spacing sensor for inkjet platen defect compensation
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Solution Overview
Problem
Ink-jet printing apparatuses face challenges due to platen defects such as imperfect planarity or cylindricity, which can lead to compromised print quality and potential printhead damage, requiring resource-intensive processes for defect detection and compensation that may endanger printer integrity.
Innovation Solution
A sensor mounted to the carriage measures printhead-to-platen spacing (PPS) with high precision, enabling dynamic compensation of printing fluid drop firing through a chipset module, allowing for automatic delay adjustments based on the computed PPS profile, position, and velocity to compensate for platen defects without printing on the medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional defect detection methods are used (printing a test plot, scanning, and analyzing), then platen defects can be detected, but it consumes significant resources (printing fluid, substrate, operator time) and may endanger printhead integrity
Solution Approach 1:
The patent replaces the mechanical printing-and-scanning detection system with an optical measurement system. A sensor mounted on the carriage directly measures the distance between the printhead and platen surface using optical or electromagnetic fields, eliminating the need to consume printing fluid and substrate for defect detection.
Solution Approach 2:
The patent introduces a sensor as an intermediary device between the printhead and platen. This sensor acts as a mediator that measures the spacing without requiring actual printing contact, thus preventing resource consumption and potential printhead damage while still enabling defect detection.
2Reliability
If a sensor measures PPS dynamically during carriage movement, then platen defects can be detected without printing on the medium, but the device complexity increases
Solution Approach 1:
The sensor system serves multiple functions: it measures printhead-to-platen spacing dynamically, detects platen defects, and provides data for compensation algorithms. This multi-functionality justifies the added complexity by eliminating separate testing procedures and resource consumption.
Solution Approach 2:
The system performs self-diagnosis and self-compensation. The sensor mounted on the carriage automatically measures PPS variations during normal operation, and the compensation algorithm automatically adjusts firing parameters without requiring external intervention or separate calibration procedures.
3Manufacturing precision
If printing fluid drop firing is delayed to compensate for PPS variations, then print quality improves, but the printing speed decreases
Solution Approach 1:
The patent implements dynamic compensation where the firing delay is not a fixed value but varies continuously based on real-time PPS measurements. The compensation algorithm dynamically adjusts the firing timing for each droplet based on the local spacing conditions, optimizing both print quality and throughput.
Solution Approach 2:
The system changes the firing parameter (timing delay) based on measured PPS variations. By dynamically adjusting this parameter according to actual spacing conditions, the system maintains print quality without requiring uniform speed reduction across the entire printing process.
Data Source
AI summary
In one example, an apparatus is described, which includes a platen locating the print medium, at least one printhead for marking on the print medium, a carriage holding the at least one printhead, a sensor at least partially mounted to the carriage to measure a printhead-to-platen spacing (PPS) along scanning axis during scanning, and an integrated circuit including a dynamic compensation module and a PPS analysis module to delay firing of printing fluid drops from the at least one printhead to compensate platen defects based on the measured PPS.