Encoder Pulse Delay Adjustment for Inkjet Registration
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Solution Overview
Problem
Commercial inkjet printing systems face challenges in maintaining accurate color-to-color registration and print swath stitching due to variables like physical properties of the print medium, conveyance methods, ink application, and drying processes, leading to registration errors and stitching issues.
Innovation Solution
A method is introduced that adjusts the encoder pulse count delay in a printing system by determining the initial and subsequent ratios of encoder pulse rates from first and second encoders, using a processor to calculate an adjusted pulse count delay, and controlling printheads accordingly to compensate for drift and thermal changes, thereby improving registration and stitching accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the print medium is physically transported through the printing system at a high rate of speed, then productivity is improved, but manufacturing precision deteriorates due to registration errors and stitching errors
Solution Approach 1:
The system uses encoders to continuously monitor the actual position and speed of the print medium, feeding this information back to the control system. The control system then adjusts the encoder pulse count delay dynamically to compensate for variations in transport speed, maintaining accurate registration between color planes even at high transport rates
Solution Approach 2:
The invention changes the parameter of encoder pulse count delay dynamically based on measured transport conditions. By adjusting this timing parameter in response to actual encoder feedback, the system maintains precision across varying productivity levels
2Productivity
If the print medium is physically transported through the printing system at a high rate of speed, then productivity is improved, but manufacturing precision deteriorates due to stitching errors between print swaths
Solution Approach 1:
Encoders provide continuous feedback on the position of the print medium as it passes through different printhead stations. This feedback enables the control system to calculate and adjust the encoder pulse count delay for each downstream printhead, ensuring that print swaths from multiple jetting modules are stitched together accurately even at high transport speeds
3Manufacturing precision
If encoder pulse rate drift occurs due to thermal changes, then reliability deteriorates, but manufacturing precision can be maintained through adjustment
Solution Approach 1:
The system continuously monitors encoder pulse rates and compares them against expected values. When drift is detected (indicating thermal expansion or contraction of the encoder roller), the control system automatically adjusts the encoder pulse count delay to compensate, maintaining registration accuracy despite changes in encoder reliability
Solution Approach 2:
The system performs self-correction by automatically detecting encoder drift through pulse rate monitoring and adjusting its own timing parameters without external intervention. This self-service capability maintains precision even when environmental conditions affect encoder stability
Data Source
AI summary
A method for adjusting an encoder pulse count delay in a printing system for printing on a continuous web of print media using first and second printheads. First and second encoders are provided at different positions along the media transport path. An initial encoder pulse count delay is provided for use in printing with the second printhead. An initial ratio of the first encoder pulse rate to the second encoder pulse rate is determined. At a subsequent time a subsequent ratio of the first encoder pulse rate to the second encoder pulse rate is determined. An adjusted encoder pulse count delay is determined by adjusting the initial encoder pulse count delay responsive to the initial ratio and the subsequent ratio and used to control printing by the second printhead.