Ink-jet Printer Encoder Rubbing Detection
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Solution Overview
Problem
Ink-jet printers face challenges in accurately judging rubbing between the print head and recording medium due to defects or dirt on the linear encoder's scale, leading to erroneous velocity readings and potential damage or jamming.
Innovation Solution
The printer employs a controller that uses different threshold values for detecting abnormal positions on the encoder's scale to differentiate between actual rubbing and velocity drops caused by scale defects, allowing for accurate judgment of rubbing occurrences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single threshold value is used to detect rubbing based on carriage velocity, then the detection process is simple, but errors occur when scale defects cause false velocity readings
Solution Approach 1:
The detection process is segmented into two distinct modes: abnormal position detection (when no recording medium is present) and rubbing detection (when recording medium is present). This segmentation allows the system to use different threshold values appropriate for each mode, improving accuracy while maintaining operational simplicity through automated mode switching.
Solution Approach 2:
The system changes the velocity threshold parameter based on the operational mode. A first threshold value is used during abnormal position detection, and a second (different) threshold value is used during rubbing detection. This parameter adaptation allows accurate detection in both scenarios without compromising simplicity.
2Reliability
If the carriage velocity is monitored continuously to detect rubbing, then rubbing can be detected, but scale defects cause false positives leading to unnecessary halts
Solution Approach 1:
The system performs preliminary abnormal position detection before actual printing to pre-identify scale defects. By detecting and storing abnormal positions in advance, the system can distinguish between velocity drops caused by scale defects and those caused by actual rubbing during printing, preventing false positives and unnecessary halts.
Solution Approach 2:
The system uses feedback from the encoder to continuously monitor carriage velocity and compare it against threshold values. When velocity drops below the threshold during printing, the system checks whether the position corresponds to a previously identified abnormal position, providing feedback-based discrimination between true rubbing and false positives.
3Measurement precision
If a lower threshold value is used to account for scale defects, then false positives are reduced, but actual rubbing may go undetected
Solution Approach 1:
The threshold value is dynamic rather than static, changing based on the operational context. The system automatically selects between a first threshold value (for abnormal position detection) and a second threshold value (for rubbing detection) based on whether a recording medium is present, allowing optimal sensitivity for each scenario.
Solution Approach 2:
Different threshold values are applied to different operational conditions. The first threshold is optimized for detecting scale defects during abnormal position detection, while the second threshold is optimized for detecting actual rubbing during printing. This local optimization ensures both accuracy and sensitivity without compromise.
Data Source
AI summary
There is provided an ink-jet printer which includes a head, a carriage, an encoder having a scale and a sensor, a memory, and a controller. The controller executes judging whether or not a recording medium is positioned at an area that can face the carriage, and detecting an abnormal position, and printing an image on a recording medium, and comparing a velocity parameter value acquired and a first threshold value, when the carriage is at a position other than the abnormal position, and comparing the velocity parameter value acquired and a second threshold value corresponding to a velocity slower than the first threshold value, when the carriage is at the abnormal position.