Thermal Head Control for Printing Density Stability
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Solution Overview
Problem
Conventional printing devices experience issues with printing density variations and slackness in the ink ribbon due to changes in motor rotation speed and unstable back tension during high-speed printing, leading to suboptimal printing quality.
Innovation Solution
A printing device with a control system that monitors mark detection sensors to synchronize the movement and heating of the thermal head with the conveyance of the intermediate transfer film and ink ribbon, ensuring continuous conveyance and stable tension, even after reaching the printing start position, thus preventing shifts in the printing start position and maintaining consistent tension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the conveying of the intermediate transfer film and ink ribbon is temporarily halted for positioning, then the printing start position alignment is improved, but the back tension becomes unstable and slackness develops in the ink ribbon
Solution Approach 1:
The system performs preliminary positioning of the intermediate transfer film and ink ribbon before printing, using mark detection to align materials in advance. This allows the conveying to be temporarily halted only long enough for precise positioning, after which continuous conveying resumes to maintain stable back tension during the actual printing process.
Solution Approach 2:
The system uses mark detection sensors to provide feedback on the positions of the intermediate transfer film and ink ribbon. This feedback enables the control system to adjust conveying speeds and timing to achieve precise printing start position alignment while minimizing halts, thereby maintaining more stable back tension throughout the printing process.
2Productivity
If the printing speed is increased, then the productivity is improved, but the printing density becomes uneven due to motor acceleration effects
Solution Approach 1:
The system dynamically adjusts the motor speed profile during printing operations. At high printing speeds, the motor undergoes brief acceleration periods, but the system compensates by adjusting the thermal head heating timing and duration to account for speed variations. This dynamic adjustment ensures uniform printing density even when operating at high productivity levels.
Solution Approach 2:
The system changes operational parameters such as thermal head temperature, heating duration, and conveying speed in real-time based on the motor's acceleration state. When the motor accelerates during high-speed printing, the system adjusts these parameters to compensate, maintaining consistent printing density across the entire print medium.
3Manufacturing precision
If the thermal head is pressed against the platen roller, then the image transfer quality is improved, but the printing start position shifts due to trajectory changes
Solution Approach 1:
The system performs preliminary positioning of the intermediate transfer film and ink ribbon using mark detection before the thermal head is pressed against the platen roller. This advance positioning accounts for the trajectory changes that will occur when pressure is applied, ensuring that the printing start position remains accurate even after the thermal head contact.
Solution Approach 2:
The mark detection sensors provide continuous feedback on the positions of the intermediate transfer film and ink ribbon. When the thermal head is pressed against the platen roller, this feedback enables real-time detection of any position shifts, allowing the control system to compensate and maintain accurate printing start positioning despite trajectory changes.
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
This approach stabilizes the conveyance speed and tension, preventing printing density variations and improving overall printing quality by ensuring continuous conveyance and stable back tension during high-speed printing.
Implementation Method 1
heating elements that are included in the thermal head are selectively heated, and concurrently, the intermediate transfer film and the ink ribbon are conveyed, to form an image on the intermediate transfer film
Data Source
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AI summary
The present invention provides a printing device which provides high printing quality. The printing device includes: an image forming section which has a thermal head 9 and a platen roller 12; a media conveyance section for conveying an intermediate transfer film F; a ribbon conveyance section for conveying an ink ribbon R; a sensor 10 for detecting a first mark formed on the film F; and a control section for controlling the image forming section, the media conveyance section, and the ribbon conveyance section in accordance with output information from the sensor 10. The control section presses the head 9 into contact with the roller 12 when the first mark is not detected, which is when the first mark is further upstream than the position of the sensor 10, while the film F and the ribbon R are being conveyed, and selectively heats a heating element formed in the head 9 when the film F is positioned in the printing start position, which is a state in which the first mark is detected when the first mark is further downstream than the position of the sensor 10.