Dual-Surface Printing Apparatus Mark Alignment
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Solution Overview
Problem
Conventional printing technologies face accuracy issues when overprinting on the back surface of sheets due to variations in the position of pre-printed marks, leading to inconsistencies between the front and back surfaces.
Innovation Solution
A printing apparatus with sensors and print heads on both surfaces that detect and align pre-printed marks to determine precise print positions, ensuring accurate placement of images on both the front and back surfaces by using a transport mechanism and determining units to align and print marks accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single sensor is used to detect pre-printed marks for overprinting, then the device complexity is reduced, but the printing accuracy on the back surface varies depending on the position of pre-printed marks
Solution Approach 1:
The patent divides the detection function into two separate sensors: a first sensor for detecting pre-printed marks on the front surface and a second sensor for detecting printed marks on the back surface. This segmentation allows each sensor to independently detect marks at their respective positions, eliminating the accuracy variations that occur when a single sensor must detect both front and back surface marks.
2Ease of operation
If printing is performed based on the position of the latter mark in transport direction, then the printing process is simplified, but position accuracy varies between front and back surface printing
Solution Approach 1:
The patent implements a feedback mechanism where the second sensor detects the position of marks on the back surface and feeds this information back to the control unit. The control unit then adjusts the printing position based on this feedback, ensuring that the printed image on the back surface is accurately positioned relative to the pre-printed marks, regardless of transport variations.
Solution Approach 2:
The system performs preliminary detection of mark positions on both front and back surfaces before final printing. The first sensor detects pre-printed marks on the front surface, and the second sensor detects these marks after they are printed on the back surface. This preliminary detection allows the system to pre-calculate the correct printing positions, maintaining accuracy without complex real-time adjustments.
3Adaptability or versatility
If the order of pre-printed marks and printing start marks is reversed between different paper configurations, then the system must handle multiple positioning scenarios, but this increases the complexity of maintaining consistent printing accuracy
Solution Approach 1:
The patent creates a universal positioning system where the second sensor can detect marks regardless of their position on the back surface. The control unit universally applies the same detection and calculation logic whether the pre-printed mark is at the leading end or trailing end of the paper. This multi-functional approach allows the system to handle different paper configurations without requiring separate control logic for each scenario.
Data Source
AI summary
A printing apparatus includes: a mechanism transporting a print medium; a first sensor outputting a signal indicating the presence or absence of a first mark; a first determining unit determining, on a first surface, a position of a second mark and a print position of an image based on the output signal; a first print head printing the second mark and the image at the determined print positions; a second sensor outputting a signal indicating the presence or absence of the first and second marks; a second determining unit locating a position of a predetermined one of the first and second marks, based on the signal output from the second sensor, and determines, on a second surface of the print medium, a print position of a target image based on the located position of the predetermined mark; and a second print head printing the target image at the determined print position.