Print Head Frame Control for Thermal Expansion Compensation
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Solution Overview
Problem
Thermal expansion of the frame supporting print head arrays in ink jet print systems leads to varying distances between nozzle rows, compromising print resolution, especially when multiple nozzle rows are present, and existing solutions like thermally stable constructions are costly.
Innovation Solution
Incorporating a third sensor connected to one of the frame sensors via an element with minimal thermal expansion, such as invar or carbon fiber, to measure and compensate for frame expansion, ensuring accurate print resolution by adjusting timing control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional frame material is used, then the frame is cost-effective and easy to manufacture, but thermal expansion causes varying distances between print head arrays, compromising print resolution
Solution Approach 1:
A third sensor is introduced as an intermediary reference point connected to the frame via an element with minimal thermal expansion. This sensor mediates between the frame's thermal expansion and the measurement system, providing a stable reference for calculating expansion compensation without requiring the entire frame structure to be thermally stable.
Solution Approach 2:
The system dynamically changes the timing parameters of ink drop generation based on measured thermal expansion. By adjusting the timing control signals according to the derived expansion amount, the system compensates for frame expansion and maintains consistent print resolution despite temperature variations.
2Manufacturing precision
If thermally stable construction materials like carbon fibre reinforced beams are used, then print resolution is maintained, but the solution becomes rather expensive
Solution Approach 1:
Instead of making the entire frame thermally stable, the invention applies thermal stability locally only where needed - in the connection element between the frame and the third sensor. This localized approach uses expensive low-expansion material only for the critical measurement reference, while the rest of the frame can use conventional, cost-effective materials.
3Productivity
If the number of nozzle rows is increased, then more colors can be printed simultaneously, but thermal expansion causes varying distances between nozzle rows, affecting registration accuracy
Solution Approach 1:
The system uses feedback from the third sensor to continuously monitor frame expansion and adjusts the timing control signals accordingly. This feedback mechanism ensures that registration accuracy is maintained across multiple nozzle rows despite thermal expansion, allowing high productivity without sacrificing precision.
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
Maintains fixed print resolution despite thermal expansion of the frame, providing precise ink drop placement and registration across multiple nozzle rows.
Implementation Method 1
Due to changes in environment temperature, the distance between print head arrays may vary due to thermal expansion of the frame
Implementation Method 2
a third sensor connected to one of the said two sensors by an element with virtually no thermal expansion
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a print system comprising at least two page-wide arrays of ink jet print heads, positioned in a frame (40) over a conveyor belt (25) for transporting a substrate (20) underneath the arrays, three sensors (41, 42, 43) for reading markers on the conveyor belt and a control unit (50) that is configured to derive control signals from encoder signals of the three sensors. Two sensors (41, 42) are directly connected to the frame and a third sensor (43) is connected to one of the said two sensors by an element with virtually no thermal expansion, extending in transport direction. The control signals, comprising signals for controlling a transport speed of the conveyor belt and line pulses for the at least two print heads, are derived in such a way that an amount of thermal expansion of the frame is determined and an absolute print resolution is maintained.