Inkjet Printing on Curved Surfaces via Position Compensation
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Solution Overview
Problem
Inkjet printing of three-dimensionally shaped objects with curved surfaces is challenging due to positional changes during conveyance, leading to unwanted disturbances in the printed image, such as light stripes, which existing methods struggle to compensate for effectively, especially at high production speeds.
Innovation Solution
A method using two inkjet printing units with perpendicular nozzle arrays that overlap partially, where the positional change of the object is measured and compensated for by adjusting the print data and nozzle activation to ensure seamless intermeshing and minimize disturbances, with additional compensation using a piezo actuator if necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple inkjet printing units are used to print wide images, then the printing width is increased, but the object position changes during conveyance cause unwanted disturbances like light stripes in the printed image
Solution Approach 1:
The printing system is divided into multiple inkjet printing units (first printing unit and second printing unit) that print different sections of the image. Each unit has its own nozzle array that prints a portion of the complete image, allowing wide format printing while maintaining precision through individual section control and compensation.
Solution Approach 2:
A feedback mechanism is implemented where the actual position of the object during conveyance is measured and compared with the intended position. Based on this feedback, the print data for the second printing unit is dynamically adjusted to compensate for position deviations, preventing light stripes and ensuring seamless joining of printed sections.
2Productivity
If the object is conveyed faster to increase production speed, then productivity is improved, but the object experiences unwanted position changes that disrupt printing precision
Solution Approach 1:
The system performs preliminary measurements of the object's actual position during conveyance before completing the printing process. The print data for the second printing unit is pre-adjusted based on these measurements, allowing compensation for position changes even at high conveyance speeds without disrupting the printing precision.
3Manufacturing precision
If overlapping nozzle arrays are used to create seamless transitions between printed sections, then the transition smoothness is improved, but rasterized print images experience unwanted interference
Solution Approach 1:
The overlapping nozzle arrays are strategically positioned and activated only in specific local areas where seamless transitions are needed. The system selectively uses overlapping nozzles in the second printing unit's field to smooth transitions without causing interference across the entire rasterized image, applying the overlapping technique locally rather than globally.
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 method enables the generation of fault-free printed images on three-dimensional objects by accurately compensating for positional changes during conveyance, preventing unwanted disturbances like light stripes and ensuring high-quality prints even at faster production rates.
Implementation Method 1
a piezo actuator is used to adjust the position of the second inkjet printing unit (D2)
Data Source
Figure 1
Figure 2
AI summary
The method involves measuring first and second position values (H1,H2) of an object (3) at first and second positions (P1,P2) respectively. A position change of the object perpendicular to a conveying direction (5) is determined by using position values. The position change is compensated, when printing one portion (A2) of a print image (2) to other portion (A1) by essentially seamless printing by using position change of corresponding number of nozzles within an overlap region (L) of one field (F2) and complementary number of nozzles outside of overlap region.