Rotary Screen Printing Variable Speed Control
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Solution Overview
Problem
Conventional rotary screen printing systems are limited by the circumference of the printing cylinder, restricting image size and repeat length, and suffer from ink seepage issues when trying to print large or continuous designs, making it difficult to produce high-quality prints with multiple colors and large repeat lengths.
Innovation Solution
A method and apparatus using a cylindrical screen with permeable and impermeable stencil areas, where the screen rotation is controlled to suspend or reduce speed when the impermeable area is in registration with the web, allowing for extended non-printed regions and variable repeat lengths, and incorporating a squeegee mechanism to prevent ink contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the screen rotational speed is synchronized with web line-speed to maintain printing quality, then the image repeat length is limited to the screen circumference, but if the screen rotational speed is reduced to increase image size, then slip printing produces inferior quality images
Solution Approach 1:
The patent applies dynamics by making the screen rotational speed variable rather than constant. The control system dynamically adjusts the screen rotational speed based on the position of stencil areas (printing vs non-printing) to achieve both large image repeat lengths and high print quality. The screen speed is reduced during non-printing zones to extend repeat length while maintained during printing zones to ensure quality.
Solution Approach 2:
The patent changes the operational parameters of the screen rotational speed based on different operational phases. By varying the rotational speed parameter according to whether the screen is in a printing or non-printing zone, the system achieves both extended repeat lengths and maintained print quality, resolving the contradiction between these two requirements.
2Object-affected harmful factors
If the squeegee pressure is released to prevent ink seepage during non-printing zones, then ink contamination is reduced, but ink transfer to the substrate between repeats becomes difficult to prevent
Solution Approach 1:
The patent applies local quality by having different squeegee pressure levels for different zones of the screen rotation cycle. High squeegee pressure is applied during printing zones to ensure complete ink transfer, while reduced or zero pressure is applied during non-printing zones to prevent ink seepage and contamination. This localized pressure control resolves the contradiction between preventing contamination and maintaining reliable ink transfer.
Solution Approach 2:
The patent implements periodic action by cyclically varying the squeegee pressure in sync with the screen rotation. The squeegee pressure is periodically increased during printing zones and reduced during non-printing zones, creating a rhythmic pattern of high and low pressure that simultaneously achieves complete ink transfer and prevents ink seepage, resolving the reliability contradiction.
3Adaptability or versatility
If multiple print stations are used to build up large designs in stages, then the design complexity is achieved, but quality control becomes difficult and production cost increases
Solution Approach 1:
The patent applies segmentation by dividing the screen circumference into multiple independent stencil areas (printing zones and non-printing zones). Each stencil area can be independently designed and controlled, allowing complex designs to be created within a single print station. This segmentation eliminates the need for multiple print stations while maintaining design complexity and simplifying quality control.
Solution Approach 2:
The patent makes a single print station universal by enabling it to handle multiple different stencil areas and produce various design configurations within one station. The ability to incorporate multiple printing zones and variable speed control allows one print station to perform the work of multiple stations, reducing device complexity while maintaining adaptability for complex designs.
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
Enables the production of images with repeat lengths greater than the screen circumference, maintaining print quality and reducing ink contamination, suitable for large and complex designs that were previously difficult to achieve with conventional rotary screen printing.
Implementation Method 1
a screen surface with at least one permeable stencil area and at least one impermeable area
Data Source
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AI summary
Method of printing and printing apparatus whereby the repeat length is greater than the circumference of the rotary printing screen (5). This may be achieved by controlling the rotation of the screen as a non-printing zone (2) of the screen passes a moving web (w) such that an associated non-printed region formed on the screen has a length that is greater than the non-printing zone. This, in turn, may be achieved by suspending the rotation of the screen or reducing the speed of rotation when the non-printing zone is in registration with the web and then increasing the speed of rotation to a predetermined printing speed as a printing zone (1) of the screen comes into registration with the web.