Segmented Vacuum Back-Pressure Plate for Foil Web Guidance
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Solution Overview
Problem
Flat foil printing presses face challenges in guiding and separating thin, narrow embossing foil webs and sheets without deformation or creasing, leading to poor output quality and unusable prints, especially for demanding tasks like hologram embossing on tickets and banknotes.
Innovation Solution
An evacuable back-pressure plate with integrated suction regions and switchable vacuum feed lines is used to guide and separate foil webs and sheets, ensuring precise positioning and flatness by evacuating covered suction segments and disconnecting uncovered ones, maintaining sheet flatness and preventing foil web damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a blower producing laminar airflow is used to keep the sheet flat, then the sheet can be maintained level during printing, but the foil webs become stuck to the sheet causing deformation and damage after embossing
Solution Approach 1:
The back-pressure plate is divided into multiple suction segments (first, second, third suction segments) that can be independently controlled. This segmentation allows different regions of the sheet to be held with different suction forces, enabling gentle separation of foil webs from the sheet after embossing while maintaining flatness during printing, thus resolving the contradiction between sheet stability and foil web integrity
Solution Approach 2:
The suction segments are dynamically activated and deactivated in sequence during the printing and embossing process. The suction force is applied during printing to maintain sheet flatness, then gradually reduced and switched off in reverse order after embossing to enable gentle foil web separation, transforming a static system into a dynamic one that adapts to different process stages
2Productivity
If multiple foil webs are guided simultaneously for high output, then printing productivity increases, but the guidance and positioning precision becomes more difficult to maintain without deformation and arching
Solution Approach 1:
The back-pressure plate is divided into multiple independently controllable suction segments that can apply localized support forces to different foil webs and sheet regions simultaneously. This segmentation enables precise positioning of multiple foil webs during high-speed printing while preventing deformation and arching through targeted suction forces in specific zones
Solution Approach 2:
Different suction segments can be activated with different suction forces based on local requirements. This allows the system to provide enhanced support where multiple foil webs are closely spaced or particularly vulnerable to deformation, while using minimal suction where not needed, thereby maintaining positioning precision across the entire printing width during high-productivity operation
3Stability of the object's composition
If strong suction is applied to hold the sheet flat, then sheet levelness is maintained, but the foil webs become stuck and difficult to separate after embossing
Solution Approach 1:
The back-pressure plate is segmented into multiple independently controllable suction zones. During printing, suction is applied to maintain sheet levelness. After embossing, the suction segments are deactivated in reverse order (from first to last), creating a gradual reduction in suction force that enables gentle separation of foil webs from the sheet without causing deformation or damage
Solution Approach 2:
The suction force is applied periodically in a controlled manner: activated during the printing phase to maintain sheet flatness, then systematically deactivated in sequence after embossing. This periodic application and removal of suction force in controlled stages allows the system to achieve both sheet levelness during printing and easy foil web separation after embossing
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 solution ensures error-free, level guidance of foil webs and sheets post-embossing, preventing deformation and creasing, resulting in high-quality, error-free prints and improved machine output.
Implementation Method 1
an evacuable back-pressure plate (9) with integrated suction regions and which are next to and between the embossing regions (16k), in which the foil webs (6k) run
Implementation Method 2
with switchable vacuum feed lines from a vacuum source (14), so that after the embossing, all suction segments (10i) covered by the sheet are evacuated
Data Source
AI summary
The flat foil printing press comprises an evacuable back-pressure plate (9), with suction regions (15k) which run in the sheet running direction (X) and which are next to embossing regions (16k), in which foil webs (6k) run. The suction regions are subdivided into several suction segments (10i) which are successive in the sheet running direction, and are each connected to a vacuum source (14) by way of a vacuum feed line (12i) via a vacuum switching element (13i). With the running-out of an embossed sheet (5), firstly all suction segments (10i) covered by the sheet are evacuated, and subsequently the suction segments which are no longer covered by the sheet are successively disconnected from the vacuum source. This results in an error-free separation of foil webs and sheets, for a greater picture quality and machine output.