Web Printing Sensor Counter Layer Mirror Integration
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Solution Overview
Problem
Measurement errors occur in inline web observation stations, particularly when using imaging sensors, due to air cushions formed by porous or perforated counter surfaces, which hinder accurate color value measurements and cause resistance issues as web speed increases.
Innovation Solution
Incorporating a mirror and/or background lighting on the counter layer, using a white roller as a counter support, and employing additional lighting like bright and dark field illumination, along with microporous Teflon and air flow or suction to manage the web's interaction with the counter surface, reducing the distance between the web and counter layer to improve measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a porous or perforated counter surface is used to form an air cushion, then the web can float and reduce friction, but measurement errors occur and color value measurements are hindered
Solution Approach 1:
The counter surface is divided into different functional zones: a first counter surface with porous or perforated structure for air cushion formation, and a second counter surface that is flat and non-porous for accurate measurements. This segmentation allows the system to benefit from both air cushion floating and precise measurement capabilities in different locations.
Solution Approach 2:
A mirror is introduced as an intermediary element between the sensor and the web. The mirror reflects light to enable optical measurements without requiring direct contact between the sensor and the web, thereby eliminating measurement errors caused by air cushion interference while maintaining the floating capability.
2Measurement precision
If the web is pressed against the counter surface to improve measurement quality, then color measurements improve, but friction increases and resistance occurs especially at higher web speeds
Solution Approach 1:
The counter surface is segmented into a first portion for air cushion formation and a second flat portion for measurements. This allows the web to float over most of the surface, minimizing friction, while still enabling contact-based measurements on the flat second surface when needed, thus resolving the contradiction between measurement quality and friction.
Solution Approach 2:
Mechanical contact-based measurement is replaced with optical measurement using a sensor and mirror system. This substitution eliminates the need to press the web against the counter surface for measurements, thereby reducing friction and resistance forces while maintaining or improving measurement precision.
3Measurement precision
If the distance between the web and counter layer is reduced to improve measurement quality, then spectrophotometric measurements improve, but the web offers resistance and requires overcoming Bernoulli effect
Solution Approach 1:
The counter surface is divided into zones with different properties. The flat second counter surface provides a stable reference plane for measurements, allowing the web to be positioned close to it for high-quality spectrophotometric measurements without requiring the entire surface to be in close contact, thus reducing overall resistance.
Solution Approach 2:
The mirror serves as an intermediary that enables optical measurements at a distance, reducing the need to minimize the gap between web and counter surface. This eliminates the Bernoulli effect resistance while maintaining measurement quality.
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 configuration enhances the quality of printing material examination, particularly for color measurements, by minimizing air cushion interference and reducing resistance, leading to more precise spectrophotometric and imaging sensor readings.
Implementation Method 1
The backing has a porous or perforated surface through which air is forced. As a result of this measure, an air cushion is formed on which the web slides.
Implementation Method 2
the surface of the counter layer facing the material web (4) has a mirror (34) and/or a background lighting (39)
Implementation Method 3
a mirror (34) and/or a background lighting (39)
Implementation Method 4
it can be advantageous to press the material web against a counter surface, for example with an air flow
Implementation Method 5
apply negative pressure to the side of the material web facing away from the sensor and thus suck it onto the counter layer
Implementation Method 6
Once this resistance has been overcome and the web falls below a certain distance from the counter-layer, the Bernoulli effect between the web and the counter-layer comes into play and leads to further nestling between the web and the counter-layer
Data Source
AI summary
The invention relates to a machine for printing webs of material (4), comprising a station (1, 11, 41) for monitoring the printed web of material (4), said station (1, 11, 41) including a sensor for monitoring the web of material (4) and at least one opposite layer (2, 12) for guiding the web (4). The at least one opposite layer (2, 12) is located on the side of the web facing away from the sensor (3, 13), while at least part of the surface of the opposite layer facing the web of material is made of a porous or perforated material. The machine is characterized in that the surface of the opposite layer facing the web of material (4) has a mirror (34) and/or a back light (39).