Formless Printing Device Sheet Feeder Coding
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Solution Overview
Problem
In sheet-fed printing presses, printing devices without a printing form face challenges in maintaining print quality due to sheet rigidity issues, where printed sheets tend to lift and change distance, leading to inconsistent printing and potential marks from guide rollers, limiting the print area and quality.
Innovation Solution
Integrating printing devices without a printing form into the sheet feeder area, allowing for selective encoding from the top or underside, with sensors for presence and color detection, and controlled activation to ensure accurate positioning and quality, using inkjet or laser printing heads that can print over the entire format width and length without guide rollers, and allowing for flexible installation positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If printing devices without a printing form are arranged in the printing nip area, then printing can be performed on freshly printed sheets, but sheet guide rollers are required which leave marks on the sheet surface and impair print quality
Solution Approach 1:
The printing device is extracted from the printing nip area and relocated to the sheet feeder area, eliminating the need for sheet guide rollers that cause marks on the sheet surface while maintaining the capability to print on freshly printed sheets
Solution Approach 2:
A sheet support surface is introduced as an intermediary element in the sheet feeder area to hold and position sheets during printing, replacing the problematic sheet guide rollers that were previously necessary in the printing nip area
2Measurement precision
If sheet guide rollers are used to fix printed sheets on the impression cylinder, then sheet positioning is improved, but the guide rollers cover areas of the printed sheets and prevent printing over the entire format width
Solution Approach 1:
Sheet guide rollers are completely removed from the system. Instead, sheets are positioned on a sheet support surface in the sheet feeder area using alternative positioning mechanisms that do not cover the printable area
Solution Approach 2:
The printing operation is moved from the vertical printing nip area to the horizontal sheet feeder area, allowing sheets to be positioned and printed upon without the interference of vertical guide rollers that blocked the printable surface
3Productivity
If the printing formeless printing device is arranged in the printing nip area, then printing can be performed, but printed sheets tend to shoot up after leaving the printing nip causing sudden distance changes and inconsistent print quality
Solution Approach 1:
Printing is performed in advance in the sheet feeder area before sheets enter the printing nip, where sheets are stable and properly supported. This preliminary printing action ensures consistent quality without the sheets shooting up afterward
Solution Approach 2:
The printing function is copied to the sheet feeder area, creating a redundant printing capability that operates in a more favorable environment with stable sheet positioning, eliminating the quality inconsistencies caused by sheet movement in the printing nip area
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 reliable, flexible, and high-quality coding of printed sheets across the entire format, maintaining print quality by ensuring consistent sheet alignment and avoiding guide roller marks, with sensors ensuring accurate activation and positioning.
Implementation Method 1
inkjet print head working according to the so-called continuous inkjet principle
Implementation Method 2
drop-on-demand inkjet principle
Implementation Method 3
thermal inkjet principle
Implementation Method 4
sensors which detect the front and side edges of the printed sheet
Data Source
Figure 1
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AI summary
The invention relates to a sheet-fed press (10) comprising a sheet feeding device (11) for introducing sheets that are to be printed into the sheet-fed press, at least one printing unit (12) and/or coating unit (13) for printing the sheets with a static printed image that is identical for all sheets, a discharging mechanism (14) for discharging printed sheets from the sheet-fed press, and at least one printing device (1) which includes no printing form and is integrated into the sheet-fed press (10) to print the sheets with an especially dynamic, variable printed image. According to the invention, the printing device (1) is integrated in the region of a supply strip (19) in the sheet-fed press (10) which guides a stream of products to the first of the printing units (12).