Screen Printing Squeegee Control for Ink Buildup Prevention
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Solution Overview
Problem
In screen printing machines, unwanted ink build-up on the screen printing cylinder leads to contamination of the impression cylinder during intermediate drying, causing color build-up, damage to the screen printing form, and difficulty in ink removal, especially during the first sheet of a production run.
Innovation Solution
The squeegee is positioned to remove ink from the screen printing exterior before it distributes undesirably, and the squeegee movement is synchronized with the rotational position of the impression cylinder to reduce ink penetration and operating speeds, thereby minimizing cleaning efforts and risk of damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the screen printing cylinder is stationary during intermediate drying, then ink can be removed from the screen surface, but ink buildup and hardening occur on the outer surface of the screen
Solution Approach 1:
The doctor blade is activated before the screen printing cylinder enters the drying zone to remove ink from the outer surface of the screen in advance, preventing ink buildup and hardening that would occur if the cylinder remained stationary during drying
2Object-generated harmful factors
If the doctor blade is engaged to remove ink from the screen surface, then ink buildup is reduced, but the screen printing form can be damaged
Solution Approach 1:
The doctor blade is mechanically engaged and disengaged independently of the cylinder rotation, allowing dynamic control of the blade's contact with the screen surface to remove ink without causing damage
Solution Approach 2:
The doctor blade operates periodically - engaged during specific phases (before drying zone) to remove ink, and disengaged during other phases - creating a cyclic pattern that prevents both ink buildup and form damage
3Productivity
If intermediate drying is performed using a dryer directed at the cylinder's outer surface, then drying efficiency is improved, but ink hardens and forms peaks that damage the screen printing stencil
Solution Approach 1:
The doctor blade removes ink from the screen surface before the cylinder enters the drying zone, performing a preliminary cleaning action that prevents ink from hardening and forming peaks during the subsequent drying process
4Productivity
If the screen printing cylinder rotates at normal speed, then production efficiency is maintained, but ink distributes to undesirable areas and contaminates the impression cylinder
Solution Approach 1:
The doctor blade is disengaged during specific phases of the cycle when the cylinder is rotating, allowing the cylinder to rotate at normal speed for production efficiency while preventing ink from distributing to undesirable areas and contaminating the impression cylinder during those disengaged phases
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 approach significantly reduces the effort required for cleaning the impression cylinder and minimizes the risk of damage to the screen printing form by preventing ink build-up and contamination, while also reducing ink penetration during the printing process.
Implementation Method 1
The squeegee is positioned to remove ink from the screen printing exterior before it distributes undesirably
Implementation Method 2
intermediate drying is performed using a dryer directed at the cylinder's outer surface
Data Source
Figure 1
Figure 2a~2b
Figure 3~4
AI summary
The aim of the invention is to operate a screen-printing unit (19, 23) in a printing machine comprising a screen cylinder (18, 22) which carries a screen-printing stencil (31, 32) and in which a squeegee (34) is moved from the inside into contact with and away from the screen-printing stencil, the screen cylinder (18, 22) being moved into contact with an impression cylinder (21) such that a printing position (06, 07) is formed, and away therefrom such that a gap is formed. To this end, the screen cylinder (18, 22) is moved away from the impression cylinder (21) in a first phase when the squeegee (34) is in a non-contacting position. In a second phase, at least one sheet of printing material (02) is passed through the printing position (06, 07) when the squeegee (34) continues to be in a non-contacting position and the screen cylinder (18, 22) is at least temporarily in a contacting position, before finally, for subsequent sheets of printing material (02), in a third phase, the screen-printing unit is operated with the squeegee (34) permanently or cyclically, i.e. at least once for each sheet of printing material (02), in a contacting position.