Rotary Encoder Support Point Repositioning for Cylinder Synchronization
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Solution Overview
Problem
In offset printing presses with individual cylinder drives, synchronization issues arise during pivoting movements, leading to relative movements and torque disruptions between cylinder surfaces, causing image blurring and vibrations due to unaccounted translational movements and control lag errors.
Innovation Solution
The solution involves repositioning the rotary encoder support point on the blanket cylinder to compensate for control-related asynchronous rotation angles by using alternative encoder support points that account for the swivel geometry and pivoting movement, allowing for precise synchronization and correction of rotational angles between the plate and blanket cylinders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the blanket cylinder is pivoted into the print-on position, then the cylinder surfaces come into contact for printing, but control lag errors cause asynchronous rotation angles leading to slippage and image blurring
Solution Approach 1:
The system performs preliminary synchronization calculations and prepares correction values before the actual pivoting operation begins. The control system pre-computes the required rotation angle corrections based on the planned pivoting movement, so that when the cylinders make contact, they are already synchronized to the required precision, eliminating slippage and image blurring.
Solution Approach 2:
The system continuously monitors the actual rotation angles of both the blanket cylinder and plate cylinder during pivoting, compares them with the target synchronized positions, and dynamically adjusts the individual drive of the plate cylinder to compensate for any deviations. This closed-loop feedback ensures that even with control lag, the cylinders maintain synchronous rotation and prevent slippage at the contact point.
2Productivity
If the blanket cylinder pivots quickly to reduce setup time, then productivity increases, but synchronization precision deteriorates causing torque disruptions and vibrations
Solution Approach 1:
The control system dynamically adapts the synchronization correction based on the actual pivoting speed and acceleration profile. During fast pivoting movements, the system calculates and applies larger correction values to compensate for the increased control lag and inertial effects. The correction factor is not static but varies dynamically with the motion state, allowing high-speed operation while maintaining angular position accuracy and preventing torque disruptions.
Solution Approach 2:
The system changes the control parameters (correction angle values, feedback gains, prediction horizons) based on the detected pivoting phase and speed. During rapid pivoting, different control parameters are applied compared to slow, steady-state operation. This allows the system to maintain precision across a wide range of operating speeds, enabling high productivity without sacrificing synchronization accuracy.
3Measurement precision
If additional position encoders are installed to detect translational movement, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The system uses the existing rotary encoder on the blanket cylinder shaft as an intermediary to indirectly measure the translational movement of the cylinder axis. By calculating the relationship between the rotation detected by the encoder and the corresponding translational displacement during pivoting, the system derives the translational position information without needing additional encoders. This mathematical modeling approach converts rotational measurements into translational position data, maintaining measurement precision while avoiding additional hardware complexity.
Solution Approach 2:
The system replaces the need for additional mechanical position sensors with a computational approach. Instead of physically measuring translational movement with extra encoders, the system uses mathematical models and control algorithms to calculate the translational position from the rotation data already provided by the existing encoder. This substitution of mechanical measurement with computational derivation reduces device complexity and cost while maintaining the required measurement precision for synchronization.
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 reliably minimizes position errors during pivoting, ensuring synchronized rotation and reducing pressure disturbances, thereby maintaining image quality and preventing blurring and vibrations.
Implementation Method 1
rotary encoders are arranged in the drive wheel train, which specify the desired rotary angle values for controlling the individual drives
Implementation Method 2
repositioning the rotary encoder support point on the blanket cylinder to compensate for control-related asynchronous rotation angles by using alternative encoder support points that account for the swivel geometry and pivoting movement
Implementation Method 3
The synchronous rotation of the adjacent cylinders is intended to ensure that the cylinder surfaces always roll off one another without slipping
Implementation Method 4
The plate cylinder is caused to rotate on the one hand by the frictional surface contact between the rubber and the printing plate
Data Source
Figure 1
AI summary
The method involves compensating a regulation-related lag by a contouring error between a target rotation angle position and an actual rotation angle position of a plate cylinder (1) during swiveling of a rubber cylinder (2) to the cylinder (1). The cylinder (2) is swiveled by shifting a transmitter support point (8.1) from another point (8.0), which provides a rotation angle-asynchronicity of the engaged cylinder (2) without considering regulating errors. The lag is compensated such that cylinder surfaces are separated from each other at a moment of touching in a synchronous position. An independent claim is also included for an arrangement for a turning angle transmitter.