Servo-Driven Dandy Roll Tension Control for Bag Making
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In bag production machines for flexible packaging, the transition from continuous to intermittent film movement leads to inconsistent film tension due to varying pneumatic piston pressure, causing micro slippage and requiring manual corrections, resulting in product rejects during machine startup and speed changes.
Innovation Solution
A device with a movable dandy roll driven by a servomotor and equipped with load cells for continuous tension monitoring, using a PID controller to adjust torque and maintain constant film tension, ensuring closed-loop control and minimizing slippage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If pneumatic pistons are used to tension the dandy roll, then the film can be tensioned during forward movement and stopping phases, but the tension varies due to pressure changes in the pistons
Solution Approach 1:
A load cell is installed to continuously measure the actual tension force on the film. This measurement is fed back to a control system that adjusts the pneumatic piston pressure in real-time to maintain constant tension, compensating for pressure variations during forward movement and stopping phases.
Solution Approach 2:
The manual or open-loop pneumatic tensioning system is replaced with a closed-loop controlled system using a load cell for measurement and a control unit for automatic adjustment, transforming it from a purely mechanical system to an electromechanical feedback system.
2Speed
If the dandy roll moves rapidly to recover film during stopping phases, then the film can be accumulated, but the tension drops due to insufficient air pressure compensation
Solution Approach 1:
The load cell detects tension drops during rapid dandy roll recovery and immediately signals the control system to increase pneumatic piston pressure, maintaining constant tension even during high-speed film accumulation phases.
Solution Approach 2:
The system dynamically adjusts pneumatic pressure based on real-time tension measurements, allowing the dandy roll to operate at variable speeds during different phases (forward movement, stopping, recovery) while maintaining optimal film tension throughout the cycle.
3Productivity
If micro slippage occurs on transport calenders due to tension variation, then operations are performed on different film portions, but manual corrections are required increasing complexity
Solution Approach 1:
By continuously monitoring tension with a load cell and automatically adjusting pneumatic pressure, the system prevents micro slippage from occurring in the first place, eliminating the need for manual workstation corrections and reducing operational complexity.
Solution Approach 2:
The closed-loop control system automatically detects and corrects tension variations without human intervention, making the system self-regulating and eliminating the need for operators to manually adjust workstation positions to compensate for slippage.
4Adaptability or versatility
If product change operations are performed during startup and stopping phases, then versatility is achieved, but variable slippage causes considerable product rejects
Solution Approach 1:
During product change operations, the load cell continuously monitors tension and the control system dynamically adjusts pneumatic pressure to maintain constant tension despite speed variations, ensuring operational precision even during transient phases.
Solution Approach 2:
The system dynamically adapts pneumatic pressure during product change operations and speed transitions, maintaining optimal tension control throughout the entire operational cycle including startup, stopping, and product change 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
The solution maintains consistent film tension across the production line, reducing slippage and eliminating the need for manual corrections, thereby minimizing product rejects and ensuring reliable operation.
Implementation Method 1
at least one load cell is provided along the path of the film apt to continuously monitor the tension applied to the film
Implementation Method 2
a servomotor is provided for the movement of said dandy roll
Data Source
Figure 1
Figure 2a~2b
Figure 3
AI summary
Device (100) apt to change the forward movement of a film (12) into a machine (10) from continuous mode to intermittent mode for producing bags (1) for packaging and the like, comprising a dandy roll (20) mounted movably backwards and forwards between a feed calender (21) which operates in continuous mode and a transport calender (22) which operates in intermittent mode, the dandy roll (20) moving towards said transport calender (22) when the latter is operating, in order to feed the film (12) and moving in the opposite direction when the transport calender (22) is stopped in order to recover the input film coming from the feed calender (21), wherein a servomotor (50) is provided for the movement of said dandy roll (20), and wherein at least one load cell (55) is provided along the path of the film (12) apt to continuously monitor the tension applied to the film (12) and to instantly change the torque applied to the motor (50).