Hydraulic Dancer Roll Control for Stable Strip Tension in Flexible Rolling
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Solution Overview
Problem
Existing rolling mills face challenges in maintaining constant strip tension during flexible rolling of metal strips at high speeds due to rapid changes in strip speed and thickness, leading to variations in strip thickness tolerances and limitations in coil weight and rolling speed.
Innovation Solution
An apparatus with an adjustable dancer roll, hydraulic drive, hydraulic tank, controllable valve arrangement, and hydraulic pressure accumulator is used to control strip tension, allowing for fast and accurate adjustments in strip tension by inferring hydraulic pressure and using a pulsation damper to prevent cavitation, with a displacement measuring system to adjust reel speeds and maintain optimal dancer roll position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If reel speeds are adjusted to compensate for strip speed changes, then strip tension can be maintained, but coil weight is limited and rolling speed must be reduced due to mass inertia
Solution Approach 1:
A dancer roll is introduced as an intermediary device between the reel and the rolling mill. The dancer roll absorbs strip tension variations through its vertical movement, decoupling the reel speed control from the strip tension control. This allows the reel to run at constant high speed while the dancer roll compensates for thickness variations, resolving the contradiction between high rolling speed and reliable strip tension control.
Solution Approach 2:
A hydraulic drive system with a high-response valve arrangement is used to control the dancer roll position. The hydraulic system provides fast and precise adjustment of the dancer roll to maintain constant strip tension despite rapid changes in strip speed and thickness, enabling reliable tension control at high rolling speeds.
2Manufacturing precision
If dancer roll position is adjusted to maintain constant strip tension, then strip thickness tolerances improve, but rapid speed changes cause tension fluctuations
Solution Approach 1:
The dancer roll position is dynamically adjusted in real-time based on strip thickness measurements and speed variations. The hydraulic drive system with high-response valve arrangement enables rapid position changes to compensate for speed variations, maintaining constant strip tension and improving thickness tolerances even at rapidly changing speeds.
Solution Approach 2:
A feedback control system continuously monitors strip thickness and dancer roll position, and adjusts the hydraulic drive accordingly. This closed-loop control ensures that strip tension remains constant despite rapid speed changes, improving manufacturing precision while accommodating high rolling speeds.
3Speed
If hydraulic pump delivers hydraulic fluid at high rate, then dancer roll adjusts quickly, but cavitation occurs in hydraulic lines
Solution Approach 1:
A pulsation damper is installed in the hydraulic supply line to the high-response valve arrangement. The pulsation damper pre-compresses hydraulic fluid and dampens pressure fluctuations, preventing cavitation when the valve delivers hydraulic fluid at high rates for rapid dancer roll adjustment.
4Productivity
If coil mass is increased to allow higher rolling speeds, then productivity improves, but reaction time increases due to mass inertia
Solution Approach 1:
The dancer roll acts as an intermediary that decouples the inertial mass of the coil from the strip tension control system. By using the dancer roll's vertical movement to absorb tension variations, the system can use larger coil masses for higher productivity without suffering from increased reaction time, as the dancer roll isolates the tension control from the reel's rotational inertia.
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 solution enables precise control of strip tension, reducing fluctuations below 35% and maintaining consistent strip thickness, even at high rolling speeds, by rapidly supplying hydraulic fluid and minimizing line losses and cavitation, thus improving strip thickness tolerances and reducing non-productive times.
Implementation Method 1
at least one hydraulic pressure accumulator for temporarily storing hydraulic fluid previously delivered by the hydraulic pump, the hydraulic pressure accumulator being disposed between the hydraulic pump and the valve arrangement
Implementation Method 2
The hydraulic drive is supplied with hydraulic fluid from the hydraulic tank by means of a hydraulic pump
Implementation Method 3
A controllable valve arrangement is disposed between the hydraulic tank and the hydraulic drive for controlling the hydraulic drive
Implementation Method 4
at least one hydraulic drive coupled to the dancer roll for adjusting the dancer roll
Data Source
AI summary
An apparatus for controlling a strip tension during flexible rolling of metal strip comprises a roll arrangement with at least one dancer roll, the position of said dancer roll being adjustable for controlling the strip tension of the metal strip,at least one hydraulic drive coupled to the dancer roll for adjusting the dancer roll, a hydraulic tank for hydraulic fluid, which is fluidly connected to the hydraulic drive via a hydraulic supply line, a controllable valve arrangement between the hydraulic tank and the hydraulic drive for controlling the hydraulic drive, a hydraulic pump with which the hydraulic drive is supplied with hydraulic fluid from the hydraulic tank, and at least one hydraulic pressure accumulator for temporarily storing hydraulic fluid previously delivered by the hydraulic pump, the hydraulic pressure accumulator being arranged between the hydraulic pump and the valve arrangement,wherein a pressure sensor is arranged in the hydraulic drive for determining the hydraulic pressure.