Roll Gap Hydraulic Valve Split for Fast and Precise Positioning
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Solution Overview
Problem
Existing hydraulic control systems for roll stands in strip rolling mills face challenges in achieving high-speed, flexible rolling with precise control of the roll gap to accommodate variable thickness profiles, as they often require large position changes quickly while maintaining high accuracy.
Innovation Solution
A hydraulic arrangement featuring a first and second double-acting valve arrangement with different flow rates, where the second valve arrangement has a larger flow rate, allowing for rapid and precise control of the roll gap by dividing the stroke path into sections for high-speed and precise positioning, respectively, using a system with pressures exceeding 200 bar to achieve dynamic roll gap adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a single hydraulic valve arrangement is used for roll gap control, then the system structure is simple, but it cannot achieve both high-speed positioning and high-precision adjustment simultaneously
Solution Approach 1:
The hydraulic control system is segmented into two independent valve arrangements: a first valve arrangement with smaller nominal volume flow for precision control, and a second valve arrangement with larger nominal volume flow for high-speed positioning. This segmentation allows each valve arrangement to specialize in one function, resolving the contradiction between speed and precision.
Solution Approach 2:
The control system dynamically switches between the two valve arrangements based on the rolling process requirements. The control unit activates the second valve arrangement when rapid roll gap changes are needed, and switches to the first valve arrangement when precise positioning is required, making the system adaptable to different operational phases.
2Productivity
If a hydraulic arrangement with larger flow rate is used, then large position changes can be achieved quickly, but positioning precision deteriorates
Solution Approach 1:
The hydraulic control system is segmented into two independent valve arrangements: a first valve arrangement with smaller nominal volume flow for precision control, and a second valve arrangement with larger nominal volume flow for high-speed positioning. This segmentation allows each valve arrangement to specialize in one function, resolving the contradiction between speed and precision.
Solution Approach 2:
The second valve arrangement provides excessive flow capacity for rapid roll gap changes, while the first valve arrangement provides the precise partial action needed for final positioning. The control unit orchestrates their combined action to achieve both high productivity and high precision.
3Manufacturing precision
If a hydraulic arrangement with smaller flow rate is used, then positioning precision is improved, but the ability to achieve large position changes quickly deteriorates
Solution Approach 1:
The hydraulic control system is segmented into two independent valve arrangements: a first valve arrangement with smaller nominal volume flow for precision control, and a second valve arrangement with larger nominal volume flow for high-speed positioning. This segmentation allows each valve arrangement to specialize in one function, resolving the contradiction between speed and precision.
Solution Approach 2:
The two valve arrangements are merged into a single integrated hydraulic control system, sharing common hydraulic connections to the adjustment unit. This merging allows the system to combine the precision capability of the first valve arrangement with the speed capability of the second valve arrangement, achieving both high precision and high speed through coordinated operation.
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 highly dynamic and accurate regulation of the roll gap, supporting high-speed rolling with variable thickness profiles by allowing large position changes quickly and precise positioning, enhancing productivity in flexible rolling processes.
Implementation Method 1
a hydraulic adjustment unit for adjusting the roll gap
Implementation Method 2
a first double-acting valve arrangement for variable control of the screwdown unit and a second double-acting valve arrangement for variable control of the adjusting unit, which is connected in parallel with the first valve arrangement and has a larger flow rate rating
Data Source
Figure 1
Figure 2a~2d
Figure 3
AI summary
The invention relates to a roll stand, having at least one working roll for rolling strip material and having a hydraulic assembly for controlling a nip of the roll stand, comprising: at least one hydraulic positioning unit (1) for setting the nip (19), the hydraulic positioning unit (1) comprising a cylinder (17) and a positioning piston (2), which divides the cylinder (17) into a first chamber (3) and a second chamber (4); a first double-acting valve assembly (9) and a second double-acting valve assembly (10, 10'), which are each connected to the first chamber (3) and to the second chamber (4) in order to variably control the positioning unit (1), wherein: - the second double-acting valve assembly (10, 10') is connected in parallel with the first valve assembly (9) and has a greater nominal volumetric flow rate than the first valve assembly; and - a working pressure of greater than 200 bar can be applied to the positioning unit (1). The invention further relates to a corresponding method for controlling a nip in the rolling process.