Roll Gap Control for Wedge Strip Flatness
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Solution Overview
Problem
Existing rolling mill technologies face challenges in maintaining optimal flatness when rolling strips with asymmetric thickness profiles, leading to flatness errors and material rejection, especially when dealing with wedge-shaped strips where one side is thicker than the other.
Innovation Solution
A method that controls the roll gap by ensuring a constant relative reduction across the width of the strip, using information on the wedge shape in the strip thickness profile to adjust the actuators on both sides of the rolling mill independently, thereby minimizing flatness errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the roll gap is adjusted to maintain constant thickness reduction across the strip width, then the thickness control is simplified, but asymmetric flatness errors occur when rolling wedge-shaped strips
Solution Approach 1:
The patent applies asymmetry by differentiating the control approach for operator side and drive side actuators based on the detected wedge shape. When a wedge shape is detected, the system applies different roll gap adjustments to each side rather than symmetric adjustments, allowing the thicker side to receive different treatment than the thinner side to compensate for the thickness variation and maintain flatness.
Solution Approach 2:
The system performs preliminary detection of the strip thickness profile and wedge shape before rolling begins. This advance information allows the control system to pre-calculate the appropriate asymmetric roll gap adjustments for both operator and drive side actuators, preventing flatness errors rather than correcting them after they occur.
2Device complexity
If symmetric thickness corrections are applied to both sides of the mill, then the control system is simplified, but flatness errors occur in wedge-shaped strips
Solution Approach 1:
The patent eliminates flatness errors in wedge-shaped strips by implementing asymmetric control where the operator side and drive side actuators are controlled differently based on the detected wedge shape. The control system calculates and applies different roll gap adjustments to each side, matching the asymmetric nature of the wedge-shaped material to prevent flatness defects.
Solution Approach 2:
The system uses feedback from thickness profile detection to dynamically adjust the control strategy. When a wedge shape is detected, the feedback triggers asymmetric roll gap control; when no wedge shape is present, symmetric control can be used. This feedback mechanism allows the system to adapt its complexity to the actual material conditions.
Data Source
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AI summary
The invention relates to a method and a device for controlling a roll gap when rolling a strip (1) in a rolling mill including at least two rolls (3a-b,4a-b), and at least two roll gap actuators (6,7) that independently control the size of the roll gap. The device is adapted to receive information on the amount of wedge shape (POSactOS, POSactDS) in the strip thickness profile across the strip width, and to control said actuators, based on said information on the amount of wedge shape in the strip thickness profile, such that the relative reduction of the strip on both sides of the rolling mill become essentially the same.