Stretch-Bending Straightening with Limited Free Strip Length
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Solution Overview
Problem
Conventional stretch-bend straightening methods often fail to completely eliminate waviness and residual bending moments in metal strips, leading to undesirable plastic residual curvatures due to large distances between straightening rollers, which can result in elastic longitudinal waviness and the 'towel effect', especially in thin strips under high tensile stress.
Innovation Solution
The method involves adjusting the straightening rollers relative to deflection rollers to minimize the free strip length between them, ensuring that the distance between straightening rollers can be large without causing longitudinal waviness, by moving the straightening rollers tangentially or pivoting them along the deflection rollers' circumference, and using deflection rollers with significantly larger diameters to only provide an elastic effect, thus maintaining optimal flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the distance between straightening rollers is increased, then the elimination of residual bending moments is improved, but elastic longitudinal waviness develops in the strip
Solution Approach 1:
A deflection roller with larger diameter is introduced as an intermediary element between the straightening rollers. This deflection roller has a significantly larger diameter than the straightening rollers and serves to guide the strip while minimizing elastic deformation. The deflection roller acts as a mediator that allows the strip to transition between straightening rollers without developing longitudinal waviness, thus resolving the contradiction between eliminating residual bending moments and preventing elastic longitudinal waviness.
Solution Approach 2:
The diameter of the deflection roller is changed to be significantly larger than that of the straightening rollers. This parameter change ensures that the deflection roller primarily exerts an elastic effect on the strip without causing significant plastic deformation. By adjusting the diameter parameter, the system achieves optimal balance between straightening effectiveness and prevention of longitudinal waviness.
2Adaptability or versatility
If the free strip length between deflection roller and straightening roller is increased, then the adjustment range of straightening rollers is improved, but longitudinal waviness develops
Solution Approach 1:
The straightening rollers are made adjustable relative to the deflection roller, allowing dynamic modification of the free strip length. This dynamic adjustment capability enables the system to adapt to different strip conditions and processing requirements while maintaining the free strip length within limits that prevent longitudinal waviness. The adjustability provides versatility without sacrificing stability.
3Reliability
If deflection rollers with larger diameters are used, then the elastic effect is enhanced, but the device complexity increases
Solution Approach 1:
The deflection rollers are designed with locally differentiated properties - they have significantly larger diameters than the straightening rollers, creating a local quality difference. This local quality enhancement at specific positions (where deflection rollers are placed) optimizes the elastic effect precisely where needed, without requiring all rollers in the system to be complex or oversized. The complexity is localized and justified by the functional benefit.
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 allows for large distances between straightening rollers without inducing elastic longitudinal waviness, ensuring low or complete elimination of residual waviness and achieving optimal flatness in metal strips, even when processing strips of different thicknesses and widths.
Implementation Method 1
the strip is alternately bent around the straightening rollers and thereby undergoes plastic stretching
Implementation Method 2
the strip, which is under a tensile stress below the elastic limit, is bent alternately around the straightening rollers and thereby undergoes plastic stretching
Implementation Method 3
deflection rollers which have a significantly larger diameter than the straightening rollers and usually only have an elastic effect
Data Source
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AI summary
The invention relates to a method and stretch-bending straightener for straightening metal strips (1) by stretch-bending, comprising a plurality of straightening rolls (5a, 6a, 7a, 8a) which are arranged behind one another in the strip flow direction (D) and spaced from one another in the strip flow direction (D), wherein the strip (1) subject to tensile stress below the limit of elasticity is alternately bent around the straightening rolls (5a, 6a, 7a, 8a), undergoing plastic elongation, wherein a deflecting roll (5b, 6b, 7b) is arranged upstream of one or more straightening rolls (5a, 6a, 7a), respectively, wherein said straightening rolls can be adjusted relative to the strip (1) and wherein said deflecting roll has a larger diameter than the respective downstream straightening roll. Said method and said system are characterized in that, in order to vary the immersion depth, the straightening rolls (5a, 6a, 7a) can be adjusted relative to the associated deflecting roll (5b, 6b, 7a) such that the free strip length (F) between the run-off point (9) of the strip (1) from the deflecting roll to the run-on point (10) of the strip (1) onto the associated straightening roll does not exceed a predefined maximum value, above which longitudinal undulations of the strip form. The system is preferably designed such that, as the immersion depth and/or the angle of contact are varied, the free strip length never exceeds the maximum value over the entire adjusting range.