Compensation method for defects in profile rolling and bending forming of Manhart CNC machine tools

At present, various small section profile bending machines on the market cannot process large-sized profiles, and the processed profile belly plate is unstable, wrinkled and deformed, overheated due to friction between the rollers and the profile. At the same time, due to the mechanical and material properties of the profile, there will also be problems with rebound and linear segments after processing. The progress of profile bending machines lies in solving the above-mentioned shortcomings, namely eliminating the problems of web instability and wrinkling deformation, and reducing the range of rebound through precise calculation, so as to obtain accurate curvature radius, and strictly control the problem of straight line segments at both ends.

1. Solution to radius rebound problem

A method of plastic deformation during bending forming, in which the outer fibers are shortened due to elastic recovery during unloading, while the inner fibers are elongated due to elastic recovery, resulting in significant changes in the curvature and angle of the bent part. This phenomenon is called elastic rebound. The deformation process of profiles must go through elastic deformation and then plastic deformation. Rebound is a mechanical property exhibited during material deformation, which cannot be eliminated and can only be controlled as much as possible.

Based on experience, the thicker the profile, the smaller the negotiation radius; The higher the yield stress, the greater the strain stiffness modulus, and the greater the roll bending rebound; The free bending rebound amount is large, and the corrected bending rebound amount is small; The complex shape and high degree of mutual involvement result in a small amount of rebound; Cold work hardening (when steel is processed below room temperature or recrystallization temperature, it produces strong plastic deformation, causing lattice distortion, grain shear and slip, and grain elongation. These will increase the hardness of the surface layer metal and reduce the plasticity of surface layer metal deformation, known as cold work hardening), resulting in a large amount of rebound; The profile has a large external dimension, complex cross-sectional shape, high requirements for external accuracy, and a large rebound radius after forming.

The modern manufacturing industry requires that all problems that arise during the lifecycle of production problems can be solved during the design phase. Therefore, the traditional problem of controlling springback based on experience and repeated experiments can no longer be used for rolling and bending processes. Currently, the methods for controlling springback include: establishing a neural network prediction model; Develop CNC programs to control the rebound radius; Finite Element Analysis (FEM) – Dynamic Static Joint Algorithm; Mold compensation method and over bending method. And numerical simulation analysis is also an important direction for future research on rebound amount.

2. Solving the problem of torsional deformation

During the rolling process, due to the unequal friction between the roller and the profile, the profile undergoes torsional deformation. Once torsional deformation occurs, it will cause the entire profile to deform, resulting in insufficient accuracy and inability to meet usage requirements. The solution to torsional deformation is to fix the profile, add sufficient constraints on both sides of the web and edge plates, so that their degrees of freedom are zero, and prevent any radial deformation. Because smiling torsional deformation has a great impact on the accuracy of the entire profile, the cumulative error will increase many times through the transmission of the entire profile. The most effective way at present is to increase the diameter and logarithm of the rollers.