Why do sheet metals need leveling?
Under the condition of relatively large elastic-plastic bending, no matter how different the original bending degree is, the remaining bending degree difference after springback will be significantly reduced, and even tend to be the same. As the degree of repeated bending decreases, the residual bending after springback will inevitably approach zero to achieve the purpose of correction. The roller-type steel plate leveler is mainly used for straightening various specifications of plates, using the “Bauschinger effect” of the material to repeatedly bend the plates, gradually reducing the bending deflection, and gradually changing various original curvatures into a single curvature. And finally level it to achieve the leveling accuracy required by the process.
Leveling machines to improve the quality of sheet metal (relief of stress from the material)
To relieve stress in the material, the sheet is leveled. The basic principle of roll leveling is the selective extension of parts of the material. Below the yield point of the material, the shorter portions of the “fibers” of the sheet are stretched proportionally to obtain a consistent “fiber” length. Its realization is to make the material bend up and down cyclically with a smaller radius of curvature when passing through the leveling machine, so that the shorter material “fiber” is elongated. When the sheet moves toward the exit of the leveling machine tool, the amplitude of the up and down bending gradually decreases to eliminate the material deformation caused by the severe bending at the leveling entrance of the machine tool. A board is straight, or “leveled,” when all the “fibers” in the material are approximately the same length.
In order to obtain a satisfactory leveling effect, the most important thing is to choose a suitable leveling machine tool according to the processing task to be completed. In most cases, the plate that needs to be leveled starts with coil handling, and the leveler is an important part of the entire material handling line. The simplest machine tool is the flattener, which has a small number of leveling rolls and a large diameter without any support rolls. But in order to obtain higher flatness, small-diameter leveling rolls, smaller roll spacing and good support of the support rolls to the leveling rolls are essential. Therefore, simple flattening machines cannot deform the material sufficiently enough to achieve good flatness and are therefore not widely used.
What is a leveler?
The roller leveling machine is a commonly used equipment in plate processing. The finalization of the leveling machine mainly depends on the thickness, material and requirements of the strip to be calibrated. The thicker the material, the better the structural rigidity, the fewer the number of rolls, the larger the roll diameter, and the greater the power (width), and vice versa.
The leveling machine is mainly used for straightening plates of various specifications and plates cut into blocks. This machine is suitable for leveling various cold and hot rolled plates. Because of its convenient and simple operation, it is widely used in many industries such as machinery, metallurgy, building materials, chemical industry, electronics, electric power, light industry, etc., especially in shipbuilding, rolling stock, boiler bridges, metal structure factories and other industries. necessary products.
Types of sheet metal leveling process
There are many methods for thin plate correction, mainly including pressure leveling, tension leveling and roller leveling. Among them, roller correction is the most widely used. It has high production efficiency and almost gets rid of manual labor.
In the roller leveling machine, the pitch, diameter and number of rollers of the roller shaft are important conditions to ensure the leveling quality of the plate. Under the condition of strength permitting, selecting small-diameter rollers, reducing the pitch and increasing the number of rollers can increase the tension of the sheet, increase the number of reciprocating deformations of the sheet, and achieve higher leveling quality.
The sheet metal passes between the two rows of cross-arranged rollers of the multi-roller leveling machine, and each part of it is bent repeatedly and in the opposite direction under the stress exceeding its material yield point, eliminating the stress on the sheet metal In corrugated deformation, the sheet emerges from the machine either flat or with only a uniform, slight curvature over the entire length of the sheet.
Leveling machine structure
Combining some experience in the design of the leveling machine and some structural forms of the current leveling machine, a simple analysis and introduction of its function and function is made. I hope that it can be used for reference when designing and using the leveling machine.
The leveling machine is generally equipped with 5 to 11 large-diameter work rolls, whose shaft ends are supported by bearings, and generally do not have a driving device. The leveling machine can straighten the board and generate secondary bending force.
Simple structure, requiring large diameter rollers. Since only two ends are supported, as the deflection increases during operation, the center of the roller shaft will be deflected, causing the edge of the plate to deform. It is generally used for leveling thick sheets and coils with small width.
Open leveler with paired guide rollers and adjustable top roller
This leveling machine adds two pairs of guide rollers to the model. The peripheral speed of the feeding guide roller is lower than that of the shaping roller, so during the shaping process, the sheet is tensioned between the guiding roller and the shaping roller, which will straighten the large creases on the sheet and produce The peripheral speed of the material guide roller is equal to or slightly greater than that of the shaping roller. When the shaping roller has slippage, the pair of guide rollers can prevent the sheet material between them from creases.
The structure of this leveling machine is similar to that of an open leveling machine, with added guide rollers and a driving device. The shaping rollers can adjust the inclination of the upper roller row along the shaping direction, so it can greatly improve the efficiency of thin plate shaping. quality. It is generally used for thin plate shaping with a plate thickness of 4.5~ or less.
Enclosed leveler with support
The work rolls of this leveling machine have a small diameter and a small spacing. Usually, there are 11 to 19 roll shafts (the number of which increases as the thickness of the plate decreases). The roll shafts are also equipped with pinch wheels to prevent the roll shaft from out of shape. Work rolls are generally driven.
Since the work rolls are supported by pinch wheels, the deflection of the work rolls under load can be effectively reduced. It is generally used for horizontal straightening of plates and thickness correction of narrower plates. Since the deflection of the correction roller cannot be controlled over the entire length, the edge wavy deformation and central deformation of the plate will cause differences in the transverse length of the plate. It is necessary to extend the center or edge of the plate to control the plate in the entire transverse direction. When the plate is consistent, its function is Can not support.