The roll bending method is also one of the widely used bending processes. There are various forms such as three-roll bending, four-roll bending, and six-roll bending. The principle is shown in Figure 1.
Taking three-roll bending as an example, the specific operation method of this process is to place the profile between the rollers arranged in a zigzag, and the friction force generated when the rollers rotate drives the profile to move and bend it into a certain shape. During the process, the rollers rotate back and forth multiple times to obtain uniform plastic deformation and bending radius of the curved profile.
The relative position between the rollers determines the difference in the bending moment and also determines the curvature of the bent profile.
3-roll and 4-roll bending rolls
The principle of four-roll bending is the same as that of three-roll bending, but compared with three-roll bending, the existence of the fourth roll improves the bending accuracy of profiles and reduces the occurrence of section deformation, so it is more suitable for bending thin-walled profiles.
For the bending of profiles with special-shaped sections, the contour of the roller can be processed to be consistent with the shape of the contact part of the profile, which is conducive to supporting the profile during bending, ensuring that the section of the profile does not deform during bending, and improving the bending quality. The type roller is shown in the bottom right of Figure 2.
Pros and Cons
Compared with the above two methods, different mold requirements are required when obtaining profiles with different bending angles and curvatures. This process has an obvious advantage, that is, only the relative position between the rollers needs to be adjusted, which saves time, and Production costs are reduced. This process also has its disadvantages, that is, the profile will have straight sides after bending, that is, there is a section at the front and rear ends of the profile that cannot be bent, and the length of this section depends on the distance from the center roller to the two side rollers. The shortcoming of reducing the wheelbase limits the application of this process to a certain extent.
Six steps of profile bending
- Steps 1#: Loading bending metal profiles
- Steps 2#: The right lower roller up to the top roller movement achieves the pinching position
- Steps 3#: Pre-bending between the top roller and the left roller
- Steps 4#: Working phase
- Steps 5#: Pre-bending between the top roller and the right roller
- Steps 6#: Unloading of the metal profile
Main bending parameters
There are two main process parameters of the roll bending method, the relative position between the rolls and the bending time.
The longer the bending time, the more uniform the plastic deformation and curvature radius of each part of the obtained workpiece, and tend to a certain value, and the fixed value is determined by the amount of pressing or pressing.