The two lower rollers of the three-roller bending machine are fixed and driven, while the upper roller is moved up and down through a lifting screw, turbine, and worm to the central position between the two lower rollers. The left and right rotation of the two lower rollers and the up and down movement of the upper roller are all driven by a motor and reducer, and the upper roller can be adjusted to a parallel or inclined position with the help of a manual clutch.
The upper roller of the three-roller bending machine is located in the symmetrical position between the two lower rollers, with a simple and compact structure, easy to manufacture and repair, lightweight, and high precision of forming. However, it cannot bend the full length of the sheet, and both ends of the sheet have straight edges that are slightly less than half of the distance between the two lower rollers, which is called residual straight edge. This requires the use of pre-bending equipment. The upper roller is located above the lower roller and slightly offset, with a simpler structure and less residual straight edge, but the sheet needs to be re-bent, which is not very convenient and requires more force. Therefore, it is commonly used to roll thin and short light tube sections, and the working range is generally below 32×3000mm.
There are two ways to adjust the upper roller of the three-roller bending machine: manual adjustment, which is operated manually by rotating the lifting screw up and down, indicated by "S". Automatic adjustment is achieved by mechanical transmission, indicated by "Z".
The working range of the three-roller bending machine is as follows: if the width of the sheet is reduced to less than 60%, the diameter of the rolled circle is increased by more than 50%, and the yield strength of the material is less than 40% of Q235, then the sheet thickness can be appropriately increased.
Reasonable lubrication of the mechanical drive shaft, sliding surface, and tooth surface is an effective measure to reduce power consumption and improve machine life. Therefore, a specific lubrication system must be established, and appropriate lubricants must be selected.
The lubrication points of the three-roller bending machine can be found on the lubrication signboard on the machine.
Selection of lubricants: 40# mechanical oil is used for all shaft sleeves, shaft necks, and screw thread openings of the three-roller bending machine, and HT50# mechanical oil is used in the gearbox. Calcium-based grease oil is used for the tooth surface.
Lubrication system: Before using the three-roller bending machine, it must be filled with oil. The sliding surface should be filled to the point where the oil spills out at both ends, the gearbox should be filled with oil to the line on the gauge, and the tooth surface should be coated with grease. During the operation of the machine, the sliding surface should be lubricated every 2 hours, and the tooth surface should be lubricated depending on the situation. Check the oil level and oil quality of the gearbox every month. If the oil level is low or if the oil deteriorates or becomes watery, add or replace the oil immediately. Change the oil at least once a year.