Tips for selecting a hydraulic press brake:
The first important consideration when purchasing a hydraulic press brake is the parts that need to be produced. The key point is to buy a machine that can complete the processing tasks with the shortest working table and the smallest tonnage.
Carefully consider the material grade, maximum processing thickness, and length. If the majority of the work involves low carbon steel with a thickness of 16 gauge and a maximum length of 10 feet, a bending force of more than 50 tons is not necessary. However, if a significant amount of bottoming operations are involved, a 160-ton machine should be considered. If most of the parts are 5 feet or shorter, the tonnage can be reduced by about half, thus significantly reducing the acquisition cost. The part length is quite important in determining the specifications of the new machine.
Deflection
Under the same load, the deflection of a 10-foot machine's working table and ram is four times that of a 5-foot machine. This means that a shorter machine requires fewer shim adjustments to produce qualified parts. Reducing shim adjustments also shortens setup time.
The second consideration is the material grade. Compared to low carbon steel, stainless steel typically requires an increase in load of about 50%, while most grades of soft aluminum require a reduction of about 50%. You can always obtain a tonnage chart from the hydraulic press brake manufacturer, which shows the estimated tonnage required per foot length for different thicknesses and materials.
The third consideration is the use of air bending, where the bending radius is 0.156 times the die opening distance. In the air bending process, the die opening distance should be eight times the thickness of the metal material. If the bending radius is smaller than the material thickness, a punch with a front-end radius smaller than the material thickness and the assistance of coining bending may be required. This will require a pressure that is 10 times higher than air bending.
Typically, the springback angle generated by the air bending die on a new hydraulic press brake is ≤2°, and the bending radius is equal to 0.156 times the die opening distance.
For bottoming operations, the die angle is generally 86-90°. At the bottom of the stroke, there should be a gap slightly larger than the material thickness between the punch and die. The forming angle can be improved because the tonnage for bottoming operations is larger (about 4 times that of air bending), reducing the stress that typically causes springback within the range of the bending radius.
Coining bending is similar to bottoming operations, except that the front end of the punch is machined to the desired bending radius, and the gap between the punch and die at the bottom of the stroke is smaller than the material thickness. By applying sufficient pressure (approximately 10 times that of air bending) to force the front end of the punch to contact the material, springback is essentially avoided.
To select the lowest tonnage specification, it is best to plan for bending radii that are larger than the material thickness and use the air bending method as much as possible. When the bending radius is larger, it often does not affect the quality of the finished part and its future use.
Disadvantages of hydraulic press brakes:
The upper roll of the hydraulic press brake is positioned symmetrically between the two lower rolls through the hydraulic oil in the hydraulic cylinder, which causes the piston to move up and down vertically. The cooperative rotational motion of the gear on the last stage of the main reducer drives the gears of the two lower rolls, supplying torque for the sheet metal rolling. By applying downward pressure with the upper roll and rotational motion with the lower rolls, the metal sheet undergoes multiple continuous bending operations, resulting in permanent plastic deformation and forming the desired shapes such as cylinders and cones. The disadvantage of this hydraulic three-roll press brake is that the ends of the sheet metal need to be pre-bent using other equipment. The disadvantages of hydraulic press brakes are as follows:
1. Interface signal check: Use a programmable hydraulic press brake controller to check the interface signals of the machine control system and compare them with the correct signals in the interface manual to identify corresponding faults.
2. Instrument measurement: When faults occur in the hydraulic press brake system, conventional electrical testing instruments and tools can be used to measure voltages, power supplies, pulse signals, etc., according to the system circuit diagram and machine circuit diagram, to determine the fault locations. For example, if the input voltage of the power supply exceeds the limit, causing the power supply to malfunction, the network voltage can be measured with a voltmeter or monitored in real-time with a voltage tester to eliminate other possible causes. If there is a fault in the position control loop of the hydraulic press brake, an oscilloscope can be used.
3. Analysis of PLC intermittent situations using a programmable controller: When a fault occurs in the programmable controller, the intermittent cause can be recalled using the method of intermittent memory storage. By using a hydraulic press brake programmer, the intermittent storage space and block storage space can be accessed in the event of a system interruption, and the fault location can be identified based on the indicated cause.
Beite specializes in providing maintenance and repair services for bending machines and shearing machines. We have a professional team equipped with advanced and specialized maintenance equipment, as well as high-level and skilled professionals, to provide efficient and cost-effective services.
