How to Operate a Press Brake and Troubleshoot Machine Faults

Last updated:
August 24, 2023

Table Of Contents

Adjustments to the press brake machine:

1.1. Adjustment of the ram upper limit:

By adjusting the position of collision block II, the rising ram can be made to stop at the desired top dead center position. This can shorten the ram stroke distance, reduce the working cycle time, and increase productivity.

2.2. Adjustment of the slow motion of the ram:

When the ram is descending, collision block “I” triggers the stroke switch to make the ram move in slow motion. The length of the slow motion time can be adjusted using a variable resistor.

  1. Adjustment of the upper and lower die clearance (the ram must stop at top dead center):

a. Press the buttons on the button box located at the lower right of the operating table and follow the direction indicated on the label. The initial clearance should be greater than the plate thickness, and the clearance should be adjusted according to the angle of the workpiece to be bent. Fine adjustments can also be made using the handwheel. The adjustment value is displayed on the calculator, and each increase or decrease of a digit is 0.1mm (0.1mm/turn).

b. If the angles at the two ends of the workpiece are not consistent, loosen the support pins, move the connecting rod to the left, disengage the left and right rotating connections, and turn the handwheel (up or down) to change the distance of one end of the mechanical limit, thus achieving the purpose of fine-tuning the angle of the workpiece end.

Note: After the adjustment is completed, restore the sleeve 18 to its original position and tighten the support pin, otherwise mechanical accidents may occur.

c. If the angles at the two ends of the workpiece are consistent, but the middle angle (large or small) is inconsistent, the upper die can be fine-tuned. When using the fine adjustment, bring the upper die close to the lower die slot, slightly loosen the screws on the adjustment block and the upper die contact plate (with the principle of not allowing the upper die to fall), and then gently tap the adjustment block (left or right) in the middle section. In the area where the middle angle is small, allow the upper die to protrude slightly, tighten the support pin, and test the bend until the angle of the entire workpiece reaches the allowable value.

  1. Adjustment of the bending force of the press brake:

Calculate the bending force in kilonewtons based on the table or the bending force calculation formula for the sheet metal, and then calculate the indicated pressure value P based on table 1. Finally, adjust the handwheel of the relief valve 8 to produce a force slightly greater than the bending force of the plate.

  1. Adjustment of the distance of the back gauge:

The back gauge is used for positioning in the length direction during sheet metal bending. It is adjusted by the motor controlled by the buttons on the front button box. The adjustment value can be read from the rotation table on the button box, with a conversion value of 0.1mm/turn, and fine adjustments can be made using the handwheel.

  1. The foot pedal switch can make the ram move up or down, with easy operation.

Testing and Operation of the Press Brake Machine

Before testing, calcium-based lubricating grease must be added to each lubrication point (see lubrication label), and 46# hydraulic oil should be added to the hydraulic system oil tank. The oil should be replaced after the first month of use and then replaced annually based on the specific situation. The minimum oil temperature should not be lower than 15℃.

During the initial test, start the oil pump motor unit for idle operation, and then test the machine’s action using “jog” mode. Then test the performance of “single” and “continuous” actions, as well as the stroke and back gauge control. Only when the machine is proven to operate normally can the following steps be taken:

  1. Calculate or refer to the bending force and the V-shaped groove opening size of the lower die based on the plate thickness and bending length (the groove size should generally be equal to or greater than 8 times the plate thickness).
  2. Align the centers of the upper and lower dies.
  3. Determine and adjust the clearance between the upper and lower dies.
  4. Determine the position of the back gauge.
  5. Select the action mode “jog”, “single” or “continuous” using the conversion switch.
  6. Place the workpiece in the middle position of the machine’s worktable and test the pressure.
  7. Adjust the die clearance again, if necessary, the upper die adjustment block can be adjusted.
  8. Pay attention to the sealing condition of each seal, and replace the seal promptly if any leakage is found.
  9. The plate bending should be in the middle of the machine, and should not be unevenly loaded or loaded on one side to avoid affecting the accuracy of the workpiece and the machine. If some workpieces require one-sided operation, the load should be less than 100KN, but two-sided bending should be performed as much as possible to solve the problem of one-sided loading.
  10. Bending plates with a length less than 600mm are not allowed to work at full load (1000), and the bending load of each 100mm length should not exceed 100KN.
  11. Pay attention to the motor rotation direction (counterclockwise) during testing.

Machine Maintenance, Care, and Troubleshooting

Anyone who operates or maintains this machine must carefully read this manual, understand the main structure, performance, and use of the machine, and carry out regular maintenance and care work. Record daily usage to facilitate future reference.

  1. A dedicated person must be responsible for operating the machine, and the operator should be familiar with and correctly follow the operating procedures and calculate the bending force of the workpiece.
  2. Keep the oil clean and unobstructed to prevent the oil pump from sucking air, causing pipeline vibration or rupture, and avoid the locking and rubbing of related hydraulic components.
  3. The machine adopts decentralized lubrication. Lubrication should be added according to the indication diagram of the machine’s lubrication points, based on working conditions (the left wall panel of the machine is equipped with a lubrication label).
  4. The bending force of the workpiece should not be greater than the nominal force.
  5. Do not perform one-sided or single-point load work.
  6. Electrical and hydraulic components must ensure flexible action and correct position.
  7. Adjust the clearance between the upper and lower dies based on the thickness of the bending material, which is generally about 1mm larger than the thickness of the plate. The specific value may be adjusted according to the plate thickness, but it must be greater than the plate thickness to avoid damaging the dies due to the clearance.
  8. Users must regularly have the random spare parts provided with the machine.
  9. If abnormal phenomena or noises are found, stop immediately and find the cause for inspection and repair.

Common hydraulic system failures of the press brake include valve malfunction or slow switching, leaks, and faults in the solenoid valve.

(1) Valve malfunction or slow switching is often caused by poor lubrication, stuck or damaged springs, or oil or debris clogging the sliding parts of the valve.

In this case, the operation of the oil mist separator and the viscosity of the lubricating oil should be checked first. If necessary, the lubricating oil should be replaced, the sliding parts of the valve should be cleaned, or the spring and valve should be replaced.

(2) After prolonged use, the valve core sealing ring, valve stem, and valve seat of the switching valve may become worn or damaged, leading to internal leaks, slow valve action, or failure to switch properly.

In this case, the sealing ring, valve stem, and valve seat should be replaced or the switching valve should be replaced entirely.

(3) If the intake and exhaust holes of the solenoid valve are clogged with oil sludge or other debris, the seal is not tight, the moving iron core is stuck, or there is a fault in the circuit, the switching valve may not operate properly.

For the first three cases, the oil sludge and debris on the solenoid valve and the moving iron core should be cleaned. Circuit failures are generally divided into control circuit failures and solenoid coil failures. Before checking the circuit failure, turn the manual knob of the switching valve several times to see if the switching valve can switch properly under the rated pressure.

If it can switch properly, there is a circuit failure. When checking, the voltage of the solenoid coil can be measured with an instrument to see if it reaches the rated voltage. If the voltage is too low, the power supply and related stroke switch circuits of the control circuit should be further checked.

If the switching valve cannot switch properly under the rated voltage, the connection (plug) of the solenoid coil should be checked for looseness or poor contact. To do this, unplug the plug and measure the resistance of the coil.

If the resistance is too high or too low, the solenoid coil has been damaged and should be replaced.

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