The CNC press brake is a complex machine for sheet metal processing.
The operation of the press brake is carried out under the control of the CNC controller and the operator.
Parameters and procedures need to be carefully set before operation.
However, the press brake used for a long time may also have some mechanical failures.
For example, the workpiece and tools vibrate during bending, or the bending machine leaks oil.
Some faults may lead to inaccurate size and accuracy of workpieces or waste of materials.
In serious cases, it will damage the machine and even endanger the safety of the operator.
This blog will introduce the causes of errors in press brake bending and how to prevent and avoid them.
The machine is not kept clean.
This is a common problem in the use of the press brake.
If the press brake is not effectively cleaned for a long time, the accumulated dirt will cause wear of parts and molds.
Some debris will scratch the workpiece, and the dust in the machine will affect the operation of the press brake.
Clean the press brake and tools before and after the use of the press brake.
Remove all debris, oil, and dust to prevent dust from entering the press brake.
Regular cleaning of the press brake can prolong the service life of the machine.
The ram is not vertical when running
The long-term use and wear of the guide rail and poor lubrication lead to increased clearance.
It is necessary to check the wear degree of the guide rail and adjust the clearance.
If the wear is serious, the guide rail pressing plate needs to be replaced.
Untimely lubrication will aggravate friction between sliding parts.
The automatic or semi-automatic lubrication system can prevent untimely lubrication.
Choose a tin bronze plate or ductile iron. The joint surface is processed by a grinder.
The connecting bolt is lower than the joint surface and is provided with a serrated lubricating oil groove
Long-term bending will cause the ram of the press brake and the middle part of the workbench to bulge.
This kind of protrusion is called deflection, which refers to the protrusion of the ram and the base under the maximum tonnage load.
The ram protrudes upward at the center, and the center of the workbench bends downward.
And the deflection of the press brake is limited by the maximum tonnage load.
If removed by the load, the ram and the worktable can return to normal conditions.
However, if the ram and workbench are defective and the tonnage load is too large,
This may cause a temporary or permanent upset of the center of the ram and worktable.
The distance between the center of the ram and base is greater than the distance at both ends thereof.
For long workpieces, the angle of bending at the center is greater than the angle of bending at both ends.
Obviously, this defect will affect the accuracy of bending workpieces and forming workpieces in the shape of canoes.
If the tonnage of the machine is adjustable, the load shall be gradually adjusted within the rated range of the tonnage.
It is also necessary to equip the machine with a crowning device and use shims to offset the deflection of the ram.
If the deflection can no longer be compensated, it can only be corrected by remachining the ram and the worktable.
The ram cannot move down quickly / slowly
When the ram moves down, the speed is too slow, possibly because the guide rail is too tight.
There is no signal from the servo valve, or each axis of the back gauge is not adjusted in place.
It is also possible that the ram does not return to the top position.
Leakage of filling valve and sealing ring, or the filling valve is stuck.
It is necessary to check whether the tightness of the ram guide rail is appropriate.
Check whether the servo proportional valve has an electric signal.
Check whether the axis of the rear gauge is in place according to the programming of the controller.
Check whether the filling valve is stuck and whether the sealing ring leaks.
Incorrect bending radius
If the bending radius is too small, the pressure on the die tip will be too large.
This will damage the toolings and lead to inaccurate bending of the workpiece.
Because different materials have different ductility and tensile strength.
The workpiece opening is too close to the bending radius.
Take the following measures to avoid toolings and workpiece damage.
The bending radius is determined according to the material specification of each process.
The bending radius of longitudinal bending is larger, and the bending radius of transverse bending is smaller.
The opening of the workpiece, such as a notch, notch, etc., is too close to the bending diameter, which will cause deformation of the workpiece.
The distance between the plate opening and the bending line shall be at least three times the thickness of the plate.
The main motor cannot be started
The main motor fails, for example, the wiring is loose and the control power supply is faulty.
It also needs to be considered that the emergency stop button is not released.
There is also damage to the AC contactor, circuit overload, and thermal relay.
Check whether the switch power supply wiring is loose and whether the emergency stop button is released.
Whether the circuit has overload protection and whether other parts are damaged.
The workpiece is cracked and uneven after bending
After bending, there will be cracks on the surface of the workpiece.
This is because the inner bending radius of the die is too small and the bending gap is too small.
It is also possible that the material itself is defective and the burr of the material faces outward.
Sometimes, the curved end face of the workpiece will be expanded and uneven.
This is because the outer surface of the material will shrink and deform after being stretched.
The inner surface will be folded and deformed after being compressed.
It is necessary to improve the smoothness of the tools and increase the bending radius of the tools.
Adjust the bending gap and use metal materials with good plasticity.
Make the die fillet radius correspond to the external fillet of the part.
The hydraulic system has no bending pressure
The throttle hole and valve element are blocked, and the piston sealing ring of the cylinder leaks.
Check whether the throttle valve and valve element are blocked, and clean the blockage in time.
Check whether the filling port of the oil tank is covered with hydraulic oil.
The hydraulic oil needs to completely fill the tank in order to vent the gas.
Check the piston sealing ring for leakage and replace the sealing ring in time.
We talked about some common press brake problems and solutions.
There are many problems with the press brake, so I won't list them here.
If you need more information about the press brake, you can contact us for detailed answers.
The press brake needs careful maintenance to be more efficient in use and prolong its service life.
How to calibrate bending angle?
To adjust the angle of the press brake, the bending force required for bending the metal sheet shall be calculated according to the calculation formula.
Then calculate the value of the indicated pressure P, and adjust the force of the overflow valve handwheel to slightly greater than the force of the bent metal plate.
Adjusting the distance of the back gauge can change the positioning in the length direction during bending.
The upper and lower positions of the ram can be changed by adjusting the parameters of the controller.
The ram speed can be changed through the stroke switch, and the stroke time can be adjusted through the potentiometer.
Adjust the gap between the upper and lower toolings through the button at the lower right of the workbench.
How to calibrate the backgauge?
If the backgauge bar is inaccurate, we need to align and calibrate it. First, loosen the fastening bolts under the backgauge bar.
Adjust the front and rear screws, and adjust the rear backgauge wheel forward to make it parallel.
Use the probe to check and measure the values on the left and right sides. Then loosen the front and rear flat head bolts. Then measure the value to ensure that the backgauge and the probe are parallel.
Finally, adjust the X-axis datum to the correct size. It can be adjusted by the controller programming parameters.
What are the types of bending methods used on the brake press？
The three bending methods of the press brake are air bending, bottom bending, and coining.
When air bending, the punch only contacts the plate at the bottom die shoulder. The deeper the punch descends, the sharper the bending angle.
In the bottom bending, the top of the punch is in contact with the metal plate. The tonnage required for bottom bending is small, so the plate will rebound. It is necessary to bend to a sharp angle to obtain the required bending angle.
The bending method of coining comes from the previous coinage technology. Coining requires a very high tonnage so that the die and plate are in full contact.