Causes and solutions of common faults of press brake

The oil pump motor cannot be started #

Cause analysis

1. The starting circuit of the main motor fails, such as the emergency stop button is not released, the cable wiring is loose, 24V control power supply, etc;
2. Failure of relevant components of the starting part of the main motor, such as thermal relay, circuit breaker, AC contactor and other overload protection or damaged;
3. Power supply problem;

Solution

1. Check whether the main motor starting circuit has emergency stop, not released, loose wiring and 24V control power supply;
2. Check whether the components of the starting circuit of the main motor have overload protection. If so, analyze the causes and check whether the components are damaged;
3. Check whether the three-phase power supply is normal;

The ram cannot go down quickly #

Cause analysis

1. The ram guide rail is adjusted too tightly;
2. The backgauge shaft is not in place;
3. The ram is no longer at the top dead center position;
4. Failure of foot switch, relay and other components;
5. The proportional servo valve is faulty;

Solution

1. Check whether the ram guide rail is suitable;
2. Check whether there is a cursor at the actual position of X on the system, or check whether the programmed value of the backgauge shaft is consistent with the actual value in the manual interface;
3. The status of the Y-axis on the system should be “1”. If it is “6”, check the actual coordinates of the Y-axis, and the value should be less than the difference between Y-axis and return;
4. Check whether the foot switch, relay and other signals are normal according to the electrical schematic diagram;
5. Check whether the feedback of proportional servo valve is normal;

The ram move to bend or the bending speed is very slow #

Cause analysis

1. The ram does not reach the speed conversion point;
2. The parameter setting of the Y-axis bending part of the system is not good;
3. Insufficient pressure, such as programming operation, machine tool parameter setting, hydraulic pressure, etc;

Solution

1. Check whether the status of the Y-axis changes from “2” to “3”, and the actual value of the Y-axis should be greater than the value of the speed conversion point. If not, adjust the parameters of fast forward;
2. Readjust some parameters of Y-axis bending;
3. Check whether it is caused by programming operation, parameter setting or hydraulic pressure; with the help of pressure gauge and multimeter, first detect the signals of main pressure and proportional pressure valve, then check whether the proportional pressure valve and main pressure reducing valve are stuck, then check the filter element and oil fluid, and finally check the oil pump and its coupling;

Sometimes the ram cannot return when bending #

Cause analysis

1. During no-load the ram can not return, which may be a parameter problem or hydraulic failure;

2. Cannot return during processing, and the workpiece angle does not reach the set value;

3. Cannot return during processing, and the workpiece angle has exceeded the set value;

Solution

1. Debug some parameters of Y-axis bending. The bending parameters should be debugged according to the actual situation.

If the gain is too small, the ram will not fold or fold in place, and if the gain is too large, the ram will shake.

The parameters should be adjusted so that the ram does not shake during action, and the gain should be as large as possible; or the left and right valve offsets are not set well in the diagnostic program, the Y-axis is too small to be in place, and the Y-axis is too large to be unloaded;

If it is a hydraulic fault, check the main pressure and check whether PV valve S5 is always in the power on position;

2. The parameter gain of the Y-axis bending part may be set too small and can be increased appropriately; Or the pressure is not enough.

Analyze the reasons for the insufficient pressure, whether it is the programming reason or the signal and hydraulic part;

The programming reasons mainly include die selection, plate thickness, material, workpiece length, bending mode, etc.

The hydraulic reasons mainly include whether the oil pump leaks, whether the proportional pressure valve is polluted or damaged, whether the filter element is blocked, whether the oil has been polluted, etc;

3. Mainly for programming and operation reasons, check the programmed and processed workpieces;

Poor ram movement #

Cause analysis

1. Improper tightness of ram guide rail;
2. The lock nut of the ram is loose;
3. Machine tool parameters need to be adjusted;
4. The gain and zero position of the proportional servo valve amplifier need to be adjusted;
5. The pressure setting of the back pressure valve is incorrect or both sides are unbalanced. If the back pressure setting is too small, the ram will slide slowly and shake during work progress; The back pressure is unbalanced on both sides, and the ram will twist when running;

Solution

1. Readjust the guide rail clearance;
2. Re lock. If the lock nut fits too loosely with the screw, it needs to be replaced;
3. If there is a reference curve, it shall be adjusted according to the reference curve;
4. Only Bosch and Rexroth valves are adjustable, but caution is required;
5. Use the pressure gauge to adjust the pressure of the back pressure valve and make both sides consistent;

Sometimes the main motor stops automatically and is protected by thermal relay and circuit breaker #

Cause analysis

1. The proportional pressure valve and main pressure reducing valve are stuck, and the press brake is always pressurized;
2. The filter element is blocked, the oil outlet is not smooth, and the pressure of the oil pump is always very high;
3. The oil has been used for too long and has been polluted;
4. Poor oil quality;
5. If the circuit breaker and thermal relay fail to reach the rated current, they will act;
6. The system control pressure output part fails and sends out wrong signals to make the proportional pressure valve work all the time;

Solution

1. Clean the proportional pressure valve and main pressure reducing valve;
2. Replace the filter element and check the contamination degree of the oil;
3. Replace the oil filter element immediately;
4. Replace with the recommended oil;
5. Replace the circuit breaker and thermal relay;
6. Check system output;

Any valve stuck #

Cause analysis

1. The oil has been used for too long and has been polluted;
2. Poor oil quality;
3. Whether the rubber skin at the oil inlet in the oil tank is aged;

Solution

1. The customer is advised to change the oil on time;
2. Replace the recommended oil;
3. Replace the oil resistant rubber plate;

Cylinder slide down #

Cause analysis

1. Dirty or damaged back pressure valve and lifting valve;
2. Small back pressure;
3. Gripe ring is strained and worn;
4. The inner wall of the oil cylinder is strained;
5. If the ram stops at any position and slides slowly, it is normal if it slides less than 0.50mm in 5 minutes. This phenomenon is mainly caused by the characteristics of hydraulic oil;

Solution

1. Clean the back pressure valve and lift valve, and replace them if damaged;
2. Readjust the pressure of the back pressure valve according to the standard;
3. Replace the gripping ring and check the causes of gripping and wear of the gripping ring;
4. Generally, due to oil pollution, replace the cylinder barrel and sealing ring;
5. No treatment required;

When pressing the die, the height of both sides is inconsistent #

Cause analysis

The back pressure on both sides is inconsistent, and the back pressure setting may be too high;

Solution

Adjust the back pressure on both sides to the specified value and keep it consistent;

The waiting time at the speed conversion point is too long when the ram is moving #

Cause analysis

1. The oil suction port in the oil tank leaks;
2. If the charging valve fails, the valve core is stuck due to improper installation, or the spring tension is not enough
3. Y-axis work progress parameters are not set properly;

Solution

1. Check the sealing of the rubber plate and reinstall the cover plate;
2. Check the installation of the filling valve, check the action of the valve core and check the spring tension;
3. Adjust the working progress parameters of Y axis;

The length angle of the workpiece changes too much during bending #

Cause analysis

1. Improper inertia parameter setting of the machine;
2. Material of bending;

Solution

1. Readjust the inertia parameters of the machine;
2. Check the material of the plate;

When the workpiece has multiple bends, the dimension error of the accumulated error is too large #

Cause analysis

1. There are many bends in the workpiece, resulting in large cumulative error;
2. Unreasonable bending sequence;

Solution

1. Fine adjust the accuracy of each bend to make the angle as negative as possible and the size as accurate as possible;
2. Adjust the bending sequence when possible;

The pressure automatically calculated by the system is greater than the die impedance; #

Cause analysis

1. Unreasonable selection of lower module during programming;
2. The impedance setting of the die is incorrect;
3. The bending mode is not selected correctly during programming;
4. The parameters of machine tool constants are modified, such as material parameters, unit selection and other parameters;

Solution

1. The die shall be selected according to the relationship between plate thickness and lower die opening;
2. Correctly set the die impedance;
3. Check the program;
4. Check machine constant parameters

When programming large arc bending, the system calculation is very slow or crashes; #

Cause analysis

The X value set during programming exceeds the maximum value of X axis in the parameter;

Solution

Check the program;

Oil temperature too high #

Cause analysis

1. Hydraulic failure, such as blocked filter element, oil pollution, deterioration, etc;
2. Working under high pressure for a long time;

Solution

1. Check the filter element and oil, and replace it if necessary;
2. Check whether the reason for long-time high-voltage work is actual need or other reasons

Inaccurate angle of machined workpiece #

Cause analysis

1. If the error is very large, it may be programming error, loose ram connection, grating ruler failure, etc;
2. It is normal if there is a little error and can be corrected on the system. If it can work stably after correction, it is normal;
3. The angle is unstable and often changes, which may be related to loose connection of ram, failure of grating ruler, material, etc;

Solution

1. Check the running program, focusing on whether the mold, material, plate thickness, workpiece length and bending mode in the program are consistent with the actual operation, whether the ram connection is loose and whether the grating ruler connection is firm;
2. Normally, there is a little error, which can be caused by many reasons, such as the error between the programmed material thickness and the actual thickness; Material uniformity, die wear, operation and other reasons;
3. Check the Y-axis repeated positioning accuracy, and check whether the ram connection and grating ruler connection are normal. If normal, it is likely to be related to the material;

Inaccurate size of processed workpiece #

Cause analysis

1. The size is unstable and often changes, which may be related to machine tool power supply, servo drive, servo motor encoder and related cables, systems, lead screw mechanical connection, synchronous belt (wheel), etc;
2. The dimension is deviated but stable, which is mostly related to the parallelism, straightness, parallelism and perpendicularity of the backgauge beam;
3. When positioning with the bending edge, the bending angle is greater than 90 °, resulting in small size;

Solution

1. Check the repeated positioning accuracy of the rear retaining shaft, which is generally less than 0.02mm. If the difference is large, check the possible factors one by one. If it is caused by servo drive, servo motor encoder, system, etc., it is best to be handled by the manufacturer;
2. First check the parallelism and straightness of the beam, and then check the parallelism and perpendicularity of the stop finger;
3. If the bending edge is used for positioning, try to make this bend no more than 90 °;