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  • Repair and maintenance of CNC press brake

Press Brake FAQs

  • How to adjust the size of the press brake?
  • How to adjust the angle of the press brake?
  • How to compensate deflection of press brake machine?
  • The press brake can’t go up and down. What’s the matter?
  • How to bend an arc with a press brake?
  • Comparison between grating ruler and magnetic grating ruler of press brake
  • Up and down moving type of press brake, which is better?
  • What is the problem that the downward speed of the hydraulic press brake suddenly slows down during operation?
  • The bending angle of the press brake is different
  • How long to change the hydraulic oil of the press brake?
  • List of hazard sources and risk assessment form of press brake
  • List of minimum bending radius of common metal materials
  • How many press brake controllers are there? How to choose?
  • How to choose between open loop and closed loop press brake?
  • What is a three cylinder press brake?
  • What is a four cylinder press brake?
  • What is the difference between three cylinder press brake and two cylinder press brake?
  • Why can’t the press brake machine return?
  • What are the functions of three motors of ordinary press brake machine?
  • What are the functions of the three relief valves on the press brake?
  • What if the press brake doesn’t go up when it comes down?
  • The press brake is normal up and down, but it is not pressurized!
  • Where does the number of backgauge axis (X,Y,Z,R) of press brake refer to?
  • How does the X-axis of press brake return to the origin?
  • Why the Y-axis of press brake does not return?
  • How many times to bend a large arc and how to calculate the bending angle?
  • How to adjust the stroke of the press brake?
  • The pressure at both ends of the hydraulic press brake is not the same. How to adjust it?
  • The cylinder stroke on both sides of the press brake is different. How to adjust it?
  • How to program CNC press brake?
  • How to adjust the downward speed of the press brake?
  • How to calculate the size and angle of sheet metal bending?
  • How to calculate the nominal pressure required by the press brake according to the thickness and length of the steel plate to be bent?
  • How to calculate the unfolded dimension of sheet metal bending?
  • How is the bending coefficient of sheet metal calculated
  • What is the relationship between bending factor and plate thickness, bending angle and bending radius?
  • How to calculate the bending coefficient of sheet stainless steel?
  • How to calculate the tolerance of sheet bending machine?
  • What is the reason why the middle of the folded workpiece is bent?
  • Why can’t the hydraulic press brake go up and down?
  • How can the angle of the press brake be adjusted if it cannot be pressed at right angles
  • How to fold different angles with a press brake?
  • How to disassemble the oil cylinder of the press brake?
  • The press brake cannot be started
  • How to eliminate the bending indentation of stainless steel press brake die
  • How to adjust the downward speed of the press brake machine?
  • What’s wrong with the unstable pressure of the press brake?
  • Why can’t the press brake machine rise?
  • What about the deformation of the press brake ram?
  • How does press brake bend a cone?
  • How to use press brake to fold a large circular arc?
  • What’s the matter with the slow down speed of the press brake?
  • What if the downward speed of the press brake is fast?
  • The downward speed of the hydraulic press brake becomes slow and the upward jitter!
  • What happened to the hydraulic oil leakage on one side of the press brake?
  • The two cylinders of the press brake are not synchronized
  • What if the workpiece interferes with the press brake machine?
  • Can the press brake machine fold the U-groove?
  • Environmental requirements of CNC press brake
  • What happened to the abnormal noise of the press brake oil pump motor?
  • A simple method for electric heating of hydraulic oil of press brake
  • What’s wrong that the press brake punch can’t lower to the bottom?
  • How to select the size of the lower V groove for sheet metal bending according to the plate thickness
  • How to break the lock of the press brake?
  • How to determine the bending radius of sheet metal?
  • How to solve the problem that the press brake pressurizes too slowly? How to pressurize quickly
  • What hydraulic oil does the press brake use?
  • How many years to change the press brake hydraulic oil?
  • What determines the sheet metal bend radius?
  • Stress relief of stainless steel 304 after bending
  • What are the corresponding protective devices of the press brake?
  • How to adjust CNC press brake?
  • What is the reason for the noise of press brake?
  • How to solve the oil leakage of oil cylinder of the press brake?
  • How to repair the scratches on mirror stainless steel?
  • How much can the bending tolerance of the press brake be controlled?
  • What is the minimum bending size of the press brake?
  • Where is the pressure relief after pressurization of the press brake adjusted?
  • How to choose electro-hydraulic servo synchronous cnc press brake?
  • How to fold a semicircle with a pres brake?
  • How is the inner radius of sheet metal bending determined?
  • How to calculate the bending radius of sheet metal?
  • How to set bending radius and bending deduction in SolidWorks?
  • The most complete sheet metal bending allowance table
  • How to set the K factor, bending deduction, bending allowance and bending calculation in SolidWorks? What’s their relationship?
  • How does the press brake accurately control the bending angle?
  • What is the reason why the blade of press brake can’t rise?
  • Which axes do the 3 + 1 axis and 4 + 1 axis of the press brake refer to respectively?
  • What does the Y value limit of press brake mean?
  • Function of time relay in press brake circuit
  • What is the difference between electro-hydraulic servo press brake and torque synchronous press brake?
  • What hydraulic pump is generally used for press brake?
  • How do you know what material the lower die of the press brake is?
  • When the press brake steps up, it cannot stop and automatically slides down
  • How to understand the N + 1 axis of press brake machine?
  • How to change the tool of press brake?
  • What material is generally used for press brake dies? What is the hardness?
  • Do you need to grind the top punch of press brake?
  • How to level the tools of press brake?
  • What is the problem that the press brake tools are not in a straight line?
  • How to repair the crack of stainless steel bending tool?
  • How to select the material of press brake die?
  • What is the problem of automatic tool drop of ordinary press brake?
  • How does the press brake go down slowly?
  • What is the difference between the acute punch and gooseneck punch of press brake?
  • The press brake tool has dents. How to repair it?
  • What is the quenching hardness of general press brake die?
  • Calculation formula of press brake die price
  • What is the general angle of the press brake dies?
  • How to select arc radius punch and die of press brake?
  • How to calculate the bending angle of the press brake?
  • What are the factors that determine the service life of press brake die?
  • How to select the top punch of the press brake?
  • Golden section size of press brake dies
  • Anti rust treatment of press brake dies
  • Comparison chart of press brake die combination
  • The press down pressure of the press brake machine is not enough, but the rising pressure is normal

Press Brake Hub

  • What is CNC press brake and it’s working principle
  • Brief introduction of synchronous system of CNC press brake
  • Workpiece bending diagram of press brake
  • Installation of CNC press brake
  • Operation of CNC press brake
  • Adjustment of bending parameters of CNC press brake
  • Bending accuracy of CNC press brake
  • Safety protection of CNC press brake
  • Press brake punch and die installation
  • Adjustment of CNC press brake
  • Hydraulic oil of CNC press brake
  • Lubrication of CNC press brake
  • Repair and maintenance of CNC press brake
  • Main structure of CNC press brake
  • Explanation of CNC press brake axis
  • Operating environment of press brake
  • Press brake punch and die selection
  • Adjustment of press brake’s mechanical part
  • Causes and solutions of common faults of press brake

Guillotine Shear Hub

  • Purpose and characteristics of the guillotine shear
  • Main structure of the guillotine shear
  • Hydraulic system of the guillotine shear
  • Lifting and installation of the guillotine shear
  • Lubrication of the guillotine shear
  • Operation and adjustment of the guillotine shear
  • Safety and maintenance of the guillotine shear
  • Guillotine Shear: Common Faults and Troubleshooting
  • Accuracy check of the guillotine shear
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  • Repair and maintenance of CNC press brake

Repair and maintenance of CNC press brake

Table of Contents
  • General requirements
  • Maintenance of CNC press brake
    • Hydraulic system
    • Connection of pipes
    • Sealings
    • Mechanical parts
    • Main overflow valve
  • Weekly inspection
  • Precautions for maintenance

General requirements #

Lubrication part:

Check the lubrication of guide rail, bearing, screw, chain and all moving and transmission parts to ensure that they are clean, rust free and adequately lubricated (replace the lubricating oil if necessary).

Fill lubricating oil according to the specified brand, check and dredge the lubricating nozzle and pipeline to ensure their normal operation.

Mechanical part:

Check whether the transmission parts operate normally and wear, and the bolt fastening of key parts.

Hydraulic part:

Clean or replace the filter, dredge the hydraulic pipeline, clean the oil tank, check the state of the oil, filter or replace the appropriate hydraulic oil if necessary, check the hydraulic pipeline, tighten the pipe joint to prevent oil leakage.

Electrical part:

(Turn off the power supply) clean the electrical cabinet, wipe the motor surface, tidy the wires and trunking in the cabinet, ensure that they are neat and beautiful, there are no sundries in the cabinet, and remove the dust in the cabinet.

Check the working status of the exhaust fan and motor fan to ensure their good operation.

Replace damaged switches, buttons, indicator lights and instruments, and tighten the main circuit terminal of electrical appliances above 5kW in the electrical cabinet.

Machine surface:

Scrub the external surface of the machine, such as guide rail, column, protective cover, etc.

Safety devices:

Various safety devices of the equipment are effective without missing, such as photoelectric protection switch, emergency stop button, etc.

Press brake maintenance table

▲Spot check  ■Cleaning  ●Supplement ★Replace

Position No. Item Recommended cycle
Daily Weekly Monthly Quartely Yearly
Lubrication part 1 Check the lubrication of ram guide rail, chain and lead screw ▲ ■
Mechanical part 1 Check the looseness of bolts (e.g. hydraulic valves, oil circuit pipe joints, motors / pumps, etc.) ▲
2 Check the cleanliness of the guide rail and lead screw for pulling, grinding and bumping ▲
3 Check whether the geometric accuracy of the equipment meets the requirements ▲
Hydraulic part 1 Clean the hydraulic station ■
2 Check the oil level of the hydraulic oil tank and replenish it if necessary ▲ ●
3 Check whether each pressure value of the hydraulic unit is normal ▲
4 Check the temperature rise of hydraulic oil tank or hydraulic oil cooling system ▲
5 Check and clean various filters and replace them if necessary ▲■
6 Check the cleanliness of hydraulic oil, filter or replace appropriate hydraulic oil if necessary ▲● ★
7 Check whether the hydraulic pipeline is unobstructed, free of damage and leakage ▲
Electric part 1 Check whether the cooling fan of the electrical cabinet works well ▲
2 Clean the dust screen of the electrical cabinet ■
3 Clean the interior of the electrical cabinet, and there shall be no sundries and dust in the cabinet ■
4 Tighten the main circuit terminal of electrical appliances above 5kW in the electrical cabinet ▲
5 Check the temperature rise of each motor and whether the motor fan works well ▲
6 Clean each heat sink of the motor to ensure that there is no scale ■
7 Check all emergency stop switches, buttons and limiters ▲ ▲
Cooling part 1 Check whether the oil cooling device works normally ▲
Machine cleaning 1 Clean the external surface of the equipment ■
2 Clean the surrounding environment of the equipment to ensure that there are no iron filings and sundries ■
Safety device 1 Check whether various safety devices on the equipment are effective without missing. For example: photoelectric protection switch, emergency stop button, etc ▲

Maintenance of CNC press brake #

Hydraulic system #

Hydraulic oil

1) Filling method of hydraulic oil

  • Move the ram to the upper dead center and support both ends of the ram with equal height wood blocks.
  • Unscrew the plug on the oil drain at the bottom of the oil tank to drain the hydraulic oil.
  • Clean the oil tank.
  • Refill new hydraulic oil through the air filter at the oil filler to the 2 / 3 position of the oil standard, and stop the ram at the top dead center position.
  • Allow the hydraulic oil to circulate for about 1 hour before restarting the machine
  • After circulation, reinsert a 10um filter element

2) The following hydraulic oils are recommended for press brake

Manufacturer Hydraulic oil
CALTEX 46#
ESSO NUTO  H46
SHELL TELLUS  46
GULF HARMONY  46  AW
BP HLP46
TBXACO RANDO  OIL  46
MOBIL OIL MOBIL  DTE  25
TOTAL AZOLLA ZS46

Note: do not mix hydraulic oils of different brands.

3) Some precautions

The oil level must be checked every quarter.

When the ram is at the top dead center position, the oil level can be seen by observing the scale line of liquid level and liquid temperature agent.

If necessary, fill hydraulic oil through the air filter at the oil tank filler.

When the ram is at the top dead center position, the oil level must reach the upper scribed line of the liquid temperature agent (visible from the rear of the oil tank).

After working for 200 hours, the filter element must be cleaned and checked every 6 months or 1000 working hours.

The oil temperature in the oil tank works within the range of 10 ℃ ~ 60 ℃. If it exceeds this range, temperature rise or drop measures shall be taken.

The hydraulic oil must be replaced every 2 years or 4000 working hours, and the first time should be after 2000 working hours of machine operation. 500 working hours for the first time change and 2000 working hours for the future use will be a good option.

Oil filter

Regularly clean the oil filter in the system with solvent (gasoline, trichloroethylene, etc.).

The CNC press brake shall be cleaned for the first time one month after commissioning, and then regularly every two months.

Air filter

The air filter is installed on the oil tank cover.

It shall be cleaned for the first time two months after the commissioning of the machine.

After washing in solvent (gasoline, trichloroethylene, etc.), it shall be cleaned regularly every four months.

Connection of pipes #

In case of leakage, tighten the pipe joint. If this is not helpful, replace the joint.

Sometimes, the high-pressure oil pipe in the hydraulic oil circuit must be replaced.

When installing the ferrule type pipe joint on the high-pressure pipe, the following provisions must be observed:

  • The angle of pipe sawing shall be correct and the pipe orifice shall be deburred
  • The nut and ring can slide on the tube, and the thick edge of the ferrule faces the nut
  • The pipe joint thread, ferrule and nut must be lubricated and screwed on by hand at the beginning
  • Then tighten it with a wrench until the pipe cannot rotate on the pipe joint
  • Then screw the nut with a wrench for 1 ~ 1.25 turns

Sealings #

If the valve block leaks, please replace the corresponding O-ring or combined seal ring in time.

If the oil cylinder leaks, please replace the sealing ring of the oil cylinder in time.

Mechanical parts #

Regularly check the fasteners of all mechanical parts for looseness and lubrication and wear of sliding block guide rail.

If any abnormality is found, it must be corrected in time before it can be used again.

Good lubrication is an important condition to ensure the normal operation and prolong the service life of the press brake.

The machine should be lubricated weekly (or every 40 working hours). No. 3 calcium base grease is selected and injected into each lubrication point with a grease gun.

Even if there is no lubrication point on the sliding surface of exposed parts and rolling bearings, it should also be lubricated once a week.

The location and name of each lubrication point are shown in the figure below:

lubrication point of press brake

Lubrication point Name Oil quantity Refueling clearance time

Type and brand of lubricating oil

1

Left and right lead screws Middle 40 hours No. 3 calcium base grease

2

Left and right guide rails Middle 40 hours

No. 3 calcium base grease

3 Ram left and right Middle 40 hours

No. 3 calcium base grease

Main overflow valve #

The adjustment of the main relief valve is very important for the operation of the machine. The normal setting value is equal to the maximum allowable pressure.

Weekly inspection #

  • Basic detection
  • Check parallelism
  • Inspect the drive components
  • Mold: check cleanliness and damage
  • All screw connection tests
  • Guide rail detection
  • Guide rails: Lubrication
  • Sensor signal transmission detection
  • Ram tightness test
  • Rear stop: check the tension of the synchronous belt
  • The reference point position of each axis of the rear stop must be tested once a week. If there is any deviation, it shall be compensated on the NC system
  • Rear stop drive detection
  • Rear retaining material tightness test

Precautions for maintenance #

When operating or overhauling the press brake, please follow the following specifications to ensure safety.

1. When energizing the machine, confirm the safety of the surrounding environment.
2. Stop the machine and cut off the power supply before replacing components, checking and repairing.
3. Do not wear loose clothes, gloves and ties to operate the machine.
4. When operating the machine, the electric cabinet door must be closed, and the external power supply must be cut off during maintenance in the electric cabinet.
5. At the beginning of the operation, it is necessary to check whether there are obstacles within the movement range of each axis.
6. Do not unplug electrical components, cable plugs and wiring when the machine is powered on and operating.
7. In order to ensure safety, the machine must operate in a bright, clean and orderly environment.
8. When entering the dangerous area of the machine, make sure whether the emergency stop button on the operation panel is pressed.

Related:

  • Causes and solutions of common faults of press brake
  • Brief introduction of synchronous system of CNC press brake
  • Installation of CNC press brake
  • Adjustment of press brake's mechanical part
  • Lubrication of CNC press brake
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Updated on May 31, 2022
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Table of Contents
  • General requirements
  • Maintenance of CNC press brake
    • Hydraulic system
    • Connection of pipes
    • Sealings
    • Mechanical parts
    • Main overflow valve
  • Weekly inspection
  • Precautions for maintenance
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