Electro-Hydraulic Servo Press Brake Operation: Expert Guide

Electro-hydraulic servo press brake operation manual fea

Functions and Ranges of Work

Electro-hydraulic servo press brake

The Electro-Hydraulic Servo Numeric-Control Press Brake is known for its high efficiency and precision in bending sheet metal.

The size of the V-groove on the lower die should be adjusted according to the thickness of the sheet. It is typically larger than 8 times the thickness of the sheet.

By using different types of upper and lower dies, a wide range of workpieces can be bent.

For desired bending force, refer to the Sheet Metal Bending Chart on the body of the press brake machine or use the bending formula to calculate it.

Press Brake Bending Force Chart_MachineMfg

One pass of the slider results in a bend in the sheet, and complex shapes can be achieved by bending the workpiece multiple times.

The Hydraulic Press Brake is constructed with steel plates, providing the necessary strength and rigidity.

Its hydraulic drive prevents the machine from experiencing serious overload accidents, even with changes in sheet thickness or incorrect lower die selection.

In addition, this press brake is known for its stability during operation, ease of use, and reliable safety features.

The connection to the upper die includes a compensation device, which compensates for any deflection in the worktable and slider during bending, ensuring high precision.

It is equipped with hydraulic electric control and adjustable slider travels, making it convenient for trial and adjustment purposes.

This press brake machine is advanced in technology and reliable in performance, making it an ideal shaping tool.

It is widely used in the plane, automobile, shipbuilding, and machinery industries due to its high production efficiency.

Hoisting and Installation


Due to its high center of gravity, the bending brake is heavy in the front and light in the rear. Therefore, care must be taken to ensure the stability of the machine and prevent it from tipping over.

In order to maintain consistency, silk ropes should be used at a narrow angle of incidence.

Hoist of Press Brake


Hoist of Press Brake


Clear up

Before running the hydraulic press brake, you must get rid of the rust protection oil on the following moving parts.

  • —The surface of piston pole
  • —Surface of slider raster guide rail
  • —The surface of guide rail, axis, supporting on the bake gauge
  • —The surface of slider guide rail
  • —The surface of worktable and mold set

Note: Permit to use gasoline and coal oil to clean, prohibit using the dissolvent wash.


Note: The machine should be placed on a level surface before performing precision adjustments. Ensure that all parts of the machine, including electrical components, are properly connected before proceeding.

The process is as follows:

  • Place the slider block on the upper dead center.
  • Place a gradienter (precision of ±0.05mm/m) on both sides of the slider blocks.
  • Adjust the vertical level.
  • Adjust the horizontal level by placing a gradienter (precision of ±0.05mm/m) in the center of the worktable.

And in all this process, the bottom screw must be connected well.

Note: The level must be check and adjust again after using for 30-50 hours.

The connections of electric

After connecting the main switch (power phases: R, S, T, PE), check the orientation of the hydraulic pump by performing a short test start. If the orientation is incorrect, immediately turn off the power and switch the two phase lines (refer to the hydraulic pump’s directional arrow).

The cable entry can be located at the bottom of the electrical box.


(1) Ensure that the voltages are consistent.

(2) It is recommended that a trained electrician or someone who is knowledgeable of the manual perform the electrical connection of the machine.

Working theory

The Electro-Hydraulic Servo Press Brake integrates numerical technology, servo, and hydraulic systems. The movement of the control valve causes the upper crossbeam to move up and down periodically, with the movement measurement taken by the rasters on both sides of the machine.

The DNC controls the opening and closing of the two valves in the left and right oil cylinders. If necessary, the servo can reallocate the flow in the oil cylinder, causing the upper crossbeam to move vertically. The movement measurement is determined by the new pulse count. (Figure 3)

Electro-hydraulic servo press brake working theory


The signal from the DNC controller is transmitted to the servo valve, which converts it into a hydraulic pressure signal and controls the movement of the valve. Each cylinder in the hydraulic system has its own independent control loop, which includes the servo valve and the filling valve.

Backgauge Axis

The definition of axis

The DNC controls the following axes:

  • The left oil cylinder of the slider block is the Y1 axis.
  • The right oil cylinder of the slider block is the Y2 axis.
  • The lower crowning table is the V axis.
  • The back gauge movement, both forwards and backwards, is the X axis.
  • The back gauge movement, up and down, is the R axis.

Note: The position of the slider block can be programmed using the absolute value equation and the angle size.

Manual adjustments or controller control can be applied to the Z1, Z2, R1, and R2 axes.

The position and character of each axis

Axis Zero position Actual numerical value
Y1 left slider block(up or

(up or down)

Surface of worktable Distance between the surface of the worktable and mold of the slider block
Y2 right slider block(up or

(up or down)

Surface of worktable Distance between the surface of the worktable and mold of the slider block
X、X1、X2 back gauge

〔front and back〕

The center of lower die Max distance between the center of upper

die and back gauge

R、R1、R2 back gauge

(up and down)

Surface of worktable(and the lowest spot of back gauge) The distance between the surface of the worktable and the lowest spot of back gauge
Z1 the left of the back gauge

〔left to right〕

Left of machine body The distance between the most left side of the machine body and left the end of the back gauge
Z2 the right of the back gauge

〔right to left〕

Left of machine body The distance between the most left side of the machine body and left the end of the back gauge


(1) Follow the instructions in the DNC manual to program the axes.

(2) The terms “left” and “right” in the table refer to the front of the machine when facing it.


(1) The operator should be cautious of the position of the back gauge. If it moves into the area of the mold, it may cause damage to the machine.

(2) When adjusting the Z-axis manually, only do so from the back of the machine.

(3) Take care when adjusting the back gauge to avoid hitting the lower die.

The back gauge is composed of a beam that extends from one side of the machine to the other, supported by straight-line guides and ball bearing lead screws. The guides for the back gauge are located on both sides of the machine body, leaving ample room for movement. The X axis controls the movement of the back gauge through the DNC control, and it is driven by a servo motor.

Press brake hydraulic parts

Hydraulic pressure oil box

The hydraulic pressure oil tank is welded inside the body of the machine. The intake is located within the tank, while the motor, oil pump, high-pressure valve, control valve, and electronic system are located outside. The filtering core and valve pedestal are placed at the top, and the oil discharge screw is located at the bottom of the tank.

Electric motor

3-phase four-grade motor

Oil pump

The high-pressure gear pump and the main motor are connected by a flexible coupling shaft.

The inhaler

The level of filtration is 10μm and the maximum pressure is 400 bar. If the filter becomes clogged or if the oil needs to be changed, the filter must be replaced.

Synchro servo valve

The servo valve is mounted on the top of the oil cylinder. Its flow is regulated by the DNC numerical control system and servo amplifier, allowing for control of the slider block’s speed throughout its entire travel range. The position and manner of control are as follows:

  • Quick movement
  • Bending speed
  • Lower dead spot
  • Return travel
  • Upper dead spot

Fill in valve

The servo valve is located on top of the oil cylinder. When the slider moves quickly, oil flows into the cylinder from the oil box through the fill-in valve. The valve is closed during the bending process.

Pressure valve

The pressure valve is in the servo valve, back pressure when adjustable return travels.


The overtravel protection is controlled by the DNC. At startup, the DNC checks the time and pressure of the oil path for overtravel, also known as oil pressure leak checking.

NC system parameters


  • 1st, before ordering the machine tool, all parameters must be established by the manufacturer to ensure operational safety.
  • 2nd, changes to the machine tool parameters can only be made after obtaining the manufacturer’s approval.
  • 3rd, if the 2nd requirement is not met and changes are made to the machine tool parameters, it can result in equipment accidents.

The selection of lower die (See Picture 4)

Press Brake Lower Die

Fig. 4 The sketch map o the lower die

F: The requiring bending force (KN/m) of per meter when the material tensile strength is 400 N/mm.

If the material tensile strength is 800N/mm, the requiring bending force (KN/m) of per meter doubles. S: Plate thickness (mm)

  • S: Plate thickness (mm)
  • B: Minimum bending width (mm)
  • V: The width of lower die opening (mm) R: The bending half diameter (mm)
  • R: The bending radius (mm)
  • V: width of V lower die, must determinate according to the material thickness S and the general formula is: S<3mm    V=(6~8) ×S

S<3mm    V=(6~8) ×S

S>3mm    V=(8~12) ×S

Only by changing the minimum bending width and bending angle can the overall dimension of the lower die’s limit be scientifically determined.

-8 -28 -1 -4
1 8 110 1 4
8 80 1.2 5
10 70 1.5 6
1.2 8 120 1.2 5
10 100 1.5 6
12 80 1.8 7
1.5 10 150 1.5 6
12 130 1.8 7
16 90 2.4 9.5
2 12 220 1.8 7
18 170 2.4 9.5
20 130 3 12
2.5 18 250 2.5 9.5
20 210 3 12
24 130 3.6 15
3 20 300 3 12
24 250 3.6 15
32 190 4.8 20
4 24 440 3.6 15
32 340 4.8 20
40 270 6 25
5 32 550 4.8 20
40 420 6 25
50 320 7.5 32
6 40 600 6.5 25
50 480 8 32
60 400 9.5 38
8 50 880 8 32
60 720 10 38
80 530 12.5 51
10 60 1100 10 38
80 850 13 51
100 570 16 62
12 80 1200 13 51
100 960 16 62
120 800 19 73
14 100 1310 15 62
120 1090 18 73
140 980 21 85
15 100 1500 15 62
120 1250 18 73
140 1070 21 85
16 120 1420 18 68
140 1230 21 79
160 1070 24 90
18 140 1545 21 87
160 1350 24 100
180 1200 27 112
20 140 1900 25 85
180 1700 28 98
200 1350 38 121
25 180 2550 28 100
200 2100 38 121
250 1700 41 131
30 200 3000 38 125
250 2550 41 131
300 2100 53 143

During the bending process, the bending force is concentrated on the worktable surface and acts on the tooling at the same time. Therefore, the load that the tooling can bear should not exceed its capacity.

For example:

  • S=2mm F=150KN (15t/m)
  • F=150KN (15t/m)
  • B min=10mm R=2mm
  • R=2mm

When selecting the lower die, the options are V12, V16, and V20. When choosing V16, it is best to take the thickness of the plate into consideration.

  • F=170KN (17t/m)
  • B min=9.5mm
  • R=2.4mm

Relatively speaking, the radius is not very significant, and when the bending width (b) is greater than the minimum bending radius, different thickness plates can be processed with the same lower die.

V16           S= 1.5mmm, 2mm, 2.5mm

Note: If it’s a molding tool, the bending force must be two or three times greater.

FP= (2….3)Fb

Bending Force
Bending Force Chart

You can also calculate the required press brake tonnage by Press Brake Bending Force Calculator.

Selection of press brake top punch

The selection of the upper die must also be based on the bending force and the load capacity should not be exceeded. Additionally, customers can choose special tooling, but they should be aware of the differing load capacity compared to standard tooling.

Note: The operator must follow safety principles in dangerous areas of the machine, as shown in Figures 5 and 6.

Selection of press brake upper die

A. It is forbidden to pass through the tooling.

B. To prevent accidents, before installing the upper and lower dies, the starting button should be set to the second control position and the NC driving button should be set to “axis stop”.

  • Install the lower die and adjust the clamping bolts.
  • Slowly move the slider block until the distance between it and the lower die is approximately the thickness of the plate.
  • Secure the upper die and upper die pedestal, and place it on the slider block. Then, slightly tighten the clamping bolts or close the clamping portion.
  • Apply a small amount of force to align the mold. The centers of the upper and lower die must be in a straight line. After one edge of the mold is fully connected, tighten the clamping portion.

The material of sheet metal

The table below is for reference only. If there are any questions, please refer to the processing material.

Type Tensile strength Kg/mm2
Aluminum Soft rigidity 10.5
Middling 13.3
High 19.6
Brass Soft 32.9
Mennir high strength resists corrosion the constantan Middling 42
High 59.5
Copper Rolled 25.9
Chromeplate Aluminum Soft 24.5
Heat treatment 38.5
Iron Wrought iron 35
Steel 0.25%c 46.9
0.5%c 66.5
0.75%c 80.5
1.0%c 91
1.2%c 105
1# Volume steel   52.5
Stainless steel 18-8   66.5


The impossible faults and resolve methods


Before starting, ensure that it will not cause any harm.

The machine tool must be in a safe and suitable condition to run, with all protective measures and safety devices in place.

Avoid any dangerous operations and follow safety precautions.

If a fault occurs, immediately stop the machine and address the issue.

Fault resolution must be carried out under the supervision of a qualified technician or expert.

Regularly inspect the exterior of the machine for damage or faults and stop it if necessary.

The operator must thoroughly read the operation manual.


Press engine can not move quicklyGuide rail move spang, exchange valve EV1/2 damaged, control valve SV1/2 damaged
Press engine can not produce pressureExchange EV1/2 didn’t work, filling in valve V5/6 opened, pressure adjustment damaged, pump wear and tear
The press engine stop at the stopping position for 5-10 seconds then do slow movementFilling in valve EV5/6 closed, oil position is too low in the oil cylinder
The press head moving back slightly first then start slowlySingle  valve  V11/V12  opened,  the  setting  parameters wrong
Bending not correctControl valve  failure,  basic setting  wrong,  transducer doesn’t adjust well, or transducer damaged.
The press head can not go back, the press head go back slowlyControl valve SV1/2 damaged, exchange valve Ev1/2 have no response, filling in valve jammed at the closing position, single valve EV9/8 at the closing position, pressure adjustment valve EVP damaged, wrong parameter setting, guide rail move spang, stroke pressure is too low.
The press head stopped at the high position, up to 2-3mm go back, slowly move down and the speed does not exceed 2mm/minSingle-way V7/8 opened, exchange EV1/2 leak or plug

Note: A qualified individual is required to resolve any potential failures and comply with inspection and maintenance procedures. During the warranty period, notify the maintenance personnel. If the failure is due to incorrect operation, the maintenance personnel will not be held responsible.

The maintenance of press brake machine


  1. before the machine working, it’s important that the tooling match the control program

Stop the machine after working

Two ways of stop:

  • Stopped at the center of lower dead spot

—Move the slider block to the center of the lower dead spot

—Close the main motor switch

—Set the operation selection switch to “0”

—Set the main switch to “0”

  • Use two same height wood to stop (Using for maintainance period)

—Place the two pieces of wood on the work table

—Turn the “operation selection” key switch to “2” (for adjustment)

—Operate in “manual” mode

After the machine stopped, move the slider block down manual until it connecting the wood slightly.

—Turn off the main motor

—Change the operation selection switch to “0”

—Set the main switch to “0”

Use the emergency stop button

When activating this button, all axes will stop and the pump will shut down, but the control system will remain active. To restart the machine:

—Release the emergency button

—Press the green “main motor run” button. There is no need to restart the machine tool.

Proofread the slider block

In the event of a stop, if one side of the slider block is tilted or lower than the level position, it can be manually adjusted, but the machine must be turned off and restarted under normal conditions.

Note: If the slider block cannot be corrected or the positioning function fails repeatedly, this may indicate a failure in the control system or hydraulic system.

Maintenance Request

The person responsible for maintenance and testing must thoroughly read the operation manual and have ample experience.

It is recommended to have the manufacturer of this machine conduct a check.

The machine operator should perform a daily inspection for any potential leaks or loose parts.

If the user is unable to resolve a malfunction, they should immediately notify the manufacturer.

The maintenance instruction of the machine parts.

Weekly Maintenance Checklist:

  • Guideway lubrication
  • Back gauge lubrication
  • Inspection of the tightness of the drive belt
  • Verification of the parallel alignment
  • Cleaning of the index plate
  • Inspection of the drive components
  • Mold cleaning and damage assessment.

The maintenance instruction of hydraulic system

Hydraulic Oil Refilling:

  • Check the oil level daily when the slider block is at the top. Observe the oil level gauge and refill if necessary.
  • If the oil level exceeds 10% of the oil tank’s capacity, allow the hydraulic oil to circulate in one direction for a time calculated based on the oil tank capacity and the frequency of the hydraulic pump.
  • When the slider block is at the upper dead spot, add oil to the middle of the oil level gauge (visible from the back of the oil tank).

T = V /Q* 5

  • T——Circulating time (minute)
  • V——Oil box cubage (litre)
  • Q—— The circulating frequency of oil pump

High-power filter

Filter Core Replacement Schedule:

  • Replace the filter core after 200 hours of operation, and then every 6 months or after 1000 hours of operation, or when the yellow “replace filter” indicator light illuminates.
  • The filter requires a 10 micron rating. After replacing the core, allow the oil to circulate for at least one hour as described above.

Note: If the yellow “replace filter” indicator light illuminates, the core must be replaced within 8 hours of operation.

Back gauge

If necessary, the zero position of all axes on the machine (without a back gauge locator) must be checked weekly or receive compensation from DNC.

Inspection of machine function

Regular Inspection Items:

  • Carrier measurement system inspection
  • Machine adjustment component inspection
  • Screw connection and rail inspection
  • Transducer signal transfer inspection
  • Slider block tightening component inspection
  • Back gauge drive component inspection
  • Back gauge tightening component inspection
  • Mold adjustment inspection
  • Inspection of the thickness of different bending plates.

Inspection of checking valves

Valve Inspection Schedule:

Valves V7, V8, V9, and V10 must be inspected every six months using the following procedures:

  • Move the slider block to the upper dead spot
  • Disconnect the single-way pins EV1 and EV2
  • Operate two manual control switches
  • The check valve should prevent oil from flowing from the bottom of the oil cylinder to the oil tank through the servo valve (with the slider block at the upper dead spot)
  • If the slider moves downward, contact the manufacturer for a valve replacement.
  • Move the slider block to the upper dead spot
  • Turn off the switch
  • Operate the single-way valves EV1 and EV2 through the pin on the end cover
  • The slider block should move at a speed of approximately 10mm/s
  • If the slider block moves downward quickly, replace the relevant valve

Note: The check valves mentioned above are part of the safety system. Do not start the machine tool before replacing any potentially damaged valves.

Pressure Adjustment Valve Inspection:

The mechanical pressure adjustment valve’s safety seal ring must be inspected annually.

Note: If the above adjustment cannot be performed, any claims for compensation for quality issues during the warranty period will be void.

Replacing the oil

Hydraulic Oil Replacement Schedule:

  • Replace the hydraulic oil every three years or after 6000 hours of operation.
  • Move the slider block to the upper dead spot and secure it in place.
  • Adjust the screw to drain the hydraulic oil.
  • Fill the new hydraulic oil to the middle level, with the slider block at the upper dead spot.
  • Before restarting the machine, allow the hydraulic oil to circulate for approximately one hour.
  • After circulation, insert a 10 micron filter core.

Recommending hydraulic oil and lubricant

ManufacturerHydraulic oilGrease

Press Brake Safety Labels

Here are the drawings:

Warning Label 1

Warning Label 2

Warning Label 3

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Founder of MachineMFG

As the founder of MachineMFG, I have dedicated over a decade of my career to the metalworking industry. My extensive experience has allowed me to become an expert in the fields of sheet metal fabrication, machining, mechanical engineering, and machine tools for metals. I am constantly thinking, reading, and writing about these subjects, constantly striving to stay at the forefront of my field. Let my knowledge and expertise be an asset to your business.

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