Electro-Hydraulic Servo Press Brake Operation Manual

Electro-hydraulic servo press brake

Functions and Ranges of Work

The electro-hydraulic servo numeric-control press brake is of high-efficiency and high-precision in sheet metal bending.

The opening size of V-groove on lower dies, usually larger than 8 times of the sheet thickness, should be regulated for sheets in different thickness.

Using different kinds of upper and lower dies can bend all kinds of workpieces.

And see the Sheet Metal Bending Chart of Bending Brake (on the body of the press brake machine) for desired bending force or calculate the bending force using bending formula.

Press Brake Bending Force Chart_MachineMfg

One slider travel makes a sheet bending and the complicated shape workpiece may be achieved through bending many times.

The hydraulic press brake is structured in steel plate fabrication with sufficient strength and rigidity.

The hydraulic drive prevents the machine from serious overload operation accidents caused by the change of sheet thickness or bad choice of the lower die cavity.

Additionally, this press brake  is also featured by the steadiness of work, convenience of operation, and reliable safety.

The connecting section to the upper die is provided with a compensation device, which compensates the deflection of worktable and slider in bending and guarantees the high work precision.

It is equipped with hydraulic electric control, freely adjustable slider travels and inching operating criterion convenient for module trial and adjustment.

This press brake machine is advanced in technology and reliable in performance, and among the ideal shaping apparatuses.

It is widely used in the plane, automobile, shipbuilding, and machine with high production efficiency.

Hoisting and Installation


Given a high center of gravity, the bending brake is heavy in the front and light in the rear. So attention must be paid to the center of gravity in order to avoid the turnover of the machine.

Silk ropes should be used at a small included angle to assure the consistency of machine.

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: Place the machine on the horizontal underlay. To do the precision adjustment after all parts of the machine are connect well including electrical parts.

The process is:

  • Set the slider block on the upper dead spot
  • Set a gradienter (precision is ±0.05mm/m) on the two sides of slider blocks
  • Adjust the vertical level
  • The horizontal level adjustment – set a gradienter (precision is ±0.05mm/m) in the middle 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 the main switch (power phases: R, S, T, PE) coupling, check the hydraulic pump orientation through the short testing start. If the orientation is wrong, cut the power right away, and exchange the two phase-lines (see the hydraulic pump moving arrowhead).

The cable entrance can be set on the bottom of the electric box.


(1) Confirm the voltages are matching.

(2) Make sure to let the expert on electric or expert according to the manual to instruct the person to do the electric connection of machine.

Working theory

The electro-hydraulic servo press brake is gathering with numerical technology, servo and hydraulic, upper crossbeam through the movement of the control valve to carry out moving up and down periodically, the measure of movement read by the rasters at two sides of the machine.

DNC control the hatches of two valves in left and right oil cylinders. If need, the flux in oil cylinder can be reassigned by the servo, make the upper crossbeam to move straight into the vertical orientation, and the measure of movement is decided by new measured pulse number. (Fig. 3)

Electro-hydraulic servo press brake working theory


The signal from the DNC controller through the servo valve to come to the hydraulic pressure signal and control the movement of the valve, each cylinder all has its own independence control loop in the hydraulic system, as well as the servo valve and the filling valve.

Backgauge Axis

The definition of axis

Through DNC to control axis

Left oil cylinder of slider block: Y1 axis

Right oil cylinder of slider block: Y2 axis

Lower crowing table: V axis

The back gauge moving front and bake: X axis

The back gauge moving up and down: R axis

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

Manual adjusting or controller control: Z1, Z2, R1, R2 axis

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) According to the DNC manual operation to do the programs of axes

(2) The left and right in the table mean we face the front of the machine.


(1) The operator should pay attention to the position of back gauge, if it through the area of mold, the machine will be damaged.

(2) When adjusting the Z-axis manual only allow to do it from the back of machine

(3) Must be careful when adjusting back gauge to avoid hit the lower die.

The back gauge is supported by straight-line guide and ball bearing lead screw, is composed by a beam from one side of machine to another side, and the guide of back gauge equipped on the two sides of machine body, behind has free moving working space, X to move the part by the DNC control, the back gauge is driving by servo motor.

Press brake hydraulic parts

Hydraulic pressure oil box

The hydraulic pressure oil box welded inside of the machine body, the inhaler equipped with it, and the motor, oil pump, high-pressure valve, control valve and electron system are equipped outside, the filtrating core and valve pedestal are equipped on the peak, discharging oil screw equipped on the bottom of oil box.

Electric motor

3-phase four-grade motor

Oil pump

High-pressure gear pump and the main motor connected by flexibility joining shaft.

The inhaler

The grade of filtration is 10μm, and max pressure is 400bar when the filter was jammed or change the oil, the filter must be instead.

Synchro servo valve

The servo valve is equipped on the top of oil cylinder; its flux is controlled by DNC numerical control system and servo amplifier, then control the slider block speed in the whole travel range, the position and manner it can control are as follows:

Moving quickly Bending speed Lower dead spot Return travel Upper dead spot

Bending speed Lower dead spot Return travel Upper dead spot

Lower dead spot Return travel Upper dead spot

Return travel Upper dead spot

Upper dead spot

Fill in valve

It’s on the top of oil cylinder, when the slider moving quickly, the oil in the oil box through the fill-in valve flow in the oil cylinder, it’s closed when bending.

Pressure valve

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


The overtravel protection controlled by DNC, the DNC check the time and pressure oil way of over travel when start. This is also called oil pressure leaking checking.

NC system parameters


  • 1st, before the manufacturer orders all machine tool parameter has all established, these parameters can guarantee the operational security.
  • 2nd, the machine tool parameter change, only then to carry on after obtained the manufacturer notice
  • 3rd, when the 2nd request cannot obtain observes, can cause the machine tool parameter change, creates the equipment accident.

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

At the same time, min bending width and bending angle are changed, only this, can determinate the limit of lower die overall dimension scientifically.

-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

In the bending process, the bending force will flock together on the worktable surface, and function on the tooling at the same time, so the burthen of tooling can bear should not overload.

For example:

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

Selecting lower die is V12, V16, V20, when selecting V16 lower die should try to according the thickness of the plate.

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

Relatively, the radius is not very important, and when b>Min bending radius, different thickness plate can do on the same lower die.

V16           S= 1.5mmm, 2mm, 2.5mm

Note: If it’s the tooling molding, the bending force must be 2 times or 3 times

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 upper die also need to according to the bending force and the limit burthen can not be overloaded.

In addition, the customer can choose the special tooling and should pay attention to the burthen which is different from the standard tooling.

Note: In the dangerous area of the machine, the operator must abide the safety principle, Fig.5, Fig.6.

Selection of press brake upper die

A. Forbid passing through the tooling

B. In order to avoid accidence, before equipping the upper and lower dies, should set the starting button on the second control position and NC driving button to “axes stop”.

Equip the lower die and adjust the clamping bolts.

Move the slider block slowly until the distance between slider block and lower die is about the thickness of the plate.

Fix the upper die and upper die pedestal, and then set it on the slider block, screw the clamping bolts slightly or close the part of clamping.

Using little force to press the mold in harness, the center of upper and lower die must be in a straight line. After one side of the mold edge totally connected, screw down the clamp part.

The material of sheet metal

The table below only for reference, if there are questions, check 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


  • Make sure the starting will not make any harm before starting.
  • The machine tool must under the condition of safety and suitable for working to run, all the protector and safety measure must be positioned.
  • Avoid any dangerous operation referring to safety.
  • Once appears faults should stop the machine and remove the fault right away.
  • Resolving faults must be instructed under the suffice fitter people or expert.
  • Normally, check whether there is damage or fault from the outside of the machine and report it, stop the machine if necessary.
  • The operator must carefully read the operation manual


Failure Reasons
Press engine can not move quickly Guide rail move spang, exchange valve EV1/2 damaged, control valve SV1/2 damaged
Press engine can not produce pressure Exchange 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 movement Filling in valve EV5/6 closed, oil position is too low in the oil cylinder
The press head moving back slightly first then start slowly Single  valve  V11/V12  opened,  the  setting  parameters wrong
Bending not correct Control 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 slowly Control 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/min Single-way V7/8 opened, exchange EV1/2 leak or plug

Note: we require the competent person to solve the possible failure, and abide the inspection technology rule, in the warranty period, should notice the maintenance people, if the failure caused by wrong operation, the maintenance people will not suffer any duty.

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

—Slider block move to the center of lower dead spot

—Close the main motor

—Set the operation selecting switch to “0”

—The main switch set to “0”

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

—Place the two wood on the worktable

—Rotate the “operation selecting” key switch to “2” (adjustment)

—operate as the “manual”

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

—Close the main motor

—Set the operation selecting switch to “0”

—The main switch set to “0”

Use the emergency stop button

When using this button, all axes stop and the pump closed, while the control system will not close. Restart the machine:

—Release the emergency button

—Press the green light “run the main motor” button. Don’t need to restart the machine tool

Proofread the slider block

In case of stop, one side of the slider block inclined or lower than the level position can adjust manual, but need to off the machine, and then start it in the normal condition.

Note: If the slider block can not be proofread or the position function is closed for several times, this can determinant the control system or hydraulic system failure.

Maintenance Request

  • The maintaining and testing person must read this operation manual and full of experience
  • Suggesting letting the manufacturer of this machine have a check to this machine
  • The operator of the machine must do the checking every day to the impossible leaking and loose part
  • If the fault can not resolve by the user, should notice the manufacturer right away.

The maintenance instruction of the machine parts.

Checking weekly Guideway: Lubrication

Back gauge: Lubrication

Checking the loosing and tight of the driving belt Checking the parallel

Clear the index plate Checking the driving parts

Molds: Clean and check the damage

The maintenance instruction of hydraulic system

Fill in the hydraulic oil:

Check the position of the oil everyday, when the slider block on the top, observe the oil position meter, if need, fill in oil.

Filling oil exceed the 10% of the oil box cubage, must let the hydraulic oil circulating for single way, the time can calculate the oil box cubage and the circulating frequency of hydraulic pump.

When the slider block is at the upper dead spot, adding the oil to the middle of oil staff gauge (from the back of oil box can see it).

T = V /Q* 5

T——Circulating time (minute)

V——Oil box cubage (litre)

Q—— The circulating frequency of oil pump

High-power filter

After working for 200 hours, the filter core must be instead for the first, after that, instead it every 6 months or after working 1000 hours, or the yellow indicator light “instead of the filter” bright. Filter net requests the 10U, after exchanging the core, the oil must be circulating working more than 1 hour as the mentioned above.

Note: After the yellow indicator light “instead of the filter” bright, must change the core in 8 working hours.

Back gauge

If need, all the axes zero position of the machine which the back gauge without localizer, must be checked once a week or get the compensation from DNC.

Inspection of machine function

Inspection of carrying measure system

The parts of machine adjustment inspection

Inspection of all screw connection rail way inspection

Inspection of transducer signal transfer Inspection of slider block tighten parts Inspection of back gauge driving parts Inspection of back gauge tighten parts Inspection of mould adjustment

Inspection of bending different plates (thickness)

Inspection of checking valves

The checking valves V7, V8, V9 and V10must be inspected for every six months, and the inspecting ways are as follows:

——moving the slider block to the upper dead spot

——Get away the connecting pin single-way EV1, EV2

——Run two manual control switches

——The checking valve must prohibit the oil from the bottom of oil cylinder through servo valve flow to oil box. (Slider block must stop at the upper dead spot)

——If the slider downhill, should ask the manufacturer to change the valve.

—– moving the slider block to the upper dead spot

—–Close the switch

—–Run the single-way valve EV1 and EV2 through the pin on the end cover

—–The moving speed of the slider block should nearly 10mm/s

—–If the slider block moving down quickly, should exchange the relevant valve

Note: The checking valves mentioned above are the part of the safety system, before exchange the potential damage valve should not start the machine tool.

Inspection of the pressure adjustment valve.

The safety seal ring of mechanical pressure adjustment valve must be inspected once every year.

Note: If cannot do the adjustment above, any claim for compensation of quality problem in warranty period is inefficacy.

Replacing the oil

——Hydraulic oil must be exchanged for every three years or after working 6000 hours

——Moving the slider block to upper dead spot and support well

——Adjust the screw to egest hydraulic oil

——Filling in new hydraulic oil to the middle position, and let the slider to stop at the upper dead spot

——Before restart the machine, make the hydraulic oil circulating for about one hour.

——After circulating, reinsert a 10um filtrate core

Recommending hydraulic oil and lubricant

Manufacturer Hydraulic oil Grease

Press Brake Safety Labels

Here are the drawings:

Warning Label 1

Warning Label 2

Warning Label 3

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