What is press brake? What does a hydraulic press brake do?
A lot of people keep asking questions like this.
I just collect that official definition here for you to under what is press brake. I also put my own understanding here.
Here we go.
The press brake is a machine for sheet metal fabrication, to realize the sheet metal bending function by bending mold.
Wikipedia also gives its definition:
“A press brake is a machine tool for bending sheet and plate material, most commonly sheet metal. It forms predetermined bends by clamping the workpiece between a matching punch and die.”
The press brake (bending machine) is a sheet metal processing machine.
The bending function of the metal plate is realized by bending mold (punch and dies).
It can be divided into the manual press brake, hydraulic press brake and CNC press brake.
By way of synchronization, hydraulic press brake can be divided into twist axis synchronization, mechanical hydraulic synchronization, and electro-hydraulic synchronization.
By way of motion method, the hydraulic press brake can be divided into upward moving and downward moving press brake, which includes brackets, workbenches and clamping plates.
The working table is placed on the front support and consists of a base and a pressure plate while the base is connected to the clamping plate through hinges and consists of the housing, coil, and cover.
The coil is placed in the recess of the housing, and the top of the depression is covered with a cover plate.
Besides, for the “Bending” in the metalworking industry, wiki says:
Bending is a manufacturing process that produces a V-shape, U-shape, or channel shape along a straight axis in ductile materials, most commonly sheet metal. Commonly used equipment include box and pan brakes, brake presses, and other specialized machine presses. Typical products that are made like this are boxes such as electrical enclosures and rectangular ductwork.
Here we will discuss everything about press brakes or brake presses.
Let’s dive into it.
Press brake is divided into below several types:
Manual Press Brake
It is the most common one among press brakes.
Manual press brakes are required to manually adjust the bending dimensions and angles when used. Manual press brake also contains worktable, supporters, and the clamping plate. The worktable is also mounted on the supporters, which consists of a base and a pressure plate.
Manual press brakes are much more complex in operation than other types of press brakes, therefore, to make mass production after confirming bending size and bending angles. When finished one batch of mass production, adjusting bending size and bending angles for continued production.
Hydraulic Press Brake
Classified by synchronization, the hydraulic press brake can be divided into Torsion Synchronization Press Brake, Hybrid Press Brake, and Electric Hydraulic Synchronization Press Brake.
Classified by movement, the hydraulic press brake can be divided into: Up Moving Press Brake, Down Moving Press Brake.
Hydraulic press brake contains supporters, worktable and clamping plate. The worktable is placed on the supporters, consist of base and pressure plate. The base is connected with the clamping plate by means of a hinge and it is composed of shell, coil and cover plate. The coil is placed in the recess of the shell while the top of the recess is covered with a cover.
CNC Press Brake
CNC press brake is one kind of press brakes to realize bending function by controlling slider stroke and back gauge.
When using CNC press brake, you only need to input the pieces number of the workpiece which required for bending as well as bending angle for each step, the CNC press brake will finish bending according to the steps you just set in the controller.
Advanced CNC press brake mainly adopts hydro-electric servo system and grating ruler to form closed-loop control. It features high control accuracy, as well as bending accuracy and repositioning accuracy.
The operation of CNC press brake can be flexible, both overlength plates bending with Tandem Press Brake and short workpiece fabrication with normal press brake can be realized, which not only improve press brake utilization ratio but also reduce energy consumption.
Fix the top punch and bottom die on the upper and lower worktable, utilize the relative motion of the worktable driven by hydraulic transmission as well as the shape of punch and die, to achieve the bending formation for sheet metal materials.
” A press brake is a machine tool for bending sheet and plate material, most commonly sheet metal. It forms predetermined bends by clamping the workpiece between a matching punch and die.
Typically, two C-frames form the sides of the press brake, connected to a table at the bottom and on a movable beam at the top. The bottom tool is mounted on the table with the top tool mounted on the upper beam.”
Generally, the press brake machine including four main parts: mechanical parts, electrical parts, hydraulic part, and NC controller. The details are as follows:
1. Press Brake Frame
The frame of press brake is welded by the left and right upright plate, worktable, supporting bodies and fuel tanks. The worktable is under the left and right uprights. The fuel tank is welded with the uprights, which can improve the rigidity and strength of the frame, as well as increase the heat dissipation area of the hydraulic oil, it is advantageous to the normal operation of the hydraulic system.
Features of Press Brake Structure:
- Adopt fully welded structure, with sufficient strength and rigidity;
- Up transmission of hydraulic oil, the cylinders on both ends of press brake are installed on the slider, directly drive the sliding work;
- Slider adopt torsion to force synchronization;
- Adopt mechanical stopper, stable and reliable;
- Slider stroke is adjusted by the controller, fine adjustment manually, counter display;
- Wedge-shaped crowning, to ensure a higher bending accuracy.
The ram is made from the whole steel plate, and is connected with the piston rod in the center of the left and right oil cylinder, the cylinder is fixed on the connecting plate of the left and right wall plate, and the piston rod is driven by hydraulic drive to move the slider up and down.
In order to ensure the accurate positioning of the ram in the upper dead point, a grating ruler is arranged on both sides of the ram to transfer the position information back to NC controller, and the position is adjusted by controller. At the same time to ensure the synchronous operation of the ram.
Adopt hydraulic transmission, slider part consists of the slider, oil cylinder and mechanical stopper for fine adjustment. The left and right cylinders are fixed on the frame, and the piston (rod) is driven by the hydraulic pressure to move the slider up and down. The mechanical stopper is controlled by the numerical control system.
Controller by button box, the forward and backward movement of back stopper is driven by motor, and the moving distance of back stopper is controlled by CNC controller, with minimum reading 0.01mm (there is stroke limit switch both at front and back position)
4. Synchronization System
The mechanical synchronization mechanism, which consists of torsion, swing arm, joint bearings etc, has simple structure, stable and reliable performance, as well as high precision synchronization.
The position of the mechanical press brake stops is adjusted by the motor, while the data is controlled by CNC controller.
5. Press Brake Back Gauge
The backgauge of the CNC press brake adopt motor driving transmission, to realize synchronous movement of two ball screw timing belt. The backgauge distance is controlled by CNC controller.
6. Press Brake Axis Diagram
Press Brake coordinates
X, Y, Z directions of press brake is as follows, the arrow in the figure is positive.
Press brake axis can be classified as follows:
Y1, Y2-axis: control the upward and downward movement of ram
V-axis: control press brake crowning
X1, X2, R, Z1, Z2-axis: all is backgauge control axis to control backgauge positioning
7. Press Brake Exploded View
8. Press Brake Work Support Arms
The front supporter arms of press brake are fixed on the T-groove or linear guide in front of the machine and is designed with a manually adjusted back position claw.
9. Press Brake Foot Pedal Switch
10. Press Brake Clamps
Press Brake clamps including normal standard clamps and quick clamping tools for quick change.
Clearly, quick clamping tools will make it much easier for change punch die, not only convenient but also time-saving.
11. Press Brake Kits and Accessories (Parts)
|1||User Manual||1 Copy|
|2||Foundation Screw||4 Pieces|
|4||Oil Gun||1 Set|
|5||Front Supporter||2 Pieces|
|6||Pedal Switch||1 Set|
12. Press Brake Guarding
** Press Brake Safety Guards
** Press Brake Light Curtains
** Press Brake Laser Guard
13. Press Brake Laser Alignment
14. Press Brake Hydraulic System
The motor, oil pump, valve etc are installed in the fuel tank, in order to ensure that the oil tank is filled with oil when the ram is rapidly falling, the structure of filling valve is adopted. To improve the travel speed of the ram, and save energy.
- How Does the Press Brake Hydraulic System Work?
- Open Loop v.s Close Loop: Machine Tools Hydraulic Control Analysis
15. Hydraulic Oil Cylinder
16. Press Brake Seal Ring
17. Press Brake Weight
The weight of press brake ranges from 5T to 300T, this is much depending on the size of the machine. For example, for 80Tx2000mm press brake, the weight is around 6T, however, the weight for 2000Tx12000mm press brake is over 300T.
18. Press Brake Crowing
The press brake is pressurized by two working cylinders at both ends of the sliding block. The deformation force of the bending workpiece is in the middle, so the sliding block and the worktable are deformed together with the upper and lower die, which causes the sheet material to be uneven along the length of the die edge, which directly affects the accuracy and straightness of the bending workpiece.
Therefore, it is necessary to take corresponding measures to reduce or eliminate the deflection caused by the deformation.
The so-called deflection compensation device has preset a deformation in the direction of the opposite force-deformation in the sliding block and the upper die or the worktable and the lower die working table, and the deformation has the same amount of deformation generated in the actual work. Therefore, to realize the compensation of the relative deformation of the slider to the worktable, the pressure distribution between the dies is more uniform and the bending quality of the sheet material is improved.
At present, the press brake crowning mainly has three kinds – geometric crowning, hydraulic crowning, and mechanical crowning.
- Geometric crowning
Generally, not adopt this type of crowning method.
Working table fixed convex, that is, at the time of manufacture, the worktable was machined into arc shape with a slightly convex in the middle to compensate for the deflection caused by bending.
To make the appropriate correction for the upper mold, so that the middle part of the mold slightly curved, so that when the slider occurs upward deflection deformation, the upper die edge basically tends to be straight, so that it keeps each bending point along the bend line generate the same bending force for the plate.
The advantages of the geometrical compensation method are low cost and easy to manufacture, but there are some disadvantages which can only realize the compensation of fixed deformation and small compensation flexibility.
In addition, the compensation block arc correction quantity needs to pass through the precise calculation. The calculation method which based on the mechanics’ theory and the finite element calculation all has the certain error, therefore, even this kind of crowning method can achieve the deflection compensation effect, but it is very difficult to realize.
- Hydraulic Crowning
Mainly used on the electro-hydraulic synchronous CNC press brake, because the amount of compensation needs to be controlled from the CNC system, such as DA56 DA66, etc.
On the press brake frame, in addition, to installing two hydraulic cylinders at two sides, install another two-auxiliary hydraulic cylinder in the middle of the machine. When stroke down, the auxiliary cylinder filled with liquid oil and go downward. During bending process, hydraulic oil inlet into the auxiliary cylinder, so that the slider generate downward deflection for compensation.
Install the auxiliary hydraulic cylinder in the lower part of the worktable. During bending process, it generates an upward force on the worktable, which forms the automatic crowning system.
The pressure compensation device is composed of several small oil cylinders, comprising an oil cylinder, a motherboard, an auxiliary plate and a pin shaft, and a compensating cylinder is placed on the worktable, and a pressure compensation system is formed with a proportional relief valve.
When working, the auxiliary plate supports the oil cylinder, the oil cylinder holds up the motherboard up, just overcomes the deformation of the slider and the worktable. The convex device is controlled by a numerical control system, so that the preload can be determined according to the thickness of the plate, the opening of the die and the tensile strength of the material when bending different sheet materials.
The advantage of hydraulic crowning is that it can realize the deflection compensation for continuous variable deformation with large compensation flexibility, but there are some disadvantages of complex structure and relatively high cost.
- Mechanical Crowning
Most widely used crowning method for the ordinary press brake, with good compensation effect and low cost. In real operation, it is very convenient and easy for operators.
Mechanical crowning is a kind of new deflection compensation method, which is generally used triangular oblique wedge structure.
The principle is that the two-triangle wedge block with α angles, the upper wedge moving is fixed at x-direction, can only move in y-direction. When the wedge moves the △x distance along the X-direction, the upper wedge moves up the H distance under the lower wedge force, which is the principle of the mechanical crowning.
Regarding existing mechanical compensation structure, two bolster plates are placed in full length on the worktable, the upper and lower plates are connected through the disc spring and bolts. The upper and lower plates are consist of a number of oblique wedges with different slopes, through the motor drive to make them relatively moving, forming an ideal curve for a set of convex position.
19. Press Brake Stroke
Press brakes are widely used in energy, transportation, automobile, machinery, metallurgy, shipbuilding, aviation, military, agricultural machinery, petroleum machinery, power generation industries.
Press brake standard toolings including punch and die, for the stamping and separation of sheet metal. The die for forming has a cavity, while for separation it has blade edge.
You can check the ultimate guide for press brake toolings first.
Commonly Used Press Brake Toolings
In order to extend the service life of mold, the press brake punch and dies are designed with rounded corners as far as possible. Commonly used press brake toolings are as follows.
Generally, the height of flanged edge L≥3t (t=plate thickness). If the height of flanged edge is too small, even use bending mold is not conducive to forming.
- Non-indentation Bending Technology and Die Application
- Determinants of Press Brake Toolings Accuracy and Angle
Press Brake Toolings Materials
Generally, the materials of press brake toolings including T8 steel, T10 steel, 42CrMo, and Cr12MoV.
Cr12MoV is also a good material. The using performance can be satisfied, the process performance is also good, but the price will be high.
42CrMo is a high strength alloy quenched and tempered steel with high strength and strong toughness. It can work under the temperature of -500℃.
It mainly requires high strength, high toughness, and good wear resistance.
- Press Brakes Toolings Materials Selection and Performance Features
- Manufacturing Technique Analysis of Precision Press Brake Toolings
How to Choose Press Brake Toolings
Press Brake Toolings Pictures
Press Brake Toolings Drawings
Press Brake Punch Point Radius (R) and Punch Angles
Commonly used punch radius including:
（1）0.2R （2）0.6R （3）0.8R （4）1.5R （5）3.0R
Generally, for plate below 3mm with R0.6 standard punch, the point angles have:
The dihedral angle of punch should less than fabrication angle. For example, if we bending workpiece with 90°, the punch with 88° point angle should be chosen.
Press Brake Dies Shape
Generally, press brake dies have single-V shape and double-V shape, among these two shapes, it also has separation die and full-length die. Different dies are suitable for different fabrication purpose.
In short, the single-V die has much wider application than double-V die, while separation die has wider application than full-length die.
Die V Width and V Dihedral Angle
The relationship between V width and plate thickness (T):
Spring-back angle Δα=b-a
In the formula:
b—The actual angle of the workpiece after spring-back
Spring-back Angle for single 90 o free bending
|Steel||r/t||Plate Thickness t (mm)|
|Medium carbon steel σb=400-500MPa||<1||5°||2°||0°|
|Hard brass σb=350-400MPa||1-5||6°||3°||1°|
|Hard bronze σb=350-400MPa||>5||8°||5°||3°|
|High carbon steel σb>550MPa||<1||7°||4°||2°|
The factors that affect the resilience and the measures to reduce the spring back:
- Mechanical properties of the material
The spring back angle is proportional to the yield point of the material and is inversely proportional to the elastic modulus E. In order to reduce the spring back for those sheet metal which requires high precision, the low carbon steel should be the first consideration, do not choose high carbon steel and stainless steel.
- The larger the relative bending radius r / t, the smaller the degree of deformation, the greater the rebound angle Δα.
This is one very important concept. In the case of material properties permitting, the small bend radius should be chosen to improve accuracy. In particular, attention should be made to avoid designing large arcs as much as possible, as shown in the following figure. Such large arcs have a greater impact on production and quality control:
Press Brake Dies Cabinet
How to Choose Press Brake Die
You can check out previous written blog post about How to Choose Press Brake Die.
The commonly used press brake gauge including angle gauge, angle ruler and venier.
Click to view the list of world top 100 machine tools manufacturer, many of them are also world best CNC hydraulic press brake producer. Among them, you will also find best and largest press brake equipment manufacturers in China.
A lot of people want to know world’s best press brake manufacturers, or top 10 press brake manufacturers, however, very few of them will choose these best press brake in the world.
There is only one reason: expensive.
Their price is expensive, not means the machine is good. Just because their labor cost is high, steel price is high, the component price is high, which finally makes the press brake high.
If you don’t have enough budget, or if you want to find the most cost-effective press brake, I personally suggest you put your eyes in China’s press brake manufacturer.
The reason is simple:
China is rank top 1st for steel manufacturing, 1st for machine tools consumption, 1st for machine tools manufacturing…
I can use 10000 words here to explain the reason why you can choose press brake manufacturer from China, but there is no need. Because here I want to explain other things to make you fully understand press brakes.
Continue your reading.
Correct way to hold workpieces
Correct operation of press brake
Open the power switch → Hold up the pedal switch to start pump → Turn on the boot key → L-axis reset → D-axis reset → Commissioning
- Commissioning CNC Press Brakes to Improve the Sheet Metal Bending Efficiency
- How CNC Press Brakes Improve the Working Efficiency – 6 points
Install Punch & Die
First installed on punch, then die, loosen the two screws under the guide rail to do the alignment. Raise the height of the punch at first, then slowly step on the pedal, to check whether the mold is concentric, always check the pressure gauge to not exceed the pressure range.
Pickup & placement of workpiece
Do not reach the hands between the folded workpiece and die, so as not to pinch the finger, when aligning the mold, the hand and any part of the body are not allowed to be placed between the upper and lower mold. When bending large pieces, the rebound of the workpiece may hurt the operator’s face, so please pay more attention to this. If the press brake is operated by two more people, one of the operators should control the pedal switch well enough.
- 5 Steps to Use CNC Press Brakes
- 4 Ways for Press Brakes Controller Return to the Reference Point
- 4 Steps to Adjust the Parallelism of Bending Workpiece
- 4 Best Fabricating Problem Solution of CNC Bending Machine
- 12 Solutions for Sheet Metal Bending Problems
25 Safety rules for CNC press brakes
- Strictly abide by the safety regulations of machine tool workers, and wear labor protective supplies according to stipulations.
- Before starting the press brake, to carefully check whether the motor, switch, wire, and grounding is normal and firm, check the whether the control parts of equipment and buttons are in the correct position.
- Check the degree of coincidence and robustness of the upper and lower dies, and check whether the positioning devices meet the requirements of the fabrication.
- Reset the program when the upper slide plate and the position axes are not in the Origin state.
- If discovers the abnormal sound or breakdown 1-2 minutes after the equipment starts the empty running, and the upper slide plate finished 2-3 times movement, immediately stop the press brake. Start the press brake operation only after everything is confirmed normal.
- During the operation of the press brake, it should be unified command by 1 people, so that the close cooperation between operators and feed suppression personnel to ensure that send out bending signal after all personnel in a safe position.
- According to the bending sheet thickness, shape size, adjust the slider stroke and adjust the selection of upper and lower die and bending force. Select the V-width of the lower die and check the bending force of the workpiece, must refer to the press brake bending force chart at the right side of the machine, work bending force should not greater than the nominal force.
- When adjusting the clearance of upper and lower mold, the slider must be parked on the dead point. Clearance must be adjusted from large to small. The initial adjustment of the clearance of up and down mold generally can be 1 mm larger than the thickness of the plate, the gap must be greater than the thickness of the plate, in order to avoid damage the mold due to no clearance.
- When bending over two people, you must designate one person to step on the brakes and cut off the power when you leave the machine.
- Do not make unilateral and single point load work.
- The sheet bending must be compacted to prevent wounding caused by the warping of the sheet during bending.
- Do not stack sundries and gauges between the top and bottom molds.
- The power supply must be cut off and the press brake stopped working when adjusting the mold.
- The correct choice of bending mold, the fastening position of upper and lower die to be correct, to prevent trauma when installing the top and bottom die.
- When changing the opening of a variable die, no material is allowed to contact the lower die.
- Correct selection of bending pressure, the eccentric load should be 1/2 less than the maximum pressure.
- Bending workpiece length must not be 1/3 less than the worktable length while under the maximum bending pressure.
- Do not allow the stand of the person at the back of the press brake during its operation.
- It is strictly prohibited to press the sheet material at one end alone.
- When the workpiece or mold is found not straight during operation, the press brake should be stopped and corrected. It is strictly forbidden to use hand correction in operation to prevent injury.
- It is forbidden to fold the ultra-thick iron sheet or quenched steel plate, advanced alloy steel, square steel and the sheet material which exceeds the performance of the press brake in order to prevent damage of the press brake.
- Check the coincidence degree of the upper and lower molds regularly; Check the indication of the pressure gauge for compliance.
- If abnormal thing happened, stop the press brake immediately, check the reasons and notify the relevant personnel to troubleshoot promptly.
- Before shutting down, place the wood block on the lower die under the cylinder at both ends and drop the top slide onto the wood.
- After completion, exit control system procedures first, after cutting off the power, cleaning the work site.
The best training is provide you the manuals, you can learn wherever you are, and anytime you want. Here I collect some of the most popular manuals for your reference:
If you press brake operators, you should read below 17 press brake common failure analysis carefully, probably it will help you solve big problems.
Before the press brake maintenance or cleaning of the machine should align the top punch with the bottom die before drop it, then shutdown the press brake until the completion of the work. If required to start the machine or other operations, select the jog mode, and ensure safety.
The maintenance content is as follows:
Hydraulic oil circuit
- Weekly inspection of the oil levels in oil tanks, it should also be checked for hydraulic system maintenance. If oil level below the oil window, the oil tank should be filled with hydraulic oil;
- The hydraulic oil used in press brake is ISO HM46 or Mobil DTE25;
- The new press brake should change oil after 2000 hours running, after that change oil for every 4,000-6,000 hours operation. Clean the fuel tank for every oil changing;
- System oil temperature should be between 35℃~60℃, no more than 70 ℃, the too high temperature will lead to deterioration of oily and accessory damage.
- Each time during oil change, the filter should be replaced or thoroughly cleaned;
- If the press brake has the related alarm or the oily is not clean, or some other unusual things for filter, the filter should be replaced;
- Clean the air filter on the tank every 3 months, preferably change it every year.
- Monthly cleaning of hydraulic components (substrates, valves, motors, pumps, tubing, etc.), to prevent dirt from entering the system, can not use detergent;
- One month after the use of the new press brake machine, check whether the bending point of the tubing has deformation, if yes then it should be replaced. After the use of two months, should be fastened to all parts of the connection, the press brake should be shut down to ensure that there was no pressure of the system when doing this work.
- Standard test order does not mean the actual test order, it is changeable
- Adjusting the mechanism and parts which may affect the precision is prohibited during the test process.
- Workpiece precision inspection conditions:
- Requirements on workpiece
- If the workpiece is made by A3 steel plate, it’s tensile strength Qb≤ 450MPa
- The number of workpieces shall not less than 3 pieces
- The opening size of lower die shall be 8-10 times as large as workpiece thickness
- Workpiece should be put on the worktable middle position
- Bending angle is 90°
- Measure from end 100mm
The inspection method and accuracy range shall be based on GBT-14349-2011-Metal Press Brake- Precision
Note: the worktable is floated, inspection G2,G3 shall refer worktable vertical plate as a benchmark.
- Bending Radius
There should have bending radius for sheet metal bending, bending radius should not be too large or too small, it should be chosen appropriately. If the bending radius is too small, it will cause cracking at the bend position; if the bending radius is too large, it is easy to rebound.
The optimum bending radius of different thickness of various materials (bend inner RADIUS) see table below:
|Metal||Annealing Condition||Cold Hardening State|
|The corresponding position of bending direction and fiber direction|
The data in the table above is the preferred data for reference only. In fact, the rounded corners of press brake are usually 0.3, and a small number of the rounded corners of the press brake punch is 0.5.
For ordinary low carbon steel plate, anti-rust aluminum plate, yellow copper, purple copper, etc., the inner radius 0.2 is no problem, but for some high carbon steel, hard aluminum, super-hard aluminum, the use 0.2 radius will lead to bending fracture or the outer radius crack.
- Press Brake Bending Force Calculation Formula
- Press Brake Air Bending Tonnage Charts
- Press Brake Tonnage Calculator
Click above link you will get the answers.
Sometimes, the workshop owners need to bend steel, just for several pieces of steel, so buy a completely new press brake is not the best way. That’s why they want to build a press brake on their own, just to diy some simple press brake for bending purpose.
Therefore, the homemade metal brake press is what they want.
Here I collect some videos for home build press brake, hope you can make one with the tutorials been provided.
Different manufacturers will design different press brake wiring diagram. When you purchase it, the suppliers will send you the wiring diagram together with the hydraulic diagram as well as the installation and operation manuals. If you did not see it when you receive the machine, please contact your supplier immediately.
Below press brake wiring diagram is from us, just for your reference.
There are two popular press brake controllers, one is from China’s Estun, which is the sole agent of DELEM control in China, the other one is DELEM from Holland.
The key factor for press brake including two parts, one is the machine itself, such as the quality, accuracy, etc, the other one is the control system.
The installation manual and operation manual of press brake controllers in PDF form can be downloaded from below link.
The above operation manual and installation manual of press brake controllers have explained the programming and setup very clear, please download it from the last topic and read it carefully.
How to use the press brake
According to fabricate Q235 mild steel with hydraulic press brake to do a simple introduction:
- First, connect the power, turn on the key switch on the control panel, and then press the pump to start, then you can hear the oil pump rotating sound. (The machine does not run at current time)
- Stroke adjustment. You must pay attention to stroke adjustment for press brake operation, it must be tested before bending. Must ensure that there is clearance which equals to the thickness of the plate when the top punch down to the bottom of the lower die. Otherwise, the mold and press brake will be damaged. The adjustment of the stroke also has the electric quick adjustment and the manual fine adjusts.
- Regarding V-width choosing, generally, the width of V opening should be 8 times the thickness of the plate. For example, for bending 4mm plate, you should choose 32mm V-opening die.
- Back gauge adjustment generally has electric fast adjustment and manual fine-adjustment.
- Step down the pedal switch to start bending, you can loosen at any time. If loosen the foot, the bending machine will stop, step again to continue bending.
Here we provide press brake operation manuals to guide you operating press brake. Download the press brake operating instructions here.
Clean the Hydraulic Oil
The hydraulic system has a high requirement for the cleanliness of hydraulic oil. The clean of the oil tank is very important.
When replacing the hydraulic oil, you must discharge the cover of the oil tank. Use the towel to clean the bottom of the tank (do not use cotton yarn), then wash with cleaning coal oil gasoline. For limitation of tank cover, the arm cannot reach the end of the tank; you can wrap the towel on the bamboo or stick to wipe each corner. Loosen the leaking plug or brake valve to leak out the dirty oil.
Use the cleaning towel to dry the sides and bottom of the tank until it’s clean. If necessary, roll the dough at the welding seam or difficult cleaning places to cling the dirt, and then put on the cover.
Choose the hydraulic oil
The mark value of hydraulic oil is equal to the average value of viscosity when the temperature is 40℃.
If the working pressure and temperature of the hydraulic system are higher, and the working speeds slower, the chose hydraulic oil mark is higher.
It is recommended to use antiwar hydraulic oil ISO VG46# (the average value of viscosity is46mm2/s, when the temperature is 40℃.). If the machine operates under 5℃ for a long period, you can choose hydraulic oil ISO VG32#.
It is also recommended not to use the machine at very low temperatures (below -5°). However, should this occur, and then let the machine run idle for a while. An oil heater can be fitted in the circuit if required.
Under the normal working conditions, the oil temperature must not exceed 70C. Under special conditions, oil cooler can be fitted necessary.
Fill the oil
The using oil must clean. Screw the nut of air filter, filling through the air filter. If using the filling equipment with filter, you can open the cover of the oil tank and fill directly. Observe oil gauge, when ram stops at Top Dead Spot, the hydraulic oil fills at 80~90% of interspaces.
Make the machine work, first idling then at the maximum stroke to expel any air bubbles in the hydraulic circuit.
- A Brief Introduction of CNC Press Brakes Hydraulic System
- The Commissioning of CNC Press Brakes Hydraulic System
CNC Bending Machine power supply using three-phase AC 50HZ 380V power, can not only be directly used for the main motor operation, but also for the rear gear servo and equipment lighting use after output AC voltage through the system internal transformer. The other group form into two sets of DC 24V after rectification, one way for CNC controller use, the other for the use of controlling loop.
The following five questions will help sheet metal manufacturers assess whether robots should be used for bending operations.
■ Does the factory have an operator with rich experience and proficient in the computer to run the automatic bending unit?
Some experts believe that having an automated bending unit work is to allow an experienced bending worker to accept robots instead of artificial processes because automation will inevitably lead to job cuts, which can lead to the collective exclusion of workers. The welding workers in the sheet metal factory have undergone a tortuous process from rejection to acceptance of the automatic welder, and the popularization of the automatic bending unit will undergo a similar transformation.
There are also experts who believe that bending workers must discard the previous practice, that is, rely on the accumulation of small tips to manually produce a high-quality parts and components but should input these tips into the bending programs to guide those unskilled workers or robots for automated production. Only skilled workers, with a willingness to open-minded and willing to use new technologies, can ensure that an automated unit is successful.
However, the current software is quite mature, even if the first-line workers with little experience, can easily operate most advanced bending units. The time is gone to take a few days to teach a robot to do a few simple bending operations for bending mere 5,000 parts.
■ What production tasks are best suited for using robots?
It depends on the actual situation of production, but the scope of application of the robot is very wide. Specifically, three production tasks are suitable for automated bends:
First, the large volume and repetitive operation of the task, occupy a lot of time for the operators and resulting in tedious pain.
Second, small batches, but frequently occurring tasks, as shown in the picture.
It is not only a large batch of tasks suitable for the use of robot bends, small batches, recurring tasks are also suitable.
Third, it takes two people to carry up the extra large parts of the material or may cause personal injury for the operator.
My view is that if it does not exceed the working radius of the robot, and within the load range of the press brake production tasks are appropriate. The core of the automation unit is that a manual bender and an automated unit can be charged by an operator nearby. It is very meaningful for a worker to be able to do two bending tasks on both the manual and automatic bending units. Robotic bends require more time to set than manual bends, but it is also worthwhile because productivity is significantly increased.
■ How much time does it take to program?
Almost all professionals admit that in the past few years, automated bending programming technology has made significant progress. It is not necessarily to understand the robot like engineering experts to program the automation unit. A programmer needs only a CAD module, after submitting the data, the software will generate the bend order and operation instructions. In some cases, people have to make a real bend test based on the recommendations, but software developers point out that such tests may be superfluous.
Now the software program is embedded in 3-D simulation module, can simulate the robot and press brake movements, before the production instructions reach the machine, can simulate detection, and visually confirm the order of the bend. In addition, the software can generate instructions (see Figure 3) for choosing clamping tools (see Figure 2), robot motion and material end picker.
Robot bending machines can be quickly converted between different production tasks due to improvements such as automatic clamping tools replacement devices.
On such a replacement workbench, the robot can replace the material end picker within a short 25s
In most cases, the programming can be done in the case of disconnection to ensure that the automatic bending unit is undisturbed.
■ What is additional investment required in addition to capital equipment investment?
You can’t talk about robot automation without leaving the security behind. The question concerns whether a sheet metal factory is willing to invest in a tangible fence, or a more open and secure grating to keep people safe. Two of investments are worth considering.
A safety cover is the cheapest option, but it takes up a lot of space, which is not good for the layout of the workshop. Take the bending unit of a major machine tool manufacturer, for example, it occupies an area of 12m long and 5m wide, including a feeder robot, but does not include space to accommodate the security fence. For a cramped production workshop, automated production with security guarantees is difficult to achieve.
For workers who are interested in safety gratings, note that the Automation unit may stop working in unexpected situations. The problem with the safety grating is not that it should not be used, but that most people do not know where the boundaries are, that some people simply have no intention of waving their hands through the workshop, without knowingly triggering the light of the safety grating, thus closing the bending unit.
However, safety gratings are suitable for use in relatively open workshops and are more suitable for companies that strictly restrict the entry of people into the workshop and clearly label the boundaries of the production unit. Investment in quick-change clamping tools has been mentioned before, and the next step behind this investment is to add an investment in the newly emerging automated mold library, as shown in Figure 4.
In the latest generation of the automatic bending unit, the mold can be installed and downloaded according to program instructions, do not need to be manually installed.
After the program is programmed, the mold library is automatically installed and unloaded in the upper and lower die replacement device, which has a rotating disc that carries the mold, adjusts the mold to a suitable position, and installs it to one of the top and bottom two clamping devices.
■ How to determine the reasonable cost of a robot?
This depends primarily on the effective working time of the press brake, which will help assess whether it should be purchased. When you can have an operator take care of two bending machines at the same time, the productivity improvement is very obvious. But investors should pay more attention to the utilization of equipment. If the automatic press brake always shut down, other than the continuous production of parts, then it will not continue to create a return on investment.
To improve device utilization, a company should improve all aspects of the automation unit. In many practices, the time to set the preparation is as much as the time of production and fabrication. What is the point of an automated unit that does not match a quick-change device? Compared with the traditional two-axis back gauge, how much faster can the components of a six-axis back gauge be produced on the automation unit? If every process is not very smooth, then enhance the efficiency of a single process is meaningless.
It is, of course, necessary to think about the length of the production cycle, but in many practices shortening the cycle of production is not as effective as increasing the number of components in one shift or one day. The key to the problem is to reduce the standby time of the press brake so that it can be in working condition for a long time to increase the production significantly.
If you want to get some press brake tips and tricks, please read this article again carefully.
Press Brake Operator’s Job Responsibilities：
- Under the leadership of the director in sheet metal workshop, conscientiously learn to obey the rules and regulations of the company, obey the arrangement of the leadership work, unite the staff, make positive efforts, and do the saving work well, produce the qualified products.
- Responsible for routine maintenance, inspection, repair, adjustment, fastening, and do a good record for the press brake.
- Familiar with the safety technical procedures, in strict accordance with the safety technology disclosure and operating procedures. Master the normal operation method of the press brake. Can accurately judge, timely and correctly take urgent measures under the abnormal situation of machinery.
- Check whether there is enough oil in the tank, checking valve, pipeline leakage, and oil pressure after start the pump, confirm where they meet the requirements.
- Before start press brake must carefully check whether the motor, switch, wire, and grounding are normal and firm, check whether the control parts of equipment and buttons are in the correct position.
- Check the coincidence degree and robustness of the upper and lower mold, and check whether the positioning devices meet the requirements of the fabrication.
- Back to the origin program when the upper slide plate and each positioning axis are not in the Origin state.
- 1-2 minutes after the equipment starts the empty operation, and the stroke finished 2-3 times movement, if discovers has the abnormal sound or has the breakdown, stop the press brake immediately, eliminate the trouble. After everything is confirmed in good condition to start to continue operation.
- During work there should be 1 people take the command so that the operators and feed suppression personnel can work closely; send a bend signal after confirming all the personnel is in a safe position.
- Sheet metal must be compacted in order to prevent the injuries due to the warping during bending operation.
- The power must be cut off and waiting for the machine stopped before adjusting the punch.
- When changing the V opening of the bottom dies, no material is allowed to contact the lower die.
- Check whether the fastening screws are loose frequently.
- Do not operate the press brake alone, should be coordinated by 2 people to feed, control the size of precision, and material takes. The site should be commanded by one person.
- No other items should be placed on the workbench.
- The press brake must be stopped before adjustment and cleaning.
- Stack the finished products well, clean the site, cut off the power and lock the switch box before off duty.
Press Brake Operator’s Salary
In China, the wages for press brake operators are around 450-800usd per month. And the salary is different in various countries.
For companies planning to purchase a new type of press brake, the manufacturers can offer a variety of pricing with different controllers.
But experience shows that it is not easy to consider the overall situation.
The ideal way is to analyze your own needs and place them in the core position of the selection process.
And where should these considerations be started?
Four principles should be followed when choosing press brake:
- Precision used in the operation of the mechanical system.
In principle, it can be argued that the error of the radius is physically unavoidable, so the point is how much deviation can be accepted by the user.
Slightly less accurate for simple parts is acceptable, but most parts often require high precision, especially in the case of continue fabrication after bending.
- How flexible the new machinery must be.
The wider range of the parts, the more species, then the more requirement for flexibility of the press brake machine.
In other words, for economic reasons, the press brake in the hardware and software operations must be very simple.
Even when the order changes frequently and is rarely repeated, the adjustment time can be minimized.
- Need to determine the production capacity and size of the press brake machine.
From the dimensions of the part, the pressure, bending length, stroke and structural height must be measured
- It is advisable for the prospective buyer to consider carefully from the end use of the machine, the possible deflection of the known machine, the bending radius of the part, etc.
In order to help customers to buy the right press brake, we wrote 7 factors you should consider before purchasing press brake
Press Brake FAQ
Press Brake vs Folding Machine
In recent years in Europe and the United States, 30% of the sheet metal factory is willing to invest in the use of folding machine instead of press brake for bending fabrication.
It is mainly because folding machine operation is more convenient, and it is a kind of bending equipment with many advantages.
Certainly, these two kinds of equipment have their own characteristics.
I will compare the characteristics of two kinds of equipment from the principle of work, for your reference:
- In the entire bending process, the operator must hold the sheet material and rely on manual delivery to the back gauge for positioning.
- Unsafe for large and heavy-duty sheet operators.
- Because the weight of the sheet causes the bending angle becomes larger.
- One operator is difficult to complete the bending of large workpieces.
- The bending angle is determined by the depth of the upper die into the lower die.
- A small deviation of plate thickness causes inconsistent bending angle.
- Different plate thickness bends need to be configured with the different punch and dies.
- The installation and commissioning of the machine require professional knowledge, long boot time.
- The high cost of buying, replacing and keeping molds.
- Maximum Bending width is limited by upright.
- Press brake is more complex to use.
- The operator must be trained into the professional skilled worker.
- A longer work cycle for each step.
- The repetition accuracy of the workpiece depends on the technology of the operator.
- In the bending process, the sheet material is placed on the worktable of back gauge, to ensure the bending distance and hold the plate.
- In manual mode, the safety of operators is greatly improved.
- The errors for small thickness will not affect bending accuracy.
- Bending different thickness of plate does not need to replace the mold.
- Skill requirements for operators are not high.
- High bending efficiency
What do you think?
Quick calculation method of sheet metal bend expansion
For sheet metal bending and expansion, one side of the sheet will be elongated, the other side will be compressed. The affecting factors including material type, material thickness, heat treatment and bending angle.
Expand Calculation Principle:
- During the bending process, the outer layer is subjected to tensile stress, and the inner layers are subjected to compressive stress. There is a transition layer which is neither tensile nor pressure from pull to pressure, which is called the neutral layer. The length of the neutral layer remains unchanged in the bending process, same as the length before the bending, so the neutral layer is the basis for calculating the expansion length of the bending piece.
- The position of the neutral layer is related to the degree of deformation.
When the bending radius is larger and the bending angle is small, the deformation degree is small, and the neutral layer is near the center of the sheet thickness; When the bending radius becomes smaller and the bending angle increases, the degree of deformation increases, and the position of the neutral layer moves toward the inner part of the bending center gradually. The distance from the neutral layer to the inside of the sheet is expressed in λ.
Basic Formula for Expansion Calculation:
Expansion length = inner layer + inner layer + compensation amount
Calculation of minimum bending edge of one bend
The starting state of the L-bend is shown in the following illustration:
Reference table for bending inner R and minimum bending height of cold rolled sheet
|No.||Thickness||Die Groove Width||Convex die R||Min Bending Height|
The starting state of the Z-bend is shown in the following illustration:
The minimum bending size (L) of the sheet metal corresponding to Z-bend for materials with different thickness is shown in the following table:
|No.||Thickness||Die Groove Width||Convex die R||Z Bending Height|
Press Brake Bending Allowance (Tolerances)
1) Tolerance Standards for Common Bending
2) Tolerance Standards for Z Bending
3) Tolerance Standards for V Bending
4) Tolerance Standards for U Bending
Remarks: We will keep updating this post, so leave your comment if you have any questions for above content.