Why Should You Choose CNC Press Brake?

The CNC Press Brake mentioned in this article is an electro-hydraulic synchronous double-cylinder up-moving CNC Press Brake.

The principle of CNC Press Brake

Why Should You Choose CNC Press Brake? 1

The bending principle is basically the same as the angle-forming principle of the ordinary press brake machine (as shown in Fig. 1).

The forming of the bending angle (air bending method) is controlled by the depth (bending depth) of the punch pressing sheet in the lower die mouth, or the workpiece is pressed to the same angle (shape) as the die (bottoming bending method).

Related reading: Bending Depth Calculator

Press Brake Ram Depth Calculator

So what is CNC Press Brake?

The CNC system controls the electro-hydraulic proportional directional valve and forms a digital control mode of full closed loop bending depth through the feedback of the grating ruler.

The numerical control system controls the ball screw driven by the AC digital servo system, and uses a disc type photoelectric encoder to form a semi-closed loop digital control mode for the positioning position of the rear stopper.

Related reading: Open Loop vs Closed Loop

Therefore, what is a CNC Press Brake can be simply summarized as: a bending machine controlled by CNC system for automatic compensation of the rear stopper positioning system, ram bending depth and worktable deformation

Why Should You Choose CNC Press Brake? 2

Fig. 1: Angle forming process of press brake machine

At present, there is a more advanced CNC Press Brake in the world.

The most fundamental difference between it and the CNC Press Brake described above is that this most advanced CNC Press Brake adopts the angle closed-loop control mode, while the former adopts the bending depth closed-loop control mode.

Related reading: Top 10 Press Brake Manufacturers

Advantages of CNC Press Brake

Then, what are the advantages of CNC Press Brake compared with ordinary press brake machine?

It is easy to see from some of the basic functions listed below.

1. Left and right synchronization of ram

The synchronization performance is stable and flexible, and the CNC system has the function of slide tilt detection and correction.

2. Bend angle (depth)

The CNC system can automatically calculate the bending depth according to the selected die angle, opening, R size and sheet thickness.

3. Feedback of bending depth

The imported grating ruler directly measures the position of both sides of the ram, and has a throat deformation compensation mechanism to ensure the consistency of the same angle.

4. Torsion compensation of worktable

The CNC system can automatically calculate the pressure of the compensation cylinder required for the deformation of the worktable during the bending process, thus ensuring the uniformity of the full length angle of the bending workpiece and effectively improving the straightness of the workpiece.

5. Angle correction

If there is an error between the programmed angle and the actual molding angle, the user only needs to enter the error value, and the system can automatically compensate and correct.

6. Retaining position

The system can automatically calculate the position of each axis of the stopper according to the bending height;

It can change steps automatically, and the correction is convenient and fast.

7. Programming mode

With graphic and data programming functions, the program is easy to modify and edit.

8. Unfold length

The numerical control system can calculate the unfold length according to the graphic programming with external dimensions (or internal dimensions).

9. Interference calculation

The CNC system can automatically determine the reasonable bending process according to the programming graphics, mold and machine tool profile, and can alarm the bending interference.

The bending process can also be manually modified and determined.

Axis configuration of CNC Press Brake 

What are CNC press brake axis?

It can be simply described as — the movements and functional parts controlled by the CNC system in the CNC Press Brake can be referred to as the CNC axis for short.

In general, the names of CNC axis are named according to their spatial positions in the machine tool in accordance with the coordinate system, while some other motion and functional parts are named according to conventional usage or international customary standards.

Related reading: Explanation of CNC press brake axis

Why Should You Choose CNC Press Brake? 3

Then, a CNC Press Brake is configured with several axes, which are generally configured reasonably according to the process requirements of the user for processing the workpiece.

Fig. 2 describes the configuration of common CNC axes of CNC Press Brake.

CNC axis setting and configuration selection table

The functions defined by each axis are described in the following table:

AxisAxis function description
Y1Left cylinder electro-hydraulic synchronous full closed loop control shaft
Y2Right cylinder electro-hydraulic synchronous full closed loop control shaft
XRear stopper semi-closed loop mechanical movement shaft. If equipped with X1 axle, this is the left-finger stop control axle.
X1The right rear stopper finger control shaft.
RRear stop finger refers to the vertical lifting control axis.
Z1The left side stopper refers to the mechanical shaft moving left and right on the stopper beam.
Z2The right stopper refers to the mechanical shaft moving left and right on the stopper beam.

CNC Press Brake Troubleshooting

1. The NC system cannot be started

1. The oil pump is not started.

2. DM02 module 14 # input signal lamp is not on, check the DC24V control circuit (refer to the electrical schematic diagram in Appendix C and D).

2. No downward movement of the ram

1. Check that the input signal lamp of DM02 module 15 should be on after stepping down the foot switch.

2. After the foot switch is checked, check the DC24V power supply (WS checks Line 200, PB checks Line 214).

3. For WS model, check whether the enabling signal (green light should be on) of BOSCH proportional valve magnifying plate 7KA3 is engaged.

4. Check the quick release relay 7KA1, that is, check whether the quick release electromagnet is energized. (WS model, PB model).

5. Check whether the proportional valve is open (check the feedback voltage).

3. No slow down bending of ram

1. Check whether the programming pressure is too low.

2. When the upper die contacts the sheet metal, it does not reach the programmed speed conversion point

3. If the pressure of the hydraulic system cannot be established, check the electrical signal and clean the pressure valve block.

4. If the flushing valve of the hydraulic system is not closed, clean valve 100 (PB) and valve 3 (WS).

5. Check whether 7KA2 is damaged.

4. The ram slides at the top dead center

The ram oscillates after the transition point

1. Clean No. 8 valve (WS model)

2. Clean No. 50 valve (PB model)

5. No automatic return of ram

1. The programming angle is too small, and the ram cannot reach the end point of bending programming.

2. For WS model, check whether the enabling signal of BOSCH proportional valve enlarged plate (green light should be on) 7KA3 is engaged (refer to Appendix C and D).

3. The return pressure is too small (no system pressure, clean the pressure valve).

4. The proportional valve is not reversed, and the proportional valve is cleaned (the left side is not returned to clean the left side, and the right side is cleaned the proportional valve on the right valve stack).

6. The rear stopper cannot move

1. Check whether the IRT and Panasonic drives have alarms.

2. Check the limit switch of each axis.

3. Check the reliability of connectors.

Related reading: 56 Press Brake Bending Problems: Proved Troubleshooting & Repair Solutions

Why Should You Choose CNC Press Brake? 4

CNC Press Brake Application and Development Analysis

1. Discussion on numerical control technology

There are control shafts in CNC press brakes, which generally have more than two axis.

The two important axis are the rear stop axis, which is also called X-axis, and its accuracy is generally required to be less than 0.1mm.

The other axis is called ram, also known as Y axis. The accuracy of this axis needs to be controlled below 0.01 mm.

Press Brake Axis Diagram

After explaining the axis of CNC press brake, we will further elaborate and explain the development of NC system.

1. Multi axis control technology

In the numerical control system, if we want to improve the accuracy of control and make the operation process more convenient and fast, we often add something called motion axis in the numerical control system.

There are many cases similar to adding axis to operate together, but there is only one ultimate purpose, which is to improve the quality of products and the efficiency of operation process.

2. Replacing DC servo motor with AC servo motor

AC motor is characterized by its reliable operability, high frequency torque, high output power, high dynamic servo and low moment of inertia.

In short, AC servo motor has high advantages over DC servo motor, so we generally use AC servo motor to replace DC servo motor.

3. Adoption and application of advanced CPU

CNC system has been well developed from being discovered to now.

At first, the CNC system was 8-bit, then developed into 16 bit, and then to the 32-bit CNC system, the whole system has been well improved and developed in many aspects, such as great changes in control, programming and management.

The graphics programming process and bending process developed to the later stage can display the pictures and bending process with a very high resolution, which makes people more intuitive when observing the bending operation of the NC system.

Another point is that after using the high-level CPU processing system, the control system has more storage space on both hard disk and floppy disk, so that the system can carry more things.

4. Carry out research on rich software and good operation adaptability

We can use the software disk or the keyboard engraved with standard characters and letters to write the program. In this way, the programming process can be more simple and clear, easy to be mastered and understood by people.

Let’s give a substantive example, such as LVD company in Belgium, whose plate processing equipment is very famous in the world.


The CNC system of the press brake owned by this company has reached a high level.

There are many different types of systems in their company, which are suitable for different jobs.

2. Application of CAD and CAPP

When NC programming is completed, this process is generally operated by humans.

This process has high requirements for people.

People not only need to describe and understand each process of the programming process, but also need to understand the accurate position of each axis of the press brake and the adjustment of some auxiliary functions.

This step is a very complex process.

In addition to this complex process, we also need to consider a series of problems, such as improving productivity and minimizing the time required for programming.

In our NC bending technology, our current research direction is to apply CAD and CAPP to automatic programming system.

In the following, we will conduct a detailed study and description of the functions of the automatic scheduling processing process.

1. Determine the optimal scheme of the workpiece in the bending process

The best we define here is not the best in the traditional sense.

The optimization we point out here is a better scheme relative to the required accuracy of the workpiece and the production standard.

It is a relatively optimal concept.

We should make intelligent modification according to the actual situation when making automatic arrangement, and we can’t stick to the rules.

For example, when the program written does not meet the user’s requirements for this work, the user can modify it freely. Users can modify the content of the program according to their specific needs, so as to meet their requirements for program writing.

2. Simulated bending process

During the bending process, we can use pictures to show the proper operation of this part at a certain position during the bending process.

We can visually observe and analyze the operation process in the form of pictures, so that the operation process can qualitatively display the details of the bending operation process in the form of pictures.

We can also dynamically show the bending process through video, so that people can observe the bending process more directly.

Through the video, the bending process can be observed and demonstrated through dynamic observation. This not only improves the authenticity of the operation process, but also reduces the sense of distance with people during operation, so that people can show and express the bending process more closely.

In this way, the bending parameters can also be expressed, and the bad and fault can be alarmed to provide information for people.

3. Generate NC program

NC programs are programs that are programmed automatically.

This program can make the machine tool bend the parts automatically, improve the work efficiency, reduce the use and consumption of manpower, and reduce the use of manpower and material resources.

One program associated with DC is DNC program.

This line requires the system through the control device of the press brake.

After the line sends the required command to input the NC program, the NC program will be input after the command is returned by consent.

In some cases, we can also modify the contents of the sent instructions, and the modified information will be returned to the computer.

In the process calculation, the step of calculating the compensation amount of springback is a particularly important aspect.

When we are processing a part, we should choose a correct angle.

If the angle has some deviation, we need to adjust the angle properly, and then transfer the adjusted angle to the control device.

When the system knows a correct angle, it will carry out reasonable operation.

When making process arrangement, we should clarify the purpose of process arrangement.

The arrangement of the process is generally to determine the motion sequence and speed between each axis.

In addition, we also need to adhere to the established principles of arrangement.

This principle is to avoid interference between the workpiece to be processed and the machine tool and die, and process in different ways according to different accuracy requirements for workpiece processing.

3. Summary

Based on the current development and related applications of the CNC press brake, we can see that the press brake machine has become more and faster in operation after combining intelligent and automation technology, which greatly facilitates our use of the machine for bending processing.

It not only greatly improves our work efficiency and work quality during bending, but also lays a foundation for our observation of the bending process, and provides us with very good observation conditions, so that we can observe the picture with relatively clear picture quality, and let us have a more intuitive and specific understanding and observation of the bending operation.

In short, the development of press brake has great prospects.

In terms of CNC bending, we still have a broad development space and prospects.

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