How to Choose Hydraulic Press Brake? (NC vs. CNC)

What is press brake?

Press brake is a machine that uses the equipped punch and die (general or special die set) to bend the cold metal plate into workpieces with various geometric section shapes.

Press brake generally adopts special CNC system for bending machine.

The coordinate axis of the press brake machine has developed from single axis to 12 axis, which is classified as follows according to function:

  • X-axis: control the forward and backward movement of the rear stopper
  • Y axis: control cylinder stroke
  • Z-axis: control the left and right movement of the rear stop
  • R-axis: control the up and down movement of the rear stop
  • AP axis: front support axis
  • P axis: multiple V mouth of the lower die automatically change the opening position of the lower die
  • W-axis: mechanical crowning axis

Related reading: Press Brake Axis Explained

The numerical control system can automatically realize the depth control of ram operation, the ram adjustment of the left and right tilting, the front and rear/left and right adjustment of the rear stopper, the adjustment of the pressure tonnage and the adjustment of the ram approaching the working speed.

Related reading: Press Brake Bending Depth Calculator

The hydraulic press brake can easily realize the actions of ram downward, inching, continuous, pressure maintaining, return and midway stop, and complete multi elbow bending at the same angle or different angles at one time.

Parts of hydraulic press brake

Ram part

It is generally hydraulic transmission. In terms of composition, it includes ram, oil cylinder and mechanical stop fine-tuning structure.

Moreover, the numerical value of the mechanical stop is controlled and adjusted by the numerical control system.

Synchronous system

It is mainly a mechanical synchronous system.

The main advantage is simple structure and stable and reliable performance.

Its main parts are torsion shaft, swing arm and joint bearing.

Workbench section

Its operation is completed by the button box.

The moving distance is controlled by the numerical control system, and the travel switch limit device is configured in the front and rear positions.

Backgauge mechanism

It is generally driven by motor, and its movement is mainly controlled by NC system.

Types of press brake

Press brake mainly refers to plate bending machine, which is used for bending and forming various metal plates.

The equipment is often used for sheet bending, which is a common large machine.

It should be selected according to the use, working environment, degree of bending required, thickness of plate and other conditions.

How to correctly select the correct type is our primary knowledge.

Press brake can be divided into different types according to working characteristics and modes.

The following is a comprehensive and detailed introduction to the classification of press brakes.

There are many types of press brakes, which can be generally divided into manual press brake, hydraulic press brake and NC/CNC press brake.

1. Manual press brake

Manual press brake includes mechanical manual press brake and electric manual press brake.

They are popular at home and abroad because of their small size, low energy consumption, high work efficiency, large and fast production, many fields of use and convenient transportation.

The structure of this type of press brake is relatively simple and laborious through manual operation.

It is suitable for processing and manufacturing of small workpieces.

2. Hydraulic press brake

According to different synchronization modes, hydraulic press brake can be divided into torsional shaft synchronous press brake, mechanical-hydraulic synchronous press brake and electro-hydraulic synchronous press brake.

According to different movement modes, hydraulic press brake is divided into up moving press brake and down moving press brake.

Hydraulic press brake is mainly used in sheet metal industry, such as automobile, door and window, steel structure, etc; V-groove for sheet metal etc.

Its structure and working characteristics are:

  • All steel welded structure, vibration stress relief, high strength and good rigidity.
  • Hydraulic transmission, stable and reliable.
  • Mechanical stop, torsional shaft synchronization, high precision.
  • The distance of the rear stopper and the stroke of the upper slider are electrically adjusted, manually fine tuned and digitally displayed.

3. NC/CNC press brake

The essence of the NC/CNC press brake is the press brake tools for bending the sheet. The tools is composed of support, workbench and clamping plate.

The force on the pressing plate is generated by energizing the coil, so as to clamp the sheet between the pressing plate and the base.

Because the electromagnetic force clamping method is adopted, the pressing plate is made according to the specific workpiece requirements, the operation is simple, and the workpiece with side wall can be processed.

NC/CNC press brake is a new large-scale machine. Its high precision is favored by many people.

It can adopt flexible operation mode.

It can not only linkage between two press brake machines to solve the problem of long plate processing, but also be operated and processed by a single machine, which can effectively improve the utilization rate, reduce energy consumption, and automatically adjust the compensation by the CNC system, which is convenient.

There are different models of NC/CNC press brake, such as G-type, F-type, WC67k type, etc.

Different kinds of press brakes have different performance and application fields. Therefore, we should select the appropriate machinery according to the use situation and operating environment to achieve the ideal performance.

Related reading: Types of Press Brake Bending

NC press brake vs CNC press brake

What are the differences between torsion shaft synchro press brake and electro-hydraulic synchro press brake? (Following refer to NC press brake and CNC press brake)

Nowadays, there are many kinds of press brakes on the market, and the installed configurations and corresponding systems are also diverse.

Among them, the torsion shaft press brake and electro-hydraulic press brake are often pulled out for comparison because of their similar functions, but their advantages in accessories, systems and prices.

So how to choose a “not backward” high-performance, cost-effective and easy-to-use press brake among many press brake machines?

Next, we will introduce the differences between NC press brake and CNC press brake from multiple angles.

Different structural principles

The design principles of the two models are different, resulting in different structures to ensure synchronization on both sides of the bending ram.

The NC press brake uses the torsion axis to link the left and right swing rods to form the torsion axis forced synchronization mechanism to move up and down the oil cylinders on both sides.

Therefore, the NC press brake is a mechanical forced synchronization mode, and the parallelism of the ram cannot be automatically checked and adjusted.

The CNC press brake is to install a grating ruler on the ram or bed.

The CNC system can analyze the synchronization on both sides of the ram through the information fed back by the grating ruler at any time.

In case of error, the CNC system will adjust through the proportional electro-hydraulic servo valve to synchronize the stroke on both sides of the ram.

Numerical control system, hydraulic control valve group and grating ruler constitute the feedback closed-loop control of CNC press brake.

Workpiece accuracy

The parallelism of the ram determines the angle of the workpiece.

The NC press brake keep the ram synchronized mechanically.

There is no real-time error feedback. The machine itself cannot make automatic mediation, resulting in poor machining accuracy.

In addition, its partial load capacity is poor, because the NC press brake forces the synchronous mechanism to move up and down the oil cylinders on both sides through the torsion shaft.

If the long-term partial load will lead to the deformation of the torsion shaft.

The CNC press brake controls the ram synchronization through the proportional electro-hydraulic valve group, and the grating ruler provides real-time error feedback.

In case of error, the system adjusts through the proportional valve to keep the ram synchronized and improve the machining accuracy.

Running speed

During the operation of the machine, three points determine its running speed:

(1) Ram speed

(2) Rear stop speed

(3) Bending steps

The 6:1 or 8:1 oil cylinder is selected for the NC press brake, which is slow, while the 13:1 or 15:1 oil cylinder is selected for the CNC press brake, which is fast.

Therefore, the fast down speed and return speed of CNC press brake are much higher than those of NC press brake.

When the ram of the NC press brake goes down, although the speed has the functions of fast down and slow down, the fast down and return speeds are only 80mm/s, and the speed conversion is not smooth.

The running speed of rear retaining material is only 100mm/s.

When the ram of the CNC press brake goes down, the speed has the functions of fast down and slow down.

The fast down and return speed can reach 200mm/s, and the speed conversion is smooth, which can greatly improve the production efficiency.

At the same time, the running speed of the rear stop reaches 400mm/s.

Mechanical strength

Due to its own design, the NC press brake cannot bend under eccentric load.

If it bends under eccentric load for a long time, the torsion shaft will be deformed.

The CNC press brake does not have such a problem.

The Y1 and Y2 axes on the left and right sides operate independently, so it can bend under partial load.

Practical operation

Most NC press brake are not equipped with CNC system, and there is no v-axis compensation.

Therefore, when processing according to the drawings, we can only rely on the experience of old workers to set out and do trial bending first.

If it fails to meet the standard, it is necessary to continue the trial.

This process not only generates waste, but also has a small selection range and high salary when recruiting operators.

Of course, you can also choose to add a manual crowning system.

CNC press brake is controlled by professional CNC system, with v-axis compensation, simple operation and low requirements for workers’ experience.

It has the function of simulating bending without trial bending.

It only needs to correct the drawing, input the steps and sizes and bend directly.

Numerical control axis

The more the number of control axis of the NC press brake, the worse the effect. Generally, it only controls the X-axis and Y-axis.

The CNC press brake is not controlled by the range of axis number.

It is 3 + 1 axis, that is, the automatic program design can meet high requirements, such as 4 + 1 axis, 5 + 1 axis, 6 + 1 axis, 7 + 1 axis, 8 + 1 axis, etc.

Good optional components

The NC press brake can be equipped with some better components on the basis of the original machine, such as ordinary quick clamp, manual crowning, lifting stop finger, ball screw and linear guide rail rear stop, oil cooler, light curtain protection, etc.

However, the CNC press brake can not only be equipped with these basic components, but also can be equipped with a variety of good accessories.

For example,

  • Tyokko type quick clamp or Amada type quick clamp shall be equipped on the basis of ordinary quick clamp.
  • The lifting back finger refers to not only manual, but also electric finger running on the guide rail through AC motor.
  • The light curtain protection can also be replaced by more sensitive laser protection.
  • In addition, the servo pump control system with many advantages such as energy saving, low noise, fast stamping speed and less fuel consumption can be equiped;
  • Manipulator that can greatly improve production efficiency;
  • Hydraulic clamping system;
  • Follow up supporter and laser angle detector.

The main difference between CNC press brake and NC press brake lies in whether there is feedback closed loop and CNC crowning.

See also:

The two should be clearly distinguished.

The NC press brake mechanically adjusts the cylinder stroke, and the CNC press brake controls the stroke by hydraulic pressure.

The NC press brake is controlled by the balance shaft, and the CNC press brake is synchronized by the servo proportional valves on both sides.

CNC press brake combines the advantages of electrical and hydraulic.

It has the advantages of high control precision, fast response speed, large output power, flexible signal processing, easy to realize the feedback of various parameters and so on.

The working efficiency of one CNC press brake can be equal to that of two to three NC press brakes.

CNC press brake advantages

Ram left and right synchronization

The synchronization performance is stable and flexible.

The CNC system has the function of ram tilt detection and deviation correction.

Bend angle (depth)

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

Feedback of bending depth

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

Deflection compensation of worktable

The CNC system can automatically calculate the pressure of the compensation cylinder required for the deformation of the worktable in the bending process, so as to ensure the uniformity of the full-length angle of the bending workpiece and effectively improve the straightness of the workpiece.

Angle correction

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

Stop position

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

It can automatically change steps and correct conveniently and quickly.

Programming mode

It has the functions of graphics and data programming, and the program modification and editing are convenient and fast.

Expansion length

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

Interference calculation

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

You can also manually modify and determine the bending process.

How to choose hydraulic press brake?

To sum up, the press brake is selected according to the actual processing requirements.

The CNC press brake has high precision, real-time error feedback and strong anti bias load ability of bending ram;

The NC press brake has low precision, no error feedback, and the anti deflection load capacity of the bending ram is poor.

The CNC press brake is more complex than the NC press brake, and the price of the whole machine is higher.

According to the above introduction, you can select the appropriate press brake from the following specific aspects.

Accuracy requirements for machining workpiece

CNC press brake has higher accuracy than NC press brake.

Machine working hours per day

The CNC press brake has high efficiency, which can shorten the working hours and reduce the labor cost.

Are the machine operators old employees?

The NC press brake can only be debugged through experience, which is difficult for novices to operate, while the CNC press brake is controlled by the system, which is simple and convenient.

Understand failure rate

Frequent failures will reduce work efficiency and delay the construction period, and the failure rate of CNC press brake is very low.

Available funds

If you have a sufficient budget, you can directly buy CNC press brake without considering it; If the budget is limited, you can only consider purchasing NC press brake.

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