If you are considering purchasing a press brake to increase parts processing capacity and increase production efficiency, please take a moment to carefully read the following information.
Are you aware that many people face financial ruin due to purchasing the wrong machine.
I'm not creating panic. This type of situation occurs frequently. With almost 10 years in this industry, I have seen this happen firsthand.
However, if you take the time to research thoroughly, you will gain a clear understanding of the type of bending machine you need, the important factors to consider, and how to make the best decision possible.
For companies looking to purchase a press brake, manufacturers offer a variety of pricing options with various controllers.
However, it can be challenging to consider all the factors. So what type of press brake should you choose?
The best approach is to assess your own needs and make them the center of the selection process.
Where should you start? The following press brake buying guide can help you.
Let's dive into this now.
What is a bending machine?
You may already know the definition of a press brake, but I still want to emphasize what it is.
See too:
- What is a press brake (and why is it called that)？
Many people who are buying a press brake for the first time or buying the machine for someone else may not have much knowledge.
Press brake is a machine used to bend metal sheets and is composed of a bench, ram, backgauge, oil cylinder, etc. Using a set of simple punches and dies, sheet metal can be shaped into a specific geometry. To bend plates with varying thicknesses, V-shaped grooves with different openings for the lower die should be chosen.
The required bending force can be calculated from the bending force chart.
See too:
- Press Brake Tonnage Calculator (It's FREE to use)
Bending machines are versatile equipment used to complete the bending of sheet metal using a simple punch and overall die assembly. They can bend parts into various shapes and perform other processes such as stamping, punching, crimping and surface stretching. These machines are widely used in various industries, including household appliances, electronics, containers, metal structures, instrumentation, daily hardware, building materials and others.
For more information about bending machines, including their composition, tools and bending force, you can refer to the following articles:
- Press Brake 101: Everything You Need to Know
What precautions would you ignore when choosing a bending machine?
1. Equipment market share
In the age of the Internet, when searching for a product, you may find many manufacturers promoting their offerings, making exaggerated claims and denigrating their competitors.
However, the most reliable indicator of a product's quality is often its market share. In your industry, you can usually determine which machine is widely used, easy to use, and which is considered a bad choice based on user experiences.
User feedback and reputation are essential as they provide first-hand insights and direct contact with the product. Ignoring their opinions is not advisable.
2. Enterprise scale
When considering purchasing a product, it is important to take into account the manufacturer's reputation and the quality of after-sales service. In the age of the Internet, it can be difficult to separate facts from marketing claims, but a product's market share in its industry can give you a good idea of its popularity and reliability.
It is also important to look for a regular, healthy company with a clear division of labor, as this often indicates that they are trustworthy and capable of providing reliable after-sales service. To assess the size and quality of an enterprise, it is advisable to personally visit its factory to check its level of formality and production activity.
3. Machine quality
The two points mentioned above are general terms that are not specifically linked to the machine. Now, I want to discuss the quality of the machine.
It can be difficult to compare machines if you are not familiar with bending machines.
One factor to consider is the volume and weight of the machine. Larger, heavier machines are typically stronger and higher quality than lighter machines, as the main component used in the machine is steel.
Another factor is accuracy. Ideally, you would take your own machined parts to the factory to test the machine's accuracy, but this is not always possible. A machine's accuracy is affected by backgauge, side column strength, and mold.
If the backstop is still powered by a chain, it will not be considered accurate. Aluminum beams may look attractive, but they can deform after repeated impacts.
A third factor is the screw and guide rail. Progressive companies now use ball screws and linear guide rails.
Finally, the resistance of the lateral column is related to the thickness of the plate used.
4. Punch and die
If we compare machines to soldiers, then molds are like their weapons. If these weapons are not of good quality, it will be difficult to defeat others.
So how can we determine the quality of a mold?
An important factor is the material. Currently, 42CrMo is considered a high-quality material for press brake tools, and other materials such as Cr6W2Si are also considered good.
Ordinary users may not be able to differentiate materials until after using them for a certain period of time.
Additionally, most molds undergo high-frequency quenching, which involves heat treating the knife edge. However, high-quality factories use full-body heat treatment.
A mold that has undergone full-body heat treatment is distinguished by a hole in the mold, which is a clear indication of this process.
It is important to note that the production cost of full body heat treatment is significantly higher compared to knife edge heat treatment.
See too:
- Press Brake Dies (Tools): The Definitive Guide
Principles for choosing the press brake
When choosing a press brake, the following four principles must be taken into consideration:
Principle #1:
Precision in the operation of the mechanical system.
It is understood that some physical error in the radius is inevitable, but the question is how much deviation can be tolerated by the user.
For simpler parts, a slight lack of precision may be acceptable, but for most parts, high precision is often required, especially when it comes to continuous manufacturing after bending.
Principle #2:
The necessary flexibility of the machinery.
The more diverse the parts and their varieties, the greater the need for flexibility in the bending machine.
In other words, for economic reasons, the press brake must be easy to operate in both hardware and software.
This way, even when orders change frequently and are rarely repeated, adjustment time can be minimized.
Principle #3:
Determine the production capacity and size of the bending machine.
Part dimensions, pressure, bending length, stroke and structural height must be taken into consideration.
Principle #4:
The potential buyer should carefully consider the end use of the machine, the known potential machine deflection, and the bend radius of the part, among other factors.
Factors to Consider Before Buying Press Brake
Press brake and other CNC equipment differ in terms of processing field and technology. As a manufacturer, you need to take into consideration all relevant factors such as application, deflection, bending radius of parts, etc. before making the decision to purchase a press brake.
As a decision maker, you have the responsibility to understand the performance, processing range, functions and precision of a press brake.
This is not a trivial issue, as a wrong decision can result in increased production costs and make cost recovery impossible.
Therefore, before making a purchasing decision, it is important to carefully consider the following 7 factors that can help you make the right choice.
1. What parts will you produce ?
The goal is to purchase a press brake that can effectively handle your processing tasks, not necessarily the one with the shortest worktable and minimum tonnage.
It is important to consider the type of steel sheet, as well as its maximum thickness and length.
If you are working with low carbon sheets with a maximum thickness of 3 mm and a length of 2,500 mm, an air bending force of 80 tons is sufficient.
For more information on how to calculate press brake bending force, you can refer to this article.
However, if you need to process a hollow block at the bottom, consider purchasing a press brake with a force of about 150 tons.
If the sheet is low carbon steel with a thickness of 6 mm and a length of 2,500 mm, then a 100 ton press brake is appropriate.
If you need to bend sheet metal with a hollow block at the bottom (bottom), you will need a large CNC press brake.
For sheet metal with a length of 1250mm or less, a smaller CNC press brake may be more suitable, even if it is half the size of a larger press brake.
This can significantly reduce the purchase cost.
It is important to remember that the length of the sheet metal is one of the key factors when choosing the right press brake.
2. Coronation
During the bending process, especially when bending long parts, deflection is inevitable for the CNC press brake.
The longer the workpiece, the greater the deflection of the press brake.
Under the same load, the deflection of a press brake processing a 2500 mm sheet is four times greater than that of a press brake processing a 1250 mm sheet.
In other words, a shorter press brake with less joint adjustment can produce higher quality products.
Reducing joint fit also reduces setup time.
Fortunately, most CNC hydraulic presses have already added a hydraulic deflection compensation function during the manufacturing process, which reduces the need for operator adjustments and improves bending accuracy and production efficiency.
This function is controlled by the CNC system.
Hydraulic oil is directed to a compensating oil cylinder via a magnetic servo valve, which pushes the work table upwards.
At the same time, the deflection compensation force increases along with the bending force of the press brake, effectively compensating the deflection.
Mechanical deflection compensation is also a viable option.
3. Texture of materials
When compared to low carbon steel, the bending strength required for stainless steel needs to be increased by about 50%.
However, for soft aluminum sheets, the required bending force will decrease by 50%.
You can obtain standard bending pressure parameters from press brake manufacturers.
The following datasheet shows the bending force required for 1000mm sheet metal of various thicknesses and materials.
There is a quick way to calculate the bending force required by the press brake.
You can use our online press brake bending force calculator to calculate the required press brake tonnage.
4. Workpiece bending radius
When bending workpieces, it is important to also consider the radius of the bending angle.
The radius of curvature is 0.156 times the dimension of the V-groove opening.
During the air bending process, the opening dimension of the V-groove should be 8 times that of the sheet metal thickness.
For example, if a press brake with a 12mm V-groove opening is used to bend a 1.5mm low-carbon sheet metal, the bending radius should be 1.9mm.
If the bend radius is close to or less than the thickness of the sheet metal, a bottom die must be used.
However, the bending force required in this case will be four times that of air bending.
When air bending, it is important to pay attention to the gap between the punch and the die at the bottom of the stroke, as well as the resilience when bending sheet metal at 90°.
Typically, air bending molds will result in a resilience angle of less than 2 degrees on a new press brake.
The radius of curvature is equal to 0.156 times the mold opening distance.
Therefore, for common up and down bending processing, the upper punch angle should be 86°-90°.
At the bottom of the line, there should be a gap slightly larger than the thickness of the sheet metal.
- How to calculate bending force in air bending (sheet metal)?
5. Angle Bending
The reason for the improved punch angle is the use of larger bottom dies with a bending tonnage that is four times greater than air bending dies.
This helps to reduce the resilience force within the specified bending radius.
Coining is similar to air bending, with the only difference being the front end of the punch being rotated to the required bend radius.
The resilience force is also reduced because the gap between the punch and the die at the bottom of the stroke is smaller than the thickness of the sheet metal and there is sufficient bending force (10 times greater than air bending). The front end of the punch comes into contact with the sheet metal.
To choose a lower tonnage press brake, it is better to choose one with a bending radius greater than the sheet thickness and opt for air bending. This will not affect the quality of the finished product and will ensure a long service life for the press brake.
- 6 types of press brake bending
6. Bending accuracy requirement
The choice between a CNC press brake and a common NC press brake depends on the accuracy requirements.
If ±0.5 degree accuracy is required and cannot be changed, then a CNC press brake should be considered. The ram repositioning accuracy can be controlled within ±0.01 mm.
For high-precision finished products, a press brake with high precision and good performance is required.
However, the ram repositioning accuracy of an NC press brake is about ±0.5 mm and, under suitable conditions, can still result in ±2 to 3 degrees of deviation.
In addition, CNC press brakes are typically equipped with a CNC controller for quick punch installation and clamping. If you need to process many small parts, this should be an important consideration.
7. Punch and die
Press brake tools are used to form sheet metal and have a direct influence on the accuracy of the bending process.
- Press Brake Dies (Tools): The Definitive Guide
Therefore, it is important to carefully inspect the punch and die.
There are various tool shapes and different punches and dies are used for different parts.
To achieve the desired shape of parts, the physical properties of materials are changed mainly through molding.
The press brake mold is a tool that transforms blanks into parts with a specific shape and size under the influence of the bending force of the press brake.
Standard press brake molds can be divided into punches and dies for stamping and separating sheet metal.
The forming mold has a cavity and the separating mold has a blade.
Press brake dies typically use T8 or T10 steel, and some better tools use 42CrMo material, which requires high strength, high toughness and good wear resistance.
Cold working dies on Cr12MoV steel is also a good material.
42CrMo is a high-strength quenched and tempered alloy steel that has high strength, good toughness and can work at temperatures below 500 degrees.
It is important to check the wear of each die by measuring the length of the punch from the front to the shoulder and the length between the shoulders of the die.
For conventional molds, the deviation per foot should be around ±0.001 inches and the total length deviation should not exceed ±0.005 inches.
For fine grinding tools, the accuracy per foot shall be ±0.0004 inches and the total accuracy shall be no more than ±0.002 inches.
It is best to use fine grinding tools for CNC press brakes and conventional tools for manual and NC press brakes.
Frequently asked questions before making a press brake purchase decision
1. How many types of press brake machines are there?
Based on various needs and development stages, there are various types of press brakes, including manual press brakes, pneumatic press brakes, mechanical press brakes, hydraulic press brakes, hybrid press brakes, servo electric press brakes and all-electric press brakes, among others. .
2. How many types of press brake dies are there?
There are many types of dies for press brakes, including standard top punches for right angle bending, acute punches, flattening punches and dies, radial punches, gooseneck punches, 1V bottom dies, 2V bottom dies, 3V bottom dies, 4V lower dies, polyurethane lower dies, hard rubber lower dies, lower die guides, lower die bases, offset dies, forming dies, hemming dies, bending die sets, unmarked bending dies, among others .
Furthermore, various non-standard punches and dies can be designed to meet different situations.
- Common standard punch and die:
To bend between 90° and 180°.
Advantages: Universal for thick and thin sheets, durable and widely used.
- Sharp Punch:
Used to bend between 20° and 180°.
Advantages: It can bend small angles and sizes, and the radius after bending is small, attractive and angular.
- Gooseneck punch:
For bending between 30° and 180°.
Advantages: Used for “U” shaped products that cannot be completed with standard dies and sharp punches, with a wide range of applications.
- Hem Punch:
Used to hem the edge and is suitable for sharp punch use.
First, bend the workpiece at an angle of less than 45° using the sharp punch, and then press it to the edge of the hem with the flattening die, mainly used to reinforce the structure.
- Offset punch (also known as “Z” type punch):
Mainly used for single bending of small “Z” shaped parts and is available in fixed and adjustable types.
- Forming mold:
Including punch and radius die, door frame forming die, U-shaped forming die, lamp post die, etc.
Typically used to bend complex products with a variety of angles and bending styles, therefore, the single bend forming die is designed to improve bending accuracy and efficiency.
- Co-coring mold:
It refers to the lower die used to support the CNC press brake and is composed of a die holder and a segmented lower die.
The same core means that when using any notch, you only need to switch to the specified notch without re-centering the punch and die positions, making die changes convenient and ensuring high bending accuracy.
3. Mechanical crowning or hydraulic crowning, which one to choose?
When using hydraulic crowning, the compensation pressure is separated from the pressure of the entire system. This means that when the compensation valve works, the pressure of the entire system will partially decrease. In addition, hydraulic oil control may cause oil leakage and pollution if the oil pipe breaks, the compensating cylinder sealing ring becomes old, or the gasket is loose.
Mechanical crowning, on the other hand, uses the numerical control system to automatically calculate the compensation value based on the thickness and length of the material to be bent and the selected mold. The system module then controls the positive and negative rotation of the compensation motor to adjust the compensation deformation, which is fed back through a potentiometer.
The advantage of mechanical crowning is that the compensation deformation will not change with changes in the pressure retention time of the ram, and it does not require energy every time the ram enters the deceleration position. This helps conserve energy throughout the system and eliminates the risk of oil leaks and pollution. Furthermore, the use of an integral bench reduces manufacturing cost.
The following articles will allow you to learn more:
- Press Brake Hydraulic Crowning vs Mechanical Crowning: Detailed Comparison Analysis
- What is press brake crowning and 3 types of it
- What is the influence of press brake crowning device on accuracy？
- Influence of the hydraulic crowning device of the press brake on the deflection curve of the work table (analysis and optimization)
4. How to choose open circuit and closed circuit in bending machine?
Closed circuit
Closed-loop control is also known as feedback control system. This system compares the actual output of the system with the desired value, generating a deviation signal, which is then used to control and adjust the output so that it approaches the desired value.
Closed-loop control is highly accurate and fast in its response, as it takes into account the functioning of each part of the machine tool. However, compared to open-loop systems, closed-loop systems have a more complex structure and are more expensive due to the involvement of multiple elements.
Open cycle
Compared to closed-loop control, open-loop control does not provide feedback on the current system control results. As a result, the accuracy of the bending process in an open circuit bending machine depends solely on the accuracy of each individual component of the machine.
The system is unable to control and compensate for changes in parameters during the bending process, leading to low accuracy. External disturbances can also cause changes to the machine's internal parameters, but the open-loop design is simpler and more stable, making installation and maintenance easier.
Wrap it up
Therefore, whether you should choose open loop or closed loop depends on your specific budget and requirements for bending your workpieces. However, it is important to keep in mind that if you choose the closed-loop method, you must select a company with strong research and development capabilities.
Only these companies can make the press brake truly utilize the closed-loop function and remain unchanged over time. Typically, small businesses do not have the ability to effectively utilize the closed loop system on a press brake.
5. What is the difference between CNC press brake machine and ordinary press brake machine?
The following article explains in detail the difference between CNC press brake machine and ordinary press brake machine.
- How to choose the press brake controller, NC or CNC?
- Press Brake vs. CNC folder (the ultimate difference analysis)
In short, the main difference between them is the presence of computational control and automatic feedback. This results in differences in processing speed, accuracy and efficiency.
6. What are the factors that affect the price of bending machine?
The factors affecting the price of CNC press brake machine mainly include the tonnage of the press brake machine, body width, component brand, mold type, product quality, service, etc.
7. Which brand of press brake machine is good?
The world's top ten press brake brands are the best choice. You can choose according to your geographic location and the brand's local reputation.
You can learn about the top ten press brake brands through the following links:
- Top 10 Global Press Brake Manufacturers
8. What is the difference between twist synchronization press brake and hydroelectric press brake?
Electro-hydraulic servo press brake
The main cylinders on both sides are synchronously controlled by hydraulic control systems such as electro-hydraulic proportional servo valves and grid rulers, which are independently controlled by CNC. Accurate data is fed back to ensure the accuracy of RAM operation.
Torque Synchronous Press Brake
A torsion shaft is used to connect the left and right rocker rods, forming a torsion shaft forced synchronization mechanism that keeps the up and down movement of the oil cylinders on both sides synchronized.
9. How to choose the CNC system of the press brake machine?
When choosing the CNC system for a press brake, there are several popular brands to consider, such as Delem, Cyblec, and ESA. Many press brake manufacturers also use their own in-house CNC system. To learn more about choosing the right CNC system for your press brake machine, you can refer to relevant articles.
- How to choose the press brake controller, NC or CNC?
- How to choose the hydraulic press brake? (NC x CNC)
10. How to buy a good bending machine?
If you carefully read the above content, you should now have a clear understanding of the factors to consider when purchasing a good press brake machine. The next step is to communicate directly with the manufacturer, deeply understand the manufacturer and their products, and make a final decision based on your budget.
Final thoughts
After many years of working in this field, I understand the importance of purchasing a high-quality bending machine for the end user. “Good” not only refers to quality, but also includes reasonable price and excellent after-sales services.
I have seen many cases where people purchase bending machines from small factories without adequate service, only to be left without support when problems arise. I have also witnessed agents losing a significant amount of money due to choosing the wrong vendor.
To avoid these problems, I highly recommend that you take the time to thoroughly research your options before making a final decision. Trust me, the time invested will be worth it.
