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Press Brake Buyer’s Guide: 4 Principles, 7 Factors to Consider

If you are planning to buy a press brake machine to expand the processing scale of parts and improve production efficiency, please calm down and carefully read the following contents.

Press Brake Buyer’s Guide: 4 Principles, 7 Factors to Consider 1

You know, many people go bankrupt because they buy the wrong machine.

I’m not an alarmist. This kind of thing happens every day. I have been in this industry for nearly 10 years and have witnessed these things with my own eyes.

However, as long as you take some time to do some homework carefully, you will clearly know what kind of press brake machine you need, what factors to consider, and how to make the most correct choice.

Press Brake Buyer’s Guide: 4 Principles, 7 Factors to Consider 2

For companies planning to purchase a 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. Then which type of press brake to buy?

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? The following press brake buying guide might be helpful for you.

Let’s dive right into it now.

What is a press brake machine?

Maybe you already know the definition of press brake machine, but I still want to emphasize what is it.

See also:

Many people who buy press brakes for the first time or purchase the machine for others may not know very well.

Press Brake Buyer’s Guide: 4 Principles, 7 Factors to Consider 3

Press brake is a kind of general equipment to complete sheet metal bending, which is composed of workbench part, ram part, backgauge part, oil cylinder part, etc.

Using a set of simple general punch and die, the metal sheet can be pressed into a certain geometric shape.

For plates with different thicknesses, V-shaped grooves with different opening sizes should be selected for the lower die.

The required bending force can be calculated by the bending force chart.

See also:

Using different shapes of molds can bend workpieces of various shapes. If equipped with corresponding process equipment, it can also be used as stamping, punching, crimping, shallow stretching, etc.

Therefore, this machine is widely used in electrical appliances, electronics, containers, metal structures, instrumentation, daily hardware, building materials and other industrial sectors.

For more articles on what is a press brake machine, the composition of the press brake machine, the toolings of the press brake machine, and the bending force of the press brake machine, you can read the following articles:

Press Brake Buyer’s Guide: 4 Principles, 7 Factors to Consider 4

What precautions would you ignore when choosing a press brake machine?

1. Market share of equipment

In the Internet age, when you need a product, many manufacturers will promote their products, constantly boast about themselves and belittle others.

But are these convincing?

At this time, the most convincing thing is the market share.

In your industry, you can basically know which machine you use more, which machine is easy to use, and which machine is basically a scrap.

The reputation for the users is very important, because they are the people who are at the forefront and the most direct contacts of products. You can’t ignore their advice.

2. Enterprise scale

This directly affects after-sales.

You can’t expect a small enterprise with only a dozen employees to bring you immediate after-sales service.

A regular and healthy enterprise has a clear division of labor.

Only in such an enterprise can you believe in bringing you trustworthy products.

How to measure the size of the enterprise?

Generally, I persuade customers to visit the factory directly. Whether the enterprise is formal and whether the production is busy is clear at a glance.

3. Quality of the machine

Press Brake Buyer’s Guide: 4 Principles, 7 Factors to Consider 5

The two points mentioned above refer to general terms, which are not directly related to the machine. Next, I want to talk about the quality of the machine.

How can you compare when you don’t know a press brake machine well?

The first is the volume and weight of the machine.

The main consumables used by a machine are steel. Machines with advantages in size and weight are generally stronger and of better quality than light machines.

The second is accuracy.

To understand the accuracy of a machine, it is best to take your own machined parts to the machine in the factory, but generally there is no such condition.

The accuracy of the machine is affected by the backgauge, the strength of the side column, and the mold.

If the rear stopper is still driven by chain, it can’t be said to have accuracy. The beam made of aluminum looks good, however, the beam will deform after be hitting a few times.

The third is the screw and guide rail. Now the enterprises that have the ability are equipped with ball screw and linear guide rail.

The last is the side column. The strength of the side column is directly related to the thickness of the plate.

4. Punch and die

Press Brake Buyer’s Guide: 4 Principles, 7 Factors to Consider 6

If machines are compared to soldiers, molds are soldiers’ weapons. If weapons are not good, you can’t beat others.

And how to distinguish the quality of the mold?

The first is the material. 42CrMo is a very good material for press brake toolings at present, and other materials such as Cr6W2Si are also good.

Ordinary users are not able to distinguish the materials until after a period of time.

In addition, the general mold is high-frequency quenching, that is, the knife edge is heat treated.

And good factories adopt whole body heat treatment.

Such a mold is characterized by a hole in the mold, which is an obvious feature of whole-body heat treatment.

The production cost of whole body heat treatment is much higher than that of knife edge heat treatment.

See also:

Principles For Choosing Press Brake

CNC Hybrid Press Brake Machine

The below four principles should be followed when choosing press brake: 

  • Principles#1: The 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 continued fabrication after bending.

  • Principles#2: How flexible 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.

  • Principles#3: 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

  • Principles#4: 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.

Factors To Consider Before Buying Press Brake

7 Factors You Should Consider Before Purchasing Press Brake

Press brake and other CNC equipment are different in aspect to processing field and technology, so as the manufacturers, you have to take full consideration (including the application, deflection, bending radius of parts, etc) before you made the decision to buy a press brake.

Bending Work Station

As the decision-maker, you gonna have the responsibility to understand the performance, processing range, function, precision of press brake.

This is not the trivial matter because once you made the wrong decision, your production cost will surge and your cost recovering gonna be an impossibility.

Therefore, before making a purchase decision, you should carefully consider the following 7 factors that can help you make the right decision.

1. What parts you gonna produce?

7 Factors You Should Consider Before Purchasing Press Brake

 

The point is you need to purchase one press brake which can help you finish the processing task, rather than the one with the shortest worktable and the minimum tonnage.

Check the types of steel sheets as well as the max thickness and length.

If it’s low carbon sheet metal with max 3mm thickness and 2500mm length, then the air bending force has no need to exceed 80 tons.

Regarding how to calculate the press brake bending force, you can read this article.

However, if you need to process a hollowing block at the bottom, probably you should consider purchasing one press brake with about 150-ton force.

If the sheet metal is low carbon steel with 6mm thickness and 2500mm length, then you should purchase a 100-ton press brake.

If you need to bending sheet metal with a hollowing block at the bottom (bottoming), then you gonna need a large CNC press brake.

If the sheet metal is about 1250mm or shorter, then a smaller CNC press brake should be choosing, even half above size.

In this way, your purchase cost will decrease a lot.

You should remember that the length of sheet metal is one of the key factors for you to choose a suitable press brake.

2. Crowning

Fig. 6 Long parts bending and crowning

 

During the bending process, especially bending those long workpieces, the CNC press brake must have deflection.

The longer of the workpiece, the larger deflection of the press brake.

Under the same load, the deflection of those press brake which processing 2500mm sheet metal is four times than those processing 1250mm sheet.

That is to say, the shorter press brake with less gasket adjustment will make qualified products.

Reducing the adjustment of gasket also helps short preparing time.

The good thing is, most CNC hydraulic press brakes have already added the hydraulic deflection compensation function during the manufacturing process, which is helpful for reducing the operator’s adjustment of machines.

Meanwhile, it improved the accuracy of bending as well as production efficiency.

The hydraulic deflection compensation function is controlled by the CNC system.

Hydraulic oil enters into a compensation oil cylinder via a magnetic servo valve, and pushes the worktable upward.

At the same time, the deflection compensation force increased with the bending force of the press brake, which plays the function of deflection compensation.

Mechanical deflection compensation is also a good option.

3. Texture of the materials

7 Factors You Should Consider Before Purchasing Press Brake

Compared with low carbon steel, the bending force needs to increase by about 50% for stainless steel.

But for soft aluminum sheet metal, the bending force will decrease by 50%.

You can get the standard bending pressure parameters from press brake manufacturers.

The following datasheet shows the bending force which will be needed for 1000mm sheet metal with different thicknesses and materials.

Air Bending Force Chart - Mild Steel
Air Bending Force Chart - Stainless Steel

There is one quick way to calculate the bending force which is required by your press brake.

You can use our online press brake bending force calculator to calculate the required press brake tonnage.

4. Bending radius of the workpiece

press brake bending radius

During the bending process, the bending angle radius of the workpiece should also be taken into consideration.

The bending radius is 0.156 times compared to the V groove opening dimension.

During the air bending process, the dimension of V groove opening should be 8 times larger than the thickness of the metal sheet.

For example, if use press brake with a 12mm V groove opening to bend 1.5mm low carbon sheet metal, the bending radius should be 1.9mm.

If the bending radius close to the thickness of the metal sheet or less than it, then the bottoming die should be used.

However, the required bending force will be four times larger than air bending.

For air bending, please pay attention to the clearance between the punch and die at the bottom of the stroke, and the resilience of when bending sheet metal with 90°.

Generally, the air bending mold will generate less than 2 degrees’ resilience angle on the new press brake.

And the bending radius equals to 0.156 times of down mold opening distance.

Thus, for common up and down bending processing, the top punch angle will be 86°-90°.

At the bottom of the stroke, there should have one clearance which is slightly larger than the thickness of sheet metal.

5. Bending Angle

Press Brake Buyer’s Guide: 4 Principles, 7 Factors to Consider 7

 

The reason why the angle of punch improved is that larger bending tonnage of bottoming dies been used (4 times bigger than air bending die).

This is helpful for reducing the resilience force within the scope of the bending radius.

Coining is the same as air bending.

The only difference is the front end of the punch been turned into the bending radius which gonna be needed.

Meanwhile, the resilience force is avoided because the clearance between the punch and die at the bottom of the stroke is less than the thickness of sheet metal, plus enough bending force (10 times than air bending), the front end of the punch will contact with the sheet metal.

In order to choose the press brake with the lowest tonnage, you better choose the one with a bending radius larger than the thickness of sheet metal.

And choose air bending because a large bending radius will not affect the quality of finished products and will ensure the long service life of the press brake.

6. Bending accuracy requirement

Press Brake Buyer’s Guide: 4 Principles, 7 Factors to Consider 8

 

It is just the factor that determines you choose CNC press brake or common NC press brake.

If the accuracy requirement is ±0.5 degrees and can’t be changed, then you should put your eye on the CNC press brake. The repositioning accuracy of the ram can be controlled at ±0.01mm.

So for those highly precise finished products, you have to choose such a press brake with high accuracy and good performance.

However, the ram’s repositioning accuracy of NC press brake is about ±0.5mm. Under the proper condition of the punch, it still will cause ±2~3 degree deviation.

Besides, CNC press brake always equipped with a CNC controller for quick punch installation and clamping. If you need to process many small parts, then this factor has to be your first consideration.

7. Punch and die

Press Brake Buyer’s Guide: 4 Principles, 7 Factors to Consider 9

 

Press brake toolings are been used for forming sheet metal and have a direct influence on the accuracy of the bending process.

Therefore, the punch and die should be checked carefully.

The tool has a variety of shapes, different punches and dies are been used for different parts.

In order to get the desired shape of the parts, the physical properties of the materials are mainly been changed through the molding.

It is a tool for making the blanks into parts with a specific shape and size under the influence of the press brake bending force.

Press brake standard mold can be divided into punches and dies, for sheet metal stamping and separation.

The forming mold has a cavity and the separation mold has a blade.

Press brake dies generally use T8 or T10 steel, and some better toolings use the 42CrMo material.

It requires high strength, high toughness and good wear resistance.

Cold work dies steel Cr12MoV is also a good material.

While 42CrMo is a high strength alloy quenched and tempered steel, with high strength, good toughness, and can work below 500 degrees.

Besides, the wear of each mold must be checked by measuring the length of the punch from front to the shoulder and the length between the die shoulders.

For conventional molds, the deviation per foot should be around ± 0.001 inches and the total length deviation should not be greater than ± 0.005 inches.

As for the fine grinding toolings, the accuracy per foot should be ± 0.0004 inches, the total accuracy should not more than ± 0.002 inches.

It is best to use fine grinding toolings for CNC press brakes, and conventional toolings for manual and NC press brakes.

FAQ before press brake buying decision

How many types of press brake machines are there?

According to different use needs and development stages, the types of press brake machines include manual press brake, pneumatic press brake, mechanical press brake, hydraulic press brake, hybrid press brake, servo electric press brake, full electric press brake, etc.

How many types of press brake dies are there?

There are many kinds of press brake ****dies, generally including standard top punch for right angle bending, acute punch, flattening punch and die, Radius punch, gooseneck punch, 1V lower die, 2V lower die, 3V lower die, 4V lower die, polyurethane lower die, hard rubber lower die, lower die guide, lower die base, offset die, forming die, hemming die, bending die set, mark free bending die, etc., and various non-standard punches and dies can be designed according to different situations.

1. Common standard punch and die:

For bending 90 ° -180 °.

Advantages: thick and thin plates are universal, durable and widely used.

2. Acute punch

Used for bending 20 ° -180 °.

Advantages: smaller angle and size can be bent, and the radius after bending is small, beautiful and angular.

3. Gooseneck punch

For bending 30 ° -180 °.

Advantages: it is used for “U” type products that cannot be completed by standard dies and acute punches, and has a wide range of applications.

4. Hemming punch

It is used to hem edge, which is suitable for matching with the sharp punch.

First, bend the workpiece into an angle of less than 45 ° with the acute punch, and then press it into the hemming edge with the flattening die, which is mainly used for the reinforcement of the frame.

5. Offset punch

(also known as “Z” type punch) it is mainly used for one-time bending of small-size “Z” type workpiece, which is divided into fixed and adjustable type.

6. Forming die

Including radius punch and die, door frame forming die, U-shaped forming die, light pole die, etc.

It is usually used to bend complex products, including a variety of bending angles and styles, so the one-time bending forming die is designed to improve the bending accuracy and efficiency.

7. Co-coring mold

It usually refers to the lower die used for supporting the CNC press brake machine, which is composed of die holder and segmented lower die.

The same core means that when using any notch, you only need to change to the specified notch without re-centering the punch and die positions.

The die change is very convenient and the bending accuracy is high.

Mechanical crowning or hydraulic crowning, which one to choose?

If hydraulic crowning is adopted, the compensation pressure is separated from the pressure of the whole system.

Therefore, when the compensation valve works, the pressure of the whole system will be partially lost.

Because of the hydraulic oil control, if the oil pipe is broken, the sealing ring of the compensation cylinder is aged or the joint is loose, oil leakage will cause pollution.

With mechanical crowning, when the ram stops at the top dead center position, the numerical control system will automatically calculate the compensation amount according to the thickness and length of the bending material and the selected mold.

The system module controls the positive and negative rotation of the compensation motor to adjust the compensation deformation, and then feeds back the change of the position of the upper and lower base plates through a potentiometer.

After the compensation motor is adjusted in place, the compensation deformation will not change with the change of the pressure holding time of the ram at the bottom dead center position, and it is not necessary to power on every time the ram enters the slow down position, so that the pressure of the whole system will not have energy loss.

Since there is no hydraulic pipeline, there will be no oil leakage and pollution.

In addition, because the machine tool is using an integral workbench, the manufacturing cost is saved.

The following articles will let you know more:

How to choose the open loop and closed loop in the press brake machine?

Closed loop

Closed loop is also called feedback control system.

The system compares the measured value of the system output with the expected given value, so as to generate a deviation signal, and then uses the signal deviation to control and adjust, so that the output value can be close to the expected value.

Closed loop control is based on the operation of each part of the machine tool, with high accuracy and response speed.

Because the closed-loop control system involves many elements, compared with the open-loop system, the structure of the whole system is more complex and the price is higher.

Open loop

Compared with the closed loop, open-loop control does not feed back the current system control results.

Therefore, in the open-loop system of the press brake machine, the accuracy of bending depends on the accuracy of each part of the machine tool.

The system cannot control and compensate the parameter changes in the bending process, resulting in low bending accuracy.

Once the outside of the machine tool is disturbed, the internal parameters of the machine tool will change.

However, in terms of system design, open-loop design is simpler and more stable.

The installation in the early stage and the subsequent maintenance of the machines are simpler.

Wrap it up

Therefore, whether you should choose open-loop or closed-loop depends on your specific budget and workpiece bending requirements.

However, here I would like to remind you that if you want to adopt the closed-loop method, you must choose enterprises with strong R & D ability. Only they can make the press brake machine truly play the function of closed-loop, and will not be affected by the time of use.

Generally, small enterprises do not have this ability to make good use of the closed-loop system on the press brake machine.

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.

In short, the difference between them lies in whether there is computer control and whether there is automatic feedback.

The result is the difference in processing speed, accuracy and efficiency.

What are the factors that affect the price of press brake machine?

The factors that affect 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.

What brand of press brake machine is good?

The top ten press brake brands in the world are the best choice. You can choose according to your geographical location and the local reputation of the brand.

You can learn about the top ten press brake brands through the following links:

What’s the difference between torsion sync press brake vs hydro-electric press brake?

Electro hydraulic servo press brake

The main cylinders on both sides are synchronously controlled by hydraulic control systems such as proportional electro-hydraulic servo valve and grating ruler, which are independently limited by CNC.

Feed back accurate data to ensure the accuracy of ram operation.

Torque synchronous press brake

The torsion shaft is used to connect the left and right swing rods to form a torsion shaft forced synchronization mechanism to keep the up and down movement of the oil cylinders on both sides synchronized.

How to choose CNC system of press brake machine?

At present, the popular brands of press brake machine CNC system in the market include Delem, Cyblec and ESA, and many press brake manufacturers also use their own CNC system.

You can read the following article to learn how to choose the CNC system of press brake machine.

How to buy a good press brake machine?

If you read the above content carefully, I think you have a clear understanding of what aspects to consider to buy a good press brake machine.

What you need to do next is to communicate with the manufacturer in person, understand the manufacturer and products from all aspects, and make the final decision in combination with your own budget.

Final thoughts

After working in this field for so many years, I know how important it is for the end-user to buy one good press brake machine.

Here I say “Good” not just mean the quality, also include good price, good after-sale services. I’ve seen many people buy press brake machines from those small factories without services, once the problem comes, the seller always chooses to disappear.

I’ve seen some agents lose a lot of money just because they choose the wrong supplier.

So please spend some time to do your homework first before making your decision to work with the seller.

You will find that the time you spend is worth it.

Need a price quote? Any questions?

Send us a message to let us know your deailed requirement.

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