Choosing the right press brake

A press brake is a machine tool used for bending metal parts and sheets up to 20 mm thick. It is composed of a V-shaped or U-shaped die (depending on the desired bending shape) and a punch. The material to be bent is placed on the die and pressed by the punch which then bends the sheet to the selected degree.
Press brakes are used in sheet metal work and production plants in many fields, such as the automotive and aeronautic sectors.

How to choose a press brake?

Before choosing your press brake, you must first know the type of metal you want to bend (stainless steel, 16 gauge mild steel, etc.)
Then you will need to determine the particular characteristics to be taken into account when calculating the part bend. This includes, for example:
1. The tensile strength
2. The thickness and length of the metal
3. The press brake’s folding or bending length
4. The width of the V
5. The inner radius of the parts

Once these characteristics have been determined, you must then calculate the tonnage required for the bending operation.
The tonnage is the pressing force of the press brake. It determines the amount of pressure that can be applied by the punch during the bending operation.
1. High tonnage allows thick and hard metals to be bent.
2. Low tonnage is suitable for thin metals.
Warning: incorrect tonnage (too high or low) can damage your press brake or the part you are bending. To calculate the tonnage of your press brake, refer to the operating manual or a tonnage table.

There are three types of technology for press brakes:

The hydraulic press brake: https://www.harsle.com/Smart-Press-Brake.html

1. The punch moves by means of a system of hydraulic cylinders.
2. It allows high bending capacities (bending length up to 8 m, force up to 1,200 tonnes).
3. It operates continuously even if it is not bending, which generates electricity costs.
4. It requires significant maintenance regularly.
5. It’s stronger than an electric press brake.
6. It is also cheaper.
7. It is suitable for simple bending operations.

The electric press brake: https://www.directindustry.com/indus...ke-133499.html
1. It is equipped with servomotors instead of hydraulic cylinders.
2. It achieves greater productivity gains.
3. The servomotors only use energy when the machine is performing bending operations.
4. There is less maintenance.
5. The machine offers more flexibility.
6. It is more expensive than the hydraulic press brake, but operating costs are lower.

The hybrid press brake: https://www.harsle.com/Hybrid-Servo-...d94380246.html
1. It is a hydraulic press brake equipped with electric motors.
2. Having electric motors reduces the use of the hydraulic system.
3. It combines the advantages of electric and hydraulic press brakes.

What configuration should I choose for my press brake?

There are different configurations for press brakes, namely:
The tandem press brake: https://www.harsle.com/CNC-Synchroni...d94156926.html

1. It is a combination of 2 press brakes that operate synchronously with mechanical alignment.
2. This type of press brake is suitable for bending long and thick parts.
3. For parts over 14 meters long, there are even tridem press brakes.


The robotic press brake: https://www.amada.eu/uk-en/products/...bending-cells/

1. More and more press brakes are now being paired with robots to form an automated bending system.
2. With an integrated robotic system, the machine is able to choose the right bend according to the parts to be produced and the production volume, without the intervention of an operator.
3. This technology provides significant productivity gains.

What type of bending should you choose?

There are 2 types of bending:
1. Air bending
2. Bottom bending

In what cases should you choose air bending?

In air bending, the end of the punch and the 2 edges of the V allow the sheet metal to be bent. But this type of bending means there is a spring back effect of the work piece. As the bending force is weaker, the metal sheet springs backwards like an elastic when the punch is removed.

You must therefore adjust the bending angle according to the metal spring back and calculate the margin. As such, for a 90° bend, the punch must go down to 85° for example.

Other elements should be taken into account when calculating this margin, such as the thickness of the punch blade, the length of the fold and the opening of the V.

This type of bending is most commonly used for sheet metal working as it is suitable for machines with reduced capacities, unlike bottom bending, which requires more force.


In what cases should you choose bottom bending?

In bottom bending, the punch curves the metal sheet with a high force (3 to 5 times greater than air bending) which reduces or even prevents the spring back effect generally associated with air bending. The process begins with air bending then continues with cold forging carried out at the bottom of the V.
This method provides a high level of angular precision.
It is suitable for sheet metal over 2 mm thick.


What are the other selection criteria for a press brake?

What other criteria are important to consider when choosing a press brake?

1. The back gauge
1.1. This is an adjustable gauge that stops the part by centering the bending line on the V-shaped opening of the die.
1.2. It allows the part to be bent to be in the right position.

2. The angle control
2.1. It is used to compensate for any inaccuracies in the press brake.
2.2. Warning: the angle control is limited on some parts (if they are too small, parts with negative angles, etc.).

3. Tools
3.1. Using hydraulic clamping allows for shorter tool change times, for example.
3.2. The clamping length also has an effect on the tool accuracy.
3.3. Be sure to respect the maximum press force to avoid damaging to the tools.

4. Operator safety
4.1. When changing tools, make sure to stop the press brake motor or turn it to minimum.
4.2. Operators should never put their hands in the tool work surface.
4.3. They must also not wear loose or flowing clothing.
4.4. Lastly, operators must not work at the back of the machine.