Types and techniques of folding

Bending with a press brake is a process commonly used in industry to form metal sheets by giving them a precise curve or angle. Here are the common types of bending performed with a press brake:

Air Bending

Description: The sheet metal is partially pressed between the punch (upper tool) and the die (lower tool), but without touching the bottom of the die.
Benefits :
Allows great flexibility in corners.
Requires less force compared to other methods.
Disadvantages:
Accuracy depends on variations in thickness and hardness of the material.

Bottoming

Description: The sheet metal is pressed until it touches the bottom of the die, ensuring a precise angle.
Benefits :
High precision in the bending angle.
Good repeatability.
Disadvantages:
Requires greater force.
Risk of increased tool wear.

Coining

Description: The sheet metal is completely crushed between the punch and the bottom of the die, which prints the exact shape.
Benefits :
Very high precision and dimensional stability.
Disadvantages:
Consumes a lot of energy.
Requires sturdy tools.

Offset Bending

Description: Produces two close folds to create a Z-shaped offset.
Applications: Used to manufacture parts where surfaces must be parallel but at different heights.

Controlled radius bending

Description: The press brake is equipped with specific tools to obtain a controlled bending radius.
Advantages: Suitable for sensitive materials where sudden bending could cause cracks.

Crush folding (Hemming)

Description: The sheet metal is bent and then crushed to obtain a flat and safe edge.
Applications: Used for aesthetic finishes or to reinforce an edge.

Compensated springback folding

Description: Technique taking into account the elastic return of the material to obtain the desired final angle.
Benefits: Increased accuracy for high resilience materials.

Off-axis bending (Offset Bending)

Description: The press is set to produce asymmetrical or complex shapes.
Applications: Used for special designs.

Important factors in bending with a press brake:
Choice of tools (punches and dies): Depends on thickness, type of material, and type of bending.
Bending parameters: Pressure, speed and angle must be adjusted precisely.
Material: Thickness and mechanical properties influence the process.
Elastic Return: Must be compensated to ensure accuracy.

Main sheet metal bending techniques:

Sheet metal bending is a mechanical forming operation used to give an angular or curved shape to a metal part. Here is an overview of the main sheet metal bending techniques, their characteristics and applications:

1. Folding with a press brake:
   Principle: A press equipped with a punch and a die exerts pressure to bend the sheet metal to the desired angle.
   Advantages: High precision, versatility for different angles and shapes.
   Applications: Used for mass production or prototypes in various sectors, such as the automotive or household appliance industry.
2. Roller folding (or rolling):
   Principle: The sheet metal passes between three rollers which gradually bend it to obtain curved or cylindrical shapes.
   Benefits: Ideal for creating rounded shapes or tubes.
   Applications: Construction of tanks, pipes, or metal structures.
3. Folding by manual folding or using manual folding machines:
   Principle: The sheet metal is bent using hand tools or a light bending machine, exerting a direct force.
   Advantages: Simple, inexpensive, suitable for small parts or limited series.
   Applications: Craft work, repairs, or small workshops.
4. Bending with a hydraulic press:
   Principle: A hydraulic press applies a uniform force to bend thick or complex sheets.
   Advantages: High bending capacity, suitable for thick sheets.
   Applications: Heavy industries such as shipbuilding or industrial equipment manufacturing.
5. Stamping folding:
   Principle: Sheet metal is placed in a die and deformed by a punch to create a specific shape in a single operation.
   Advantages: High productivity for large series, complex shapes possible.
   Applications: Manufacture of standardized parts (automobiles, aeronautics).
7. Bending by CNC (Computer Numerical Control) bending:
   Principle: The CNC press brakes allow precise and automated folding using computer programs.
   Advantages: High precision, repeatability, and time saving.
   Applications: Mass production requiring tight tolerances.

Factors to consider:
Material Type: Aluminum, stainless steel, copper, etc. Each material has different properties (ductility, strength).
Sheet metal thickness: Determines proper method and equipment.
Bend angle and radius: Affect internal stress and bend quality.
Fold Type: Single fold, multiple fold, or complex shape.