Bending
In the industrial sector, bending is a process that is frequently used to manufacture a large number of parts, usually flat ones. Bending is generally carried out using a specialised machine tool configuration known as a ‘press brake’ (also known as a folding machine).
These presses, which are dedicated solely to sheet metal working and are fitted with specific equipment, can bend metal materials with great precision and ensure the production of small or medium-sized series. Their hydraulic technology does not allow them to achieve high output rates, unlike mechanical presses, for example, and they cannot bend small parts because of their size, unlike presses in the EMG range.
In the case of bending carried out with mechanical, manual, pneumatic or hydropneumatic presses such as those manufactured by EMG, the operations concern smaller parts and can also involve bending.
What is bending and press-bending?
Bending is an operation that consists of deforming or shaping the material according to a bend, an angle defined by a shaping tool (punch and die). During deformation, the outer part of the sheet metal bend stretches while the inner part compresses, causing the sheet metal to vary in thickness, sometimes significantly.
Each type of material (metal: steel, stainless steel, aluminium, etc.) has its own mechanical characteristics, such as its elasticity.
When designing the part, it is important to anticipate these variations in thickness as far as possible in order to respect the minimum radii of the metal sheets to be bent.
There are several abacuses for bending, with values for the ‘K coefficient’, the ‘fish coefficient’ or the ‘Young's modulus’ adapted to each type of material. Nevertheless, experience is by far the best ally of the set-up engineer in making all the necessary bends accurately and to the nearest millimetre, without the risk of applying a force greater than the material can withstand.
Dedicated press brake or bending with an EMG press: what factors influence the choice of bending method?
The choice of bending method depends on a number of factors, including the size, thickness and quality of the material.
The desired radius and angle of deformation are other important factors.
Finally, the precision required for the project often determines the method for bending or cambering and, of course, the choice of press to be used.
What are the main methods for bending metal parts?
● V or U bending
V or U bending is one of the most commonly used methods today. For this process, the punch presses the part into a V- or U-shaped die without compressing it completely. Steel, aluminium or stainless steel of varying thicknesses are the main materials used. A large number of different angles can be precisely achieved by adjusting the depth of the punch.
● Roll bending
Roll bending is ideal for bending. By passing between rollers, the metal sheets are deformed. Curves are obtained according to an initially defined radius. This does exist, but not with a press. It's a rolling machine. Important for SEO?
● Impact folding
Strike bending is a technique used to make high-precision bends by pushing the sheet to the bottom of the die. This type of bending meets a very specific need, such as the production of metal bearings.
How does the bending process work?
Similar to folding, bending involves deforming a metal part by creating a smooth, rounded curve. Once the characteristics of the sheet to be bent and the desired angle have been defined, the choice of bending press is made.
The workpiece is then fed into the bending press. As the material is pushed against the lower die, the part or sheet takes on the shape of the die. Initial calculations are required to define the optimum V-angle, or die shape, depending on the thickness of each metal sheet, and to compensate for the sheet's tendency to return to its initial shape (springback).
Correct positioning reduces the risk of shifting during bending or cambering operations. The press applies pressure to deform the material according to the desired result, the type of material or the thickness of the metal sheet.