1. What is Metal Bending?
Metal bending is one of the most common metal fabrication operation. The sheet metal bending process involves applying a force to a sheet metal part to change its geometry. This force causes stress on the sheet metal beyond its yield strength and permanent physically deform without breaking or failing.
The press brake is a commonly used equipment for sheet metal bending. It works by lowering a mould onto a sheet metal work piece positioned on a die, creating the desired form.
The formed bend is dependent upon the tools used, the material yield strength and the material thickness. Setting up a bending operation accurately requires knowledge in the tooling, material, forces and the sequence of the different steps so it requires a skilled operator.
2. Types of Metal Bending
There are mainly 3 types of metal bending: air bending, bottoming, and coining. This classification is based on the end tool’s position to the thickness of the material.
Air bending is the most common type of bending for sheet metals. In this process the work piece squeezed between the outside edges of the die and the punch tip. The punch is then forced past the top of the die into the v-opening without coming into contact with the bottom of the v. The v opening is typically deeper than the angle which is sought in the work piece
In bottom bending, the punch and die are brought together so the work piece makes contact with the punch tip and the V-opening sidewalls. Since bottom bending uses less force than coining, the work piece does not totally conform to the tooling’s bend angle.
Coining is a type of bending in which the material is stamped between the punch and die. Both the punch tip and the punch actually penetrate into the work piece past the neutral axis under a considerable amount of force
3. Types of Metal Press Brakes
There are 3 types of press brakes which deliver different techniques of force applied; mechanical, pneumatic and hydraulic.
Mechanical press brakes are ideal for air bending due to their design nature. Speed and accuracy are the fundamentals advantages of the mechanical brakes over others, however their offer limited flexibility when it comes complex bending works.
These press brakes utilize air compressor to move their rams up and down. They are similar to hydraulic presses but usually have a much lower pressure limit.
Hydraulic presses operate by means of two synchronized hydraulic cylinders on the C-frames moving the upper beam. Servo-electric brakes use a servo-motor to drive a belt drive to exert tonnage on the ram. Hydraulic press brakes often equipped with the CNC control units are best used for precise bending of metal sheet, which makes them a popular choice for sheet metal bending.
4. Metal Bending Hints
Bend allowance is defined as the material required to add to the overall length of the sheet metal in order for it to get cut in the right size. During the design of the metal part, bend allowance based on the bending type and material thickness should be taken into consideration in order to get the accurate final dimensions.
Some material grades are likely to break or crack when bending is made from the force. Appropriate material grade for cold forming should be selected to prevent any cracks during bending.
Holes and slots are likely to deform when placed near a bend, therefore appropriate clearance should be considered in the part design.
The minimum radius of bends must be calculated in respect to the material thickness to prevent parts from cracking. The inside bend radius should be equal to the thickness of the material that you’re forming.
For shapes requiring multiple bends, it is essential to plan the bending sequence in order to not end up with a faulty product. It is recommended to try the sequence with a small test part and check the outcome before going with the real work piece.
- CNC machines for Repetitive parts
For repetitive bends, CNC press brakes offer great benefit by saving the bending settings on the machine and using pre generated settings for all the remaining parts. This will provide a standardized outcome and consistency in the quality of the end product.
5. What is Novelty Steel offering?
Novelty Steel is an experienced fabricator with various press brakes in its machinery park.
With vast CNC Machinery Park and experienced engineering team, Novelty Steel fabricates bespoke bended sheet metal parts with up to 20 mm thickness according to the EN 1090-2 European Norms.