Most of the bent parts are made by processes and methods such as hanging bending, in-mold bending, flanging and pressing. The method of operation follows the same principle: the punch presses the workpiece into the lower die of the die. Therefore, the bending machine that performs the above process and method is called a press brake. In addition to press brakes, TRUMPF also offers swing arm bending machines.
Hanging bend
Air bending: The punch presses the workpiece into the die without pressing it against the die wall. During the downward movement of the punch, the edge of the workpiece bends upward and forms an angle. The deeper the punch presses the workpiece into the die, the smaller the angle. At this time, there is a gap between the punch and the die. Hanging bending is also known as a path-dependent process. Each angle requires a specific path. The machine control system simultaneously calculates the path and the corresponding punching force. Path and punching force depend on tooling, material and product properties (angle, length).
In-mould bending
In-die bending: The punch presses the workpiece completely into the die, so there is no gap between the die, workpiece and punch. This process is called clamping. Punch and die must fit each other precisely. Therefore, each angle and shape requires a corresponding mold assembly. Once the workpiece is fully pressed in, the punch cannot move further down. The machine tool control system continues to increase the stamping force until it reaches the specified value. The pressure applied to the workpiece thus rises, taking on the contours of the punch and die. The included angle is gradually stabilized under high pressure, almost completely eliminating the problem of spring back.
Folding and pressing
Sheet edges are usually fully bent (eg box edges) and then folded parallel to each other. The finished part as a whole is therefore more stable or forms an edge protection. Other parts usually need to be hooked into the flange subsequently. Folding and pressing are done in two steps: first, the operator pre-folds the 30° angle, then reinserts the workpiece and presses the angle. If there is a gap between the edges, it is called a hem. During pressing, the flanges are completely pressed against each other. Hemming is path-dependent, but pressing is force-dependent.
Flap bending
The bending arm built into the machine consists of a C-shaped profile on which the lower and upper bending tools are mounted. During bending, the C-profile moves up or down, or makes a small elliptical movement, i.e. flips. The semi-automatic operation of the swing arm bending machine is famous for its speed and flexibility, and it is not inferior to the production of small batches. In addition, flap bending technology enables efficient bending of various radius sizes on a single component using the same tool.
