Metalworking has been developing since primitive times and with increasingly complex instruments. However, only in the last decades of the 20th century and thanks to new technologies that use high-precision computerized equipment, the range of benefits in the treatment of metal plates or sheets has expanded considerably.
All operations with plates are carried out cold. One of these operations is folded or folded, which involves the deformation of a sheet so that it adopts an angle with respect to an axis that, in most cases, is straight. Straight line deformation is done with machines called sheet metal bending machines.
The basic principle of sheet metal bending in machines it is based on the impact, by means of a pressure force, of a punch on a matrix or die, in the middle of which the metal sheet is placed to fold.
The versatility of these machines folding machines (or presses) varies widely depending on the size of the sheet to be processed, but some process materials up to 20 mm thick. Certain industrial press brakes They can measure up to 18-20 meters long, which allows accommodating a large number of dies to make different consecutive folds.
Although there is currently a diversity of models, four types of sheet metal bending machines, which differ depending on the mechanism used for the folding operation. The choice of each type of folder will depend on the application, required accuracy, repeatability and production capacity.
Each of these types is briefly described below, in order of increasing complexity and performance.
manual folding machine
Although this is a simple and small-sized machine, some versions incorporate not only the hydraulic drive mechanism, but also sophisticated CNC (computer numerical control) controllers. That is why the various options of manual folding machines They range from simple, lightweight tabletop machines to those with counterweights and a base that must be set firmly on the floor.
In general, the use of manual folding machines it is limited to very thin sheets, from 20 gauge to 8 or 9, depending on the material (iron, aluminum or stainless steel) and the model. They are machines often used by auto body builders, but other applications also include the production of distribution boxes and panels, fuse and switch boxes, and transportation. It is a highly efficient machine, with great energy savings and easy to move.
The other types of folding machines They have larger sizes and more complex designs that are similar to each other, incorporating a power source for mechanical or hydraulic actuation or a combination of both. The components common to these folding machines are indicated in the figure.
The three types of folding machines that respond to this basic design are used in the manufacture of containers, profiles, cabinets, panels, boxes and casings for household appliances, among other multiple uses.
mechanical folding machine
The mechanical folding machines they introduce a flywheel, generally in the upper left part of the frame, which produces the energy to start the rammer. A mechanical device connects the flywheel with the rammer. When disengaged, the flywheel accumulates inertia which, when engaged, allows the rammer to move up and down. This stored inertia is what is used to create, at the bottom of the stroke, the necessary tonnage for the bending process.
Although still widely used, mechanical folding machines based on the positive flywheel/clutch mechanism often present a great risk to the inexperienced operator, as if the full stroke of the machine is not allowed, the rammer could drop into the bed before the clutch mechanism re-engages, trapping the operator’s hands, tools or sheet metal. In this kind of folding machines, the installation of protective guards is highly recommended to prevent injuries.
Hydra-mechanical press brake
Very similar in design to the mechanics, the hydraulic-mechanical press brake It presents the difference of replacing the steering wheel with a hydraulic pump, which provides the necessary inertia to activate the rammer. This hydraulic pressure allows a hydraulic motor to drive an eccentric shaft, causing the rammer to move up and down and generate the power required for the rammer. creased of the plate. In other words, hydraulic-mechanical press brakes They convert hydraulic energy into mechanical energy by means of a hydraulic motor connected to an eccentric shaft.
The advantage of hydraulic-mechanical press brakes versus the mechanics is that they do not need to complete a race to reach the maximum tonnage, but this can be achieved at any point in the race. Therefore, in addition to presenting a notable improvement in capacity and operation with respect to the mechanical ones, the hydraulic-mechanical press brakes they are also much safer. Furthermore, this type of folding machines it can reach very high tonnages through a lever effect which, in turn, allows the rammer to move up and down. This additional force, while detrimental to accuracy and repeatability, makes it easier to use hydraulic-mechanical press brakes in heavy-gauge sheets and minting works.
hydraulic press brake
The most modern and powerful of these machines, the hydraulic press brake it differs from the hydraulic-mechanical one in that it uses a hydraulic pump and hydraulic cylinders to drive the rammer. This results in remarkable accuracy, speed, and efficiency that far exceed the performance of other types of folding machines.
while the others folding machines they operate only with the ram in descending movement, the hydraulics also incorporates the ascending movement. Some prefer this design because it minimizes the effects of ram repeatability loss from normal machine wear and tear.
However, the vast majority of folding machines of sheets used today are hydraulic press brakes downward movement. They are driven by CNC or direct numerical control, which control a system of valves capable of giving the rammer great accuracy in the bending angles.
Types of press brakes
The following video shows some operations of creased made with a hydraulic press brake.