Listogib

Bending machines are stationary and mobile. In addition, listogiby depending on the method of bending are divided into:

• press with a punch and a matrix,
• swivel with bending beam
• rotary with two, three and four rolls .

Bending drives are:

• Hydraulic operated by hydraulic drive. There are both stationary and mobile.
• Pneumatic working with pneumatic cylinders. There are both stationary and mobile. Basically, the type of "swing beam".
• Electromechanical - stationary bending machines working due to an electric motor, gearbox and drive system (belts, chains, etc.).
• Mechanical - stationary bending machines working due to the transfer of kinetic energy of a previously untwisted flywheel .
• Manual workers due to muscular strength, also, basically, of the type of "swing beam". The worker using the strength of his own muscles and the device of the bending machine as a lever gives the metal the desired shape. Most manual bending machines are mobile and are used directly at the place of manufacture of sheet products.

In addition, according to the method of supplying the workpiece: with manual and automatic.

Dimensioning can be manual and automatic (CNC).

The sheet bending machine is used in various sectors of the national economy: mechanical engineering, auto, aircraft, instrument making and construction for the production of various closed and open profiles, boxes, boxes as well as cylinders, cones, etc.

The main purpose of listogib - the manufacture of various products from sheet materials.

Press brake - a machine , which is a machine that develops the force used for production purposes, mainly for bending sheet metal products.

It is characterized by basic parameters, such as developed effort, working length; and additional parameters: the amplitude of the traverse , the speed of work (bending process), the distance between the stands of the bed , the presence of a device for compensating for deflection of the table, the presence of additional devices that improve productivity and ease of use, such as support for the workpiece, a sensor for the obtained bending angle, a programming system and so forth

In industry, mechanical , pneumatic and hydraulic and “manual” (in the case of piece and small-scale production) press brakes have become widespread. The name comes from the principle of the development of efforts on a particular machine. The basis of a mechanical press brake is a crank mechanism, the operation of which, coupled with the energy of the flywheel, allows the drive to be driven. Pneumatic and hydraulic presses are used as an energy source - air pressure or hydraulic oil pressure, respectively.

Until the first half of the 20th century, the world industry produced mainly mechanical press brakes due to the relatively low cost of their production, ease of execution, and reliable operation. However, mechanical presses, in spite of the above advantages, have significant drawbacks, mainly related to the increased requirements of enterprises operating these machines. Such disadvantages of mechanical presses are: a large mass, high energy consumption, a high level of noise and vibration, the inconvenience of readjustment, a high level of danger of injury from working on a mechanical press, and a low level of quality of manufactured products.

Pneumatic press brakes have occupied a vast niche in the field of sheet metal processing, due to their limitations, mainly due to the small developed effort, and the requirements for supplying a compressed air line, which imposes a narrow scope for their application. Pneumatic presses are mainly used in production areas where a lot of effort is not required for the production process, and hydraulic or mechanical presses are impractical for reasons of their higher cost.

Starting from the second half of the 20th century, in connection with the development of technologies, as well as for reasons of higher requirements of enterprises manufacturing sheet metal products, the production of hydraulic press brakes begins to dominate, which have a number of advantages compared to mechanical and pneumatic presses.

Such advantages are: high quality of manufactured products, high reliability, a much lower level of danger of injury to working personnel, low level of electricity consumption.

Further development of technologies allowed the introduction of new control and safety systems, which gave a number of new opportunities: a graphical user interface with the ability to automatically calculate the sequence of bending operations, setting program steps, protecting the operator with a laser control device for the bending line, protecting the tool from overload by pressure, electronic adjusting the traverse speed, the use of additional equipment that works simultaneously with the bending process - front th support of the workpiece, a sensor for monitoring the obtained bending angle, and other improvements.

The essence of the press brake is to provide the necessary effort and working stroke of the beam - a steel rigid beam on which the necessary tool is installed, depending on the required manufactured product and the bending mode.

The beam travel is controlled by linear displacement sensors, as a rule there are two of them, which control the left and right sides of the beam to ensure uniform travel and synchronization of movement. As an additional equipment installed on the press brake, as a rule, a back stop is used, with the possibility of programming its position, depending on the required size of the bent edge.

An equally important part of the press is the security system, which primarily serves to protect personnel from injury and, as an auxiliary function, to limit the working stroke in case of violation of certain technological operations.

The security system is a complex of hardware and software that processes signals from various devices that monitor the necessary process. The most important is the device for laser control of the absence of a foreign object (operator’s hands) in the working area of ​​the machine.

For control, laser beams are used that form a plane under the upper tool, at a distance of about 3-5 mm below it. If the operator’s hands fall into the working area during the traverse movement, the laser beams or one of them will be crossed, and the control system will command to stop the movement immediately.

As a rule, the operation algorithm of a press brake machine looks like this:

1. The traverse is at the top dead center (TDC). The concept of TDC is conditional here, since it comes originally from the construction of the crank mechanism, which is used in mechanical presses. Hydraulic presses have the ability to adjust the upper position of the crosshead, but this position is also referred to as the top dead center.

2. At the moment of pressing the pedal or two-handed control button, the traverse starts to move down at a certain speed. This speed is usually higher than the speed of the directly bending process, so this movement occurs to a certain point of switching speeds and is called the speed of "free fall". This is also a conditional concept, since in reality no traverse falls, because through the hydraulic control system, the speed is fixed in a certain range.

3. Having reached the speed switching point, the control system switches the speed to a lower one, called the operating speed. At the speed switching point, the movement of the left and right side of the traverse is also synchronized, for which the readings from the linear displacement sensors are compared and the signals for the required adjustment to the control hardware are issued - servo valves that allow you to adjust the speed of oil supply to the working cylinders of the machine.

4. After the speed switching point, the traverse further moves to the bottom dead center (as a rule, it has the ability to adjust / program), reaching the bottom dead center there is an exposure under pressure. This is the time required to distribute the force along the entire length of the workpiece, since this factor affects the quality of manufactured products.

5. After the exposure time, it is necessary to release the part from the force. For this, the crosshead rises up to the required value at a slow speed. This process is called decompression.

6. After decompression, the traverse rises to the top dead center.

7. The machine will move after another pedal or two-handed operation button is pressed.

• Scoring
• Bending extension

• Press brake . // “Metals and alloys. Handbook. ”Edited by Yu. P. Solntsev; NPO Professional, NGO Peace and Family; St. Petersburg, 2003