Press brakes are made on the hydraulic principle of operation. The accuracy of the movement of nodes is controlled by sensors: circular encoders or linear readings. The holding mechanisms serve as a safety knot and protect the workpieces from sliding off the clamping elements.
Equipment design features
Press brakes are the next and more productive generation of pneumatic machines. The first designs lacked the effort to perform an accurate bend. Models are divided according to the main criteria: maximum force, workpiece length.
Press brakes for simple movements with low requirements can be made based on elementary logic without controlling the main parameters. More complex products require automated CNC systems with traverse position sensors and bend angle control. A backgauge is often used to hold the workpiece in position.
For example, for an Asian press brake, the price is formed by summing up the cost of the machine base and a set of options. The amount of investments varies from hundreds of thousands of rubles to millions of dollars for unique models. Options includeadditional control of parameters, positions of stops, sensors of the security system. There are also a huge number of applications available to users that facilitate the creation of programs for products of standard shapes.
Why do you need two controllers?
Press brakes are complex machines. The standard controller is suitable for processing simple signals and is not designed to control a large number of axes. At a minimum, a separate control unit is required, which affects the final price of the machine.
Special CNC controller allows you to bring the machine ready for work at high speed, position the traverse along several axes at the same time. Process parameters, retraction speed from the part, pressing time and many other equipment states are processed by software: oil temperature, system activity, control of the integrity of working parts. The hydraulic sheet bending press provides high repeatability of the bending angle, the main quality of the products depends on it. You can't do without precise rulers. The drive system affects the timely retraction of the traverse, if the holding time is violated, the machine starts to produce defective products.
CNC press brake is mostly used to produce rather long and thin products. Therefore, a reinforced traverse is used in the design. But for all the rigidity of the metal, it still sags by a few millimeters.
Thesevalues must be taken into account to ensure high accuracy. The CNC system makes corrections according to the entered parameters, eliminating possible errors. This compensation is required for machines longer than 2 meters. Energy saving mode is implemented by many press manufacturers. At moments of downtime, stationary units are turned off, pumps are turned off, the power supply to the engines is turned off. Equally important is the ability of the equipment to connect using standard protocols to control the entire technological chain of the production line.
The frame bears the main load of the unit and keeps it from swinging during the operation of the upper part - the traverse. A tool for press brakes is mounted on the moving part. The servomotors are connected through propeller pairs and gearboxes to the caliper located on the sliding guides. Rolling bearings have low performance properties, but can be used in cheaper models. This is a significant design flaw.
The selection criterion is the method of fixing the tool, the type of hydraulic cylinders used, the method of installing punches, the presence of guards and automatic protection. Many manufacturers have software assistance in calculations, the most successful parameters have already been entered into the database. It remains only to specify the type of material and the dimensions of the part according to the drawing. The machine will do the rest on its own after starting the automatic cycle.
Machines are equipped with several types of beds,different in form. Each of them has its own advantages and disadvantages depending on the type of part produced and placement in the shop:
- The C-shape of the bed has a wide front part, a pocket is formed behind. Manufacturers use it to service the working area, it is also possible to place additional equipment there: a cooler, a compressor. The disadvantages include the following: if the load of the press was once exceeded, the bed can lead, and it will, as it were, open a little. You will need to re-align the structure.
- The O-shape of the bed is more reliable and will not open under high loads. But along with this, the weight of the machine and dimensions increase. If the previous forms can be combined in a line, then this model is used only as a piece of equipment. It is also difficult to remove finished products from the side, which slows down the production process.
The main replaceable element of the machine is the tool. It depends on him the quality of parts, dimensional accuracy. The corresponding material of the working part is selected for each workpiece.
The tool dimensions are entered into the CNC memory using the software. The next changeover is carried out in just a few minutes, loading the required configuration into the processing area.