AC servo motor drive is the research hotspot of advanced forging equipment and the new development direction of the international press.
AC servo press has the advantages of high productivity, high flexibility, high precision, energy saving and environmental protection, which fully reflects the future development trend of forging machine tools.
This post mainly introduces the transmission mode, working principle, classification and technical advantages of servo press, and looks forward to the development prospect of servo press.
With the rapid development of iron and steel, non-ferrous metallurgy, aerospace, railway high-speed locomotives, ships, nuclear power, wind power and military industry, the demand for high-performance parts is increasing.
Mechanical press is one of the most important process equipment in electronic information, electrical appliances, machinery, automobile, instrument, office equipment and other industries.
However, the stroke of the traditional press is fixed, the pressure is not easy to control, especially the motion characteristics of the slider are fixed, and the adaptability to the process is poor.
In recent years, with the development of science and technology, the emergence of new materials and the complexity of product shape, more strict requirements are put forward for the working performance of stamping equipment, and a new generation of the flexible press needs to be developed.
What is servo press
Servo press usually refers to the press driven and controlled by servo motor.
A servo motor drives the eccentric gear to realize the movement of the slider.
Through complex electrification control, the servo press can program the stroke, speed and pressure of the slider arbitrarily, and even reach the nominal tonnage of the press at low speed.
Structure of AC servo press
The structure of AC servo press is mainly composed of main drive, actuator and auxiliary mechanism.
The main function of the main transmission mechanism of AC servo press is to transfer the energy required for forging from the servo motor to the actuator.
The common transmission modes include gear transmission, belt transmission, screw transmission and hydraulic transmission.
The main function of the actuator is to drive the slider to do reciprocating motion and complete the forging process.
The common actuators are crank slider mechanism and crank wedge mechanism.
The main function of the auxiliary mechanism is to improve the working reliability of the AC servo press and expand the process application of the servo press.
Common auxiliary mechanisms include balance cylinder, brake, jacking device, position detection device, etc.
According to the driving mode of servo motor, the main drive system of servo press can be divided into two types: the actuator directly driven by servo motor and the actuator driven by servo motor through reducer.
The servo press in the form of direct drive adopts a low-speed high torque servo motor, which is directly connected with the actuator.
There is no deceleration mechanism, short transmission chain, simple structure, high transmission efficiency and low noise.
However, limited by the torque of the servo motor, the main transmission system is only suitable for small tonnage servo press.
At present, the main transmission system of servo motor deceleration force increasing mechanism is widely used in commercial servo presses, which can be divided into three transmission structures: motor deceleration crank connecting rod, motor deceleration crank elbow rod and motor deceleration screw elbow rod.
It has become the mainstream trend of the development of servo press to use deceleration mechanism and force increasing mechanism as the main transmission system of servo press to realize high-speed and small torque servo motor to drive large tonnage press.
Table 1 Comparison of project parameters
|Project||Robot automatic line||Automatic line of single arm manipulator||Crossbar double arm transmission high speed line||Single slider multi station production line|
|Single line automation cost||About 12 million yuan||About 20 million yuan||About 30 million yuan||About 15 million yuan|
|Line speed / SPM||5~10||6~12||10~15||12~25|
|Production applicability||Multi variety and small batch||Multi variety, medium batch||Multiple varieties and large quantities||Variety, mass|
|Mold change time / min||15||15||5||５|
|Requirements for press||Operation mode||Single time||Single time||Single, continuous||continuity|
|Press spacing / M||6.5~8||6~9||4.5~7||／|
Advantages of servo press
As shown in Table 1, the beat of the cross bar double arm transmission high-speed line is 10 ~ 15SPM.
If the servo press is used, the beat of the high-speed line can be increased to the maximum 18SPM.
As shown in Figure 1, the servo press can set different curves according to different situations.
Fig. 1 Servo press can set different curves
Figure 2 shows the power flow during acceleration and deceleration.
Fig. 2 Current flow direction of servo motor during operation
Reduce drawing speed
As shown in Fig. 3, the drawing speed is low, the impact on the die is reduced, the die life is improved and the die cost is reduced.
Fig. 3 Schematic diagram of drawing speed
Reducing the size of equipment can reduce the investment in plant, infrastructure and other facilities.
As shown in Fig. 4, take the four sequence press as an example: the traditional mechanical press production line is composed of one multi link press and three eccentric presses.
The full length of the foundation of the four presses is about 25m, while the full length of the foundation of the four servo presses is about 16m.
Fig. 4 Comparison between traditional mechanical press and servo press
Fig. 5 shows the Schuler double servo bottom drive multi station press.
Fig. 5 Schuler double servo bottom drive press
The double servo bottom drive press is driven by the left and right servo motor groups to drive the four guide columns on the left and right sides respectively to drive the sliding block to move up and down.
Because the transmission mechanisms on the left and right sides are independent, the left and right dimensions of the table can be very large. It is suitable for large table and large tonnage press (Fig. 6).
Fig. 6 Double servo multi station press
The double servo bottom drive press realizes the synchronous movement of the left and right sides of the slider through the high-precision control of two servo motor groups.
At the same time, in case of eccentric load of the slider, the parallelism of the slider is compensated through electrical control, so that the parallelism of the slider becomes flexible and controllable to meet the user’s use requirements to a greater extent.
The eccentric load strength curve and precision curve of bottom drive press are better than those of ordinary press.
On the premise of meeting the accuracy requirements, the bottom drive press not only has stronger anti eccentric load performance, but also allows a larger eccentric load area.
With the increasingly fierce international competition in the manufacturing industry, the demand for servo presses to manufacture high-precision and high-quality products with high efficiency is becoming stronger and stronger.
Servo press has the advantages of compounding, high efficiency, high precision, high flexibility, low noise, energy saving and environmental protection, which fully reflects the future development trend of forging machine tools.
The servo press can set different stroke and forming speed according to different production needs. It can always ensure the forming accuracy of the bottom dead center, effectively suppress the emergence of product burr and other problems.
At the same time, the die vibration is small, which can greatly improve the die life.
The servo press breaks through the design concept of conventional mechanical press, removes the flywheel, clutch and brake of traditional mechanical press, and greatly reduces the use cost of the machine.
Servo press will play a more and more important role in some important manufacturing fields, such as electronic products, automobile and other precision manufacturing fields.
The press driven by AC servo motor can greatly improve the flexibility and intelligence of the equipment and improve the working characteristics of the press.
It is the development direction of the new generation of forming equipment.
With the development of related technologies and the competition with imported products, the market price will decrease rapidly, and the servo technology will be more and more widely used in the field of forming equipment.