Different Forging Screw Press Types Comparison - Friction &Electric Forging Screw Press

In the development process of forging screw press, there are several different types, among which there are four main widely used types: friction forging screw press, hydraulic forging screw press, clutch forging screw press, and electric forging screw press. What’s the differences between different types of forging screw press？ Following are detailed comparison.

Friction forging screw press

Friction forging press is the oldest type of forging screw press, simple structure and low price are its main advantages. The there are also some disadvantages:

• Low transmission efficiency. Energy utilization rate is only about 10%. The energy consumption is high. In the situation of energy shortage, the application of friction press will be restricted.
• The friction belt is easy to wear and needs to be replaced frequently.
• It is not easy to control the strike energy accurately.
• The content of heavy metals in friction belt wear powder is high, which is harmful to human inhalation.

Hydraulic forging screw press

The hydraulic screw press is a kind of forging screw press which uses the hydraulic transmission to drive the flywheel to rotate and realize the up and down movement of the slider. The performance of hydraulic screw press is better than friction press, but the following problems exist.

• The hydraulic system is complex, the pipeline laying is heavy, and the hydraulic leakage pollutes the environment.
• The technical level of maintenance is high, and it is difficult to maintain in general forging factory.
• The price is much higher than friction forging screw press.

Clutch forging screw press

Clutch type electric forging screw press, also known as high-energy screw press, was launched in the late 1970s. Its characteristic is that the screw quickly drives the slider, the slider can output the rated energy value and reach the maximum forging force in the small travel, and the forging frequency is high. Most of the forging screw presses introduced into Germany by China's forging enterprises are of this type. But there are the following problems:

• The structure of the machine is very complex. It has not only mechanical clutch drive, but also hydraulic drive for slider return.
• The commonly used way of slider return is to use hydraulic cylinder to push the slider and make the screw move reversely. In forging and return stroke, the main screw and nut screw teeth are the same stress surface, and the lubricating fluid is not easy to supplement, resulting in the nut screw teeth easily damaged. To solve this problem, a German company uses a low-speed large torque hydraulic motor to drive the slider return stroke through the screw, which makes the originally very complex machine more complex.

Electric forging screw press

The electric forging screw press uses the motor to drive the flywheel directly, and the main structure is simpler than the friction press. Because of the great progress in power electronic technology in recent years, the electric screw press has been greatly developed and widely used at home and abroad.

How many types of electric forging screw press?

These products are divided into two categories:

One is the direct transmission form of the motor with the rotor and the screw as a whole. The feature of this scheme is that there are few transmission links, but it is necessary to design a special motor with low speed and large torque. The air gap of the motor will be affected by the wear of the screw guide sleeve. The motor is prone to failure and maintenance difficulties due to the impact of vibration. Therefore, foreign countries mainly focus on medium and small specifications. This technology has been studied and promoted in China in recent years Technology, mainly in small specifications, most forging users are in wait-and-see state.

The second type is the mechanical transmission form of the motor which drives the flywheel screw through the gear or belt. Because the motors used in this kind of products are generally high-speed and low torque type, it is necessary to reduce speed and improve torque through reduction device. Due to different types of motors and corresponding control systems, this type of forging screw press has two structures:

Switched reluctance motor + control system

Switched reluctance motor (SRM) is a variable reluctance motor with two salient poles. The salient poles of its stator and rotor are made of common silicon steel sheets. The rotor has neither winding nor permanent magnet, and the stator pole is wound with concentrated winding.

Advantage：The starting current and inertia of the rotor are small. There is no heating.

Disadvantage：

• The stator and rotor of the motor have a small number of cogging. When the motor rotates, the cogging effect is large, the motor vibrates greatly, and the noise is large; 
• The low-speed torque ripple is large; 
• The power density of the motor is low, which is lower than the traditional asynchronous motor, and even lower than the permanent magnet motor. 
• In addition, it is difficult to achieve servo level, which limits its application to high-precision occasions.

AC asynchronous motor + inverter control system:

AC asynchronous variable frequency motor is an improved type of squirrel cage induction motor which is widely used in China. In order to adapt to the working condition of screw press, some improvements have been made in the aspects of base strength, protection level, ventilation and heat dissipation. The structural characteristics of its stator and rotor are essentially the same as that of three-phase squirrel cage induction asynchronous motor. The stator is equipped with symmetrical three-phase winding, while the rotor of cylinder adopts cast aluminum structure, which generates electromagnetic torque by electromagnetic induction.

Advantage: Induction asynchronous motor is widely used and easy to maintain.

Disadvantages: Large starting current, large inertia of rotor, and current passing. In the case of frequent positive and negative rotation, it is easy to heat up.

Electric Forging Screw Press Manufacturers

The electric forging screw press designed by Anyang Forging Press adopts AC asynchronous motor and inverter control system. With years of in-depth study of the specific characteristics of various transmission forms of forging screw press, we have developed and designed a pinion made of high polymer materials, high strength and light weight, inertia less than 1 / 5 of the same size of steel gear, which can ensure that the motor shaft in frequent positive and negative impact of the smallest damage. This technical development greatly eliminates the disadvantages of electric forging screw press with AC asynchronous motor and inverter control system, the longest life. We can also provide automatic forging line design with electric screw forging press.