What Is a Screw Press?

Screw press (Screw Press) is a general term for press machinery that generates a form of pressure by rotating more than one set of outer and inner bolts in a frame.

Screw press

The screw press can be divided into two ways, one is to apply torque to the bolt to generate static pressure, and the other is to concentrate the rotating energy of the flywheel on the bolt for molding at one time.

As long as it is a press that uses a helical structure to generate a vertical forming torque on the slider, it is considered a type of screw press.

The screw press originated in Germany in the 15th century. A man named John Dondeberger invented a movable type printing machine. The movable type plate coated with ink was pressed against the paper by a spiral device. This machine is used as a wooden bolt press for grape and olive oil, and can be said to be the origin of all press machinery. It uses a method of applying static pressure that gradually takes time to compress.

Screw presses are mainly used to process various high, medium, and low-grade refractory products, or various metal materials (cold and hot forging, cold forging, casting and forging).

The lower part of the general screw press is equipped with a forging ejection device. The screw press has the functions of various forging machines such as die forging hammers and mechanical presses. It is versatile and can be used for die forging, punching, deep drawing and other processes. In addition, screw presses, especially friction presses, are simple in construction and easy to manufacture, so they are widely used. The disadvantages of screw presses are low productivity and mechanical efficiency.

A forging press that uses a screw and a nut as a transmission mechanism, and converts the forward and reverse rotary motion of the flywheel into the up and down reciprocating motion of the slider by screw transmission. When working, the motor accelerates the flywheel to save energy, and at the same time pushes the slider down through the screw and nut. When the slider contacts the workpiece, the flywheel is forced to decelerate to a complete stop, the stored rotational kinetic energy is converted into impact energy, and the workpiece is hit by the slider to deform it. After the blow, the motor reverses the flywheel, driving the slider up and back to the original position. The specifications of screw presses are expressed by the nominal working force.

The screw press usually uses a motor to drive the flywheel rim through the friction disk to rotate the flywheel. Therefore, this type of press is also called a friction press. The largest friction press in China is 25 trillion newtons. Larger screw presses use a hydraulic system to drive the flywheel, which is called a hydraulic screw press. The maximum size is 125 trillion Newtons. Later, there was an electric screw press that directly driven the flywheel with a motor. It has a compact structure and few transmission links. Due to the frequent commutation, it requires higher control electronics and requires a special motor.

The screw press does not have a fixed bottom dead point. For larger die forgings, it can be repeatedly formed, and it can be single, continuous and inching. The impact force is related to the amount of deformation of the workpiece. The impact force is small when the deformation is large, and the impact force is large when the deformation is small (such as cold strike). In these respects, it is similar to a hammer. However, the speed of its slider is low (about 0.5 m / s, only 1/10 of the forging hammer), and the striking force is closed by the frame, so the work is stable, the vibration is much smaller than that of the forging hammer, and no large foundation is required. The screw press is equipped with a slip insurance mechanism to limit the maximum strike force to less than 2 times the nominal pressure to protect the equipment.

Basic working principle of electric screw press

The flywheel, sleeve shaft and nut of the motor-driven screw press frequently move forward and backward together with the nut, the nut and the screw form a motion pair, and the nut drives the screw and the slider to move up and down to generate a striking force. The control system with PLC as the core is designed with several working program sections, and the striking speed of each program section can be adjusted by the corresponding electrical; the striking number of each program section can be set through the corresponding counter. It can collect the instantaneous working status of the press for logical determination, and complete the control of the motor and the brake, the feeding and discharging device, and the pneumatic die ejection control. Equipped with input and output devices corresponding to various types of workpieces, the press can achieve full automatic work.