What Is a Mechanical Press?

Mechanical press is a forging machine driven by a crank link or toggle lever mechanism, cam mechanism, and screw mechanism. It is a machine tool for pressure processing of materials. It is processed by applying strong pressure to the blank to deform and break it. Components. It has stable work, high precision, good operating conditions, high productivity, easy to realize mechanization and automation, suitable for working on automatic lines, and widely used in industrial machinery presses such as automobiles and ships. The first mechanical press made in China was successfully manufactured in Jinan Second Machine Tool Plant in December 1955.

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When the mechanical press works, it is passed by the motor

Mechanical presses are generally distinguished according to the body structure type and application characteristics.

Divided by body structure type

There are two types of open and closed.

Open press: also called

Selection of press type

The type of mechanical press is selected according to the basis, according to the number of production batches, the precision and size of the stamping parts, the following we will analyze the selection of the type of mechanical pressure.

In the production of small and medium-sized stamping parts, it is mainly used in open mechanical presses. Generally, because the manufacturing of machinery is regulated, single-column mechanical pressure has an easier way to operate and is in operation. The cost is very low. On the other hand, the effect of the mechanical pressure on the start-up can analyze the gap of the die and minimize the quality of the mold.

Since a large number of complex parts are to be produced, in order to ensure its production quality, a high-speed press or a multi-station automatic press should be selected. In some small parts, a high-speed press or a friction press should be selected because There are no specified specifications for hydraulic presses, which will not cause other failures due to some unexpected reasons. There are certain advantages in some aspects, but there are also great problems in other aspects. The productivity of hydraulic presses is low, and when working It also has certain instability, and the friction press has great advantages. For example, the structure of the friction press is very simple, so the cost is relatively low in terms of cost, and the structure of the friction press is not fixed, so it can be used in use. It can be arbitrarily changed according to the use situation and will not be greatly affected. However, on the other hand, the number of strokes of the friction press is relatively small, the productivity is relatively low, and the operation is troublesome.

Attention must be paid to the rigidity and accuracy of the mechanical press. The rigidity of the mechanical press is composed of three parts: bed rigidity, guide rigidity, and rotational rigidity. This is also a great deal of research, because only when the rigidity of the press is sufficient , His static accuracy can only be stored under the condition of overload stiffness, otherwise, the static accuracy will lose its meaning and value. ^[2]

1) The crankshaft support of the press, there are great design flaws in the design and manufacture of mechanical presses, so the relevant designers should pay attention to it. For example, some redesigns of the press will be fixed at both ends of the crankshaft. These designs are not reasonable. It should be that one shaft is fixed, and the other shaft needs to have the possibility of extension. For the crankshaft, because of the temperature, it can only be limited at one end of the crankshaft. The other crankshafts must have clearances, so that the crankshaft can be subjected to temperature. Able to stretch freely and reduce losses.

2) The stress concentration of the crankshaft structure, the crankshaft structure should be highly valued, especially the two places where the crank and the crankshaft are connected are very unfavorable to the pressure on the crank bearing, so the designer should modify the unreasonable design. The scope of mechanical design considerations is small, so the design structure will be very unreasonable. For the transmission of large power, the load it bears is mostly the fatigue exchange load. In order to prevent these unnecessary self-weights and reduce rotation Sex.

3) Welding structure of pressure base. Welding of the base of large-scale presses is more prone to errors and cause unnecessary losses. Some welding is arranged in the direction of the floor thickness. The range of consideration is relatively small, and some of the joints are subject to large forces. Can not bear the weight of the press, so it is more likely to cause layered fracture. These issues should be considered in the design. The design should be simpler and the stress on the weld joints should be reduced. Construction machinery and equipment need to spend a lot of money, so in During the construction process, we can do a lot of things that cannot be done by manpower, so we should strengthen the care of the equipment, and often maintain the equipment to increase the life of the equipment.

4) The design of the piston rod of the balancer should follow a lot of design rules under the design of the mechanical press, and every detail should be paid attention to. For example, the design of the piston rod of the press should be designed with the design scale. Take care to avoid scratching the inner surface of the seal. ^[2]

Crank press is the most commonly used cold stamping equipment, used as a working platform for cold stamping dies. Its structure is simple and easy to use. It mainly uses the crank-slider mechanism to convert the rotary motion of the motor into the linear reciprocating motion required for stamping. It uses a crank shaft, a crank shaft and an eccentric wheel as its input members. It has a rigid kinematic connection. With the help of the closed force system from the actuator and the table to the bed, the blank is deformed to make a forged part of a certain shape. There are many types of crank presses, of which universal crank presses are widely used for punching, bending, forming, shallow drawing, etc. The press has stable movement and reliable work, and is the most widely used equipment in stamping equipment.

Principle of crank press

The output power and motion of the motor are transmitted to the intermediate drive shaft through a belt drive, and then transmitted to the crankshaft through a gear drive, and the slider is driven to make a linear motion up and down through a connecting rod. The rotary motion of the crankshaft becomes a reciprocating motion of the slider through the connecting rod. The upper mold is fixed on the slider, and the lower mold is fixed on the worktable pad. The press can press the material placed between the upper and lower molds, and rely on the mold to make a workpiece to achieve pressure processing.

Classification of crank press

According to the process, crank presses can be divided into two categories: general presses and special presses. The universal press is suitable for a variety of process uses, such as punching, bending, forming, shallow drawing, etc. The special presses are used for a single purpose, such as tensile presses, sheet bending machines, shears, high-speed presses and so on.

Basic structure of crank press

Crank presses are generally composed of the following parts, including the working mechanism, transmission system, operating system, energy system, support system, and various auxiliary systems and auxiliary systems, such as lubrication systems, top devices, protection devices, slider balance devices, safety Device, etc.

Operating procedure of crank press

(1) When installing the mold, the closing height of the mold must be adapted to the closing height of the crank press. When adjusting the closing height of the press, an inching stroke should be used. The workbench of the press is not allowed to be in the lowest limit position, but should be in the middle limit of its adjustment amount, and the mold must be firmly fixed.

(2) Check the pressure of compressed air carefully before work. Do not start the press when it is less than 3.92MPa (40kgf / cm ² ). Check the operating system of the crank press and its lubrication system. Check that the clutches and brakes and protective devices are safe and intact.

(3) To prevent the slider of the press from being stuck, it is strictly forbidden to work on the equipment with overload.

(4) A safety cover should be installed on the pedal control panel of the crank press to prevent accidental accidents caused by sudden sliding down of the slider caused by accidental pressure by others or foreign objects.

(5) At the end of the work, the slider of the crank press should be lowered to the bottom dead center position, the compressed air should be closed, the work site should be arranged, and the transfer work should be done.

Maintenance of crank press

As with other equipment, presses can reduce mechanical failures, prolong their service life, give full play to their functions, and ensure product quality and avoid accidents to the greatest extent only by proper use and maintenance. The following describes the crank press from the aspects of capacity, structure, operation, maintenance and mold use.

First, the normal play of the ability of the crank press

The normal functioning of the crank press depends on the correct use and maintenance of the crank press by the user:

(1) Correct use of the press. The user of the press must know the processing capacity of the press (nominal pressure, allowable load diagram, rated power of the motor), and leave room for the press's capacity during use. This is critical to the life of the press components, the life of the mold, and avoiding damage to the press caused by overload.

(2) Correct maintenance of the press. The clearance at each movable connection of the press cannot be too large, otherwise the accuracy will be reduced. The following methods can be used to test: When the slider is punched down, touch the side of the slider with your finger. If there is vibration at the bottom dead center, the gap is too large and must be adjusted. When adjusting the guide gap of the slider, be careful not to over-tighten the slider too tightly, which will cause heat and wear. Proper clearance is necessary to improve lubrication and extend service life. All relative moving parts must ensure good lubrication, and lubricating oil is added as required.

(3) The influence of the mold on the correct use of the press. The size of the mold and the size of the press table should be adapted. The small mold should be used on a press with a small table area. If it is used for a large table press and the punching pressure is close to the nominal force, it will make the table and work The force of the table pad is too concentrated, causing local overload and damage. At this time, a pad can be added under the mold to disperse the punching pressure. For closed high and small molds, a backup plate should also be used to prevent the height adjustment screw from extending too long, which will reduce the strength and stiffness of the connecting rod and cause danger.

Second, the crank press operation should be accurate

Press operation errors will not only cause damage to the press, molds and workpieces, but may even lead to personal safety accidents. Therefore, correct operation is an important part of the safe use of the press and must be paid attention to.

(1) The mold installation must be fastened to ensure that the mold gap is uniform, the closed state is good, and the stamping process does not shift.

(2) Strictly abide by the operating rules of the press, remove the workpieces and waste materials on the workbench in time during the work, and do not save trouble, and clear them directly with bare hands. You must use special tools such as hooks or brushes to clean up.

(3) During production, the blanks should be avoided from being put into the mold for stamping. Pay attention to the working status of the press at any time. When abnormal phenomena occur, stop working immediately, cut off the power, check and handle, and resume production after troubleshooting.

(4) After the work is completed, the clutch should be disengaged before the power can be cut off, the debris on the workbench should be removed, and the oil should be cleaned and rust-proof.

Third, regular maintenance

After using the press for a period of time, the mechanical parts will wear out. The lighter will prevent the press from functioning normally, and the heavy one will have mechanical failure or even an accident. The purpose of regular maintenance is to keep the press in good condition through daily, weekly, monthly, semi-annual or one-year inspection and maintenance to ensure the normal work of the press and ensure the safety of the operator. Regular inspection and maintenance of the press, including the maintenance of clutches and brakes, inspection of the working mechanism of the crank slider, intermittent adjustment of the guide slip, inspection of bolted parts, inspection of the oil supply device and gas supply system, periodic inspection of accuracy, etc. . In addition to the above items, the regular maintenance of the press should also include the inspection and maintenance of the functions of the drive system, electrical system and various auxiliary devices. Daily inspection is an important part of regular equipment maintenance. It can prevent problems before they occur. It must be included in the operating procedures of the press. Before daily work, start-up processing, and after operation, the corresponding items should be inspected and maintained. ^[3-4]