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2 Types of Press Brake Hydraulic Automatic Clamping Design

As one of the most widely used sheet metal bending equipment, the CNC press brake is widely used in sheet metal processing and equipment manufacturing industry.

It is an indispensable supporting equipment for sheet metal processing with CNC turret punch, CNC plate shearing machine and CNC laser cutting machine.

It uses a simple general die, through the repeated movement of the ram to bend the sheet into a variety of complex cross-section shapes.

With the development and application of new technologies such as CNC, servo and die, the development of CNC press brake technology is mainly reflected in energy saving and high efficiency.

At the same time, with the continuous improvement of bending accuracy and bending efficiency, various functional components become more and more abundant.

Some enterprises with strong scientific research strength begin to focus on the R & D and design of various functional components, and strive to improve the degree of automation of machine tools.

Among all the functional parts, the most prominent influence on bending accuracy and bending efficiency is the upper die quick clamping device, especially in the multi-variety and small-batch bending production, the improvement of die change efficiency is particularly prominent.

Therefore, this article introduces two new clamping devices for upper die, which are easy to operate, easy to use, energy-saving and efficient.

The technical principle, mechanism design, technical characteristics and working process are mainly introduced.

1. Introduction of traditional clamping device technology

China’s CNC press brake upper die clamping device usually adopts mechanical structure, as shown in Fig. 1 and Fig. 2.

Eccentric quick clamping mechanism and Thread type quick clamping mechanism

The eccentric quick clamping mechanism is adopted in Fig. 1, which is mainly characterized by that the end of the operating handle is a cam rod, the operating handle is fixed with the front clamping block through a cylindrical pin, and spring is clamped between the front clamp block and the fixed block.

When the upper die of the press brake machine is quickly clamped, the upper die of the press brake machine should be inserted from the side of the quick clamping device, and the upper die can be quickly clamped by rotating the operating handle,

When the operating handle is rotated reversely, the front clamping block is quickly reset by the spring between the front clamping block and the fixed block, and the die is released and transported out from the side.

The device is easy to use and easy to operate, but there are some problems such as uneven clamping force and the need to insert the die from the side.

Figure 2 uses a threaded quick clamping mechanism.

When the die of the press brake machine is clamped quickly, the upper die of the press brake machine should be inserted from the side of the quick clamping device.

The screw is driven to rotate by rotating the operating handle and the screw then drives the front clamping block to move forward to clamp the die.

When the handle is rotated reversely, the front clamping block moves backward driven by the screw to release the die and transport it from the side.

This structure has the advantages of large clamping force, good self-locking and simple operation, but it has some problems such as uneven clamping force and slow clamping speed.

2. Design of hydraulic automatic clamping device

2.1 Scheme design

According to the characteristics of the hydraulic automatic clamping device for the upper die of the bending machine, the stress situation and the size of the upper die of the press brake machine, two solutions are proposed in this paper.

Scheme 1:

The die is clamped by the expansion force produced by injecting pressure oil into the compressed rubber hose.

A safety lock is set at both ends of the clamping device.

When the upper die is clamped, the safety pin in the safety lock is inserted into the pinhole of the die.

When the internal pressure of the rubber hose disappears, the safety of the operator and the die can be effectively protected.

The hydraulic automatic clamping device is suitable for large-scale forming die, such as arc die for pressing arc-shaped doors and windows in the automobile industry.

Scheme 2:

The expansion force produced by the compression hose is also used to extrude the die.

In addition, the hydraulic automatic clamping device also includes the upper die deflection compensation mechanism and the safety locking mechanism.

By adjusting the upper wedge of the deflection compensation mechanism, the top pin extrudes the die, so as to achieve the purpose of compensating the deflection of the upper die;

The safety pin in the safety locking structure can effectively protect the operator and the upper die.

The hydraulic automatic clamping device is suitable for ordinary standard dies, and the die can be segmented.

2.2 Structural design

According to the design idea of scheme 1, the hydraulic automatic clamping device of upper die as shown in Fig. 3 and Fig. 4 can be obtained.

 Upper die hydraulic automatic clamping mechanism

Fig. 3 Scheme 1: Upper die hydraulic automatic clamping mechanism

Safety lock mechanism

Fig. 4 Safety lock mechanism

The hydraulic automatic clamping device of the upper die includes clamping mechanism and safety locking mechanism. The clamping mechanism includes the upper die base, rebound screw, top plate, spring, coverplate, rubber sac, follow-up hose, transition joint and plug.

The upper die base is fixed at the bottom of the sliding block by a number of screws.

The upper die seat is vertically machined with a groove for placing the upper die handle, and a number of parallel distributed countersunk holes are processed on one side.

In the countersunk holes, there are rebound screws for extrusion dies and springs for spring-back screws reset.

A cover-plate is fixed on the side of the upper die base, and a through groove is arranged in the cover plate.

A top plate and a rubber tube are installed through the groove, and the top plate is between the rebound screw and the rubber tube.

The hose is in a compression state under non-working conditions.

As shown in Fig. 4, a safety lock mechanism is arranged on both sides of the clamping device, which includes air cylinder, safety pin, etc.

Pinholes are arranged on the left and right sides of the upper die seat and the press brake machine.

When the upper die is clamped, the cylinder pushes the safety pin through the pinhole of the upper die seat and inserts into the pinhole of the upper die to ensure that the upper die of the bending machine can still be suspended in the groove of the upper die seat when the internal pressure of the rubber hose suddenly disappears to ensure the safety of the operator and the die.

According to the design idea of scheme 2, the second hydraulic automatic clamping device for the upper die can be obtained, and its structure diagram is shown in Fig. 5, 6 and 7.

structure diagram

It can be seen from the schematic diagram that the hydraulic automatic clamping device of the upper die includes clamping mechanism, deflection compensation mechanism and safety locking mechanism.

The utility model comprises a first cover plate, a clamping head, a clamping head, a clamping head, a top plate, a clamping head and a rubber tube.

The upper die base is fixed with the bottom of the sliding block by screws.

The bottom of the upper die base is provided with a horizontal through groove, and the side is provided with a first countersunk hole.

The first countersunk hole is equipped with a first spring which is set on the surface of the springback screw.

The spring back screw passes through the first countersunk hole and contacts with the upper die handle of the bending machine.

One end of the through pipe is provided with a through pipe, and one end of the rubber pipe is connected with the rubber sac.

A roof is arranged between the hose and the springback screw.

In the initial state, the hose is flattened under the action of the first spring preload.

As shown in Fig. 6, the device also includes a safety locking mechanism, which comprises a safety pin, a jacking screw and a second spring.

A number of second countersunk holes are arranged on the side of the upper die base. One end of the second countersunk hole is connected with the horizontal through groove, and the other end is provided with thread.

The safety pin passes through the second countersunk hole and contacts with the groove of the upper die of the bending machine.

The preload of the second spring can be adjusted by rotating the top screw to adjust the extrusion force between the safety pin and the upper die of the bending machine,

When the clamping mechanism stops working, the upper die can still be suspended in the upper die seat to ensure the safety of the operator and the die.

As shown in Fig. 7, the device also includes the upper die deflection compensation mechanism, which includes several upper wedges, lower wedges, jacking pins, disc spring groups and the third spring.

The upper part of the upper die base is provided with a number of grooves, each groove is provided with two third countersunk holes, one end of the third countersunk hole is connected with the lower part of the upper die base.

The upper and lower wedges slide together and are installed in the groove of the upper die base, and the upper and lower wedges are connected with the upper die base by screws, and a disc spring group is arranged between the upper wedge and the upper die base.

A third spring set on the surface of the ejector pin is installed in the third countersunk hole, and the ejector pin contacts with the upper die of the bending machine through the third countersunk hole.

2.3 Technical features

1) The hydraulic automatic clamping device designed in this paper is more important than the mechanical clamping device. It can not only realize automation, but also operate more simply. The die can be directly inserted into the groove of the upper die seat;

2) In this paper, the clamping device adopts hydraulic clamping, the clamping force can be accurately adjusted, the clamping force distribution is uniform, and the reliability is increased;

3) The clamping device is equipped with a safety mechanism, which can effectively protect the safety of the operator and the die;

4) In this paper, the clamping device adopts the rubber tube expansion extrusion die, which has the advantages of simple structure, good economy and practicability;

5) In scheme 2, the clamping device is equipped with a deflection compensation mechanism, which can effectively improve the bending accuracy;

6) In scheme 2, the upper die of the bending machine can be segmented, and different upper dies of the press brake machine can be assembled.

2.4 Movement process

Scheme 1:

Firstly, the upper die of the press brake machine is placed on the lower die of the worktable through the manipulator or manual operation, and the sliding block drives the upper die seat to move downward.

The upper die handle of the press brake machine is inserted into the groove of the upper die base, the sliding block moves to the bottom dead center, and the relevant hydraulic system is started.

The pressure oil in the hydraulic circuit enters into the rubber tube for stamping, and the rubber tube expands to extrude the top plate and cover plate.

Because the cover plate is fixed with the upper die base, the roof extrudes the spring back screw, and the springback screw extrudes the upper die handle and spring, thus clamping the upper die.

At this time, the cylinder in the safety locking mechanism pushes the safety pin through the pinhole of the upper die seat and enters into the pinhole of the press brake machine.

When the middle pin is pressed and bent, the safety die is pulled out from the air cylinder.

The springback screw is ejected by the pre-tightening force of the spring, and the upper die of the bending machine is released.

At this time, the die can be changed manually or by a manipulator.

Scheme 2:

When the device works, firstly, it is necessary to insert the upper die handle of the bending machine into the through groove of the upper die base through manual operation or manipulator operation and overcome the preload of the second spring by sliding the upper die handle of the bending machine with the chamfering part of the safety pin in the safety device.

When the upper die handle of the bending machine completely enters the through groove of the upper die base, the safety pin is pressed into the groove of the upper die of the bending machine.

The safety locking mechanism locks and suspends the upper die of the bending machine in the upper die base.

The pre-tightening force of the second spring can be adjusted by adjusting the top screw, so as to adjust the extrusion force between the safety pin and the upper die of the bending machine.

When all the required upper dies of the bending machine are put into the device, the upper and lower dies of the bending machine are closed and the relevant hydraulic system is started.

The pressure oil enters the inner part of the rubber tube through the following rubber tube, and the rubber tube expands and extrudes the top plate and the cover plate. Because the cover plate and the upper die seat are fixed by screws, the roof extrudes the rebound screw, and the rebound screw extrudes the first spring and clamps the upper die of the bending machine.

At this time, the upper die deflection can be compensated by the upper die deflection compensation mechanism of the bending machine.

Firstly, the position of the upper wedge is adjusted by turning the second screw clockwise.

The upper wedge extrudes the disc spring group and the lower wedge, the lower wedge extrudes the ejector pin, and the ejector pin squeezes the second spring and the upper die of the press brake machine and compensates the deflection of the upper die.

When the deflection compensation is canceled, the second screw is turned anticlockwise, and the upper wedge is moved backward by the preload of the disc spring group.

The jacking pin and the lower wedge are jacked up by the preload of the second spring, and the deflection compensation of the upper die disappears.

When changing the die, the pressure of the rubber tube is released first, the spring-back screw is ejected by the first spring through the pre-tightening force, the rubber sac is flattened, and the upper die of the bending machine is released.

The upper die of the bending machine is removed and replaced by manual operation or manipulator operation to overcome the preload of the third spring.

3. Conclusion

With the rapid development of the processing and manufacturing industry and the rapid improvement of automation, the requirements for die change efficiency of press brake machine are higher and higher.

Therefore, it is of great significance to develop the rapid clamping device for the upper die of the press brake machine.

The research of this technology not only improves the advanced technology and efficiency of the die changing but also improves the bending accuracy.

Reasonable use of this technology will further improve the market competitiveness of enterprises and obtain rich economic benefits.

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