Design of Hydraulic Automatic Clamping Device for the punch of the Press Brake Machine
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Design of Hydraulic Automatic Clamping Device for the punch of the Press Brake Machine

Views: 252     Author: Site Editor     Publish Time: 2020-06-05      Origin: Site

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As one of the most widely used sheet bending equipment, CNC bending machine is widely used in metal sheet processing and equipment manufacturing industry. It is indispensable for the processing of metal sheet with CNC turret punch press, CNC shearing machine, CNC laser cutting machine, etc. Missing supporting equipment. It uses a simple general-purpose mold, and the sheet material is bent into more complicated various cross-sectional shapes through the repeated movement of the slider.


With the advancement and application of new technologies such as CNC, servo, and mold, the development of CNC bending machine technology is mainly reflected in energy saving and high efficiency. At the same time, as people's requirements for bending accuracy and bending efficiency continue to increase, various functional components are becoming more and more diverse. Some companies with strong scientific research strength began to focus on the research and development and design of various functional components, and strive to improve the degree of automation of machine tools. Among all the functional components, the most prominent influence on the bending accuracy and bending efficiency is the fast clamping device of the punch, especially in the production of multiple varieties and small batches of bending, the improvement of the die change efficiency is particularly prominent.


To this end, this article introduces two new punch clamping devices that are easy to operate, easy to use, energy-saving and efficient, mainly introducing its technical principles, mechanism design, technical characteristics and working process.

Brief introduction of traditional clamping device technology

The punch clamping device of the domestic CNC bending machine usually adopts a mechanical structure, as shown in Figures 1 and 2. Among them, Figure 1 uses an eccentric quick clamping mechanism. The main feature is that the end of the operating handle is a cam lever. The operating handle is fixed to the front clamp block by a cylindrical pin, and a spring is clamped between the front clamp block and the fixed block. When fast clamping the upper mold of the bending machine, first insert the upper mold of the bending machine from the side of the quick clamping device, and quickly clamp the upper mold by rotating the operation handle. The spring between the fixed block and the front clamp block is quickly reset, the mold is loosened and shipped out from the side. This device is easy to use and simple to operate, but has problems such as uneven clamping force and the need to insert the mold from the side. Figure 2 uses a screw-type quick clamping mechanism. When performing a quick clamping action on the bending machine mold, the punch of the bending machine must be inserted from the side of the rapid clamping device first, and the screw is rotated by rotating the operating handle, which in turn drives the screw The front end clamp moves forward to clamp the mold. When the handle is rotated in the reverse direction, the front end clamp moves backward under the drive of the screw, loosening the mold and transporting it from the side. This structure has large clamping force, good self-locking, and simple operation, but there are problems such as uneven clamping force and slow clamping speed.

PRESS BRAKE

Figure 1 Eccentric quick clamping mechanism Figure  2 Threaded quick clamping mechanism

Design of hydraulic automatic clamping device

(1) Program design

According to the characteristics of the hydraulic automatic clamping device of the upper mold of the bending machine, the force situation and the size of the upper mold of the bending machine, this paper introduces two solutions.

Option 1: Clamp the mold by using the expansion force generated by injecting compressed oil into the compression hose. Safety locks are provided at both ends of the clamping device. When the upper mold is clamped, the safety pin in the safety lock is inserted into the mold pin hole, When the internal pressure of the hose disappears, it can effectively protect the safety of the operator and the mold. The hydraulic automatic clamping device is suitable for large-scale forming molds, such as circular arc molds for pressing doors and windows in the automotive industry.

Option 2: The expansion force generated by the compression hose is also used to squeeze the mold. In addition, the hydraulic automatic clamping device also includes a punch deflection compensation mechanism and a safety locking mechanism. By adjusting the upper wedge in the deflection compensation mechanism to squeeze the ejector pin, the ejector pin squeezes the mold, thereby achieving compensation for the punch purpose of deflection; the safety pin in the safety locking structure can effectively protect the safety of the operator and the punch. The hydraulic automatic clamping device is suitable for ordinary standard molds, and the molds can be segmented.

(2) Structural design

According to the design idea of scheme one, the hydraulic automatic clamping device of the punch as shown in Figures 3 and 4 can be obtained. The upper mold hydraulic automatic clamping device includes a clamping mechanism and a safety locking mechanism. The clamping mechanism includes an upper mold base, a rebound screw, a top plate, a spring, a cover plate, a hose, a follower hose, a transition joint and a plug. The punch base is fixed to the bottom of the slider through several screws. The punch base is vertically machined with a groove for placing the punch shank, and a number of side-by-side countersunk holes are machined on one side. The countersunk screws for extruding the mold and for resetting the spring screws are placed in the countersunk Spring. A cover plate is fixed on the side of the upper mold base, and a through groove is opened in the cover plate, and a top plate and a rubber tube are installed in the through groove, and the top plate is between the rebound screw and the rubber tube. In the non-working state, the hose is in a compressed state. As shown in Figure 4, there are safety lock mechanisms on both sides of the clamping device. The mechanism includes cylinders, safety pins and so on. The punch base and the upper and lower sides of the punch of the bending machine are provided with pin holes. After the punch is clamped, the cylinder pushes the safety pin through the punch seat pin hole to insert into the punch pin hole to ensure that the internal pressure of the hose suddenly disappears. The upper mold of the bending machine can still be hung in the groove of the upper mold base to ensure the safety of the operator and the mold.

PRESS BRAKE

Figure 3 Scheme 1 Punch hydraulic automatic clamping mechanism

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Figure 4 Security lock mechanism

According to the design idea of scheme two, the second type of upper mold hydraulic automatic clamping device can be obtained, and its structural schematic diagrams are shown in Figures 5, 6, and 7. It can be seen from the schematic diagram that the upper mold hydraulic automatic clamping device includes a clamping mechanism, a deflection compensation mechanism and a safety locking mechanism. The clamping mechanism includes an punch base, a cover plate, a top plate, a rebound screw, a first spring, a hose, a follow-up hose, a transition joint and a plug. The punch base is fixed to the bottom of the slider by screws. The bottom of the punch base is provided with a horizontal through slot, and a first countersunk hole is provided on the side. The first countersunk hole is provided with a first spring set on the surface of the rebound screw. The rebound screw passes through the first countersunk hole and comes into contact with the punch handle of the bending machine. A cover plate is provided on the punch base, and a horizontal penetration groove is provided on the cover plate. A rubber hose is provided inside the horizontal penetration groove. One end of the hose is blocked with a plug, and the other end is connected with a transition joint and a follower hose. A top plate is installed between the hose and the rebound screw. In the initial state, the hose is in a flattened state under the action of the first spring preload.

PRESS BRAKE

Figure 5 Scheme 2 Punch hydraulic automatic clamping mechanism

Figure 6 Safety locking mechanism

PRESS BRAKE

Figure 7 Punch deflection compensation mechanism

As shown in Fig. 6, the device also includes a safety locking mechanism, which includes a safety pin, a top wire and a second spring. A plurality of second countersunk holes are opened on the side of the punch base, one end of the second countersunk hole penetrates the horizontal through slot, and the other end has a thread. The safety pin is in contact with the groove of the punch of the bending machine through the second countersunk hole, and the pretension of the second spring can be adjusted by rotating the top wire, thereby adjusting the squeezing force of the safety pin and the punch of the bending machine to ensure the clamping mechanism When the work is stopped, the upper mold can still be hung in the upper mold seat to ensure the safety of the operator and the mold. As shown in FIG. 7, the device also includes a punch deflection compensation mechanism. The punch deflection compensation mechanism includes a number of upper wedges, lower wedges, ejector pins, disc spring sets, and third springs. The upper part of the punch base is provided with a plurality of grooves, and each groove is provided with two third countersunk holes, and one end of the third countersunk hole penetrates through the lower part of the upper mold seat. The upper wedge block and the lower wedge block are slidingly fitted and installed in the groove of the upper mold base. The upper and lower wedge blocks are connected to the upper mold base by screws. A disc spring set is installed between the upper wedge block and the upper mold base. A third spring sleeved on the surface of the ejector pin is installed in the third counterbore hole, and the ejector pin passes through the third counterbore hole and contacts the punch of the bending machine.

(3) Technical characteristics

① The hydraulic automatic clamping device of the punch designed in this paper is more important than the mechanical clamping device. Not only can it be automated, but the operation is simpler, and the mold can be directly inserted into the groove of the punch holder;

②The clamping device in this article adopts hydraulic clamping, the clamping force can be adjusted accurately, the clamping force is evenly distributed, and the reliability is increased;

③ This clamping device is equipped with a safety mechanism, which can effectively protect the safety of the operator and the mold;

④The clamping device in this article adopts rubber tube expansion and extrusion die, which has simple structure, good economy and practicality;

⑤The clamping device in Scheme 2 is equipped with a deflection compensation mechanism, which can effectively improve the bending accuracy;

⑥The punch of the bending machine in scheme two can be segmented and can be assembled with different punch of the bending machine.


Conclusion

With the rapid development of the manufacturing industry and the rapid improvement of the degree of automation, the requirements for the efficiency of the die change of the bending machine are becoming higher and higher. Therefore, the successful development of the fast clamping device for the punch of the bending machine is of great significance. Through the study of this technology, it not only improves the technological advancement and die change efficiency in this field, but also improves the bending accuracy. The rational use of this technology will further improve the market competitiveness of enterprises and obtain rich economic benefits.

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