Design of automatic hydraulic clamping device for punch of bending machine

  As one of the most widely used sheet bending equipment, CNC bending machine is widely used in sheet metal processing and equipment manufacturing industry. It is not compatible with CNC turret punch press, CNC shearing machine and CNC laser cutting machine. Missing equipment. It uses a simple universal mold to bend the sheet into a more complex cross-sectional shape through 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 diverse. Some companies with strong scientific research have begun to focus on the development and design of various functional components, and strive to improve the automation of machine tools. Among the most functional parts, the most important impact on the bending accuracy and bending efficiency is the upper mold quick clamping device, especially in the multi-variety and small-batch bending production, the improvement of the mold change efficiency is particularly prominent.

  To this end, this paper introduces two new types of upper mold clamping devices that are simple to operate, easy to use, energy-efficient and efficient, mainly introducing their technical principles, mechanism design, technical features and working processes.

1. Introduction to traditional clamping device technology

  The upper CNC clamping device of the CNC bending machine usually adopts a mechanical structure, as shown in Figures 1 and 2. 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-end clamp by a cylindrical pin, and a spring is sandwiched between the front-end clamp and the fixed block. When performing quick clamping action on the upper die of the bending machine, first insert the upper die of the bending machine from the side of the quick clamping device, and quickly clamp the upper die by rotating the operating handle. When the operating handle is reversely rotated, the front clamping block is used. The spring between the block and the fixed block quickly resets the front-end clamp and the mold is loosened and carried out from the side. The 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 threaded quick clamping mechanism. When the bending machine mold is quickly clamped, the upper die of the bending machine is first inserted from the side of the quick clamping device, and the screw is rotated by the rotating operation handle. The front-end clamp moves forward to clamp the mold. When the handle is rotated in the reverse direction, the front-end clamp moves backwards under the screw to release the mold and carry it out from the side. The structure has large clamping force, good self-locking property and simple operation, but has problems such as uneven clamping force and slow clamping speed.

Figure 1——Eccentric quick clamping mechanism

Figure 2——Threaded quick clamping mechanism

2. Hydraulic automatic clamping device design

  2.1 Scheme design

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

  Scheme 1: The mold is clamped by using the expansion force generated by injecting pressure oil into the compression hose, and a safety lock is opened at each end of the clamping device. When the upper mold is clamped, the safety pin in the safety lock is inserted into the mold pin hole. It can effectively protect the operator and mold when the internal pressure of the hose disappears. The hydraulic automatic clamping device is suitable for large-scale forming molds, such as arc-shaped molds for pressing doors and windows in the automobile industry.

  Scheme 2: The expansion force generated by the compression hose is also used to squeeze the mold. And the hydraulic automatic clamping device also includes an upper mold deflection compensation mechanism and a safety locking mechanism, and the top wedge is pressed by adjusting the upper wedge in the deflection compensation mechanism, and the top pin presses the mold to thereby compensate the upper mold. The purpose of deflection; the safety pin in the safety locking structure can effectively protect the safety of the operator and the upper mold. The hydraulic automatic clamping device is suitable for common standard molds, and the mold can be segmented.

  2.2 Structural design

  According to the design idea of the first scheme, the upper mold hydraulic automatic clamping device shown in Figures 3 and 4 can be obtained. The upper mold hydraulic automatic clamping device comprises a clamping mechanism and a safety locking mechanism, and the clamping mechanism comprises an upper mold base, a rebound screw, a top plate, a spring, a cover plate, a rubber tube, a follower hose, a transition joint and a plug. The upper die holder is fixed to the bottom of the slider by a number of screws. The upper mold base is vertically processed with a groove for placing the upper mold shank, and one side is machined with a plurality of countersunk head holes, and a countersunk screw for squeezing the mold and a spring screw for resetting are placed in the counterbore hole. Spring. A cover plate is fixed on the side of the upper mold base, and a through groove is formed in the cover plate, and a top plate and a rubber tube are arranged in the through groove, and the top plate is between the rebound screw and the rubber tube. The hose is in a compressed state in the non-working state. As shown in Fig. 4, a safety lock mechanism is provided on both sides of the clamping device, and the mechanism includes a cylinder, a safety pin and the like. The upper and lower sides of the upper mold base and the bending machine are provided with pin holes. When the upper mold is clamped, the cylinder pushes the safety pin through the upper mold pin hole and inserts into the upper mold pin hole to ensure that the internal pressure of the hose suddenly disappears. The upper die of the bending machine can still be hung in the groove of the upper die seat to ensure the safety of the operator and the mold.

Figure 3——Scheme 1 punch hydraulic automatic clamping mechanism

Figure 4——Safety lock mechanism

  According to the design idea of the second scheme, the second upper mold hydraulic automatic clamping device can be obtained, and the structural schematic diagram is shown in Figs. 5, 6, and 7.

Figure 5——Scheme 2 punch hydraulic automatic clamping mechanism

  It can be seen from the schematic diagram that the upper mold hydraulic automatic clamping device comprises a clamping mechanism, a deflection compensation mechanism and a safety locking mechanism. The clamping mechanism includes an upper mold base, a cover plate, a top plate, a rebound screw, a first spring, a rubber hose, a follower hose, and a transition joint and a plug. The upper mold base is fixed by the screw and the bottom of the slider, the bottom of the upper mold base is provided with a horizontal through groove, and the first countersunk hole is opened at the side, and the first counterbore is provided with a first spring set on the surface of the rebound screw. The rebound screw passes through the first counterbore to contact the die shank of the bending machine. A cover plate is arranged on the upper mold base, a horizontal through groove is arranged on the cover plate, and a rubber pipe is arranged inside the horizontal through groove, and one end of the rubber pipe is blocked by a plug, and the other end is connected with the transition joint and the 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.

  As shown in Fig. 6, the device further includes a safety locking mechanism, and the safety mechanism is locked to include a safety pin, a top wire and a second spring. A plurality of second counterbores are opened in the side of the upper mold base, and one end of the second counterbore is penetrated by the horizontal through groove, and the other end is provided with a thread. The safety pin passes through the second counterbore hole and contacts the groove of the upper die of the bending machine. The preload of the second spring can be adjusted by rotating the top wire, thereby adjusting the pressing force of the safety pin and the upper die of the bending machine, and ensuring the clamping mechanism. When the work is stopped, the upper mold can still be hung in the upper mold base to ensure the safety of the operator and the mold.

Figure 6——Safety locking mechanism

  As shown in FIG. 7, the device further includes an upper mold deflection compensation mechanism, and the upper mold deflection compensation mechanism includes a plurality of upper wedges, a lower wedge, a top pin, a disc spring group, and a third spring. The upper part of the upper mold 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 is penetrated with the lower part of the upper mold base. The upper wedge is slidably engaged with the lower wedge and installed in the upper mold base groove, and the upper and lower wedges are connected to the upper mold base by screws, and a disc spring group is disposed between the upper wedge and the upper mold base. A third spring sleeved on the surface of the top pin is mounted in the third counterbore, and the top pin passes through the third counterbore to contact the upper die of the bending machine.

Figure 7——Punch deflection compensation mechanism

  2.3 Technical characteristics

  (1) The upper mold hydraulic automatic clamping device designed in this paper is more important than the mechanical clamping device. It can not only realize automation, but also the operation is simpler. The mold can be directly inserted into the groove of the upper mold base;

  (2) The clamping device of this paper adopts hydraulic clamping, the clamping force can be precisely adjusted, the clamping force is evenly distributed, and the reliability is increased;

  (3) The clamping device of this paper is equipped with a safety mechanism to effectively protect the safety of the operator and the mold;

  (4) The clamping device of this paper adopts the hose expansion extrusion die, which has simple structure and good economical and practicality;

  (5) In the second scheme, the clamping device is provided with a deflection compensation mechanism, which can effectively improve the bending precision;

  (6) In the second scheme, the upper die of the bending machine can be segmented, and different upper die of the bending machine can be assembled.

  2.4 Exercise process

  Scheme 1: Firstly, the upper die of the bending machine is placed on the lower die of the worktable by a robot or manual operation, the slider drives the upper die base to move downward, and the upper die holder of the bending machine is inserted into the groove of the upper die seat, the slider Move to the bottom dead center, start the relevant hydraulic system, the pressure oil in the hydraulic circuit enters the hose and press, the hose expands and squeezes the top plate and the cover plate. Because the cover plate is fixed with the upper die holder, the top plate squeezes the rebound screw and the rebound screw. The upper mold is clamped by pressing the upper mold shank and the spring. At this time, the cylinder push safety pin in the safety locking mechanism passes through the upper die seat pin hole and enters the die hole of the bending machine.

  When the mold changing operation is performed, the cylinder in the safety locking mechanism is reversely inflated, the safety pin is pulled out from the die hole of the bending machine, the rubber hose is released, and the rebound screw is ejected by the preload of the spring, and the bending machine is molded. It is released, and the mold change operation can be performed manually or by a robot.

  Scheme 2: When the device is working, first insert the mold shank part of the bending machine into the through hole of the upper die block by manual operation or manipulator operation, and chamfer the safety pin through the die shank part of the bending machine and the safety device. The sliding fit of the part overcomes the pre-tightening force of the second spring. When the die shank of the bending machine completely enters the through hole of the upper die seat, the safety pin is pressed into the groove of the upper die of the bending machine, and the safety locking mechanism will be on the bending machine. The mold is locked and suspended in the upper mold base. The second spring preload can be adjusted by adjusting the top wire to adjust the pressing force between the safety pin and the upper die of the bending machine.

  When all the upper molds of the bending machine are required to be put into the device, the upper and lower molds of the bending machine are closed and the relevant hydraulic system is started, and the pressure oil enters the inside of the rubber hose through the follow-up rubber hose, and the rubber tube expands and presses the top plate and the cover plate due to the cover. The plate and the upper mold base are fixed by screws, and the top plate presses the rebound screw, and the rebound screw presses the first spring and clamps the upper mold of the bending machine.

  At this time, the upper mold deflection can be compensated by the upper bending deflection compensation mechanism of the bending machine. First, the position of the upper wedge is adjusted by rotating the second screw clockwise, and the upper wedge is pressed against the disc spring group and the lower wedge, and the lower wedge. The block presses the top pin, and the top pin presses the second spring and the upper die of the bending machine to compensate the deflection of the upper die. When the deflection compensation is canceled, the second screw is rotated counterclockwise, the upper wedge is moved backward by the pre-tightening force of the disc spring group, and the top pin and the lower wedge are lifted up by the preload of the second spring, the upper mold. The deflection compensation disappears.

  When the mold changing operation is performed, first, the hose is released from pressure, and the first spring ejects the rebound screw by the pre-tightening force, the rubber tube is crushed, the upper mold of the bending machine is loosened, and the third spring is overcome by manual operation or robot operation. Tightly remove the upper die of the bending machine and perform the die changing operation.

  3. Conclusion

  With the rapid development of the processing industry and the rapid improvement of the degree of automation, the requirements for the die-changing efficiency of the bending machine are getting higher and higher. Therefore, the successful development of the rapid clamping device for the upper die of the bending machine is of great significance. Through the research of this technology, not only the technological advancement and mold change efficiency in this field are improved, but also the bending precision is improved. The rational use of this technology will further enhance the market competitiveness of enterprises and obtain substantial economic benefits.