CN113145716A

CN113145716A - Two-piece one-die forming method for mutually symmetrical characteristic parts

Info

Publication number: CN113145716A
Application number: CN202110319760.9A
Authority: CN
Inventors: 王国峰; 林海朋; 杜志豪; 李振伦; 刘永康
Original assignee: Harbin Institute of Technology Shenzhen
Current assignee: Beijing Dafeng Forming Technology Co ltd; Harbin Xindafeng Forming Technology Co ltd
Priority date: 2021-03-25
Filing date: 2021-03-25
Publication date: 2021-07-23
Anticipated expiration: 2041-03-25
Also published as: CN113145716B

Abstract

A two-piece-one-mold forming method for mutually symmetrical features belongs to the technical field of gas forming. The invention aims to solve the problem of long development cycle and high manufacturing cost of large aluminum alloy skin covering parts used in existing trains during forming. The problem that it is difficult to ensure the quality of parts forming, the present invention provides a two-piece one-mold forming method for mutually symmetrical features, which effectively improves the production status of rail trains that require two sets of molds for the left and right symmetrical large covers. The high-speed rail design and manufacturing cycle, which is more and more efficient, can greatly save the cost of molds and shorten the production time of trains. At the same time, the design of loose blocks is added to the molds. On the one hand, the loose blocks can fill the volume and facilitate gas filling. It can be used to disperse the local wall thickness of the anti-expansion surface, which can be adjusted flexibly and has a positive effect on the avoidance of defects.

Description

Two-piece one-die forming method for mutually symmetrical characteristic parts

Technical Field

The invention belongs to the technical field of gas forming, and particularly relates to a two-piece one-die forming method for mutually symmetrical characteristic parts.

Background

In order to facilitate the increasing travel demands of people, more and more cities begin to build and perfect a radiation traffic network from a central city area to a peripheral area, and rail lines connect thousands of households and also provide light-weight and environment-friendly requirements for the supply of rail transit vehicles. At present, the materials adopted by the urban rail train skin based on the principle of light weight mainly comprise glass fiber reinforced plastics and aluminum alloy, wherein the glass fiber reinforced plastics are also called glass fiber reinforced plastics, have the characteristics of easiness in forming and good designability, can ensure the manufacturing and production of complex vehicle body shapes, but are difficult to recycle, and have high maintenance cost in the service life cycle and short overall service life; the aluminum alloy can avoid maintenance, the material is convenient to recover and re-melt, but when the aluminum alloy is used for manufacturing the train skin with the complex shape, the forming process is difficult to determine, and the quality is difficult to ensure. When the aluminum alloy material is adopted, a hot stamping process is usually adopted in the traditional method, the springback error is reduced by means of die design adjustment and manual shape correction, and the process for the more and more complex vehicle body skin is increasingly strenuous. In recent years, with the research of scholars at home and abroad, some aluminum alloys have superplasticity, namely, the property that the elongation rate reaches over 200% under specific forming conditions under the premise of meeting the requirements of cost and use, and at the moment, the yield limit of the material is only dozens of megapascals, and the rebound quantity can be ignored, so that the application of the superplastic forming method to the rail vehicle covering part is gradually popularized.

Superplastic forming often requires ensuring that the material flows horizontally at relatively low strain rates, and the use of pneumatic or hydraulic controls is an effective means. The fixture for superplastic forming comprises an upper die and a lower die, wherein a plate to be formed is arranged between the upper die and the lower die, and holes are arranged on the upper die and the lower die to control gas to flow in and out. And after the tooling is finished, putting the workpiece into a hearth of a press machine, heating the workpiece to a target temperature, applying edge sealing force to ensure sealing, controlling the inflow speed of gas to ensure the target strain rate, maintaining the pressure for a period of time after the workpiece is completely attached to the mold, and taking out the workpiece to obtain the target part.

At present, China is in the transition period from a glass fiber reinforced plastic vehicle body to an aluminum alloy vehicle body, and urgent requirements are put forward on the process formulation and the die design of a large-scale integrated aluminum alloy train skin piece. The bilateral symmetry is a characteristic of rail transit vehicles, and not only meets artistic requirements of symmetry and beauty, but also keeps stress balance of the whole train body and ensures stability of a train running at high speed. For the bilateral symmetry structure, the bilateral symmetry structure is usually symmetrical about the central axis plane of the train and does not have the symmetry characteristic, so that two sets of dies are needed to be adopted during part forming, the cost is greatly improved, and the method for forming the two symmetrical characteristic parts by one die is provided for solving the problems.

Disclosure of Invention

The invention provides a two-piece one-die forming method for mutually symmetrical characteristic parts, which aims to solve the problems that a large aluminum alloy skin covering piece used in the existing train is long in research and development period and high in manufacturing cost during forming and the forming quality of the part is difficult to ensure;

a method of forming two-piece, one-die for symmetrical features of each other, the method comprising the steps of:

the method comprises the following steps: designing a mold: aiming at two shallow-cavity large aluminum alloy skin covering parts with symmetrical space planes, an upper die is firstly designed, the size of a cavity is determined according to the surface shape of a part by considering the effect of expansion with heat and contraction with cold, and the edge sealing platform is completely positioned on a plane parallel to the table surface of a press machine, the basic shape of a lower die can be obtained by mirror symmetry about the plane, on the basis, staggered edge sealing grooves are respectively formed in the edge sealing platforms in the upper die and the lower die, a guide mechanism, a positioning reference block, a thermocouple hole, a weight reduction groove and a jaw are arranged, and an air inlet through hole is respectively formed in the corresponding positions of the upper die and the lower die;

step two: loose piece design: designing a loose piece structure according to the depth and local characteristics of the shallow cavity in the large aluminum alloy skin covering part, and ensuring that the loose piece can be arranged in the cavity matched with the shallow cavity in the large aluminum alloy skin covering part on the die in the step one;

step three: blanking raw materials: cutting and blanking by using a plate cutting machine according to the calculated size of the flat plate, and efficiently and uniformly spraying graphite emulsion on the upper surface of the plate by adopting an air compressor and an air pressure regulating device to be connected with a spray can containing lubricating liquid;

step four: early preparation: fixing the upper die in the first step on an upper platform of a press machine, ensuring the upward die attaching direction of a plate, fixing the lower die provided with a movable block on a lower platform of the press machine by using a pressing plate, heating to a target temperature, then placing the plate, preserving heat to ensure that the plate is fully heated, and repeatedly applying a die closing force by using a hydraulic cylinder after the plate is softened to maintain the pressure so that edge sealing materials fully flow into a sealing groove;

step five: gas forming: filling gas into the die fixed on the upper platform of the press in the fourth step, so that the plate arranged in the die in the fourth step deforms under the action of air pressure and is gradually attached to the cavity structure of the upper die;

step six: taking out the parts: in the final die-attaching pressure maintaining stage, an air inlet through hole in an upper die is connected with a vacuum pump, the pump is opened in the workpiece taking stage, gas in a cavity is exhausted, the pump is closed after the die of a press is opened, and a crowbar is used for applying force through a jaw to complete part demoulding;

step seven: product treatment: after the temperature is reduced to room temperature, rough cutting and fine cutting are carried out on parts, and chemical and physical surface treatment is respectively carried out on the parts, so that one of the shallow cavity large curved surface aluminum alloy skin parts with high shape precision is obtained, the symmetrical direction part is just required to be inverted, and other processes are not changed, so that the effect of one mould for two parts can be achieved;

further, the depth of a shallow cavity arranged in the large and medium aluminum alloy skin covering piece in the first step is less than 200 mm;

furthermore, in the die structure in the first step, the upper die and the lower die are required to be provided with air inlet through holes, the plane of the edge sealing platform is parallel to the platform of the press machine, square sealing grooves are required to be designed on the upper die and the lower die, the two sealing grooves are required to be arranged in a staggered manner, the staggered horizontal distance is required to be more than 8mm, and a jaw is arranged on the edge sealing platform in the upper die and the edge sealing platform in the lower die at intervals of 400 mm;

further, the loose piece in the second step is a rough machined volume filler or a finished machined cavity entity;

further, the plate in the third step is left with plate allowance of 40-60 mm, and after the graphite emulsion is completely sprayed to the upper surface, standing is carried out for 12 minutes, so that stable attachment of the graphite emulsion is ensured;

further, in the fourth step, the temperature rising speed of the press is 2 ℃ per minute on average, the forming temperature is 460-520 ℃, the plate is placed in the press and then is kept warm for 15 minutes, and the edge sealing hydraulic pressure of a hydraulic cylinder of the press is 15-22 MPa;

further, in the fifth step, argon or nitrogen is filled into the die fixed on the upper platform of the press in the fourth step, and the temperature of the filled gas is 30-40 ℃:

further, the working process of filling gas into the die fixed on the press machine in the fourth step is to fill gas into the gas inlet through hole in the upper die for preforming, and then fill gas into the gas inlet through hole in the lower die for final forming;

further, the working process of filling gas into the die fixed on the press machine in the step four in the step five is to directly fill gas into the gas inlet through hole in the lower die for final forming;

further, the process in the step five is controlled according to the curve of the numerical simulation result during the air inflation forming, the counter inflation pressure is less than 1.5MPa, the final inflation pressure is less than 3MPa, and the pressure maintaining time after the maximum pressure is reached is more than 30 minutes;

further, the process in the step five is controlled according to the curve of the numerical simulation result during the air inflation forming, the final inflation pressure is less than 3MPa, and the pressure maintaining time after the maximum pressure is reached is more than 30 minutes;

further, after the pressure maintaining is finished and before the pressure relief is carried out in the sixth step, the air inlet through hole in the upper die is connected with a vacuum pump, when the vacuum degree is below 10000Pa, the suction force is kept, the pump is closed after the gas is exhausted, and the part demoulding is realized under the dual actions of the self gravity of the part and the prying force of the jaw;

and further, after the part in the seventh step is taken out, the molded surface of the part is accurately cut according to a three-dimensional digital-analog drawing, surface oxidation substances are removed through acid washing and alkali washing, and surface dirt is removed through a flat diaphragm machine, so that one of the shallow-cavity large-scale curved-surface aluminum alloy skin parts with high shape precision is obtained.

Compared with the prior art, the invention has the following beneficial effects:

1. the invention provides a two-piece one-die forming method for symmetrical characteristic parts, which provides a one-die two-cavity tool and a matched die for a vehicle symmetrical double-side shallow cavity complex-shaped aluminum alloy skin part, and a matched processing method, wherein the main structure of the die comprises an upper die with an air hole, a lower die with an air hole, a plate material, a movable insert block and the like, wherein the upper die cavity and the lower die cavity are of shallow cavity molded surfaces with spatially symmetrical characteristics, staggered sealing grooves are arranged at positions which the upper die cavity and the plate material are simultaneously contacted, the shape of the movable block is flexibly designed according to the shape of the cavity, the movable block is integrally arranged in a hearth of a press machine during air inflation forming, and real-time monitoring is carried out through a temperature feedback device, so that the die can realize that one set of die completes the forming of two parts, and because the upper die cavity and the lower die of the die are respectively processed, and the parts to be processed are also of symmetrical structures, the production situation that two sets of dies are needed for a symmetrical large covering part on the left side and the right side of a rail train is effectively improved, in the face of the high-speed rail design and manufacturing period which is more and more pursuing efficiency, the mold cost can be greatly saved and the train production time can be shortened.

2. The invention provides a two-piece one-die forming method for mutually symmetrical characteristic parts, which adopts the design of a movable insert block, on one hand, the movable insert block has low manufacturing cost due to low requirement on processing precision, but can effectively fill space in the gas expansion process to accelerate the gas filling speed, improve the production efficiency and inhibit a great deal of gas waste under high pressure and long-time pressure maintaining; on the other hand, according to the changeable characteristic shape of the target part, the structural shape of the loose piece can be flexibly manufactured, the loose piece is firstly attached to the reverse expansion for storing, and then the wall thickness of the position with serious local thinning is improved through the forward expansion, so that the defect is avoided.

3. The invention provides a two-piece one-die forming method for mutually symmetrical characteristic parts, wherein air inlets related in a die can also be used as air extraction holes, so that the shape precision of parts is not influenced when the parts are taken.

Drawings

FIG. 1 is a schematic diagram of the method of the present invention;

FIG. 2 is a schematic view of an upper mold used in the method of the present invention;

FIG. 3 is a schematic view of a lower mold used in the method of the present invention;

FIG. 4 is a schematic view of a matched mold in the method of the present invention;

in the figure, an upper die 1, a plate 2, a loose block 3, a lower die 4, an air inlet 5, a sealing platform 6, a sealing groove 7, a guide structure 8, a positioning reference block 9, a thermocouple hole 10 and a jaw 11 are arranged.

Detailed Description

The first embodiment is as follows: the present embodiment, which provides a two-piece, one-die molding method for symmetric features of each other, is described with reference to fig. 1 to 4, by the steps of:

the method comprises the following steps: designing a mold: aiming at two shallow-cavity large aluminum alloy skin covering parts with symmetrical spatial planes, an upper die 1 is firstly designed, the size of a cavity is determined by considering the effect of expansion with heat and contraction with cold according to the surface shape of a part, and a sealing edge platform 6 is completely positioned on a plane parallel to the table surface of a press machine, the basic shape of a lower die 4 can be obtained by mirror symmetry about the plane, on the basis, staggered sealing edge grooves 7 are respectively formed in the sealing edge platforms 6 in the upper die 1 and the lower die 4, a guide mechanism 8, a positioning reference block 9, a thermocouple hole 10, a weight reduction groove and a jaw 11 are arranged, and an air inlet through hole 5 is respectively formed in the corresponding positions of the upper die 1 and the lower die 4;

step two: loose piece design: designing a loose piece structure according to the depth and local characteristics of the shallow cavity in the large aluminum alloy skin covering part, and ensuring that the loose piece 3 can be arranged in the cavity matched with the shallow cavity in the large aluminum alloy skin covering part on the die in the step one;

step four: early preparation: fixing the upper die 1 in the first step on an upper platform of a press machine, ensuring the upward die attaching direction of a plate 2, fixing a lower die 4 provided with a movable block 3 on a lower platform of the press machine by using a pressing plate, heating to a target temperature, then placing the plate, preserving heat to fully heat the plate, and after softening, applying a die closing force by using a hydraulic cylinder for multiple times to preserve heat, so that an edge sealing material fully flows into a sealing groove;

step five: gas forming: filling gas into the die fixed on the upper platform of the press in the fourth step, so that the plate 2 arranged in the die in the fourth step deforms under the action of air pressure and is gradually attached to the cavity structure of the upper die 1;

step six: taking out the parts: in the final die-attaching and pressure-maintaining stage, an air inlet through hole 5 in the upper die 1 is connected with a vacuum pump, the pump is opened in the workpiece taking stage, gas in a cavity is exhausted, the pump is closed after the die of the press is opened, and the part demoulding can be completed by applying force through a jaw 11 by using a crowbar;

step seven: product treatment: and after the temperature is reduced to room temperature, roughly cutting and finely cutting parts, and respectively carrying out chemical and physical surface treatment to obtain one of the shallow cavity large curved surface aluminum alloy skin parts with high shape precision, wherein the symmetrical parts only need to be inverted by a mould, and other processes are not changed, so that the effect of one mould for two parts can be achieved.

In the embodiment, through improvement on the die, cavities to be formed are processed on an upper die 1 and a lower die 4 in the existing die, and a movable block 3 is arranged in the cavity on one side, so that on one hand, the movable block 3 has low manufacturing cost for processing precision, but can effectively fill space in the gas expansion process to accelerate gas filling speed, improve production efficiency and inhibit a large amount of gas waste under high-pressure long-time pressure maintaining; on the other hand, according to the changeable characteristic shape of the target part, the structural shape of the loose piece 3 can be flexibly manufactured, the loose piece is firstly attached to the reverse expansion for storing materials, and then the wall thickness of the position with serious local thinning is improved through the forward expansion, so that the defect is avoided, and the position of the loose piece 3 is worth noting that the air inlet hole area in the mold is not blocked;

the method has the forming principle that two sides are respectively formed, supposing that the large-scale shallow-cavity aluminum alloy skin A and the large-scale shallow-cavity aluminum alloy skin B are two parts (such as a left vehicle door and a right vehicle door) which are symmetrical about a space plane and have no symmetrical characteristic, firstly, the part A is produced in batch, the cavity A is arranged above the cavity A, the loose block is arranged in the cavity B below the cavity A, the pressure is applied after the same plate material in a hearth of a press machine is heated to superplastic temperature, and after the plate material at the edge sealing position is ensured to fully flow into an edge sealing groove, the pressure and the heat preservation are carried out; then gas is introduced from the gas inlet hole of the die cavity B, meanwhile, the gas hole of the die cavity A also has the function of exhausting, the movable block has the functions of occupying volume and saving gas, and the change of gas expansion pressure is controlled to ensure that the plates are completely attached to the die; and finally, releasing gas pressure, and demolding under the action of the self gravity of the part and the pressure of the jaw crowbar after the die is opened, so that the hot shape of the part can be further ensured, and the part A can be produced by vacuumizing through the air hole of the cavity B. Similarly, after the die is turned upside down, the batch manufacturing of the B pieces can be completed by the same process and flow.

The second embodiment is as follows: the present embodiment is described with reference to fig. 1 to 4, and the present embodiment further defines the first step of the first embodiment, and in the first step, the depth of the shallow cavity arranged in the large aluminum alloy skin covering piece is less than 200 mm. Other components and connection modes are the same as those of the first embodiment.

So set up, the application range that the physiosis takes shape is considered, if the shallow chamber degree of depth of will be too big, the physiosis takes shape and is difficult to satisfy the requirement, can lead to along with the continuous inflation of gas simultaneously, and the regional atress in the shallow chamber is uneven in large-scale aluminum alloy skin covering, easily influences the shaping effect.

The third concrete implementation mode: the embodiment is described with reference to fig. 1 to 4, and is further limited to the first step described in the second embodiment, in the structure of the mold in the first step, the upper mold 1 and the lower mold 4 need to be provided with the air inlet through hole 5, the plane of the edge sealing platform 6 is parallel to the press platform, square sealing grooves need to be designed on the upper mold 1 and the lower mold 4, the two sealing grooves need to be arranged in a staggered manner, the horizontal distance of the staggered manner needs to be more than 8mm, and a jaw 11 is designed on the edge sealing platform 6 in the upper mold 1 and the edge sealing platform 6 in the lower mold 4 every 400 mm. The other components and the connection mode are the same as those of the second embodiment.

Due to the arrangement, the sealing grooves in the two dies are arranged in a staggered manner, so that the plate can be effectively ensured to fully flow into the upper and lower edge sealing grooves, and both sides of the plate have good airtight effects; the jaws 11 arranged at equal intervals on the edge sealing platform 6 are matched, so that the formed workpiece is separated from the die conveniently, and the workpiece is taken efficiently.

The fourth concrete implementation mode: the present embodiment will be described with reference to fig. 1 to 4, and is further limited to the second step described in the third embodiment, and in the present embodiment, the loose piece 3 in the second step is a rough volume filler or a finished solid cavity. Other components and connection modes are the same as those of the third embodiment.

In this embodiment, the loose piece 3 can be flexibly adjusted according to the shape of the part: the volume filler can be roughly processed, so that the waste of gas in batch production can be effectively inhibited, and the production efficiency can be improved; the die cavity entity can also be subjected to finish machining, the reverse expansion degree is controlled, and the local excessive thinning and cracking are avoided.

The fifth concrete implementation mode: referring to fig. 1 to 4, the embodiment is described, and the third step is a specific embodiment, and is further limited, in the third step, a sheet 2 has a sheet margin of 40 to 60mm, and after the graphite emulsion is completely sprayed on the upper surface, the sheet is left to stand for 12 minutes, so that the stable adhesion of the graphite emulsion is ensured. The other components and the connection mode are the same as those of the fourth embodiment.

So set up, make graphite emulsion stably attached on panel surface, be favorable to panel 2 to have good drawing of patterns lubricating property after shaping, make the part drawing of patterns easier.

The sixth specific implementation mode: the fourth step is further limited to the fifth step described in the fifth embodiment, in the fourth step, the temperature rise speed of the press is 2 ℃ per minute on average, the forming temperature is 460 to 520 ℃, the temperature of the plate 2 is kept for 15 minutes after being placed in the press, and the edge sealing hydraulic pressure of the hydraulic cylinder of the press is 15 to 22 MPa. The other components and the connection mode are the same as the fifth embodiment mode.

The seventh embodiment: the present embodiment is described with reference to fig. 1 to 4, and the present embodiment further defines step five in the sixth embodiment, in the fifth embodiment, argon or nitrogen is filled into the mold fixed to the upper platen of the press in step four, and the temperature of the filled gas is 30 to 40 ℃. Other components and connection modes are the same as those of the sixth embodiment.

So set up, the gas that normal conditions directly flowed out from the liquid nitrogen bottle often the temperature is extremely low, need let in the die cavity through the intake pipe again behind many bends long-range buffer, has increased the stroke that gas flows, has consumed more part shaping time.

The specific implementation mode is eight: the present embodiment is described with reference to fig. 1 to 4, and is further limited to the step five described in the seventh embodiment, and in the present embodiment, the working process of filling gas into the die fixed to the press in the step four in the step five includes filling gas into the gas inlet through hole 5 in the upper die 1 for performing, and then filling gas into the gas inlet through hole 5 in the lower die 4 for final forming. The other components and the connection mode are the same as those of the seventh embodiment.

Due to the arrangement, the joint rate of the formed part and the die is favorably ensured, the smoothness of the surface profile of the formed part is favorably ensured, and the method is suitable for the condition that the depth of a shallow cavity in the formed workpiece is deep (the depth is between 100mm and 200 mm).

The specific implementation method nine: the present embodiment is described with reference to fig. 1 to 4, and is further limited to the fifth step of the specific embodiment, in the present embodiment, the working process of filling gas into the die fixed to the press in the fourth step is to directly fill gas into the gas inlet hole 5 in the lower die 4 for final forming. The other components and the connection mode are the same as those of the eighth embodiment.

By the arrangement, the time for forming the workpiece can be reduced, and the method is suitable for the condition that the depth of a shallow cavity in the formed workpiece is shallow (the depth is between 0mm and 100 mm).

The detailed implementation mode is ten: the present embodiment will be described with reference to fig. 1 to 4, which further defines the step five of the embodiment, wherein the process in the step five is controlled according to the curve of the numerical simulation result, the counter-expansion pressure is less than 1.5MPa, the final expansion pressure is less than 3MPa, and the pressure holding time after reaching the maximum pressure is more than 30 minutes. The other components and the connection mode are the same as those of the eighth embodiment.

The concrete implementation mode eleven: the present embodiment will be described with reference to fig. 1 to 4, and the present embodiment is further limited to the step five described in the specific embodiment, in the present embodiment, the process in the inflation forming in the step five is controlled according to the curve of the numerical simulation result, the final inflation pressure is less than 3MPa, and the pressure holding time after the maximum pressure is reached is more than 30 minutes. The other components and the connection mode are the same as those of the eighth embodiment.

The specific implementation mode twelve: the present embodiment is described with reference to fig. 1 to 4, and is further limited to the sixth step of the specific embodiment, in the present embodiment, after the pressure holding in the sixth step is finished, before the pressure relief, the air inlet through hole 5 in the upper die 1 is connected to a vacuum pump, when the vacuum degree is less than 10000Pa, the suction force is maintained, after the gas is exhausted, the pump is closed, and the part demoulding is realized under the dual actions of the self-gravity of the part and the prying force of the jaw 11. The other components and the connection mode are the same as those of the eighth embodiment.

This arrangement aims to relieve the gas pressure and facilitate the mold releasing step.

The specific implementation mode is thirteen: the present embodiment is described with reference to fig. 1 to 4, and is further limited to the seventh step of the eighth embodiment, in the present embodiment, after the part is taken out in the seventh step, the molded surface of the part is accurately cut according to the three-dimensional digital-analog drawing, the surface oxidation substance is removed by acid washing and alkali washing, and the surface dirt is removed by a flat-plate vibrating membrane machine, so that one of the shallow-cavity large curved surface aluminum alloy skin parts with high shape precision is obtained, and other components and connection modes are the same as those of the eighth embodiment.

The present invention is not limited to the above embodiments, and any person skilled in the art can make many modifications and equivalent variations by using the above-described structures and technical contents without departing from the scope of the present invention.

Claims

1. A two-piece one-mold forming method for mutually symmetrical features, characterized in that: the method is carried out through the following steps:

Step 1: Design the mold: For two large aluminum alloy skin coverings with shallow cavities that are symmetrical in the space plane, first design the upper mold (1), and determine the size of the cavity according to the surface shape of the part considering the effects of thermal expansion and contraction, and ensure edge sealing The platform (6) is completely on a plane parallel to the table top of the press. The basic shape of the lower mold (4) can be obtained by mirror symmetry about this plane. On this basis, the seals in the upper mold (1) and the lower mold (4) are Dislocation edge sealing grooves (7) are respectively provided on the edge platform (6), a guide mechanism (8), a positioning reference block (9), a thermocouple hole (10), a weight reduction groove and a jaw (11) are provided, and the upper mold ( 1) and the corresponding position of the lower mold (4) are respectively provided with an air intake through hole (5);

Step 2: Living block design: Design the loose block structure according to the depth and local characteristics of the shallow cavity in the large aluminum alloy skin cover, to ensure that the loose block (3) can be set on the mold described in step 1 and the large aluminum alloy skin. In the cavity matched with the shallow cavity in the cover;

Step 3: Raw material cutting: according to the calculated plate size, use a cutting machine to cut the material, and use an air compressor and an air pressure control device to connect a watering can containing lubricating fluid to spray graphite milk efficiently and uniformly on the upper surface of the plate;

Step 4: Preliminary preparations: Fix the upper mold (1) in step 1 on the upper platform of the press, ensure that the plate (2) is in the upward direction of the mold, and fix the lower mold (4) with the live block (3) with a pressure plate On the lower platform of the press, heat up to the target temperature and then place the sheet material to keep it warm to make it fully heated. After softening, the hydraulic cylinder will apply the clamping force for many times to keep the pressure, so that the edge sealing material can fully flow into the sealing groove;

Step 5: Gas forming: Fill gas into the mold fixed on the upper platform of the press in step 4, so that the plate (2) set in the mold in step 4 is deformed under the action of air pressure, and gradually merges with the upper mold (1). ) cavity structure fit;

Step 6: Parts take out: In the final mold sticking and pressure keeping stage, connect the air inlet through hole (5) on the upper mold (1) to the vacuum pump, open the pump in the pick-up stage, discharge the gas in the cavity, and start the press. After the mold is closed, the extractor is closed, and the part can be demolded by applying force through the jaw (11) with a crowbar;

Step 7: Product processing: Roughly cut and finely cut the parts after cooling to room temperature, respectively, after chemical and physical surface treatment, one of the large-scale curved aluminum alloy skin parts with shallow cavity and high shape accuracy is obtained. Upside down, other processes remain unchanged, you can achieve the effect of one mold and two pieces.

2. The two-piece-one-mold forming method for mutually symmetrical features according to claim 1, wherein the depth of the shallow cavity set in the large-sized aluminum alloy skin covering part in the step 1 is less than 200mm .

3. The two-piece-one-mold forming method for a mutually symmetrical feature according to claim 2, characterized in that: in the mold structure in the step 1, the upper mold (1) and the lower mold (4) ) need to open air intake through holes (5), the plane of the edge sealing platform (6) is parallel to the press platform, and the upper mold (1) and the lower mold (4) need to be designed with square sealing grooves, and the two sealing grooves must be Dislocation setting, the horizontal distance of dislocation must be more than 8mm, and design a jaw (11) every 400mm on the edge banding platform (6) in the upper die (1) and the edge banding platform (6) in the lower die (4). .

4. A two-piece-one-mold forming method for mutually symmetrical features according to claim 3, wherein the movable block (3) in the second step is a rough-machined volume filler or a fine-grained filler. Machined cavity body.

5. A two-piece-one-mold forming method for mutually symmetrical features according to claim 4, characterized in that: in the step 3, the plate (2) has a plate material allowance of 40-60 mm, After the graphite emulsion is completely sprayed on the upper surface, let it stand for 12 minutes to ensure stable adhesion of the graphite emulsion.

6. The two-piece-one-mold forming method for a mutually symmetrical feature according to claim 5, characterized in that: in the step 4, the heating rate of the press is an average of 2°C per minute, and the forming temperature is 460°C. ～520° C., the plate (2) is placed and kept for 15 minutes, and the hydraulic pressure of the hydraulic cylinder of the press is 15-22 MPa.

7. A two-piece-one-mold forming method for mutually symmetrical features according to claim 6, characterized in that: in the step 5, gas is charged into the mold fixed on the upper platform of the press in the step 4 It is argon or nitrogen, and the temperature of the filled gas is 30°C to 40°C.

8. The two-piece-one-mold forming method for mutually symmetrical features according to claim 1, characterized in that: in the step 5, in the step 4, the mold fixed in the press is filled with gas. The working process is to first fill the air inlet through hole (5) in the upper mold (1) for pre-forming, and then fill the air inlet through hole (5) in the lower mold (4) for final forming. type.

9. The two-piece-one-mold forming method for a mutually symmetrical feature according to claim 1, characterized in that: in the step 5, a gas is filled into the mold fixed in the press in the step 4. The working process is to directly charge gas into the air inlet through hole (5) in the lower mold (4) to perform final molding.

10. The two-piece-one-mold forming method for a mutually symmetrical feature according to claim 8, wherein the process is controlled according to the curve of the numerical simulation result during the inflation forming in the step 5, and the inflating process is reversed. The pressure is less than 1.5MPa, the final expansion pressure is less than 3MPa, and the holding time after reaching the maximum pressure is more than 30 minutes.

11. The two-piece-one-mold forming method for mutually symmetrical features according to claim 9, wherein the process is controlled according to the curve of the numerical simulation result during the inflation forming in the step 5, and the final inflation The pressure is less than 3MPa, and the holding time after reaching the maximum pressure is more than 30 minutes.

12. The two-piece-one-mold forming method for mutually symmetrical features according to claim 1, characterized in that: in the step 6, the upper mold (1) is fed into the upper mold (1) before the pressure is released after the pressure holding is completed. The air through hole (5) is connected to the vacuum pump. When the vacuum degree is below 10000Pa, the suction force is maintained, and the pump is turned off after exhausting the gas. The parts are removed under the dual action of the parts' own gravity and the prying power of the jaws (11). mold.

13. A two-piece-one-mold forming method for mutually symmetrical features according to claim 1, characterized in that: after the parts are taken out in the step 7, the part profiles are accurately cut according to the three-dimensional digital model drawings, The surface oxides are removed by pickling and alkali washing, and the surface dirt is removed by a flat-panel diaphragm machine to obtain one of the large-scale curved aluminum alloy skin parts with shallow cavity and high shape accuracy.