Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D26/00—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces
  • B21D26/02—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure
  • B21D26/06—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure by shock waves
  • B21D26/10—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure by shock waves generated by evaporation, e.g. of wire, of liquids
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D26/00—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces
  • B21D26/02—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure
  • B21D26/06—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure by shock waves
  • B21D26/12—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure by shock waves initiated by spark discharge
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
  • B21D22/20—Deep-drawing
  • B21D22/22—Deep-drawing with devices for holding the edge of the blanks

Definitions

• the present invention relates to a hybrid method of forming a sheet and a corresponding forming device.
• the sheet can for example be folded, rolled, stamped, ....
• the present invention relates here to the formation of a part of complex shape from a sheet by implementing a combination of known methods.
• electrohydraulic forming As a method of deforming a sheet, electrohydraulic forming is known, which deforms a sheet against a mold by applying dynamic pressure. To this end, an electric discharge is generated between at least two electrodes in a cavity filled with liquid, for example water. An electric arc is then formed between the two electrodes causing a high temperature gradient and vaporization of the liquid. A pressure wave, also commonly called a "shock wave", travels at high speed and presses the sheet against the mold. Electrohydraulic forming is particularly advantageous in comparison with other forming processes since it allows to have a reduced springback and to obtain etching type details and / or sharp angles and / or elongations before break improved on the parts to be formed.
• the preforming of the part by applying a quasi-static pressure makes it possible to promote the swallowing of the sheet in the mold, therefore to reduce the deformation of the material to be produced by electrohydraulic forming and therefore to reduce the processing time. forming in the case where it is necessary to recharge the high-voltage pulse electric generator between two discharges or to reduce the size of the generator in the case where it is desired to carry out successive discharges without having to wait between discharges for the generator to recharge.
• Document US2011 / 0088442 relates to a hydromechanical forming tool which may include electro-hydraulic forming chambers in which an electric discharge can be caused by electrodes in order to improve the level of detail that can be achieved in a mold.
• Document DE 10019594 discloses a method and a device for the hydromechanical deformation of plastically deformable sheets, in particular for producing automobile body parts, in which the sheet is placed between a forming tool and a cushion of liquid and in which under the effect of a static pressure created in the liquid cushion, the sheet is pressed against the forming tool. Simultaneously with the application of static pressure, a shock wave generator disposed in the cushion of liquid is activated to locally create an increased downforce directed towards areas of the sheet.
• Document US2012 / 103045 shows a system for the electrohydraulic forming of a sheet in an electrohydroforming machine.
• the present invention therefore aims to provide a method and a corresponding device which makes it possible to produce simply, by implementing electro-hydro-forming, vertical walls.
• the present invention provides a hybrid process for forming a material blank in which:
• the material blank is deformed by stamping using at least one punch to obtain a pre-stamped material blank.
• a cavity is filled with liquid in which there are, on the one hand, said at least one punch and, on the other hand, at least one pair of electrodes,
• At least one electric discharge is generated between at least one pair of electrodes so as to deform the pre-stamped material blank against the die.
• This method makes it possible to promote the swallowing of the material in the die while offering the possibility of creating so-called vertical walls using the punch and also to have a high quality of finish of the part thanks to the electro hydroforming.
• the relative stroke of each punch relative to the die is limited so that the material blank when pushed by the punch (s) does not come into contact of the matrix.
• the relative stroke of at least one punch relative to the die is such that the material blank when it is pushed by said at least one punch comes into contact with the die.
• the hybrid process described above may further include a step during which the liquid at contact of the material blank is pressurized so in deforming the pre-stamped material blank.
• a hydroforming step is then carried out which is preferably carried out after the deformation by the punch and before the electro-hydroforming.
• the present invention also provides a device for implementing the hybrid training method described above. It thus offers a device for hybrid forming a material blank comprising:
• a die cooperating with a blank holder the die being movable relative to the blank holder between a position called the open position in which the material blank can be placed between the die and the blank holder and be therefrom withdrawn, and another position called the closed position in which the blank holder cooperates with the die to maintain in a controlled manner the entire edge of a blank of material to be deformed,
• the tank comprises at least one movable punch relative to an assembly formed by the blank holder and the die in the closed position between a position called the remote position in which the free end of the punch is at a distance from the die and a position called the close position in which the free end of the punch is at a distance from the die less than its distance away in the remote position.
• the matrix makes it possible to define the final shape of the sheet to be deformed.
• the punch is designed to be placed in the cavity and to deform the sheet in the direction of the die by coming into contact with said sheet and by deforming it.
• the assembly formed by the blank holder and the die in the closed position is movable relative to the tank which remains fixed.
• the tank has a bottom and a peripheral wall, and that the free edge of the peripheral wall forms a punch.
• the tank and the at least one punch are preferably one piece.
• the tank has a bottom and a peripheral wall
• at least one punch is made on a free edge of a wall extending through the tank by dividing the latter into at least two compartments, and that at least one pair of electrodes is located in each of the two compartments.
• a preferred variant of a device described above provides that the blank holder is fixed on vertical candles, that the die is mounted mobile in translation relative to the blank holder on the side opposite the candles, that the tank has a bottom and a peripheral wall, and that the tank is mounted fixed while the candles are sliding relative to the tank.
• the candles can be mounted, for example, on hydraulic cushions. These candles can also be formed, for example, by a gas spring, a hydraulic cylinder or the like.
• FIG. 1 shows a first step of a hybrid method for forming a sheet, the method being implemented with a hybrid forming device
• FIG. 2 shows a second step of a hybrid sheet metal forming process, the process being implemented with a hybrid forming device
• FIG. 3 shows a third step of a hybrid sheet forming process, the process being implemented with a hybrid forming device
• FIG. 4 shows a fourth step of a hybrid sheet forming process, the process being implemented with a hybrid forming device
• FIG. 5 shows a fifth step of a hybrid sheet forming process, the process being implemented with a hybrid forming device
• Figure 1 shows a device for forming a blank of material in longitudinal section through a vertical plane. It will be assumed in the remainder of the description that the material blank to be deformed is a sheet 2, made of steel or a steel-based alloy, or else in another metal or metal alloy. Initially ( Figure 1), this sheet 2 is of a given shape, for example flat as shown in Figure 1. A sheet in the shape of a cap, for example, could also be considered.
• the sheet 2 to be deformed is placed here between a blank holder 4 and a die 6.
• the blank holder 4 is carried by candles 8 guided in housings made in a lower frame placed on the supposedly horizontal ground and on which a tank 10 is firmly fixed. It is assumed in the remainder of the description that the candles 8 extend vertically and that they support the blank holder 4 which is therefore located above the candles 8. In this way an up / down orientation is defined . It will be maintained throughout the remainder of the present description.
• the blank holder 4 is arranged here below the sheet 2. It is an annular part having an upper edge 14 adapted to the die 6 and to the shape that the sheet 2 must take after a first deformation (optional preforming operation described below).
• the blank holder 4 Around the upper edge 14, the blank holder 4 has a peripheral rim 16 serving as a support for compensating devices 18 intended to cooperate with the die 6 in order to control the clamping forces exerted by the die 6 and the clamp. blank 4 on the sheet 2.
• the blank holder 4 has a cylindrical surface 20, of section adapted to the shape of the tank 10, of vertical axis. As explained below, this cylindrical surface 20 makes it possible to produce a seal between the blank holder 4 and the tank 10.
• the blank holder 4 also has a lower base 22 which rests on the candles 8.
• the latter serve to support the blank holder 4. They could also participate in guiding the blank holder 4 relative to the tank 10
• These candles can be for example gas springs or hydraulic jacks. They can also be rods mounted on hydraulic cushions.
• external guide means are preferably provided to provide translational guidance of the assembly formed by the blank holder 4, the die 6 and the sheet 2 clamped between these two elements, relative to the tank 10.
• the die 6 is the main part of the device which determines the final shape of the sheet 2 after deformation.
• the lower face of the die 6, that is to say that facing the blank holder 4, is intended to give the final shape of the sheet 2 after deformation.
• the sheet 2 will be pushed against the die 6, more precisely against the underside of the die 6, in order to be plastically deformed and come to conform to the shape of the latter.
• the lower face of the die 6, which corresponds to the face of the die 6 located opposite, on the one hand, the blank holder 4 and, on the other hand, the tank 10 also comprises an annular zone disposed facing the upper edge 14 of the hold-down 4. The edge of the sheet 2 will be maintained during the forming process between the upper edge of the hold-down 4 and the aforementioned annular zone of the lower face of matrix 6.
• the die 6 is movable in a vertical translational movement so as to be able to approach and move away from the blank holder 4 which in a first step is intended to remain fixed.
• the blank holder 4 remaining fixed the die 6 moves between a first position, called the open position, in which the free space between the blank holder 4 and the die 6 is sufficient to introduce a sheet 2 before deformation and to remove it. after deformation, and a second position called the closed position, in which it clamps the peripheral edge of the sheet 2 to be deformed between its annular zone and the upper edge 14 of the blank holder 4.
• the compensating devices 18 ensure a constant play between the die 6 and the blank holder 4 corresponding to the thickness of the sheet 2, plus or minus an adjustment value.
• the tank 10 fulfills here, in this preferred embodiment, the dual function of receptacle for containing a liquid (preferably water) and of punch. It is hereinafter called “tank” but could also be called “punch”. As a variant, these two functions could be dissociated, a separate punch being for example associated with a tank.
• This tank 10 has in the illustrated embodiment a base plate 24 from which extends a peripheral wall 26. The base plate 24 forms the bottom of the tank 10.
• the peripheral wall 26 extends vertically and defines with the base plate 24 (which extends substantially horizontally) a cavity which can be filled with liquid (generally water).
• the outer surface of the wall peripheral 26 cooperates with the cylindrical surface 20 of the blank holder to provide a seal, for example using a seal 28, during a vertical translational movement of the blank holder 4 around the wall peripheral 26.
• Specific means for example guide columns not shown, preferably provide guidance during a translational movement of the blank holder 4 relative to the tank 10. It is noted that the cylindrical surface 20 may come form the upper edge of the cavity defined by the tank 10 and thus extend this cavity according to the relative position of the blank holder 4 with respect to the tank 10.
• the upper part of the tank 10 as mentioned above at least partially constitutes the upper face of the punch.
• the free edge (opposite to the base plate 24) of the peripheral wall 26 has a contour of shape adapted to the deformation that one wishes to impose on the sheet 2. This free edge can thus comprise parts projecting and / or recessed.
• a wall 30, substantially vertical is arranged in the tank 10, inside the peripheral wall 26. This wall 30 starts from the base plate 24 and extends vertically towards the die 6. The free end of the wall 30 forms a head 32 which is machined according to the shape to be given to the sheet 2.
• the wall 30 preferably divides the interior cavity of the tank into compartments 34.
• the compartments can be sealed relative to each other but communications (passages) can be provided between them.
• each compartment 34 or at least in at least some of them, is arranged a pair of electrodes 36 which are supplied for example through the base plate 24 (connections and insulators not shown).
• HOF stops 38 that is to say, Closed Tool Height stops, which, in a manner known to those skilled in the art, precisely limit the end of travel of the die 6 (and also of the set formed by the blank holder 4 and the sheet 2 driven by the die 6 during its movement).
• the HOF stops are arranged on a fixed surface such as for example here an upper face of the lower frame carrying the tank 10, around the peripheral wall 26 and are arranged between this base plate 24 and the lower face of the die 6. They could also come to cooperate with the lower base 22 of the blank holder 4.
• Figure 1 shows the hybrid forming device in a position corresponding to a first step of a forming process.
• the die 6 is in the open position, that is to say in its position furthest from the blank holder 4 (and from the vessel 10 including the punch 26, 32).
• the blank holder 4 and the die 6 are then sufficiently spaced from one another to allow in particular the introduction of a sheet 2 between them.
• Figure 1 illustrates the placement of this sheet 2, this placement being suggested by the arrow 40 on the left of this figure 1.
• the blank holder 4 is in a high position, that is to say a position in which the blank holder 4 which carries the sheet 2 is positioned such that the upper part of the tank 10 forming the punch cannot come into contact with the sheet 2. Water may already be present in the compartments 34 of the tank 10.
• the die 6 is arranged above the sheet 2.
• Figure 2 illustrates a subsequent step.
• the die 6 is lowered as suggested by an arrow 42.
• the peripheral edge of the sheet 2 is clamped between the annular zone of the die 6 and the upper edge of the blank holder 4.
• the clamping force between the die 6 and the blank holder 4 is regulated by the compensating devices 18 which are arranged between the peripheral edge 16 of the blank holder 4 and an edge of the die 6 (also taking into account a compensation of forces which can be carried out at each of the candles 8).
• the contact zones, on the one hand, between the sheet 2 and the die 6 and, on the other hand, between the sheet 2 and the blank holder 4 are preferably parallel.
• the clamping of the die 6 on the sheet 2 could be used in order to perform a first preforming of the sheet 2, for example to bend this last and / or to conform its edge. It is thus possible (optionally) to cause a first deformation of the sheet 2.
• the clamping of the die 6 on the blank holder 4 also makes it possible to guarantee a watertight seal between the sheet 2 and the blank holder 4.
• a Peripheral ring can also optionally be formed on the sheet 2 between the die 6 and the blank holder 4 to guarantee a good seal between the sheet 2 and the blank holder 4.
• An elastomeric seal can also fulfill this function of sealing.
• the purpose of filling with water is to come and fill the cavity so that the liquid comes into contact with the possibly preformed sheet 2. It can be carried out for example by sucking in the air located below the sheet 2. A simultaneous suction of the air above the sheet 2 is also carried out to maintain substantially the same pressure on both sides of the sheet. 2.
• the air suction between the sheet 2 and the die 6 is preferably maintained throughout the deformation process to prevent the air in this space interfering with the deformation of the sheet 2. As a variant, it is may provide for evacuating the air through evacuation holes located at a high point of the blank holder 4 when the water rises in the cavity.
• pressurized air can be used to maintain a concavity in the sheet, thus limiting air bubbles beneath it.
• the blank holder 4 remains during this filling in the same position as in Figure 1.
• the die 6 continues to descend towards the tank 10, and causes the descent of the blank holder 4 relative to the tank 10-arrow 44.
• the punch formed by the tank 10, more particularly the upper peripheral edge of the peripheral wall 26 and the head (s) 32 then come into contact with the sheet 2 and deform the latter plastically by stretching. During this movement, the punch exerts a force that pushes the sheet 2 towards the die 6.
• the sheet 2 held between the blank holder 4 and the die 6 is placed between the punch and the die 6.
• the punch and / or the tank 10 act as a male part which cooperates with the die 6, a female part which here has a housing for receiving the punch formed by the upper part of the tank 10.
• the devices compensators 18 act here to regulate the tension at the edge of the sheet 2 and allow, if necessary, a displacement of material from the sheet 2 towards the interior of the system.
• a second deformation step (the possible preforming mentioned above being the first deformation step) of the sheet 2 is carried out here.
• This is a stamping step.
• care is preferably taken, but not necessarily, that the sheet 2 does not come into contact with the die 6 in its central zone, that is to say in the zone located opposite. vis-à-vis the inside of the peripheral wall 26.
• it is for example possible to provide in certain places a “complete” deformation of the sheet 2 during this stamping operation. This avoids having to provide electrodes to "cover" the entire surface of the sheet 2.
• FIG. 4 illustrates an advantageous but optional step of the hybrid forming process. It is proposed here to have a virtually static hydroforming step of the sheet 2 during which this sheet 2 still comes close to the die 6 and can locally come into contact with it. This deformation of the sheet 2 is then obtained by putting the water in the tank 10 under pressure, for example by acting on the die 6 (arrow 42). The sheet 2 therefore separates at least locally from the punch formed by the upper part of the tank 10 and takes an intermediate position between the die 6 and the head (s) 32 and the upper edge of the peripheral wall 26 forming the punch.
• FIG. 5 illustrates a subsequent step in the process for forming the sheet 2.
• An electro-hydroforming is shown schematically here.
• a discharge chamber is formed here and completely filled with water. It includes the cavity inside the tank and extends beyond to the deformed sheet 2 and to the seal produced between the tank and the blank holder 4.
• the pairs of electrodes 36, arranged in said discharge chamber, are then supplied by a strong current from a discharge of capacitors.
• this electric discharge creates in the liquid (water) contained in the tank 10 and in the contact with sheet 2 (it is important to have a good filling of water in tank 10 so that the water is in contact with sheet 2 for this electro-hydroforming step) an explosion creating a shock wave which propagates towards the sheet 2.
• the wall (s) 30 and the peripheral wall 26 guide the shock waves and thus act to allow good deformation of the sheet 2 against the die 6.
• the drawing does not represent the last steps which relate to the withdrawal of the part which was formed from the sheet 2, with the mold opening and the tank lowering to its position illustrated in FIG. 1.
• the sheet after deformation can have vertical walls (up to the draft angle to be able to separate at the end of the process the sheet formed from the die 6), in other words, the part obtained by deformation of the sheet may have faces which extend substantially perpendicular to the orientation of the sheet before deformation.
• the sheet is initially in a horizontal plane. After deformation, it can then have almost vertical faces (before the part is withdrawn from the system).
• the forming process and the hybrid forming device proposed here make it possible to obtain by electro-hydroforming parts with almost vertical walls with a reduced cycle time.
• the cost price of such parts can thus be limited.
• the walls in the tank could for example form a honeycomb-type alveolar structure. It is provided in the illustrated embodiment that the peripheral wall of the tank is part of the punch intended to deform the sheet by stamping. This of course depends on the shape that one wishes to give to the sheet.
• the peripheral wall of the tank is not necessarily part of the punch. Provision could for example be made in FIG. 3 for the blank holder to be flush with the upper edge of the peripheral wall of the tank.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Shaping Metal By Deep-Drawing, Or The Like (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=67742521

Family Applications (1)

Country Status (6)

Family Cites Families (17)

• 2019
  • 2019-02-13 FR FR1901446A patent/FR3092504B1/fr active Active
• 2020
  • 2020-02-11 EP EP20709285.9A patent/EP3924117A1/de active Pending
  • 2020-02-11 WO PCT/FR2020/050247 patent/WO2020165538A1/fr unknown
  • 2020-02-11 JP JP2021547810A patent/JP7418456B2/ja active Active
  • 2020-02-11 US US17/430,663 patent/US11897017B2/en active Active
  • 2020-02-11 CN CN202080012999.5A patent/CN113412169B/zh active Active

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