[go: up one dir, main page]

EP3541545B1 - Method for electrohydraulic forming and associated device - Google Patents

Method for electrohydraulic forming and associated device Download PDF

Info

Publication number
EP3541545B1
EP3541545B1 EP17798192.5A EP17798192A EP3541545B1 EP 3541545 B1 EP3541545 B1 EP 3541545B1 EP 17798192 A EP17798192 A EP 17798192A EP 3541545 B1 EP3541545 B1 EP 3541545B1
Authority
EP
European Patent Office
Prior art keywords
blank
cavity
liquid
electrodes
mold
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
EP17798192.5A
Other languages
German (de)
French (fr)
Other versions
EP3541545A1 (en
Inventor
Gilles Avrillaud
Romain MERCIER
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ADM28 SARL
Original Assignee
ADM28 SARL
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by ADM28 SARL filed Critical ADM28 SARL
Publication of EP3541545A1 publication Critical patent/EP3541545A1/en
Application granted granted Critical
Publication of EP3541545B1 publication Critical patent/EP3541545B1/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

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
    • B21D26/12—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
    • 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
    • B21D26/021—Deforming sheet bodies
    • 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
    • B21D26/021—Deforming sheet bodies
    • B21D26/023—Deforming sheet bodies including an additional treatment performed by fluid pressure, e.g. perforating

Definitions

  • the present invention relates to an electrohydraulic forming method and device.
  • Electrohydraulic forming is used to deform a blank of material against a mold by applying dynamic pressure. To this end, an electrical 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 blank of material against the mold. Electrohydraulic forming is particularly advantageous compared to other forming processes since it allows for reduced elastic return and for obtaining engraving-type details and/or sharp corners and/or improved elongations before rupture on the parts to be formed.
  • Preforming the part by applying quasi-static pressure helps to promote the swallowing of the material blank into the mold, thus reducing the deformation of the material at to be carried out by electrohydraulic forming and therefore to reduce the forming time in the case where it is necessary to recharge the high-voltage pulsed 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.
  • different modules are used, charged simultaneously but triggered one after the other. In this case, the investment in terms of electric generator is reduced since fewer modules can be used.
  • Such a method has some disadvantages.
  • the time to fill the cavity with pressurized water can be relatively long, especially when using a pump with a limited flow rate.
  • the cavity must be re-filled with liquid and pressurized by a pump, which increases the time required to form the part.
  • the present invention aims in particular to overcome the aforementioned drawbacks of the prior art.
  • the liquid in the cavity is pressurized for hydraulic preforming by moving a wall of the cavity formed by the mold, the material blank and the blank holder towards the inside of the cavity.
  • the liquid in the cavity can be pressurized more quickly than using a pressurized pump with a limited flow rate. This saves cycle time.
  • the equipment to be used is less complex because it does not require generating pressurized water.
  • the blank of material is held against the mold by the blank holder and the entire blank of material moves together with the mold towards the inside of the cavity and thus approaches the electrodes.
  • the mold is then mounted on the platen of a press in order to provide the pressure necessary for hydraulic preforming.
  • a vacuum is created between the material blank and the mold after the material blank is brought into contact with the cavity liquid in order to improve the efficiency of hydraulic and electrohydraulic forming.
  • the mold and this wall can be mounted on a double-acting press.
  • the first effect can be used by the movable wall supporting at least two electrodes to pressurize the liquid present in the cavity.
  • the second effect can be used by the mold to adjust the pressure exerted on the blank of material.
  • the assembly formed by the mold and the blank of material is moved while the electrodes are fixed.
  • the cavity comprises a movable wall formed by the mold, the material blank and the blank holder, and the movement of the movable wall is capable of putting the liquid of the cavity under a pressure sufficient to generate a deformation of the material blank against the mold.
  • the use of a pressurized pump to pressurize the liquid is eliminated.
  • a pump is expensive and increases the complexity of the device.
  • the pressurization of the tank is slower.
  • the pressurization of the liquid is carried out following the movement of a movable wall, it is not necessary to refill the cavity with liquid between each forming cycle of a new part.
  • the electrohydraulic forming device comprises a vacuum pump.
  • the vacuum pump creates a vacuum between the mold and the material blank, allowing for more efficient hydraulic and electrohydraulic forming.
  • the vacuum pump can also be used to create a vacuum inside the cavity when filling the tank. This prevents air from entering between the material blank and the cavity liquid, which also allows for more efficient hydraulic and electrohydraulic forming.
  • the cavity is formed at least in part by the frame.
  • the device When the cavity is formed partly in the frame, the device is less complex and less bulky.
  • the at least two electrodes are carried by a base resting on a bottom wall of the frame.
  • the hold-down clamp is separate from the frame, the hold-down clamp extends longitudinally in the frame towards the electrodes and preferably at least partially surrounds the electrodes.
  • the hold-down plate serves as a reflector and prevents shock waves from propagating towards the walls of the cavity or the frame and avoiding their damage, particularly at the welds if it is made in a mechanically welded structure.
  • an assembly formed by the mold and the blank of material is mounted on a movable platen of a press.
  • the assembly formed by the blank of material and the mold can therefore move inside the cavity and towards the inside of the cavity to pressurize the liquid present in the cavity.
  • the blank of material is moved towards the inside of the cavity, in the direction of the electrodes, by moving the mold when the blank of material is held against the mold by the blank holder.
  • the assembly formed by the mold, the blank of material and the blank holder is mounted on a movable plate of a press.
  • the blank holder is then screwed directly onto the material blank and cooperates with the material blank.
  • the assembly formed by the mold and the blank of material is mounted on a movable plate of a press, and the The blank holder is mounted on at least one jack, a first end of each jack being fixed to the bottom wall of the frame, a second end of each jack being fixed to the blank holder.
  • the material blank is then placed on the blank holder and the mold presses on the material blank.
  • the pressure exerted by the blank holder can therefore be regulated autonomously, independently of the pressure exerted by the mold on the blank holder. This is particularly advantageous when the wall supporting the electrodes is fixed and the cavity is pressurized by moving the assembly formed by the mold and the blank holder towards the inside of the cavity.
  • the at least one cylinder is a gas spring.
  • the pressure exerted on the material blank is then constant regardless of the position of the mold in the frame, as long as the mold is in contact with the material blank.
  • FIG. 1 represents an electrohydraulic forming device 100 according to a first embodiment.
  • This electrohydraulic forming device 100 comprises a frame 110 and a movable platen 120 of a press on which a mold 130 is mounted.
  • the platen 120, and therefore the mold 130, are movable relative to the frame 110.
  • a blank of material 150 to be deformed is placed between the mold 130 and a blank holder 140.
  • the blank holder makes it possible to hold the blank of material against the mold 130.
  • the blank holder is opposite the mold, and more particularly a wall of the mold, and cooperates with the mold to hold the blank of material against it.
  • the blank holder 140 is fixed to the mold 130. The blank holder 140 is therefore separate from the frame.
  • the frame 110 comprises a bottom wall 112 and a side wall 114.
  • the bottom wall 112, the side wall 114 and the material blank 150 define a cavity intended to be filled with a liquid, for example water.
  • the cavity is made watertight by sealing means, for example by an O-ring 195 present on a side wall of the mold 130. The sealing of the cavity is therefore ensured between the mold 130 and the side wall of the frame 114.
  • Electrodes 160 On the bottom wall 112 are mounted at least two electrodes 160 connected to current supply conductors, which may be, for example, cables or insulated metal plates (not shown in the drawings). These current supply conductors may be connected to an electric generator for generating high voltage pulses sufficient to cause an electric discharge between two electrodes 160.
  • the current supply conductors may pass in a sealed manner through the walls of the frame or pass over the edges of the walls of the frame.
  • the electric generator for generating high voltage pulses can comprise several modules charged simultaneously and discharged successively by the two electrodes if the electrohydraulic forming is carried out using several successive discharges.
  • one of the electrodes is formed by the bottom wall 112 of the frame.
  • a pumping circuit associated with a pump 180 makes it possible to fill the cavity with liquid.
  • the liquid inside the cavity is pressurized by moving a movable wall of the cavity, here the material blank and more particularly the assembly formed by the mold 130, the material blank 150 and the blank holder 140.
  • a pressure gauge 182 is used to measure the pressure inside the cavity and can be associated with a regulation system to manage the pressure in the cavity. This regulation system can, among other things, control the stopping of the movable wall of the cavity, when the pressure measured in the cavity is sufficient to allow hydraulic forming of the material blank 150 against the mold 130.
  • a vacuum pump 170 makes it possible to create a vacuum in the cavity and in the space between the mold 130 and the material blank 150 to be deformed.
  • the vacuum created in the cavity makes it possible to avoid the presence of air at the interface between the material blank 150 and the liquid and at the interface between the material blank 150 and the imprint of the mold 130.
  • the efficiency of hydraulic and electrohydraulic forming is therefore improved.
  • the electrohydraulic forming device 100 comprises a valve associated with a pressure switch 184.
  • the valve associated with the pressure switch makes it possible to reduce the pressure of the liquid in the cavity before the electrohydraulic forming. This step makes it possible to reduce the voltage necessary to generate an electrical discharge between the electrodes, which would be higher by keeping the liquid under pressure.
  • the blank of material 150 to be deformed is placed between the mold 130 and the blank holder 140 and the blank holder 140 is clamped against the blank of material 150, for example using screws.
  • the liquid already present in the cavity in which the electrodes 160 are located is filled or leveled using the pump 180 while also creating a vacuum in the cavity using the vacuum pump 170.
  • the vacuum created promotes the filling or leveling of the cavity and also makes it possible to reduce the amount of air present in the cavity and thereby improve the efficiency electrohydraulic forming.
  • the cavity is filled until the material blank 150 is in contact with the liquid in the cavity.
  • a vacuum is then created between the material blank 150 and the mold 130 using the pump 170.
  • a wall of the cavity here the assembly formed by the mold 130, the material blank 150 and the blank holder 140, is moved towards the inside of the cavity so as to reduce the volume of the cavity.
  • the use of a press makes it possible to increase the liquid pressure in the cavity up to a predetermined value sufficient to allow hydraulic preforming of the material blank 150, the liquid pressure in the cavity being in this case limited by the force of the press.
  • the approach of the mold 130 is stopped by the regulation system when the predefined liquid pressure is measured by the pressure gauge 182.
  • a third step illustrated with reference to the figure 3 , at least one electrical discharge is caused between the two electrodes 160 so as to create an electric arc between the electrodes. Since the two electrodes 160 are immersed in a liquid, for example water, the electric arc causes a strong temperature gradient until the water vaporizes between the electrodes 160. This vaporization generates a pressure wave, also called a “shock wave” hereinafter, propagating in the liquid until it reaches the blank of material 150 to be deformed. Under the effect of the shock wave, the blank of material deforms against the mold as illustrated in the figure 3 . If necessary, further electrical discharges are caused between the two electrodes 160 until the blank of material has the desired shape as illustrated in the figure 4 .
  • a pressure wave also called a “shock wave” hereinafter
  • the pressure of the liquid in the cavity is reduced before electrohydraulic forming. This reduces the voltage required to generate an electrical discharge between the electrodes, which would be higher by keeping the liquid under pressure. This step makes it possible to use a less expensive and less bulky electric generator than that used in the step described above.
  • FIG. 5 illustrates a second embodiment of an electrohydraulic forming device 200 which comprises, as in the first embodiment, a frame 210, a movable platen 220 of a press on which is mounted a mold 230 and a blank holder 240 intended to hold the blank of material 250 to be deformed against the mold 230 by cooperating with the mold.
  • the frame 210 comprises a bottom wall 212 and a side wall 214.
  • the electrodes 260 are mounted on a base 290 comprising for example three feet 292 supporting a base 294.
  • the electrodes 260 are connected in a sealed manner through the base 294 to an electric generator making it possible to generate brief high voltage pulses of high electrical power sufficient to cause an electric discharge between two electrodes 260.
  • the blank holder 240 extends longitudinally in the frame in the direction of the electrodes parallel to the side wall 214 of the frame 210 and surrounds the electrodes 260.
  • the blank holder 240 makes it possible to reflect part of the shock wave generated following the electrical discharge triggered between the electrodes, which makes it possible to limit the stress on the frame. Indeed, if the frame is stressed by the shock waves very regularly, it can become fragile, for example at the welds between its different parts if it is made of a mechanically welded structure. Thus, a frame with thinner walls can be used.
  • the blank holder 240 can be mounted on one or more jacks 242 opposite the mold, and more particularly a wall of the mold, as illustrated in the figure 4 , one end of each of these jacks 242 being fixed to the bottom wall 212 of the frame and the other end is fixed to the blank holder 240.
  • the blank holder is therefore separate from the mold.
  • the pressure exerted on the material blank 250 by the blank holder 240 is controlled by the jack(s) 242, the blank holder 240 pressing on the mold.
  • the jack(s) 242 are gas springs.
  • the pressure exerted on the material blank is then constant regardless of the position of the mold in the frame, as long as the mold is in contact with the material blank.
  • the base 290, and more particularly its base 294, the blank holder 240 and the material blank 250 define a cavity intended to be filled with a liquid, for example water.
  • a pumping circuit associated with a pump 280 makes it possible to fill the cavity with liquid.
  • Such a cavity has the advantage of being able to be filled in an optimized manner with a smaller volume of liquid compared to the device described in the first embodiment.
  • the cavity is made watertight by adding sealing means, for example at least one O-ring 295, for example between the side wall of the base 294 of the base 290 and the inner wall of the blank holder 240.
  • the sealing between the blank holder 240 and the blank of material to be deformed 250 is achieved using an O-ring 296 included in the upper part of the blank holder 240 and using an O-ring 297 included in the lower part of the mold, for example.
  • the O-ring 296 makes it possible to ensure the sealing between the blank of material 250 and the blank holder 240 and the O-ring 297 makes it possible to ensure the sealing between the blank of material 250 and the mold 230.
  • the vacuum pump 270 is used to create a vacuum in the space between the mold 230 and the material blank 250 and possibly also to create a vacuum in the sealed cavity when filling or leveling it.
  • the pressurization of the liquid in the cavity is carried out with the device described above by bringing the mold 230 closer to the electrodes 260.
  • the pressure gauge 282 is used to measure the pressure inside the cavity and the regulation system is used to control the stopping of the movable wall of the cavity, when the pressure measured in the cavity is sufficient to allow hydraulic forming of the material blank 250 by application of sufficient quasi-static pressure.
  • the various stages of the electrohydraulic forming process are similar to those described with reference to Figures 1 to 4 .
  • the blank of material is no longer held against the mold using a blank holder screwed onto the mold.
  • the blank of material 250 to be deformed is placed on the blank holder 240 and then the mold 230 is lowered to come to rest on the blank of material 250 and the blank holder 240.
  • the pressure exerted on the blank of material 250 by the blank holder 240 can be controlled by the cylinder(s) 242, for example gas springs.
  • a wall of the cavity comprising the blank of material is moved, the assembly formed by the blank of material and the mold being mounted on the movable plate of a press.
  • the blank of material is moved towards the inside of the cavity, towards the electrodes, by moving the mold while the blank of material is held against the mold by the blank holder.
  • the blank of material is held against the mold by a blank holder mounted on the mold.
  • the blank holder is mounted on a jack and cooperates with the mold to hold the material blank.
  • the assembly formed by the mold, the material blank and the blank holder is mobile.
  • a wall of the cavity supporting the at least two electrodes could be moved using a press.
  • FIG. 6 illustrates an unclaimed embodiment in which the portion of the cavity wall supporting at least two electrodes is movably mounted.
  • the electrohydraulic forming device 300 comprises a frame 310, a mold 230 mounted on a first movable platen 320 of a press and a blank holder 340 intended to hold the blank of material 350 to be deformed against the mold 230.
  • the frame 310 comprises a bottom wall 312 and a side wall 314.
  • the bottom wall 312 comprises a movable wall 316 supporting at least two electrodes 360 and a fixed wall 318.
  • the movable wall 316 is mounted on a second platen 322 of the press.
  • the blank holder 340 rests on the part of the bottom wall 312 which is not movable, that is to say on the fixed wall 318.
  • the blank holder 340 is fixed and is located opposite the mold in the cavity formed by the blank holder 340, the movable wall 316 of the frame 310 supporting the electrodes 360 and the blank of material 350 to be deformed.
  • the cavity is sealed by adding sealing means, for example an O-ring 395 included in the side wall of the movable wall 316, an O-ring 396 included in the portion of the blank holder 340 in contact with the material blank 350 and a seal 397 included in the portion of the mold 330 in contact with the material blank 350.
  • the O-ring 395 makes it possible to achieve sealing between the movable wall 316 supporting the electrodes 360 and the blank holder 240 and possibly the fixed wall 318 of the bottom wall 312 of the frame 310.
  • the O-ring 396 makes it possible to achieve sealing between the material blank 350 and the mold 330 and the O-ring 397 make it possible to achieve sealing between the material blank 350 and the blank holder 340.
  • the movement of the movable wall 316 makes it possible to pressurize the liquid in the cavity formed by the blank holder 340, the movable wall 316 of the frame 310 supporting the electrodes 360 and the material blank 350 to be deformed.
  • the pressure exerted on the material blank 350 is adjusted using the pressure exerted by the platen 320 of the press when the mold 330 is in contact with the material blank 350.
  • the electrohydraulic forming device comprises a pumping circuit associated with a pump 380, a pressure gauge 382 and a vacuum pump 370 as described above. It may also comprise a valve associated with a pressure switch 384.
  • the press plate capable of providing a pressure greater than that of the other plate is preferably mounted on the movable wall 316 supporting the electrodes 360. Indeed, the force to be provided to pressurize the liquid in the cavity is often greater than that which one wishes to exert on the blank of material.
  • the platen capable of providing the highest force is the upper platen.
  • the movable wall 316 supporting the electrodes 316 is then above and the mold 330 below the blank of material to be deformed 350 as illustrated in the figure 6 .
  • the blank of material 350 to be deformed is placed on the mold 330 and the mold 330 is brought closer to the frame 310 until the blank of material is held between the blank holder 340 and the mold 330 with the desired pressure.
  • the blank holder thus cooperates with the mold to hold the blank of material.
  • the cavity formed in part by the frame is filled using the pump 380 while also advantageously creating a depression in the cavity using the vacuum pump 370.
  • the wall mobile 316 supporting the electrodes 316 is above the material blank 350 to be deformed, the liquid of the cavity is in contact with the material blank 350 as soon as the pump 380 is actuated to fill the cavity.
  • the cavity is in this case filled until the wall 316 supporting the electrodes 360 is in contact with the liquid of the cavity.
  • a vacuum is then created between the material blank 350 and the mold 330 using the vacuum pump 370.
  • the movable wall 316 of the cavity supporting the electrodes is moved toward the inside of the cavity so as to reduce the volume of the cavity.
  • the force exerted on the movable wall 316 makes it possible to increase the liquid pressure in the cavity to a predetermined value sufficient to allow hydraulic preforming of the material blank 350.
  • the approach of the movable wall 316 is stopped by means of the regulation system when the predefined liquid pressure is measured by the pressure gauge 382.
  • a third step at least one electrical discharge is caused between the two electrodes 360 so as to create an electrical arc between the electrodes and a “shock wave” propagating in the liquid until it reaches the material blank 350 to be deformed. Under the effect of the shock wave, the material blank deforms against the mold. If necessary, other electrical discharges are caused between the two electrodes 360 until the material blank has the desired shape.
  • a wall of the cavity comprising the blank of material or a wall supporting the electrodes is moved. It would also be possible to move all or part of a wall other than those supporting the electrodes or formed by the blank of material.
  • the wall is not mounted on a press but constitutes the movable wall of a piston, the cavity then forming one of the compartments of the piston.
  • an electrohydroforming device and the forming methods described above enable the cavity liquid to be pressurized more quickly than using a pressurized pump with a limited flow rate. This also avoids having to refill the tank with pressurized liquid between each forming cycle of a part. This saves cycle time.
  • the equipment to be used is less complex because it is not necessary to generate pressurized water.

Landscapes

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

Description

Arrière-plan de l'inventionBackground of the invention

La présente invention concerne un procédé et un dispositif de formage électrohydraulique.The present invention relates to an electrohydraulic forming method and device.

Il est déjà connu par le document DE 100 19 594 A1 de former des tôles par déformation hydromécanique en utilisant un générateur d'ondes de choc.It is already known from the document FROM 100 19 594 A1 to form sheets by hydromechanical deformation using a shock wave generator.

Objet et résumé de l'inventionSubject and summary of the invention

Le formage électrohydraulique permet de déformer un flan de matière contre un moule par application d'une pression dynamique. A cet effet, on génère une décharge électrique entre au moins deux électrodes dans une cavité remplie de liquide, par exemple de l'eau. Un arc électrique est alors formé entre les deux électrodes provoquant un gradient de température élevé et la vaporisation du liquide. Une onde de pression, aussi communément appelée « onde de choc », se déplace à grande vitesse et vient plaquer le flan de matière contre le moule. Le formage électrohydraulique est particulièrement avantageux en comparaison avec les autres procédés de formage puisqu'il permet d'avoir un retour élastique réduit et d'obtenir des détails de type gravure et/ou des angles vifs et/ou des allongements avant rupture améliorés sur les pièces à former.Electrohydraulic forming is used to deform a blank of material against a mold by applying dynamic pressure. To this end, an electrical 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 blank of material against the mold. Electrohydraulic forming is particularly advantageous compared to other forming processes since it allows for reduced elastic return and for obtaining engraving-type details and/or sharp corners and/or improved elongations before rupture on the parts to be formed.

Dans certains cas, notamment lorsque les pièces à former sont particulièrement profondes, on réalise plusieurs décharges électriques successives.In some cases, particularly when the parts to be formed are particularly deep, several successive electrical discharges are carried out.

Afin de réduire le nombre de décharges électriques successives nécessaires et ainsi limiter le temps de formage d'une pièce, il a été proposé de réaliser une étape de préformage hydraulique avant le formage électrohydraulique de la pièce. Pour se faire, on remplit la cavité avec du liquide sous pression tel que décrit par exemple dans le document US7802457 B2 . Lorsque la pression de liquide est suffisante, le flan de matière se déforme partiellement contre le moule. On génère ensuite des décharges électriques pour provoquer des ondes de choc et compléter le formage de la pièce jusqu'à atteindre la forme voulue. Le préformage de la pièce par application d'une pression quasi-statique permet de favoriser l'avalement du flan de matière dans le moule, donc de réduire la déformation de la matière à réaliser par formage électrohydraulique et donc de réduire le temps de formage dans le cas où il faudrait recharger le générateur électrique impulsionnel à haute tension entre deux décharges ou de réduire la taille du générateur dans le cas où l'on souhaiterait réaliser les décharges successives sans avoir à attendre entre les décharges que le générateur se recharge. Dans ce cas, on utilise différents modules chargés simultanément mais déclenchés les uns après les autres. Dans ce cas, l'investissement en termes de générateur électrique est réduit puisque l'on peut utiliser moins de modules.In order to reduce the number of successive electrical discharges required and thus limit the forming time of a part, it has been proposed to carry out a hydraulic preforming step before the electrohydraulic forming of the part. To do this, the cavity is filled with pressurized liquid as described for example in the document US7802457 B2 . When the liquid pressure is sufficient, the material blank partially deforms against the mold. Electrical discharges are then generated to cause shock waves and complete the forming of the part until the desired shape is reached. Preforming the part by applying quasi-static pressure helps to promote the swallowing of the material blank into the mold, thus reducing the deformation of the material at to be carried out by electrohydraulic forming and therefore to reduce the forming time in the case where it is necessary to recharge the high-voltage pulsed 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. In this case, different modules are used, charged simultaneously but triggered one after the other. In this case, the investment in terms of electric generator is reduced since fewer modules can be used.

Un tel procédé présente certains inconvénients. Le temps de remplissage de la cavité avec de l'eau sous pression peut être relativement long, notamment lorsque l'on utilise une pompe présentant un débit limité. De plus, entre chaque cycle de formage d'une nouvelle pièce, la cavité doit être re-remplie de liquide et être mise sous pression par une pompe ce qui augmente le temps nécessaire au formage de la pièce.Such a method has some disadvantages. The time to fill the cavity with pressurized water can be relatively long, especially when using a pump with a limited flow rate. In addition, between each forming cycle of a new part, the cavity must be re-filled with liquid and pressurized by a pump, which increases the time required to form the part.

La présente invention vise notamment à pallier aux inconvénients de l'art antérieur précités.The present invention aims in particular to overcome the aforementioned drawbacks of the prior art.

À cet effet, la présente invention propose, selon un premier aspect, un procédé de formage électrohydraulique d'un flan de matière dans lequel

  • on place un flan de matière à déformer entre un moule et un serre-flan,
  • on remplit de liquide une cavité étanche dans laquelle se trouvent des électrodes jusqu'à un niveau de liquide prédéterminé,
  • on met en contact le flan de matière avec le liquide de la cavité,
  • on réalise un préformage hydraulique du flan de matière, le flan de matière étant poussé vers le moule par le liquide de la cavité sous pression, subissant ainsi une première déformation,
  • on réalise un formage électrohydraulique du flan de matière, le flan de matière étant plaqué contre le moule par au moins une onde de pression générée par une décharge électrique entre au moins deux électrodes, subissant ainsi une deuxième déformation.
For this purpose, the present invention proposes, according to a first aspect, a method for electrohydraulic forming of a blank of material in which
  • a blank of material to be deformed is placed between a mold and a blank holder,
  • a sealed cavity containing electrodes is filled with liquid up to a predetermined liquid level,
  • the blank of material is brought into contact with the liquid in the cavity,
  • a hydraulic preforming of the material blank is carried out, the material blank being pushed towards the mold by the liquid in the cavity under pressure, thus undergoing a first deformation,
  • electrohydraulic forming of the material blank is carried out, the material blank being pressed against the mold by at least one pressure wave generated by an electric discharge between at least two electrodes, thus undergoing a second deformation.

Selon le procédé de l'invention, le liquide de la cavité est mis sous pression pour le préformage hydraulique en déplaçant une paroi de la cavité formée par le moule, le flan de matière et le serre-flan vers l'intérieur de la cavité.According to the method of the invention, the liquid in the cavity is pressurized for hydraulic preforming by moving a wall of the cavity formed by the mold, the material blank and the blank holder towards the inside of the cavity.

De cette manière, on peut mettre le liquide de la cavité sous pression plus rapidement qu'en utilisant une pompe pressurisée dont le débit est limité. On gagne ainsi en temps de cycle. Par ailleurs, les équipements à utiliser sont moins complexes car il ne faut pas générer d'eau sous pression.In this way, the liquid in the cavity can be pressurized more quickly than using a pressurized pump with a limited flow rate. This saves cycle time. In addition, the equipment to be used is less complex because it does not require generating pressurized water.

Le flan de matière est maintenu contre le moule par le serre-flan et l'intégralité du flan de matière se déplace en même temps que le moule vers l'intérieur de la cavité et se rapproche donc des électrodes. Le moule est alors monté sur le plateau d'une presse afin de fournir la pression nécessaire au préformage hydraulique.The blank of material is held against the mold by the blank holder and the entire blank of material moves together with the mold towards the inside of the cavity and thus approaches the electrodes. The mold is then mounted on the platen of a press in order to provide the pressure necessary for hydraulic preforming.

De manière avantageuse, on crée un vide entre le flan de matière et le moule après la mise en contact du flan de matière avec le liquide de la cavité afin d'améliorer l'efficacité de formage hydraulique et électrohydraulique.Advantageously, a vacuum is created between the material blank and the mold after the material blank is brought into contact with the cavity liquid in order to improve the efficiency of hydraulic and electrohydraulic forming.

Par ailleurs, en créant un vide dans la cavité lors du remplissage de liquide de la cavité, on favorise le remplissage de la cuve et on évite la présence d'air à l'interface entre le liquide et le moule, ce qui favorise également l'efficacité de formage hydraulique et électrohydraulique. On notera que d'autres moyens peuvent être utilisés pour éviter la présence d'air entre le liquide de la cavité et le flan de matière à déformer.Furthermore, by creating a vacuum in the cavity when filling the cavity with liquid, the filling of the tank is promoted and the presence of air at the interface between the liquid and the mold is avoided, which also promotes the efficiency of hydraulic and electrohydraulic forming. It should be noted that other means can be used to avoid the presence of air between the liquid of the cavity and the blank of material to be deformed.

Lorsqu'une paroi de la cavité supportant au moins l'une des électrodes est également mobile, le moule et cette paroi peuvent être montés sur une presse à double effet. Dans ce cas, le premier effet peut être utilisé par la paroi mobile supportant au moins deux électrodes pour mettre sous pression le liquide présent dans la cavité. Le deuxième effet peut être utilisé par le moule pour régler la pression exercée sur le flan de matière.When a wall of the cavity supporting at least one of the electrodes is also movable, the mold and this wall can be mounted on a double-acting press. In this case, the first effect can be used by the movable wall supporting at least two electrodes to pressurize the liquid present in the cavity. The second effect can be used by the mold to adjust the pressure exerted on the blank of material.

Dans un mode de réalisation, l'ensemble formé par le moule et le flan de matière est déplacé tandis que les électrodes sont fixes.In one embodiment, the assembly formed by the mold and the blank of material is moved while the electrodes are fixed.

Lorsque la paroi supportant les électrodes est fixe, on évite de déplacer les conducteurs d'amenée du courant reliant les électrodes au générateur de tension impulsionnel dans lesquels circulent des courants de l'ordre de quelques dizaines ou centaines de kA. Ces conducteurs d'amenée du courant sont donc lourds, volumineux, et ont tendance à s'endommager du fait des déplacements répétés.When the wall supporting the electrodes is fixed, it is avoided to move the current supply conductors connecting the electrodes to the pulse voltage generator in which currents of the order of a few tens or hundreds of kA flow. These current supply conductors are therefore heavy, bulky, and tend to be damaged due to repeated movements.

De manière optionnelle, il est également possible de rapprocher l'ensemble formé par le flan de matière et le moule des électrodes entre chaque décharge électrique. Cela permet d'augmenter l'efficacité du formage et de réduire le volume d'eau à utiliser.Optionally, it is also possible to bring the assembly formed by the blank of material and the mold of the electrodes closer together between each electrical discharge. This makes it possible to increase the efficiency of the forming and to reduce the volume of water to be used.

Par ailleurs, la présente invention propose, selon un second aspect, un dispositif de formage électrohydraulique d'un flan de matière comprenant :

  • un bâti,
  • une cavité étanche apte à être remplie par un liquide et dont l'une des parois comporte le flan de matière,
  • au moins deux électrodes placées dans la cavité,
  • un moule,
  • un serre-flan apte à maintenir le flan de matière contre le moule.
Furthermore, the present invention proposes, according to a second aspect, a device for electrohydraulic forming of a blank of material comprising:
  • a building,
  • a watertight cavity capable of being filled with a liquid and one of the walls of which includes the material blank,
  • at least two electrodes placed in the cavity,
  • a mold,
  • a blank holder capable of holding the blank of material against the mold.

En outre, la cavité comprend une paroi mobile formée par le moule, le flan de matière et le serre-flan, et le déplacement de la paroi mobile est apte à mettre le liquide de la cavité sous une pression suffisante pour générer une déformation du flan de matière contre le moule.Furthermore, the cavity comprises a movable wall formed by the mold, the material blank and the blank holder, and the movement of the movable wall is capable of putting the liquid of the cavity under a pressure sufficient to generate a deformation of the material blank against the mold.

Avec le dispositif de l'invention, on s'affranchit de l'utilisation d'une pompe pressurisée pour mettre sous pression le liquide. Une telle pompe est couteuse et augmente la complexité du dispositif. De plus, le débit d'une telle pompe étant limité, la mise en pression de la cuve est moins rapide. Par ailleurs, la mise sous pression du liquide étant faite suite au déplacement d'une paroi mobile, il n'est pas nécessaire de reremplir la cavité de liquide entre chaque cycle de formage d'une nouvelle pièce.With the device of the invention, the use of a pressurized pump to pressurize the liquid is eliminated. Such a pump is expensive and increases the complexity of the device. In addition, since the flow rate of such a pump is limited, the pressurization of the tank is slower. Furthermore, since the pressurization of the liquid is carried out following the movement of a movable wall, it is not necessary to refill the cavity with liquid between each forming cycle of a new part.

Préférentiellement, le dispositif de formage électrohydraulique comprend une pompe à vide.Preferably, the electrohydraulic forming device comprises a vacuum pump.

La pompe à vide permet de faire le vide entre le moule et le flan de matière et permet d'obtenir un formage hydraulique et électrohydraulique plus efficace. La pompe à vide peut également être utilisée pour faire le vide à l'intérieur de la cavité lors du remplissage de la cuve. On évite ainsi la présence d'air entre le flan de matière et le liquide de la cavité, ce qui permet également d'obtenir un formage hydraulique et électrohydraulique plus efficace.The vacuum pump creates a vacuum between the mold and the material blank, allowing for more efficient hydraulic and electrohydraulic forming. The vacuum pump can also be used to create a vacuum inside the cavity when filling the tank. This prevents air from entering between the material blank and the cavity liquid, which also allows for more efficient hydraulic and electrohydraulic forming.

Dans un mode de réalisation, la cavité est formée au moins en partie par le bâti.In one embodiment, the cavity is formed at least in part by the frame.

Lorsque la cavité est formée en partie dans le bâti, le dispositif est moins complexe et moins volumineux.When the cavity is formed partly in the frame, the device is less complex and less bulky.

Dans un mode de réalisation, les au moins deux électrodes sont portées par un socle reposant sur une paroi de fond du bâti.In one embodiment, the at least two electrodes are carried by a base resting on a bottom wall of the frame.

Cela permet de réduire la taille de la cavité et le volume de liquide nécessaire pour la remplir.This helps reduce the size of the cavity and the volume of liquid needed to fill it.

Dans un mode de réalisation, le serre-flan est distinct du bâti, le serre-flan s'étend longitudinalement dans le bâti en direction des électrodes et entoure préférentiellement au moins en partie les électrodes.In one embodiment, the hold-down clamp is separate from the frame, the hold-down clamp extends longitudinally in the frame towards the electrodes and preferably at least partially surrounds the electrodes.

Le serre-flan sert de réflecteur et empêche aux ondes de choc de se propager vers les parois de la cavité ou du bâti et d'éviter leur endommagement, notamment au niveau des soudures s'il est réalisé en structure mécano-soudée.The hold-down plate serves as a reflector and prevents shock waves from propagating towards the walls of the cavity or the frame and avoiding their damage, particularly at the welds if it is made in a mechanically welded structure.

Dans un mode de réalisation, un ensemble formé par le moule et le flan de matière est monté sur un plateau mobile d'une presse.In one embodiment, an assembly formed by the mold and the blank of material is mounted on a movable platen of a press.

L'ensemble formé par le flan de matière et le moule peut donc se déplacer à l'intérieur de la cavité et vers l'intérieur de la cavité pour mettre sous pression le liquide présent dans la cavité. Ainsi, on déplace le flan de matière vers l'intérieur de la cavité, en direction des électrodes, en déplaçant le moule lorsque le flan de matière est maintenu contre le moule par le serre-flan.The assembly formed by the blank of material and the mold can therefore move inside the cavity and towards the inside of the cavity to pressurize the liquid present in the cavity. Thus, the blank of material is moved towards the inside of the cavity, in the direction of the electrodes, by moving the mold when the blank of material is held against the mold by the blank holder.

Lorsque la paroi supportant les électrodes est fixe, on évite de déplacer les conducteurs d'amenée du courant reliant les électrodes au générateur de tension impulsionnel dans lesquels circulent des courants de l'ordre de quelques dizaines ou centaines de kA. Ces conducteurs d'amenée du courant sont donc lourds, volumineux, et ont tendance à s'endommager du fait des déplacements répétés.When the wall supporting the electrodes is fixed, it is avoided to move the current supply conductors connecting the electrodes to the pulse voltage generator in which currents of the order of a few tens or hundreds of kA flow. These current supply conductors are therefore heavy, bulky, and tend to be damaged due to repeated movements.

Dans un mode de réalisation particulier, l'ensemble formé par le moule, le flan de matière et le serre-flan est monté sur un plateau mobile d'une presse.In a particular embodiment, the assembly formed by the mold, the blank of material and the blank holder is mounted on a movable plate of a press.

Le serre-flan est alors directement vissé sur le flan de matière et coopère avec le flan de matière.The blank holder is then screwed directly onto the material blank and cooperates with the material blank.

Dans un autre mode de réalisation particulier, l'ensemble formé par le moule et le flan de matière est monté sur un plateau mobile d'une presse, et le serre-flan est monté sur au moins un vérin, une première extrémité de chaque vérin étant fixée sur la paroi de fond du bâti, une seconde extrémité de chaque vérin étant fixée au serre-flan.In another particular embodiment, the assembly formed by the mold and the blank of material is mounted on a movable plate of a press, and the The blank holder is mounted on at least one jack, a first end of each jack being fixed to the bottom wall of the frame, a second end of each jack being fixed to the blank holder.

Le flan de matière est alors posé sur le serre-flan et le moule vient appuyer sur le flan de matière. La pression exercée par le serre-flan peut donc être régulée de façon autonome, indépendamment de la pression exercée par le moule sur le serre-flan. Cela est particulièrement avantageux lorsque la paroi supportant les électrodes est fixe et que la cavité est mise sous pression par déplacement de l'ensemble formé par le moule et le serre-flan vers l'intérieur de la cavité.The material blank is then placed on the blank holder and the mold presses on the material blank. The pressure exerted by the blank holder can therefore be regulated autonomously, independently of the pressure exerted by the mold on the blank holder. This is particularly advantageous when the wall supporting the electrodes is fixed and the cavity is pressurized by moving the assembly formed by the mold and the blank holder towards the inside of the cavity.

Dans un mode de réalisation particulier, le au moins un vérin est un ressort à gaz.In a particular embodiment, the at least one cylinder is a gas spring.

La pression exercée sur le flan de matière est alors constante quelle que soit la position du moule dans le bâti, dès lors que le moule est en contact du flan de matière.The pressure exerted on the material blank is then constant regardless of the position of the mold in the frame, as long as the mold is in contact with the material blank.

Brève description des dessinsBrief description of the drawings

Des détails et avantages de la présente invention apparaitront mieux de la description qui suit, faite en référence aux dessins annexés sur lesquels :

  • les figures 1 à 4 illustrent différentes étapes d'un procédé de formage électrohydraulique selon l'invention, le procédé étant mis en oeuvre avec un dispositif de formage électrohydraulique selon un premier mode de réalisation,
  • la figure 5 illustre un dispositif de formage électrohydraulique selon un second mode de réalisation et un procédé de formage électrohydraulique associé, et
  • La figure 6 illustre un dispositif de formage électrohydraulique non revendiqué et un procédé de formage électrohydraulique associé.
Details and advantages of the present invention will appear more clearly from the following description, given with reference to the accompanying drawings in which:
  • THE Figures 1 to 4 illustrate different steps of an electrohydraulic forming method according to the invention, the method being implemented with an electrohydraulic forming device according to a first embodiment,
  • there figure 5 illustrates an electrohydraulic forming device according to a second embodiment and an associated electrohydraulic forming method, and
  • There figure 6 illustrates an unclaimed electrohydraulic forming device and an associated electrohydraulic forming method.

Description détaillée de plusieurs modes de réalisation de l'inventionDetailed description of several embodiments of the invention

La figure 1 représente un dispositif de formage électrohydraulique 100 selon un premier mode de réalisation. Ce dispositif de formage électrohydraulique 100 comprend un bâti 110 et un plateau mobile 120 d'une presse sur lequel est monté un moule 130. Le plateau 120, et donc le moule 130, sont mobiles par rapport au bâti 110.There figure 1 represents an electrohydraulic forming device 100 according to a first embodiment. This electrohydraulic forming device 100 comprises a frame 110 and a movable platen 120 of a press on which a mold 130 is mounted. The platen 120, and therefore the mold 130, are movable relative to the frame 110.

Un flan de matière 150 à déformer est placé entre le moule 130 et un serre-flan 140. Le serre-flan permet de maintenir le flan de matière contre le moule 130. En particulier, le serre-flan est en vis-à-vis du moule, et plus particulièrement d'une paroi du moule, et coopère avec le moule pour maintenir le flan de matière contre celui-ci. Dans le mode de réalisation décrit ici, le serre-flan 140 est fixé sur le moule 130. Le serre-flan 140 est donc distinct du bâti.A blank of material 150 to be deformed is placed between the mold 130 and a blank holder 140. The blank holder makes it possible to hold the blank of material against the mold 130. In particular, the blank holder is opposite the mold, and more particularly a wall of the mold, and cooperates with the mold to hold the blank of material against it. In the embodiment described here, the blank holder 140 is fixed to the mold 130. The blank holder 140 is therefore separate from the frame.

Le bâti 110 comporte une paroi de fond 112 et une paroi latérale 114. La paroi de fond 112, la paroi latérale 114 et le flan de matière 150 définissent une cavité destinée à être remplie par un liquide, par exemple de l'eau. La cavité est rendue étanche par des moyens d'étanchéité, par exemple par un joint torique 195 présent sur une paroi latérale du moule 130. L'étanchéité de la cavité est donc assurée entre le moule 130 et la paroi latérale du bâti 114.The frame 110 comprises a bottom wall 112 and a side wall 114. The bottom wall 112, the side wall 114 and the material blank 150 define a cavity intended to be filled with a liquid, for example water. The cavity is made watertight by sealing means, for example by an O-ring 195 present on a side wall of the mold 130. The sealing of the cavity is therefore ensured between the mold 130 and the side wall of the frame 114.

Sur la paroi de fond 112 sont montées au moins deux électrodes 160 reliées à des conducteurs d'amenée du courant, pouvant être, par exemple, des câbles ou des plaques métalliques isolées (non représentés sur les dessins). Ces conducteurs d'amenée du courant peuvent être connectés à un générateur électrique permettant de générer des impulsions de haute tension suffisantes pour provoquer une décharge électrique entre deux électrodes 160. Les conducteurs d'amenée du courant peuvent passer de manière étanche à travers les parois du bâti ou passer par-dessus les bords des parois du bâti.On the bottom wall 112 are mounted at least two electrodes 160 connected to current supply conductors, which may be, for example, cables or insulated metal plates (not shown in the drawings). These current supply conductors may be connected to an electric generator for generating high voltage pulses sufficient to cause an electric discharge between two electrodes 160. The current supply conductors may pass in a sealed manner through the walls of the frame or pass over the edges of the walls of the frame.

Le générateur électrique permettant de générer des impulsions de haute tension peut comprendre plusieurs modules chargés simultanément et déchargés successivement par les deux électrodes si l'on réalise le formage électrohydraulique à l'aide de plusieurs décharges successives.The electric generator for generating high voltage pulses can comprise several modules charged simultaneously and discharged successively by the two electrodes if the electrohydraulic forming is carried out using several successive discharges.

Dans une variante de réalisation, l'une des électrodes est formée par la paroi de fond 112 du bâti.In an alternative embodiment, one of the electrodes is formed by the bottom wall 112 of the frame.

Un circuit de pompage associé à une pompe 180 permet de remplir la cavité de liquide. Selon l'invention, le liquide à l'intérieur de la cavité est mis sous pression en déplaçant une paroi mobile de la cavité, ici le flan de matière et plus particulièrement l'ensemble formé par le moule 130, le flan de matière 150 et le serre-flan 140. Un manomètre 182 est utilisé pour mesurer la pression à l'intérieur de la cavité et peut être associé à un système de régulation pour gérer la pression dans la cavité. Ce système de régulation peut, entre autre, commander l'arrêt de la paroi mobile de la cavité, lorsque la pression mesurée dans la cavité est suffisante pour permettre un formage hydraulique du flan de matière 150 contre le moule 130.A pumping circuit associated with a pump 180 makes it possible to fill the cavity with liquid. According to the invention, the liquid inside the cavity is pressurized by moving a movable wall of the cavity, here the material blank and more particularly the assembly formed by the mold 130, the material blank 150 and the blank holder 140. A pressure gauge 182 is used to measure the pressure inside the cavity and can be associated with a regulation system to manage the pressure in the cavity. This regulation system can, among other things, control the stopping of the movable wall of the cavity, when the pressure measured in the cavity is sufficient to allow hydraulic forming of the material blank 150 against the mold 130.

Une pompe à vide 170 permet de faire le vide dans la cavité et dans l'espace entre le moule 130 et le flan de matière 150 à déformer. Le vide créé dans la cavité permet d'éviter la présence d'air à l'interface entre le flan de matière 150 et le liquide et à l'interface entre le flan de matière 150 et l'empreinte du moule 130. L'efficacité de formage hydraulique et électrohydraulique est donc améliorée.A vacuum pump 170 makes it possible to create a vacuum in the cavity and in the space between the mold 130 and the material blank 150 to be deformed. The vacuum created in the cavity makes it possible to avoid the presence of air at the interface between the material blank 150 and the liquid and at the interface between the material blank 150 and the imprint of the mold 130. The efficiency of hydraulic and electrohydraulic forming is therefore improved.

Dans une variante de réalisation, le dispositif de formage électrohydraulique 100 comporte une vanne associée à un pressostat 184. La vanne associée au pressostat permet de réduire la pression du liquide dans la cavité avant le formage électrohydraulique. Cette étape permet de réduire la tension nécessaire pour générer une décharge électrique entre les électrodes, qui serait plus élevée en gardant le liquide sous pression.In an alternative embodiment, the electrohydraulic forming device 100 comprises a valve associated with a pressure switch 184. The valve associated with the pressure switch makes it possible to reduce the pressure of the liquid in the cavity before the electrohydraulic forming. This step makes it possible to reduce the voltage necessary to generate an electrical discharge between the electrodes, which would be higher by keeping the liquid under pressure.

Différentes étapes d'un procédé de formage électrohydraulique comportant un préformage hydraulique avec le dispositif ci-dessus sont décrites en référence aux figures 1 à 4.Various steps of an electrohydraulic forming process involving hydraulic preforming with the above device are described with reference to Figures 1 to 4 .

Dans une première étape, on place le flan de matière 150 à déformer entre le moule 130 et le serre-flan 140 et on vient serrer le serre-flan 140 contre le flan de matière 150 par exemple à l'aide de vis. Ensuite, on remplit ou on met à niveau le liquide déjà présent dans la cavité dans laquelle se trouvent les électrodes 160 à l'aide de la pompe 180 tout en créant également une dépression dans la cavité à l'aide de la pompe à vide 170. La dépression créée favorise le remplissage ou la mise à niveau de la cavité et permet aussi de réduire la quantité d'air présente dans la cavité et par là d'améliorer l'efficacité du formage électrohydraulique. La cavité est remplie jusqu'à ce que le flan de matière 150 soit en contact avec le liquide de la cavité. On crée ensuite un vide entre le flan de matière 150 et le moule 130 à l'aide de la pompe 170.In a first step, the blank of material 150 to be deformed is placed between the mold 130 and the blank holder 140 and the blank holder 140 is clamped against the blank of material 150, for example using screws. Then, the liquid already present in the cavity in which the electrodes 160 are located is filled or leveled using the pump 180 while also creating a vacuum in the cavity using the vacuum pump 170. The vacuum created promotes the filling or leveling of the cavity and also makes it possible to reduce the amount of air present in the cavity and thereby improve the efficiency electrohydraulic forming. The cavity is filled until the material blank 150 is in contact with the liquid in the cavity. A vacuum is then created between the material blank 150 and the mold 130 using the pump 170.

Dans une seconde étape, illustrée par la figure 2, on déplace une paroi de la cavité, ici l'ensemble formé par le moule 130, le flan de matière 150 et le serre-flan 140, vers l'intérieur de celle-ci de manière à réduire le volume de la cavité. L'utilisation d'une presse permet d'augmenter la pression de liquide dans la cavité jusqu'à une valeur prédéterminée suffisante pour permettre un préformage hydraulique du flan de matière 150, la pression de liquide dans la cavité étant dans ce cas limitée par la force de la presse. Le rapprochement du moule 130 est stoppé grâce au système de régulation lorsque la pression de liquide prédéfinie est mesurée par le manomètre 182.In a second step, illustrated by the figure 2 , a wall of the cavity, here the assembly formed by the mold 130, the material blank 150 and the blank holder 140, is moved towards the inside of the cavity so as to reduce the volume of the cavity. The use of a press makes it possible to increase the liquid pressure in the cavity up to a predetermined value sufficient to allow hydraulic preforming of the material blank 150, the liquid pressure in the cavity being in this case limited by the force of the press. The approach of the mold 130 is stopped by the regulation system when the predefined liquid pressure is measured by the pressure gauge 182.

Dans une troisième étape, illustrée en référence à la figure 3, on provoque au moins une décharge électrique entre les deux électrodes 160 de manière à créer un arc électrique entre les électrodes. Puisque les deux électrodes 160 sont plongées dans un liquide, par exemple de l'eau, l'arc électrique provoque un fort gradient de température jusqu'à vaporisation de l'eau entre les électrodes 160. Cette vaporisation engendre une onde de pression, aussi appelée « onde de choc » par la suite, se propageant dans le liquide jusqu'à atteindre le flan de matière 150 à déformer. Sous l'effet de l'onde de choc, le flan de matière se déforme contre le moule comme illustré sur la figure 3. Si nécessaire, on provoque d'autres décharges électriques entre les deux électrodes 160 jusqu'à ce que le flan de matière ait la forme voulue tel qu'illustré sur la figure 4.In a third step, illustrated with reference to the figure 3 , at least one electrical discharge is caused between the two electrodes 160 so as to create an electric arc between the electrodes. Since the two electrodes 160 are immersed in a liquid, for example water, the electric arc causes a strong temperature gradient until the water vaporizes between the electrodes 160. This vaporization generates a pressure wave, also called a “shock wave” hereinafter, propagating in the liquid until it reaches the blank of material 150 to be deformed. Under the effect of the shock wave, the blank of material deforms against the mold as illustrated in the figure 3 . If necessary, further electrical discharges are caused between the two electrodes 160 until the blank of material has the desired shape as illustrated in the figure 4 .

Dans une variante de réalisation, on réduit la pression du liquide dans la cavité avant le formage électrohydraulique. On réduit ainsi la tension nécessaire pour générer une décharge électrique entre les électrodes, qui serait plus élevée en gardant le liquide sous pression. Cette étape permet d'utiliser un générateur électrique moins coûteux et moins volumineux que celui utilisé dans l'étape décrite précédemment.In an alternative embodiment, the pressure of the liquid in the cavity is reduced before electrohydraulic forming. This reduces the voltage required to generate an electrical discharge between the electrodes, which would be higher by keeping the liquid under pressure. This step makes it possible to use a less expensive and less bulky electric generator than that used in the step described above.

La figure 5 illustre un second mode de réalisation d'un dispositif de formage électrohydraulique 200 qui comprend, comme dans le premier mode de réalisation un bâti 210, un plateau mobile 220 d'une presse sur lequel est monté un moule 230 et un serre-flan 240 destiné à maintenir le flan de matière 250 à déformer contre le moule 230 en coopérant avec le moule.There figure 5 illustrates a second embodiment of an electrohydraulic forming device 200 which comprises, as in the first embodiment, a frame 210, a movable platen 220 of a press on which is mounted a mold 230 and a blank holder 240 intended to hold the blank of material 250 to be deformed against the mold 230 by cooperating with the mold.

Le bâti 210 comporte une paroi de fond 212 et une paroi latérale 214.The frame 210 comprises a bottom wall 212 and a side wall 214.

Les électrodes 260 sont montées sur un socle 290 comprenant par exemple trois pieds 292 soutenant une base 294. Les électrodes 260 sont reliées de manière étanche à travers la base 294 à un générateur électrique permettant de générer de brèves impulsions de haute tension de forte puissance électrique suffisantes pour provoquer une décharge électrique entre deux électrodes 260.The electrodes 260 are mounted on a base 290 comprising for example three feet 292 supporting a base 294. The electrodes 260 are connected in a sealed manner through the base 294 to an electric generator making it possible to generate brief high voltage pulses of high electrical power sufficient to cause an electric discharge between two electrodes 260.

Dans ce mode de réalisation, le serre-flan 240 s'étend longitudinalement dans le bâti en direction des électrodes parallèlement à la paroi latérale 214 du bâti 210 et entoure les électrodes 260. Le serre-flan 240 permet de réfléchir une partie de l'onde de choc générée suite à la décharge électrique déclenchée entre les électrodes, ce qui permet de limiter la sollicitation du bâti. En effet, si le bâti est sollicité par les ondes de choc très régulièrement, il peut se fragiliser, par exemple au niveau des soudures entre ses différentes parties s'il est réalisé en structure mécano-soudée. Ainsi, un bâti avec des parois de moindre épaisseur peut être utilisé. Le serre-flan 240 peut être monté sur un ou des vérins 242 en vis-à-vis du moule, et plus particulièrement d'une paroi du moule, tel qu'illustré sur la figure 4, une extrémité de chacun de ces vérins 242 étant fixée sur la paroi de fond 212 du bâti et l'autre extrémité est fixée au serre-flan 240. Le serre-flan est donc distinct du moule. La pression exercée sur le flan de matière 250 par le serre-flan 240 est contrôlée par le ou les vérins 242, le serre-flan 240 appuyant sur le moule.In this embodiment, the blank holder 240 extends longitudinally in the frame in the direction of the electrodes parallel to the side wall 214 of the frame 210 and surrounds the electrodes 260. The blank holder 240 makes it possible to reflect part of the shock wave generated following the electrical discharge triggered between the electrodes, which makes it possible to limit the stress on the frame. Indeed, if the frame is stressed by the shock waves very regularly, it can become fragile, for example at the welds between its different parts if it is made of a mechanically welded structure. Thus, a frame with thinner walls can be used. The blank holder 240 can be mounted on one or more jacks 242 opposite the mold, and more particularly a wall of the mold, as illustrated in the figure 4 , one end of each of these jacks 242 being fixed to the bottom wall 212 of the frame and the other end is fixed to the blank holder 240. The blank holder is therefore separate from the mold. The pressure exerted on the material blank 250 by the blank holder 240 is controlled by the jack(s) 242, the blank holder 240 pressing on the mold.

Dans une variante de réalisation, le ou les vérins 242 sont des ressorts à gaz. La pression exercée sur le flan de matière est alors constante quelque soit la position du moule dans le bâti, dès lors que le moule est en contact du flan de matière. Le socle 290, et plus particulièrement sa base 294, le serre-flan 240 et le flan de matière 250 définissent une cavité destinée à être remplie par un liquide, par exemple de l'eau.In an alternative embodiment, the jack(s) 242 are gas springs. The pressure exerted on the material blank is then constant regardless of the position of the mold in the frame, as long as the mold is in contact with the material blank. The base 290, and more particularly its base 294, the blank holder 240 and the material blank 250 define a cavity intended to be filled with a liquid, for example water.

Un circuit de pompage associé à une pompe 280 permet de remplir la cavité de liquide. Une telle cavité présente l'avantage de pouvoir être remplie de manière optimisée avec un plus petit volume de liquide par rapport au dispositif décrit dans le premier mode de réalisation.A pumping circuit associated with a pump 280 makes it possible to fill the cavity with liquid. Such a cavity has the advantage of being able to be filled in an optimized manner with a smaller volume of liquid compared to the device described in the first embodiment.

En outre, la cavité est rendue étanche par l'ajout de moyens d'étanchéité, par exemple au moins un joint torique 295, par exemple entre la paroi latérale de la base 294 du socle 290 et la paroi interne du serre-flan 240. L'étanchéité entre le serre-flan 240 et le flan de matière à déformer 250 est réalisée à l'aide d'un joint torique 296 compris dans la partie supérieure du serre-flan 240 et à l'aide d'un joint torique 297 compris dans la partie inférieure du moule, par exemple. Le joint torique 296 permet d'assurer l'étanchéité entre le flan de matière 250 et le serre-flan 240 et le joint torique 297permet d'assurer l'étanchéité entre le flan de matière 250 et le moule 230.In addition, the cavity is made watertight by adding sealing means, for example at least one O-ring 295, for example between the side wall of the base 294 of the base 290 and the inner wall of the blank holder 240. The sealing between the blank holder 240 and the blank of material to be deformed 250 is achieved using an O-ring 296 included in the upper part of the blank holder 240 and using an O-ring 297 included in the lower part of the mold, for example. The O-ring 296 makes it possible to ensure the sealing between the blank of material 250 and the blank holder 240 and the O-ring 297 makes it possible to ensure the sealing between the blank of material 250 and the mold 230.

Comme décrit précédemment, la pompe à vide 270 est utilisée pour faire le vide dans l'espace entre le moule 230 et le flan de matière 250 et éventuellement aussi pour créer une dépression dans la cavité étanche lors du remplissage ou de la mise à niveau de celle-ci.As previously described, the vacuum pump 270 is used to create a vacuum in the space between the mold 230 and the material blank 250 and possibly also to create a vacuum in the sealed cavity when filling or leveling it.

Comme décrit précédemment, la mise sous pression du liquide dans la cavité est effectuée avec le dispositif décrit ci-dessus en rapprochant le moule 230 des électrodes 260. Le manomètre 282 est utilisé pour mesurer la pression à l'intérieur de la cavité et le système de régulation est utilisé pour commander l'arrêt de la paroi mobile de la cavité, lorsque la pression mesurée dans la cavité est suffisante pour permettre un formage hydraulique du flan de matière 250 par application d'une pression quasi-statique suffisante.As described above, the pressurization of the liquid in the cavity is carried out with the device described above by bringing the mold 230 closer to the electrodes 260. The pressure gauge 282 is used to measure the pressure inside the cavity and the regulation system is used to control the stopping of the movable wall of the cavity, when the pressure measured in the cavity is sufficient to allow hydraulic forming of the material blank 250 by application of sufficient quasi-static pressure.

Les différentes étapes du procédé de formage électrohydraulique sont semblables à celles décrites en référence aux figures 1 à 4. En revanche, le flan de matière n'est plus maintenu contre le moule à l'aide d'un serre-flan vissé sur le moule. Dans ce mode de réalisation, le flan de matière 250 à déformer est déposé sur le serre-flan 240 puis le moule 230 est descendu pour venir s'appuyer sur le flan de matière 250 et le serre-flan 240. La pression exercée sur le flan de matière 250 par le serre-flan 240 peut être contrôlée par le ou les vérins 242, par exemple des ressorts à gaz.The various stages of the electrohydraulic forming process are similar to those described with reference to Figures 1 to 4 . On the other hand, the blank of material is no longer held against the mold using a blank holder screwed onto the mold. In this embodiment, the blank of material 250 to be deformed is placed on the blank holder 240 and then the mold 230 is lowered to come to rest on the blank of material 250 and the blank holder 240. The pressure exerted on the blank of material 250 by the blank holder 240 can be controlled by the cylinder(s) 242, for example gas springs.

On notera que dans les modes de réalisation décrits ci-dessus, on déplace une paroi de la cavité comportant le flan de matière, l'ensemble formé par le flan de matière et le moule étant monté sur le plateau mobile d'une presse. En d'autres termes, on déplace le flan de matière vers l'intérieur de la cavité, en direction des électrodes, en déplaçant le moule lorsque le flan de matière est maintenu contre le moule par le serre-flan.It will be noted that in the embodiments described above, a wall of the cavity comprising the blank of material is moved, the assembly formed by the blank of material and the mold being mounted on the movable plate of a press. In other words, the blank of material is moved towards the inside of the cavity, towards the electrodes, by moving the mold while the blank of material is held against the mold by the blank holder.

Dans le mode de réalisation décrit en référence aux figures 1 à 4, le flan de matière est maintenu contre le moule par un serre-flan monté sur le moule. Dans le mode de réalisation décrit en référence à la figure 4, le serre-flan est monté sur un vérin et coopère avec le moule pour maintenir le flan de matière. Ainsi, l'ensemble formé par le moule, le flan de matière et le serre-flan est mobile.In the embodiment described with reference to Figures 1 to 4 , the blank of material is held against the mold by a blank holder mounted on the mold. In the embodiment described with reference to the figure 4 , the blank holder is mounted on a jack and cooperates with the mold to hold the material blank. Thus, the assembly formed by the mold, the material blank and the blank holder is mobile.

Dans d'autres modes de réalisation non revendiqués, on pourrait déplacer à l'aide d'une presse une paroi de la cavité supportant les au moins deux électrodes.In other unclaimed embodiments, a wall of the cavity supporting the at least two electrodes could be moved using a press.

La figure 6 illustre un mode de réalisation non revendiqué dans lequel la partie de la paroi de la cavité supportant au moins deux électrodes est montée mobile.There figure 6 illustrates an unclaimed embodiment in which the portion of the cavity wall supporting at least two electrodes is movably mounted.

Le dispositif de formage électrohydraulique 300 comprend un bâti 310, un moule 230 monté sur un premier plateau mobile 320 d'une presse et un serre-flan 340 destiné à maintenir le flan de matière 350 à déformer contre le moule 230.The electrohydraulic forming device 300 comprises a frame 310, a mold 230 mounted on a first movable platen 320 of a press and a blank holder 340 intended to hold the blank of material 350 to be deformed against the mold 230.

Le bâti 310 comporte une paroi de fond 312 et une paroi latérale 314. La paroi de fond 312 comprend une paroi mobile 316 supportant au moins deux électrodes 360 et une paroi fixe 318. La paroi mobile 316 est montée sur un deuxième plateau 322 de la presse. Le serre-flan 340 repose sur la partie de la paroi de fond 312 qui n'est pas mobile, c'est-à-dire sur la paroi fixe 318. Le serre-flan 340 est fixe et se trouve en vis-à-vis du moule dans la cavité formée par le serre-flan 340, la paroi mobile 316 du bâti 310 supportant les électrodes 360 et le flan de matière 350 à déformer.The frame 310 comprises a bottom wall 312 and a side wall 314. The bottom wall 312 comprises a movable wall 316 supporting at least two electrodes 360 and a fixed wall 318. The movable wall 316 is mounted on a second platen 322 of the press. The blank holder 340 rests on the part of the bottom wall 312 which is not movable, that is to say on the fixed wall 318. The blank holder 340 is fixed and is located opposite the mold in the cavity formed by the blank holder 340, the movable wall 316 of the frame 310 supporting the electrodes 360 and the blank of material 350 to be deformed.

La cavité est rendue étanche par l'ajout de moyens d'étanchéité, par exemple un joint torique 395 compris dans la paroi latérale de paroi mobile 316, un joint torique 396 compris dans la partie du serre-flan 340 en contact avec le flan de matière 350 et un joint 397 compris dans la partie du moule 330 en contact avec le flan de matière 350. Le joint torique 395 permet de réaliser l'étanchéité entre la paroi mobile 316 supportant les électrodes 360 et le serre-flan 240 et éventuellement la paroi fixe 318 de la paroi de fond 312 du bâti 310. Le joint torique 396 permet de réaliser l'étanchéité entre le flan de matière 350 et le moule 330 et le joint torique 397 permet de réaliser l'étanchéité entre le flan de matière 350 et le serre-flan 340.The cavity is sealed by adding sealing means, for example an O-ring 395 included in the side wall of the movable wall 316, an O-ring 396 included in the portion of the blank holder 340 in contact with the material blank 350 and a seal 397 included in the portion of the mold 330 in contact with the material blank 350. The O-ring 395 makes it possible to achieve sealing between the movable wall 316 supporting the electrodes 360 and the blank holder 240 and possibly the fixed wall 318 of the bottom wall 312 of the frame 310. The O-ring 396 makes it possible to achieve sealing between the material blank 350 and the mold 330 and the O-ring 397 make it possible to achieve sealing between the material blank 350 and the blank holder 340.

Le déplacement de la paroi mobile 316 permet de mettre sous pression le liquide de la cavité formée par le serre-flan 340, la paroi mobile 316 du bâti 310 supportant les électrodes 360 et le flan de matière 350 à déformer. La pression exercée sur le flan de matière 350 est réglée à l'aide de la pression exercée par le plateau 320 de la presse lorsque le moule 330 est en contact avec le flan de matière 350.The movement of the movable wall 316 makes it possible to pressurize the liquid in the cavity formed by the blank holder 340, the movable wall 316 of the frame 310 supporting the electrodes 360 and the material blank 350 to be deformed. The pressure exerted on the material blank 350 is adjusted using the pressure exerted by the platen 320 of the press when the mold 330 is in contact with the material blank 350.

Comme dans les modes de réalisation décrits précédemment, le dispositif de formage électrohydraulique comprend un circuit de pompage associé à une pompe 380, un manomètre 382 et une pompe à vide 370 tel que décrit précédemment. Il peut également comporter une vanne associée à un pressostat 384.As in the embodiments described above, the electrohydraulic forming device comprises a pumping circuit associated with a pump 380, a pressure gauge 382 and a vacuum pump 370 as described above. It may also comprise a valve associated with a pressure switch 384.

Le plateau de la presse apte à fournir une pression supérieure à celle de l'autre plateau est monté préférentiellement sur la paroi mobile 316 supportant les électrodes 360. En effet, la force à fournir pour mettre sous pression le liquide dans la cavité est souvent supérieure à celle que l'on souhaite exercer sur le flan de matière.The press plate capable of providing a pressure greater than that of the other plate is preferably mounted on the movable wall 316 supporting the electrodes 360. Indeed, the force to be provided to pressurize the liquid in the cavity is often greater than that which one wishes to exert on the blank of material.

On notera que, lorsqu'une presse à double effet est utilisée, le plateau apte à fournir la force la plus élevée est le plateau supérieur.It should be noted that when a double-acting press is used, the platen capable of providing the highest force is the upper platen.

La paroi mobile 316 supportant les électrodes 316 est alors au-dessus et le moule 330 en dessous du flan de matière à déformer 350 comme illustré sur la figure 6.The movable wall 316 supporting the electrodes 316 is then above and the mold 330 below the blank of material to be deformed 350 as illustrated in the figure 6 .

Les différentes étapes d'un procédé non revendiqué de formage électrohydraulique comportant un préformage hydraulique avec le dispositif décrit en référence à la figure 6 sont décrites ci-dessous.The various steps of an unclaimed electrohydraulic forming process comprising hydraulic preforming with the device described with reference to the figure 6 are described below.

Dans une première étape, on place le flan de matière 350 à déformer sur le moule 330 et on rapproche le moule 330 du bâti 310 jusqu'à ce que le flan de matière soit maintenu entre le serre-flan 340 et le moule 330 avec la pression voulue. Le serre-flan coopère ainsi avec le moule pour maintenir le flan de matière. Ensuite, on remplit la cavité formée en partie par le bâti à l'aide de la pompe 380 tout en créant également de manière avantageuse une dépression dans la cavité à l'aide de la pompe à vide 370. Lorsque la paroi mobile 316 supportant les électrodes 316 est au-dessus du flan de matière 350 à déformer, le liquide de la cavité est en contact avec le flan de matière 350 dès que la pompe 380 est actionnée pour remplir la cavité. La cavité est dans ce cas remplie jusqu'à ce que la paroi 316 supportant les électrodes 360 soit en contact avec le liquide de la cavité. On crée ensuite un vide entre le flan de matière 350 et le moule 330 à l'aide de la pompe à vide 370.In a first step, the blank of material 350 to be deformed is placed on the mold 330 and the mold 330 is brought closer to the frame 310 until the blank of material is held between the blank holder 340 and the mold 330 with the desired pressure. The blank holder thus cooperates with the mold to hold the blank of material. Then, the cavity formed in part by the frame is filled using the pump 380 while also advantageously creating a depression in the cavity using the vacuum pump 370. When the wall mobile 316 supporting the electrodes 316 is above the material blank 350 to be deformed, the liquid of the cavity is in contact with the material blank 350 as soon as the pump 380 is actuated to fill the cavity. The cavity is in this case filled until the wall 316 supporting the electrodes 360 is in contact with the liquid of the cavity. A vacuum is then created between the material blank 350 and the mold 330 using the vacuum pump 370.

Dans une seconde étape, on déplace la paroi mobile 316 de la cavité supportant les électrodes vers l'intérieur de la cavité de manière à réduire le volume de la cavité. La force exercée sur la paroi mobile 316 permet d'augmenter la pression de liquide dans la cavité jusqu'à une valeur prédéterminée suffisante pour permettre un préformage hydraulique du flan de matière 350. Le rapprochement de la paroi mobile 316 est stoppé grâce au système de régulation lorsque la pression de liquide prédéfinie est mesurée par le manomètre 382.In a second step, the movable wall 316 of the cavity supporting the electrodes is moved toward the inside of the cavity so as to reduce the volume of the cavity. The force exerted on the movable wall 316 makes it possible to increase the liquid pressure in the cavity to a predetermined value sufficient to allow hydraulic preforming of the material blank 350. The approach of the movable wall 316 is stopped by means of the regulation system when the predefined liquid pressure is measured by the pressure gauge 382.

Dans une troisième étape, on provoque au moins une décharge électrique entre les deux électrodes 360 de manière à créer un arc électrique entre les électrodes et une « onde de choc » se propageant dans le liquide jusqu'à atteindre le flan de matière 350 à déformer. Sous l'effet de l'onde de choc, le flan de matière se déforme contre le moule. Si nécessaire, on provoque d'autres décharges électriques entre les deux électrodes 360 jusqu'à ce que le flan de matière ait la forme voulue.In a third step, at least one electrical discharge is caused between the two electrodes 360 so as to create an electrical arc between the electrodes and a “shock wave” propagating in the liquid until it reaches the material blank 350 to be deformed. Under the effect of the shock wave, the material blank deforms against the mold. If necessary, other electrical discharges are caused between the two electrodes 360 until the material blank has the desired shape.

Comme décrit précédemment, il est possible de réduire la pression du liquide dans la cavité à l'aide d'une vanne associée à un pressostat 184 avant le formage électrohydraulique. On notera que, dans les modes de réalisation décrits ici, on déplace une paroi de la cavité comportant le flan de matière ou une paroi supportant les électrodes. On pourrait par ailleurs également déplacer tout ou partie d'une paroi autre que celles supportant les électrodes ou formées par le flan de matière. Dans ce cas, la paroi n'est pas montée sur une presse mais constitue la paroi mobile d'un piston, la cavité formant alors l'un des compartiments du piston.As described above, it is possible to reduce the pressure of the liquid in the cavity using a valve associated with a pressure switch 184 before the electrohydraulic forming. It will be noted that, in the embodiments described here, a wall of the cavity comprising the blank of material or a wall supporting the electrodes is moved. It would also be possible to move all or part of a wall other than those supporting the electrodes or formed by the blank of material. In this case, the wall is not mounted on a press but constitutes the movable wall of a piston, the cavity then forming one of the compartments of the piston.

Les diverses formes de réalisation d'un dispositif d'électrohydroformage et les procédés de formage décrits ci-dessus permettent de mettre le liquide de la cavité sous pression plus rapidement qu'en utilisant une pompe pressurisée dont le débit est limité. On évite aussi d'avoir à reremplir la cuve avec du liquide pressurisé entre chaque cycle de formage d'une pièce. On gagne ainsi en temps de cycle. Par ailleurs, les équipements à utiliser sont moins complexes car il ne faut pas générer d'eau sous pression.The various embodiments of an electrohydroforming device and the forming methods described above enable the cavity liquid to be pressurized more quickly than using a pressurized pump with a limited flow rate. This also avoids having to refill the tank with pressurized liquid between each forming cycle of a part. This saves cycle time. In addition, the equipment to be used is less complex because it is not necessary to generate pressurized water.

La présente invention ne se limite pas aux différentes formes de réalisation décrites et illustrées et aux variantes évoquées mais elle concerne également les formes de réalisation à la portée de l'homme du métier dans le cadre des revendications ci-après.The present invention is not limited to the various embodiments described and illustrated and to the variants mentioned but it also concerns the embodiments within the reach of those skilled in the art within the framework of the claims below.

Claims (11)

  1. A method for electrohydraulically forming a blank of material (150; 250) wherein
    - a material blank (150; 250) to be deformed is placed between a mould (130; 230) and a blank holder (140; 240),
    - a sealed cavity is filled with liquid wherein there are at least two electrodes (160; 260) up to a predetermined liquid level,
    - the material blank (150; 250) is contacted with the liquid in the cavity,
    - a hydraulic preforming of the material blank (150; 250) is carried out, the material blank (150; 250) being pushed towards the mould (130; 230) by the liquid from the cavity under pressure, thus undergoing a first deformation,
    - an electrohydraulic forming of the material blank (150; 250) is carried out, the material blank (150; 250) being pressed against the mould (130; 230) by at least one pressure wave generated by an electrical discharge between at least two electrodes (160; 260), thus undergoing a second deformation,
    characterised in that the liquid in the cavity is pressurised for hydraulic preforming by moving a wall of the cavity formed by the mould (130; 230), the material blank (150; 250) and the blank holder (140; 240) towards the inside of the cavity.
  2. The method according to claim 1, characterised in that a vacuum is created between the material blank (150; 250) and the mould (130; 230) after the material blank (150; 250) is contacted with the liquid from the cavity.
  3. The method according to one of claims 1 or 2, characterised in that the assembly formed by the mould (130; 230) and the material blank (150; 250) is moved while the electrodes (160; 260) are fixed.
  4. An electrohydraulic forming device (100; 200) of a material blank (150; 250) comprising:
    - a frame (120; 220),
    - a sealed cavity capable of being filled with a liquid and one of the walls of which includes the material blank (150; 250),
    - at least two electrodes (160; 260) placed in the cavity,
    - a mould (130; 230),
    - a blank holder (140; 240) capable of holding the material blank (150; 250) against the mould (130; 230),
    characterised in that
    - the cavity comprises a movable wall formed by the mould (130; 230), the material blank (150; 250) and the blank holder (140; 240), and
    - the movement of the movable wall is capable of sufficiently pressurising the liquid in the cavity to generate a deformation of the material blank (150; 250) against the mould (130; 230).
  5. The electrohydraulic forming device (100; 200) according to claim 4, characterised in that it comprises a vacuum pump (170; 270).
  6. The electrohydraulic forming device (100; 200) according to one of claims 4 or 5, characterised in that the cavity is formed at least partly by the frame (120; 220).
  7. The electrohydraulic forming device (200) according to claim 6, characterised in that the at least two electrodes (260) are carried by a base (290) resting on a bottom wall (212) of the frame (210).
  8. The electrohydraulic forming device (200) according to one of claims 4 to 7, characterised in that the blank holder (240) is distinct from the frame and the blank holder extends longitudinally in the frame towards the electrodes (260).
  9. The device (100; 200) according to one of claims 4 to 8, characterised in that an assembly formed by the mould (130; 230) and the material blank (150; 250) is mounted on a movable plate (120; 220) of a press.
  10. The device (100) according to claim 9, characterised in that the assembly formed by the mould (130), the material blank (150) and the blank holder (140) is mounted on a movable plate (120) of a press.
  11. The device (200) according to claim 9, characterised in that:
    - the assembly formed by the mould (230) and the material blank (250) is mounted on a movable plate (220) of a press, and
    - the blank holder (240) is mounted on at least one cylinder (242), a first end of each cylinder (242) being fixed on the bottom wall (212) of the frame (210), a second end of each cylinder (242) being fixed to the blank holder (240).
EP17798192.5A 2016-11-15 2017-11-14 Method for electrohydraulic forming and associated device Active EP3541545B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR1661068A FR3058654B1 (en) 2016-11-15 2016-11-15 ELECTROHYDRAULIC FORMING METHOD AND DEVICE THEREOF
PCT/EP2017/079236 WO2018091481A1 (en) 2016-11-15 2017-11-14 Method for electrohydraulic forming and associated device

Publications (2)

Publication Number Publication Date
EP3541545A1 EP3541545A1 (en) 2019-09-25
EP3541545B1 true EP3541545B1 (en) 2024-10-23

Family

ID=58401663

Family Applications (1)

Application Number Title Priority Date Filing Date
EP17798192.5A Active EP3541545B1 (en) 2016-11-15 2017-11-14 Method for electrohydraulic forming and associated device

Country Status (6)

Country Link
US (1) US10994321B2 (en)
EP (1) EP3541545B1 (en)
JP (1) JP6924509B2 (en)
CN (1) CN110087793A (en)
FR (1) FR3058654B1 (en)
WO (1) WO2018091481A1 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111531860A (en) * 2020-04-28 2020-08-14 中国人民解放军军事科学院国防工程研究院工程防护研究所 Diaphragm pre-pressing forming device for shock wave simulation equipment
CN112139340B (en) * 2020-09-14 2022-06-21 哈尔滨工业大学 Aluminum alloy component ultralow-temperature forming device and forming method

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10019594A1 (en) * 2000-04-20 2001-10-25 Bayerische Motoren Werke Ag Method for pressing sheet metal has a hydromechanical press with pulse generators for producing localised pressure peaks for fine press detail
US7493787B2 (en) * 2006-12-11 2009-02-24 Ford Global Technologies, Llc Electro-hydraulic forming tool having two liquid volumes separated by a membrane
US7827838B2 (en) * 2008-05-05 2010-11-09 Ford Global Technologies, Llc Pulsed electro-hydraulic calibration of stamped panels
US7802457B2 (en) * 2008-05-05 2010-09-28 Ford Global Technologies, Llc Electrohydraulic forming tool and method of forming sheet metal blank with the same
US8534106B2 (en) * 2009-10-19 2013-09-17 Ford Global Technologies, Llc Hydromechanical drawing process and machine
CN101829732A (en) * 2010-04-15 2010-09-15 重庆理工大学 Solid particle male die forming mold with movable brake beads and radial thrust
US8844331B2 (en) * 2010-10-29 2014-09-30 Ford Global Technologies, Llc Electro-hydraulic forming process with electrodes that advance within a fluid chamber toward a workpiece
FR3000909B1 (en) * 2013-01-11 2015-05-15 Adm28 S Ar L METHOD, TOOLING AND PRESS FOR FORMING A PIECE
US20180015522A1 (en) * 2016-06-20 2018-01-18 Imam Khomeini International University High-speed hot forming and direct quenching

Also Published As

Publication number Publication date
US20190283102A1 (en) 2019-09-19
FR3058654B1 (en) 2019-06-07
FR3058654A1 (en) 2018-05-18
JP2019537514A (en) 2019-12-26
JP6924509B2 (en) 2021-08-25
CN110087793A (en) 2019-08-02
WO2018091481A1 (en) 2018-05-24
EP3541545A1 (en) 2019-09-25
US10994321B2 (en) 2021-05-04

Similar Documents

Publication Publication Date Title
EP2943297B1 (en) Method, tool and press for the electrohydraulic forming of a workpiece
EP3541545B1 (en) Method for electrohydraulic forming and associated device
EP3068557B1 (en) Electrohydraulic forming device
FR3058655B1 (en) ELECTROHYDRAULIC FORMING METHOD AND DEVICE THEREOF
FR3031056A1 (en) ENCLOSURE FOR ELECTRO-HYDRAULIC FORMING
CA2919963A1 (en) Electro-hydraulic forming machine for the plastic deformation of a projectile part of the wall of a workpiece to be formed
EP3240650B1 (en) Electrohydraulic forming apparatus
FR2987288A1 (en) HEAD OF AN ELECTROHYDRAULIC WIRE DISCHARGE DEVICE
WO2018146216A1 (en) Electrohydraulic forming device
EP3496876A1 (en) Indirect electrohydraulic press forming tool, device and method
EP3240648B1 (en) Electrohydraulic forming device comprising an optimised chamber
FR3092504A1 (en) Hybrid forming process and corresponding forming device
FR3086565A1 (en) PROCESS FOR TREATING A POROUS PART
EP3240647B1 (en) Chamber for an electrohydraulic forming device
FR3031052A1 (en) NEW ENCLOSURE ARCHITECTURE FOR ELECTRO-HYDRAULIC FORMING
FR3149812A1 (en) Electrode for electro-hydroforming enclosure

Legal Events

Date Code Title Description
STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: UNKNOWN

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE INTERNATIONAL PUBLICATION HAS BEEN MADE

PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: REQUEST FOR EXAMINATION WAS MADE

17P Request for examination filed

Effective date: 20190424

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

AX Request for extension of the european patent

Extension state: BA ME

DAV Request for validation of the european patent (deleted)
DAX Request for extension of the european patent (deleted)
STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: EXAMINATION IS IN PROGRESS

17Q First examination report despatched

Effective date: 20220826

GRAP Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOSNIGR1

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: GRANT OF PATENT IS INTENDED

INTG Intention to grant announced

Effective date: 20240528

GRAS Grant fee paid

Free format text: ORIGINAL CODE: EPIDOSNIGR3

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE PATENT HAS BEEN GRANTED

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

REG Reference to a national code

Ref country code: GB

Ref legal event code: FG4D

Free format text: NOT ENGLISH

REG Reference to a national code

Ref country code: CH

Ref legal event code: EP

REG Reference to a national code

Ref country code: DE

Ref legal event code: R096

Ref document number: 602017085668

Country of ref document: DE

REG Reference to a national code

Ref country code: IE

Ref legal event code: FG4D

Free format text: LANGUAGE OF EP DOCUMENT: FRENCH

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 20241211

Year of fee payment: 8

REG Reference to a national code

Ref country code: GB

Ref legal event code: 732E

Free format text: REGISTERED BETWEEN 20241219 AND 20241224

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 20241219

Year of fee payment: 8

REG Reference to a national code

Ref country code: DE

Ref legal event code: R081

Ref document number: 602017085668

Country of ref document: DE

Owner name: ADM28 FRANCE, FR

Free format text: FORMER OWNER: ADM28 S.AR.L., LUXEMBOURG, LU

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 20241128

Year of fee payment: 8

REG Reference to a national code

Ref country code: DE

Ref legal event code: R082

Ref document number: 602017085668

Country of ref document: DE

Representative=s name: PLASSERAUD IP GMBH, DE

REG Reference to a national code

Ref country code: LT

Ref legal event code: MG9D

REG Reference to a national code

Ref country code: NL

Ref legal event code: MP

Effective date: 20241023

REG Reference to a national code

Ref country code: AT

Ref legal event code: MK05

Ref document number: 1734432

Country of ref document: AT

Kind code of ref document: T

Effective date: 20241023