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
  • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
  • B21D22/20—Deep-drawing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
  • B21D22/02—Stamping using rigid devices or tools
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
  • B21D22/02—Stamping using rigid devices or tools
  • B21D22/06—Stamping using rigid devices or tools having relatively-movable die parts
• • 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
  • B21D37/00—Tools as parts of machines covered by this subclass
  • B21D37/08—Dies with different parts for several steps in a process

Definitions

• the present invention relates to a method and a tool for stamping a sheet material for shaping a piece of non-developable geometry.
• connection radius For a stamped part made from a conventional steel of 0.5 mm thick, locally having a connection between two disoriented zones of 20 °, the outer part of the connection radius can not be physically less than 1 .5 mm (for disorientations below about 150 °, the external form of attachment is very close to a sector of circle, hence the term "connection radius" used in this document), and this same if the punch radius takes a value of zero, rendering obsolete a reasoning based on a geometric "offset" of constant thickness.
• the invention described in this document solves this problem of limiting the connecting radii of the salient angles, thus enabling the realization of stamped geometries having sharp angles with low radii, or even zero.
• the principle of the invention is to stamp a sheet of constant thickness, and at the end of stamping stroke, to make on an outer face of the sheet a connection of a small radius by applying locally, on the inner face of the sheet a force constraining the material of the pressed sheet to a plating on the outside.
• the outer face of the sheet typically corresponds to its convex face, the important point however is that it is normally the visible side.
• the force forcing the material of the pressed sheet to be pressed at the small radius connection on its outer face is applied at a speed greater than the closing speed of the stamping press at the end of stamping race.
• the force applied locally is obtained by using a stamping tool operated by a stamping press, the tool having the side in contact with the underside of the sheet, an additional form for example integral with the carrier tool.
• the volume of this additional shape is substantially equal to the volume of material to be moved to obtain the desired connection radius.
• the additional shape has at its top a cylindrical portion.
• the additional shape can be integrated into the carrier tool, usually the punch but also to a matrix, or a movable member of the stamping tool, blade type or counter-form .
• this movable member will advantageously be displaced by means of a cam, a slider or an independent jack.
• the blade or movable counter-form can be moved in a direction the same or different from the main axis of stamping.
• the additional form that applies the force is movable relative to the carrier tool: it is advantageously in the retracted position during the stamping of the general shape of the part, until the moment when the material sheet is contact with the punch and the die ("closed tool" phase in conventional stamping). Then, while maintaining the contact between the stamped material, and the carrier tool, the additional shape is driven by a translation whose displacement stroke allows, by compensation of local thinning and constraints due to the conservation of volume, which allows to press the stamped material in the gap located in the outer part, the material thus displaced allowing the realization of a connection having a very small radius or zero.
• the direction of movement of the mobile additional shape is chosen near the bisectors of the two disoriented areas concerned by the low radius connection. This variant thus makes it possible to produce low-radius projecting angles, including those whose bisector of the connected surfaces is very different from the main stamping axis.
• the displacement of the additional mobile form can be controlled by a mechanical device, hydraulic or pneumatic, dependent or independent of the stroke of the stamping press.
• FIG. 1 an example of forming according to the prior art (FIG. 1A) and according to a first embodiment of the invention of a connection zone using a stamping tool whose punch is provided with a additional form, the forming being illustrated before ( Figure 1B) ( Figure 1B to update) and after the total closure of the stamping tool ( Figure 1 C)
• FIG. 1 -A illustrates the stamping process according to the prior art, with a sheet material 2 having a constant thickness 21 is stamped by means of a stamping tool whose press consists of a punch 1 and a die 3 having substantially complementary shapes.
• the matrix 3 comprises a zone 33 corresponding to the formation of a protruding zone on the formed sheet material.
• the sheet 2 tends to marry at this zone 33 a circle of radius 22, which tangents the directions of the matrix 3 on each side of this zone 33, the zone 31 constituting a blank space not occupied by the sheet 2.
• FIG. 1B illustrates the method according to the invention making it possible to avoid this empty space and to obtain the desired geometry including at the level of the zone 33.
• the punch 1 is provided with an additional shape 4 in the area facing the zone 33 by the addition of an additional form 4, having in its projecting part a radius of curvature January.
• the additional shape may not be rounded but rather angular, close to the radius of curvature of the zone 33.
• the volume of this additional shape advantageously corresponds to the volume of material to be moved to obtain the desired small projecting radius.
• the profile of this additional shape is advantageously chosen such that it promotes the local displacement of material, by favoring shearing and by limiting the large displacements of deformed material (symmetrical or non-symmetrical shape, depending on the orientation of the connection zone by relative to the stamping axis).
• This additional form is made to withstand the high pressures associated with the local displacement of material at the end of stamping: it will be obtained by machining and / or local metallurgical swelling and / or adjustment, in a resistant material, for example the base material of the tool and / or insert insert and / or local topcoat and / or surface treatment increasing the toughness of this tool part.
• the lubrication may be adapted to promote the local displacement of deformed material and prevent the occurrence of possible seizures on the tool and / or premature wear.
• the invention provides a second improvement for the part produced: its geometry is more accurate than in conventional stamping because the distortions due to the elastic return phenomenon are reduced. Indeed, the additional shape realizes a local displacement of material at the end of stamping stroke, which increases the plastic deformation of the area considered.
• the springback after stamping of the connection zone is less important than in conventional stamping (local opening or closing of 1 to 2 degrees, reduced by at least half thanks to the additional local lamination).
• Figures 2A, 2B and 2C show examples of possible geometries for the additional form.
• the additional shape has a smaller radius so that it forms a sphere projecting from the rest of the punch.
• the section of the additional shape is constituted by a circle sector, connected to the punch with cut edges. The choice of the type of geometry of the additional shape will normally be made according to criteria related to the technique of making and developing the tooling.
• the top of the shape of the additional shape is rounded, without this being an imperative: it is the ability of the additional shape geometry to apply the force generating the local displacement of material to outside, by favoring shearing and by limiting large displacements of deformed material, which remains predominant.
• the additional form 4 is not integral with the carrier tool (punch 1 in the figure or die or blade or against mobile form), but movable relative to the carrier tool 1, said additional mobile form 4 being actuated a mechanical, hydraulic or pneumatic device.
• the additional shape 4 in a direction different from the direction of movement of the carrier tool (punch 1 in the figure or matrix or blade or against mobile form) and / or direction general closure of the stamping tool, and particularly preferably in a direction of movement near the bisectors of the two disoriented areas concerned by the connection.
• this additional mobile form 4 will be moved between a retracted position ( Figure 3A), used during the stamping of the general shape of the part, and a projecting position ( Figure 3B), reached after the general closure. of the press.
• the speed of displacement of this additional mobile form may advantageously be greater than the average speed of the carrier tool and / or the main slide of the press (dynamic operation)

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Shaping Metal By Deep-Drawing, Or The Like (AREA)
• Auxiliary Devices For And Details Of Packaging Control (AREA)
• Package Closures (AREA)

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Publications (1)

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• 2013
  • 2013-12-17 FR FR1362829A patent/FR3014712B1/fr active Active
• 2014
  • 2014-11-25 WO PCT/FR2014/053024 patent/WO2015092185A1/fr active Application Filing
  • 2014-11-25 EP EP14821739.1A patent/EP3083094A1/fr active Pending
  • 2014-11-25 CN CN201480069210.4A patent/CN105848800B/zh active Active

Non-Patent Citations (2)

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