WO2012128707A1 - Procédé de forçage à froid d'une pièce de tôle par cintrage ou par moulage par presse - Google Patents

Procédé de forçage à froid d'une pièce de tôle par cintrage ou par moulage par presse Download PDF

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Publication number
WO2012128707A1
WO2012128707A1 PCT/SE2012/050302 SE2012050302W WO2012128707A1 WO 2012128707 A1 WO2012128707 A1 WO 2012128707A1 SE 2012050302 W SE2012050302 W SE 2012050302W WO 2012128707 A1 WO2012128707 A1 WO 2012128707A1
Authority
WO
WIPO (PCT)
Prior art keywords
sheet metal
piece
tool
bending area
bending
Prior art date
Application number
PCT/SE2012/050302
Other languages
English (en)
Inventor
Peter ALM
Original Assignee
Ssab Technology Ab
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 Ssab Technology Ab filed Critical Ssab Technology Ab
Priority to US14/006,212 priority Critical patent/US20140000336A1/en
Priority to EP12760204.3A priority patent/EP2688692A4/fr
Publication of WO2012128707A1 publication Critical patent/WO2012128707A1/fr

Links

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
    • B21D5/00—Bending sheet metal along straight lines, e.g. to form simple curves
    • B21D5/01—Bending sheet metal along straight lines, e.g. to form simple curves between rams and anvils or abutments
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
    • B21D22/20—Deep-drawing
    • B21D22/21—Deep-drawing without fixing the border of the blank
    • 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 of cold forming a piece of sheet metal by bending or press moulding.
  • the piece of sheet metal In order to achieve a permanent deformation of a piece of sheet metal by bending or press moulding, the piece of sheet metal has to be subjected to such a force that the yield point of the material is reached in the parts of the piece of sheet metal that are bent in connection with the bending/press moulding opera- tion.
  • the piece of sheet metal will be subjected to compressive stress at the inner side of the bend and tensile stress at the outer side of the bend.
  • the so-called neutral layer which constitutes a boundary between these areas.
  • the sheet metal material is plasticized in these plastic zones.
  • the neutral layer and an elastic zone in which the sheet metal material is not plasticized are located between these plastic zones.
  • the sheet metal mate- rial in a first part of the elastic zone, between the neutral layer and the first plastic zone, has compressive stress lower than the yield point, whereas the sheet metal material in a second part of the elastic zone, between the neutral layer and the second plastic zone, has tensile stress lower than the yield point.
  • the tensile stress in said second part of the elastic zone will be released and strive towards a contraction of the piece of sheet metal transversally to the longitudinal direction of the bend and thereby act for at straightening of the bend. Furthermore, when the bending force on the piece of sheet metal is released, the material at the neutral layer, which essentially has no tensile stress or compressive stress, strives to spring back to the original shape that this material had before being subjected to the bending force.
  • a high-strength metal material has a higher yield point than a softer metal material, which implies that the above-described problem with spring-back is more severe when it comes to bending or press moulding of a high-strength metal material as compared to a corresponding bending or press moulding of a softer metal material.
  • the desired final shape of a piece of sheet metal after bending or press moulding may for instance be achieved by bending the piece of sheet metal during the bending/press moulding opera- tion so far that the piece of sheet metal will spring back to the desired final shape after being released from the forming tool.
  • it is very difficult to determine how a piece of sheet metal is to be bent in order to assume a desired final shape after spring-back and extensive and time-consuming trials are therefore normally required before the correct forming geometry is achieved.
  • even very small property variations between apparently identical pieces of sheet metal may cause a different spring-back and consequently result in varying final shapes of the pieces of sheet metal after bending/press moulding thereof.
  • the object of the present invention is to achieve a new and favourable solution to the above-described problem with spring- back in connection with the cold forming of a piece of sheet metal .
  • the piece of sheet metal is bent over a bevelled edge of a tool so that the piece of sheet metal in the area of the bend thus formed , which area here being denominating bending area, is subjected to compressive stress on the side of the neutral layer facing the inner side of the bending area and tensile stress on the side of the neutral layer facing the outer side of the bending area, a gap being left between the piece of sheet metal and an edge surface of the bevelled edge on the inner side of the bending area.
  • a compressive force is thereafter exerted on the piece of sheet metal outside said bending area in such a manner that the bending area is sub- jected to compression in the extension direction of the piece of sheet metal transversally to the longitudinal direction of the bend.
  • the bending area is consequently influenced in such a manner that the zones with compressive stress and tensile stress that are initially developed in the bending area in connection with the bending of the piece of sheet metal are shifted so that tensile stress instead of com- pressive stress is developed at the inner side of the bend and compressive stress instead of tensile stress is developed at the outer side of the bend.
  • the compressive stress in the elastic zone on the side of the neutral layer facing the outer side of the bend will be released and strive towards a dilation of the piece of sheet metal transversally to the longitudinal direction of the bend and thereby act for a decrease of the bend radius.
  • the tensile stress in the elastic zone on the side of the neutral layer facing the inner side of the bend will be released and strive towards a contraction of the piece of sheet metal transversally to the longitudinal direction of the bend and thereby act for a decrease of the bend radius.
  • the released stresses in the elastic zone will consequently counteract the previously mentioned spring-back tendency of the material at the neutral layer, which implies that the spring-back of the piece of sheet metal can be reduced and even completely eliminated in dependence on the relationship between the bend radius decreasing effect of the released stresses in the elastic zone and the bend radius increasing spring-back effect of the material at the neutral layer.
  • Figs 1 a-1 d schematic illustrations of different steps in a method according to an embodiment of the present invention of cold forming a piece of sheet metal
  • Figs 2b-2d schematic diagrams over the distribution of the stresses, at the different steps according to Figs 1 b-1 d , in a cut through one of the bending areas of the piece of sheet metal .
  • Figs 1 a- 1 d Different steps in a method according to an embodiment of the present invention of cold forming a piece of sheet metal 1 of metallic material are schematically illustrated in Figs 1 a- 1 d .
  • the piece of sheet metal 1 is bent into U-shape by bending along two rectilinear and mutually parallel bending lines.
  • the method according to the invention can also be used for bending a piece of sheet metal along one or more curved bending lines by press moulding .
  • the first tool 1 0 is provided with a first bevelled edge 1 2 in order to form a first bending line in the piece of sheet metal to be formed, and a second bevelled edge 1 3 in order to form a second bending line in the piece of sheet metal to be formed .
  • These bevelled edges 1 2, 1 3 extend in parallel with each other on either side of the support surface 1 1 .
  • the respective bevelled edge 12, 1 3 has an incline edge r
  • the forming machine 2 also comprises a third tool 30, which comprises a first part 30a located on a first side of the second tool 20 and a second part 30b located on the other side of the second tool 20 opposite the first part 30a. These first and second parts 30a, 30b are consequently located on either side of the second tool 20.
  • the third tool 30 is linearly displaceable in relation to the first tool 1 0 and in relation to the second tool 20.
  • the piece of sheet metal 1 to be formed is placed with a central first part 1 A of the piece of sheet metal bearing against the support surface 1 1 on the first tool 1 0 and with lateral second and third parts 1 B, 1 C of the piece of sheet metal extending out over the bevelled edges 1 2, 1 3 of the first tool 1 0 on either side of the first part 1 A of the piece of sheet metal , as illustrated in Fig 1 a.
  • said first part 1 A of the piece of sheet metal is at a first side connected to a second part 1 B of the piece of sheet metal that extends out over the first bevelled edge 12 of the first tool and is at an opposite second side connected to a third part 1 C of the piece of sheet metal that extends out over the second bevelled edge 1 3 of the first tool .
  • the first part 1 A of the piece of sheet metal is received between the support surface 1 1 on the first tool and the support surface 21 on the second tool .
  • said support surfaces 1 1 , 21 on the first and second tools are straight.
  • the first tool 1 0 and the third tool 30 are subjected to a mutual displacement in the direction towards each other so that the second part 1 B of the piece of sheet metal is bent over the first bevelled edge 12 of the first tool 1 0 under the effect of the first part 30a of the third tool 30 and thereby bent in relation to the first part 1 A of the piece of sheet metal to form a first bending area B 1 on the piece of sheet metal , and so that the third part 1 C of the piece of sheet metal is bent over the second bevelled edge 3 of the first tool 1 0 under the effect of the second part 30b of the third tool 30 and thereby bent in relation to the first part 1 A of the piece of sheet metal to form a second bending area B2 on the piece of sheet metal , as illustrated in Fig 1 b.
  • Tensile stress is indicated with a dash-patterned area 5 and tensile stress is indicated with a dot-patterned area 6 in Figs 2b- 2d. Furthermore, the centre plane 7 of the piece of sheet metal is indicated with a broken line in Figs 2b-2d .
  • a gap is left between the piece of sheet metal 1 and the edge surface 14 of the first bevelled edge 12 on the inner side 3 of the first bending area B1 and a gap is left between the piece of sheet metal and the first part 30a of the third tool on the outer side 4 of the first bending area B1 .
  • the first and second tools 10, 20 are then subjected to a mutual displacement in the direction towards each other so that the first part 1A of the piece of sheet metal is flattened between the support surfaces 1 1 , 20 on these tools, while the third tool 30 retains the second and third parts 1 B, 1 C of the piece of sheet metal in the bent state by clamping these parts of the piece of sheet metal between the first tool 10 and said first and second parts 30a, 30b of the third tool 30, as illustrated in Fig 1 c.
  • the above-mentioned bulge of the first part 1A of the piece of sheet metal is flattened so that the piece of sheet metal 1 in the respective bending area B1 , B2 is subjected to compression in the extension direction of the piece of sheet metal transversally to the longitudinal direction of the bend.
  • Material is pressed from the first part 1 A of the piece of sheet metal into the respective bending area B1 , B2 by this flattening of the bulge of the first part 1A of the piece of sheet metal.
  • the piece of sheet metal 1 After this flattening of the first part 1 A of the piece of sheet metal, the piece of sheet metal 1 extends in a first bow over the edge surface 14 of the first bevelled edge 2 at the first bending area B1 and in a second bow over the edge surface 15 of the second bevelled edge 13 at the second bending area B2, while leaving a gap between the piece of sheet metal and the edge surface 14 of the first bevelled edge 12 on the inner side 3 of the first bending area B1 and a gap between the piece of sheet metal and the edge surface 1 5 of the second bevelled edge 1 3 on the inner side 3 of the second bending area B2.
  • the first and second tools 1 0, 30 are thereafter subjected to a continued mutual displacement in the direction towards each other, while the first part 1 A of the piece of sheet metal is retained in the flattened state between the first and second tools 1 0, 20, so that the respective bending area B 1 , B2 on the piece of sheet metal is pressed inwards by the third tool 30 against the adjacent edge surface 14, 1 5 of the first tool, as illustrated in Fig 1 d, so that tensile stress is developed in the respective bending area B 1 , B2 on the side of the neutral layer 8 facing the inner side 3 of the bending area and compressive stress is developed in the respective bending area on the side of the neutral layer 8 facing the outer side 4 of the bending area, as illustrated in Fig 2d.
  • the piece of sheet metal is in the first bending area B1 pressed in the direction towards the edge surface 14 of the first bevelled edge 1 2 under the effect of a shoulder 31 a arranged on the first part 30a of the third tool
  • the piece of sheet metal in the second bending area B2 is pressed in the direction towards the edge surface 1 5 of the second bevelled edge 1 3 under the effect of a shoulder 31 b arranged on the second part 30b of the third tool.
  • the respective shoulder 31 a, 31 b is inclined with an inclination corresponding to the inclination of the underlying edge surface 14, 1 5 of the first tool 1 0.
  • the formed piece of sheet metal 1 is finally released from the tools 1 0, 20 , 30.
  • the above-mentioned mutual displacements between the first and third tools 1 0, 30 may for instance be achieved by keeping the first tool 1 0 stationary while the third tool 30 is displaced in the direction towards the first tool, or alternatively by keeping the third tool 30 stationary while the first tool 1 0 is displaced in the direction towards the third tool .
  • the above-mentioned mutual displacement between the first and second tools 1 0, 20 may for instance be achieved by keeping the first tool 1 0 stationary while the second tool 20 is displaced in the direction towards the first tool, or alternatively by keeping the second tool 20 stationary while the first tool 1 0 is displaced in the direction towards the second tool.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Bending Of Plates, Rods, And Pipes (AREA)

Abstract

La présente invention a trait à un procédé de forçage à froid d'une pièce de tôle (1) par cintrage ou par moulage par presse, lequel procédé de forçage à froid inclut les étapes suivantes : - la pièce de tôle est cintrée au-dessus d'un bord biseauté (12, 13) d'un outil (10) de sorte que la pièce de tôle dans la zone de cintrage (B1, B2) est soumise à une contrainte de compression du côté intérieur et à une contrainte de traction du côté extérieur d'une couche neutre ; un écart est laissé entre la tôle et une surface de bord (14, 15) du bord biseauté ; - une force de compression est alors exercée sur la pièce de tôle à l'extérieur de la zone de cintrage, qui est comprimée de façon transversale vers la direction longitudinale du cintrage, après quoi une force de compression est exercée du côté extérieur de la zone de cintrage de sorte que la zone de cintrage est soumise à une contrainte de traction du côté intérieur et à une contrainte de compression du côté extérieur de la couche neutre.
PCT/SE2012/050302 2011-03-21 2012-03-20 Procédé de forçage à froid d'une pièce de tôle par cintrage ou par moulage par presse WO2012128707A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US14/006,212 US20140000336A1 (en) 2011-03-21 2012-03-20 Method of cold forming a piece of sheet metal by bending or press moulding
EP12760204.3A EP2688692A4 (fr) 2011-03-21 2012-03-20 Procédé de forçage à froid d'une pièce de tôle par cintrage ou par moulage par presse

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE1150251A SE535682C2 (sv) 2011-03-21 2011-03-21 Förfarande för kallformning av ett plåtstycke genom bockning eller pressformning
SE1150251-5 2011-03-21

Publications (1)

Publication Number Publication Date
WO2012128707A1 true WO2012128707A1 (fr) 2012-09-27

Family

ID=46879615

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE2012/050302 WO2012128707A1 (fr) 2011-03-21 2012-03-20 Procédé de forçage à froid d'une pièce de tôle par cintrage ou par moulage par presse

Country Status (4)

Country Link
US (1) US20140000336A1 (fr)
EP (1) EP2688692A4 (fr)
SE (1) SE535682C2 (fr)
WO (1) WO2012128707A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016087014A1 (fr) * 2014-12-04 2016-06-09 Audi Ag Procédé et système d'outils pour la production d'une pièce de tôle à former pourvue d'au moins un bord marquant
CN110475624A (zh) * 2017-03-28 2019-11-19 杰富意钢铁株式会社 冲压成形装置及冲压成形品的制造方法

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103990672B (zh) * 2014-05-07 2016-04-20 云嘉集团有限公司 高强钢冷冲压成形回弹控制方法
JP6376048B2 (ja) * 2015-06-16 2018-08-22 トヨタ車体株式会社 プレス成形方法及びプレス型
JP6504130B2 (ja) * 2016-08-03 2019-04-24 Ｊｆｅスチール株式会社 プレス成形品の製造方法
US10668516B2 (en) * 2016-09-01 2020-06-02 Fca Us Llc Post-compression for springback reduction
JP6777102B2 (ja) * 2017-12-13 2020-10-28 Ｊｆｅスチール株式会社 プレス成形方法
US11014225B2 (en) 2017-12-15 2021-05-25 Alfonso GARCIA MIRO PESCHIERA Workbench for the cold intervention, folding, bending, twisting or deformation of metal plates or sheets
MX2020011992A (es) * 2018-05-11 2021-09-02 Nippon Steel Corp Método de fabricación de artículo moldeado por prensado en forma de silla de montar, aparato de prensado y método de fabricación para fabricar artículo moldeado por prensado en forma de silla de montar.

Citations (3)

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Publication number Priority date Publication date Assignee Title
US3426569A (en) * 1967-01-31 1969-02-11 Cyril Bath Co Stretch forming machine and segmental adjustable die combination
US5657922A (en) * 1995-07-14 1997-08-19 Univ Oklahoma State Machine and process for forming tapered or cylindrical utility poles from flat sheet metal
GB2344546A (en) * 1998-12-10 2000-06-14 Belsize Engineering Company Li Bend forming apparatus

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JPS6182929A (ja) * 1984-09-28 1986-04-26 Toupure Kk 金属素板の曲げ方法
JP3550941B2 (ja) * 1997-04-25 2004-08-04 トヨタ自動車株式会社 プレス曲げ方法及び装置
JP5478906B2 (ja) * 2008-04-01 2014-04-23 キヤノン株式会社 曲げ加工装置、曲げ加工方法
JP4766084B2 (ja) * 2008-07-18 2011-09-07 トヨタ自動車株式会社 ワークの曲げ加工方法および装置

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3426569A (en) * 1967-01-31 1969-02-11 Cyril Bath Co Stretch forming machine and segmental adjustable die combination
US5657922A (en) * 1995-07-14 1997-08-19 Univ Oklahoma State Machine and process for forming tapered or cylindrical utility poles from flat sheet metal
GB2344546A (en) * 1998-12-10 2000-06-14 Belsize Engineering Company Li Bend forming apparatus

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP2688692A4 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016087014A1 (fr) * 2014-12-04 2016-06-09 Audi Ag Procédé et système d'outils pour la production d'une pièce de tôle à former pourvue d'au moins un bord marquant
CN110475624A (zh) * 2017-03-28 2019-11-19 杰富意钢铁株式会社 冲压成形装置及冲压成形品的制造方法
US11135634B2 (en) 2017-03-28 2021-10-05 Jfe Steel Corporation Press forming device and method for producing press-formed articles

Also Published As

Publication number Publication date
SE535682C2 (sv) 2012-11-06
SE1150251A1 (sv) 2012-09-22
EP2688692A1 (fr) 2014-01-29
EP2688692A4 (fr) 2014-08-27
US20140000336A1 (en) 2014-01-02

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