EP1480767A1 - Procede de reduction des erreurs d'angle de pliage lors du pliage - Google Patents

Procede de reduction des erreurs d'angle de pliage lors du pliage

Info

Publication number
EP1480767A1
EP1480767A1 EP03704093A EP03704093A EP1480767A1 EP 1480767 A1 EP1480767 A1 EP 1480767A1 EP 03704093 A EP03704093 A EP 03704093A EP 03704093 A EP03704093 A EP 03704093A EP 1480767 A1 EP1480767 A1 EP 1480767A1
Authority
EP
European Patent Office
Prior art keywords
bending
force
sheet
linear axes
angle
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.)
Withdrawn
Application number
EP03704093A
Other languages
German (de)
English (en)
Inventor
Christian Juricek
Kurt SCHRÖDER
Christian Zeinar
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.)
Juricek Christian
SCHROEDER, KURT
Zeinar Christian
Original Assignee
Juricek Christian
Schroder Kurt
Zeinar Christian
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 Juricek Christian, Schroder Kurt, Zeinar Christian filed Critical Juricek Christian
Publication of EP1480767A1 publication Critical patent/EP1480767A1/fr
Withdrawn legal-status Critical Current

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
    • B21D5/02—Bending sheet metal along straight lines, e.g. to form simple curves on press brakes without making use of clamping means

Definitions

  • the present invention describes a method for reducing the bending angle errors when bending a sheet in a die bending press consisting of a fixed lower tool (die) and a bending beam driven by linear axes with the upper tools (bending punch), the lower reversal point of the bending punch being based on the preset desired value of Bending angle and the force-path curve measured during the bending process is calculated in advance.
  • Die bending is a widely used process in sheet metal working.
  • Well-known bending machines consist of a C-frame on whose lower tool carrier the lower tools are attached in the form of mostly V-shaped dies.
  • the matching mostly knife-shaped upper tools are mounted on a movable press beam. This press beam is moved in the vertical direction by two linear axes arranged at its ends, which are usually driven hydraulically.
  • Bending in the die is usually carried out as free bending, i.e. the sheet lies only at two points on the V-die and at one point on the punch (viewed in cross-section).
  • the bending angle results from the lower reversing position of the bending punch.
  • This process is in contrast to embossing, in which the punch is moved into the die until there is a positive connection between the die, sheet and punch.
  • Embossing can be used to produce very precise bending angles, however, a separate tool set and 4 - 6 times the pressing force (compared to free bending) are required for each bending angle and sheet thickness, which is why this process is rarely used. In contrast, many different bending angles can be produced with a tool set when bending freely.
  • a limitation with free bending is the reduced accuracy of the bending angle achieved, which is a consequence of the springback of the sheet after the bending punch has been withdrawn from the lower reversal point.
  • the press controls of the bending presses predominantly used according to the state of the art today determine the springback to be expected on the basis of simple, mostly empirical formulas and the material parameters or workpiece dimensions entered by the operator, and then drive with them Bending punch to a slightly lower position, which leads to a "bending over" of the sheet. Ideally, the desired bending angle is then set after the load has been removed.
  • the springback angle must be measured and taken into account individually - at least for each sheet type and workpiece geometry - which is done in a two-stage process according to the state of the art.
  • a first bending step the desired end angle is not yet bent.
  • the bending punch then withdraws so far that the springback can be measured using an angle measuring system.
  • ⁇ then overbend based on the determined actual springback angle to such an extent that the desired end angle is set with an accuracy of a few 0.1 °.
  • Bending with the aid of such systems means a reduction in productivity due to the longer duration of the bending process, and the angle measuring systems used are often expensive, complicated to use or can only be used in special cases.
  • two force transducers are used in the area of the hydraulic axes used in the present case or two pressure transducers in the hydraulic system, which represents a certain additional effort compared to presses without force-displacement detection.
  • the measurement of the punch path is implemented as standard in almost all bending presses of modern design, since the corresponding data are also required for precise control of the movement of the press beam.
  • two displacement transducers are usually used for this purpose, which are fastened in the area of the linear axes of the press beam and deliver displacement signals with a resolution of the order of 20 ⁇ m.
  • the force during bending in the die is recorded at two points, that is to say, only the total force composed of two components, which is introduced along the entire bending length, is essentially available for the calculation of the material properties. Since the force transducers are permanently connected to the press, they must cover a large measuring range; they have to work both on a thin sheet with a small bending length and on a thick sheet with a large bending length. For this reason, poor accuracy can only be achieved at the lower limit of the measuring range.
  • the force introduced per length is primarily responsible for the characterization of the bending process.
  • the bending length must also be known in order to determine the relevant one to determine size "force per unit length". Since this value is not measured automatically in accordance with the prior art, the press control must be informed of the bending length before each bending operation, which means an additional complication.
  • the material properties often vary over the bending length, which is why essential information is lost when measuring the total force. An unevenness of the sheet metal or a bending punch that is not exactly parallel to the die on the sheet metal can lead to a falsification of the force-travel relationship.
  • the die With larger bending lengths or with high bending forces, according to the state of the art, the die is often prestressed in such a way that it bends slightly upwards in the unloaded state, so that it does not have any overall bending under load due to the inevitable superimposed bending in the opposite direction.
  • This deformation of the die referred to as “crowning" also produces a distortion of the force-displacement profile.
  • the device for force measurement is integrated directly into the upper tools. Since bending punches in the generally customary embodiment according to the prior art are composed of segments of a length of approximately 50 to 400 mm, the length of such a segment - especially in the case of narrow segments - is almost homogeneous. The shorter the length of the segment is chosen, the more precisely the actual force per length can be absorbed. Piezoelectric force transducers of a known type are preferably used to measure the force. Since the force range in which a bending punch of a certain design can be used is precisely defined, the force sensor can be easily adapted to the measuring range that occurs, which guarantees high-resolution measurement results. As long as it is ensured that the tool segment with the force sensor is fully seated on the sheet, the measurement result is also independent of the total bending length.
  • the force-travel relationship is recorded on one or more segments of the upper tool and fed to the press control according to the claimed method.
  • the press control determines this The lower reversal points for the linear axes of the bending press.
  • the length-resolved force measurement can also resolve fluctuations in the sheet properties over the bending length.
  • this is a fluctuating sheet thickness or varying material properties, which is particularly relevant when processing hot-rolled sheets.
  • different lower reversal points are calculated for the two linear axes of the bending press in order to best compensate for this variation over the length and to maintain a constant bending angle over the entire length.
  • the adjustment of the crown of the lower tool which is carried out according to known methods, also offers an additional degree of freedom in order to compensate for fluctuations in the sheet properties over the bending length.
  • three bending punches equipped with force transducers are therefore used, two in the edge regions of the sheet and one in the middle.
  • the three recorded force-displacement relationships are used to determine suitable reversal points of the linear axes in the press controls and a suitable setting of the crowning in order to obtain the desired bending angle.
  • the force-displacement relationship during the bending process contains a lot of information about the material used.
  • the modulus of elasticity, the plug-in limit and the tensile strength are included.
  • the position of the punch at the time of the force increase provides the actual sheet thickness at the respective measuring position.
  • the characteristic values of the material derived from this context are used to characterize the material without a priori information and then to control the bending process accordingly.
  • additional information on the recognized material stored in a database can also be included in the control of the bending process.
  • the linkage of the input data in the form of the force-travel relationship with the output data is implemented in the press control system.
  • mented neural network By evaluating each individual or selected bending process, in one embodiment of the invention, for example by measuring the bending angle achieved, this network learns from bend to bend, so that the bending results improve over time on their own.
  • the force-displacement relationship recorded is used to adapt a numerical model to the respective material and the actual geometry.
  • the model calculates the bending line of the sheet, as well as the forces and moments that occur.
  • the method according to the invention is able to ensure reproducible bending angles despite fluctuating material properties.
  • this error is excluded by using an angle measuring method according to the prior art in order to obtain feedback on the efficiency of the process control via the force-travel relationship. The angle measured in this way is used to modify the control algorithm of the press control for better results.
  • Figure 1 shows an example of an arrangement for performing the method according to the invention.
  • FIG. 2 shows a detail of a segment of the upper tool with an integrated device for force measurement.
  • a hydraulic die bending press of known design consisting of the C-frame (1) on which the lower tool holder (2) and two hydraulic linear axes (3) are mounted.
  • the two hydraulic linear axes (3) carry the movable press beam (drawn before bending (4a) and during bending (4b)), on which the bending punches are attached in the form of several segments (5).
  • the lower tool carrier (2) is also equipped with several bending dies (6). To measure the position of the punch relative to the Bending dies two position sensors (7) are used in a known manner.
  • One or more bending punches of the die bending press shown is or are now equipped according to the invention with a device for force measurement (8) which supplies an electrical signal as a function of the force acting.
  • the electrical signals of the displacement transducers (7), the force transducers (8) and the control signals for the linear axes (3) are brought together in the controller (9).
  • the control generates the signals for controlling the two linear axes from the displacement and force signals as well as the user input.
  • FIG. 2 shows in detail a preferred embodiment of the force transducer on a bending punch.
  • Two fastening pins (10) are screwed onto the bending punch (5), between which a piezoelectric force transducer (8) of known design is clamped.
  • the cylindrical force transducer releases an electrical charge proportional to the axial change in length, which is fed to a charge amplifier in a known manner through a cable (11).
  • a charge amplifier in a known manner through a cable (11).
  • the disturbance in the voltage distribution introduced by the force sensor is negligible.
  • the piezoelectric sensor produces an electric charge proportional to the force.

Landscapes

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

Abstract

L'invention concerne un procédé permettant de réduire les erreurs d'angle de pliage lors du cintrage de tôles dans une presse de pliage comprenant un outil inférieur (6) fixe et une barre de cintrage (4a, 4b) entraînée par des axes linéaires (3) avec les outils supérieurs (8). Le point d'arrêt inférieur du poinçon de matriçage est calculé au préalable sur la base de la valeur théorique préajustée de l'angle de pliage et de la courbe de l'allure force-parcours mesurée. L'allure de la courbe force-parcours est mesurée par capteur de parcours (7) et par capteur de force (8) et est traitée dans la commande (9).
EP03704093A 2002-02-27 2003-02-26 Procede de reduction des erreurs d'angle de pliage lors du pliage Withdrawn EP1480767A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
AT3002002A AT411022B (de) 2002-02-27 2002-02-27 Verfahren zur reduktion der biegewinkelfehler beim gesenkbiegen
AT3002002 2002-02-27
PCT/AT2003/000057 WO2003072278A1 (fr) 2002-02-27 2003-02-26 Procede de reduction des erreurs d'angle de pliage lors du pliage

Publications (1)

Publication Number Publication Date
EP1480767A1 true EP1480767A1 (fr) 2004-12-01

Family

ID=3671121

Family Applications (1)

Application Number Title Priority Date Filing Date
EP03704093A Withdrawn EP1480767A1 (fr) 2002-02-27 2003-02-26 Procede de reduction des erreurs d'angle de pliage lors du pliage

Country Status (4)

Country Link
EP (1) EP1480767A1 (fr)
AT (1) AT411022B (fr)
AU (1) AU2003206492A1 (fr)
WO (1) WO2003072278A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109940062A (zh) * 2019-03-28 2019-06-28 燕山大学 一种模型与数据耦合驱动的弯曲回弹补偿方法

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ITPR20040088A1 (it) * 2004-12-13 2005-03-13 Schiavi Macchine Ind Spa Metodo e dispositivo per la determinazione dello spessore o del ritorno elastico di un pezzo piegato con una pressa piegatrice.
CN102708222B (zh) * 2006-08-31 2014-11-26 新日铁住金株式会社 回弹发生原因特定方法、回弹发生原因部位特定方法、回弹对策位置特定方法以及它们的装置
CN101564745B (zh) * 2008-12-26 2011-02-02 北京机电院高技术股份有限公司 一种上转轴弯曲装置
AT515672B1 (de) * 2014-09-11 2015-11-15 Trumpf Maschinen Austria Gmbh Biegepresse
CN109101736A (zh) * 2018-08-22 2018-12-28 上海博汇模具有限公司 一种用于高张力板件的整体补偿方法
CN110303075A (zh) * 2019-05-31 2019-10-08 郑州九冶三维化工机械有限公司 一种钢箱梁u肋制作的胎具
EP4140611A1 (fr) * 2021-08-23 2023-03-01 Bystronic Laser AG Machine à plier, en particulier presse plieuse, pourvue de système de mesure de distance

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US4408471A (en) * 1980-10-29 1983-10-11 Massachusetts Institute Of Technology Press brake having spring-back compensating adaptive control
AT374706B (de) * 1982-06-07 1984-05-25 Haemmerle Ag Verfahren zum blechbiegen und biegeeinrichtung zur ausuebung des verfahrens
US4511976A (en) * 1982-07-06 1985-04-16 Cincinnati Incorporated Press brake having spring back compensation stroke reversal control
JP3136183B2 (ja) * 1992-01-20 2001-02-19 株式会社日立製作所 制御方法
DE19738955C2 (de) * 1997-09-05 2003-01-09 Audi Ag Verfahren zur Regelung eines Umformprozesses
JPH11347635A (ja) * 1998-06-12 1999-12-21 Amada Eng Center Co Ltd 曲げ角度制御方法及びその装置
KR100519521B1 (ko) * 1999-10-07 2005-10-05 무라타 기카이 가부시키가이샤 굽힘기계 및 그 운전방법

Non-Patent Citations (1)

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See references of WO03072278A1 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109940062A (zh) * 2019-03-28 2019-06-28 燕山大学 一种模型与数据耦合驱动的弯曲回弹补偿方法

Also Published As

Publication number Publication date
WO2003072278A1 (fr) 2003-09-04
ATA3002002A (de) 2003-02-15
AU2003206492A1 (en) 2003-09-09
AT411022B (de) 2003-09-25

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