Method for Bending Metal Sheet to Achieve High Angle Accuracy

Patent metadata

Field	Value
Publication number	US-2016288184-A1
Application number	US-201615085009-A
Country	US
Kind code	A1
Filing date	Mar 30, 2016
Priority date	Mar 31, 2015
Publication date	Oct 6, 2016
Grant date	—

Abstract

A method for controlling the bending of a metal sheet includes the steps of: establishing a relational database on a relationship among material parameters, forming angles, amounts of springback, and amounts of press of an upper die; blanking and reverse-engineering a material parameter of a metal sheet to be processed; comparing the material parameters in the relational database with the material parameter of the metal sheet to be processed which is obtained by the reverse-engineering; and performing an bending operation.

First claim

What is claimed is:

1 . A method for controlling bending of a metal sheet comprising the steps of:
(1) establishing a relational database on a relationship among material parameters, forming angles, amounts of springback, and amounts of press of an upper die, the establishing including
establishing a finite element simulation model for forming based on a structure parameter of a die used for a bending process, obtaining a simulated amount of springback corresponding to a forming angle by inputting a material parameter of a metal sheet for a simulation into the finite element simulation model for the forming and thus simulating the bending process of the metal sheet for the simulation, and using the simulated amount of springback as an amount of springback to be added to the relational database, and
after measuring material parameters of different metal sheets, simulating the bending process of each different metal sheet based on the obtained finite element simulation model for the forming, and for each of the different metal sheets, establishing a relational database on a relationship among a material parameter, a forming angle, an amount of springback, and an amount of press of the upper die;
(2) blanking and reverse-engineering a material parameter of a metal sheet to be processed, the blanking and reverse-engineering including
blanking the metal sheet to be processed, and thereby obtaining a blank, and
obtaining an experimental load-stroke curve of the metal sheet to be processed during a blanking experiment by measurement, establishing a finite element simulation model using a method for reverse-engineering an actual physical parameter of the metal sheet, simulating the blanking, and repeatedly reverse-engineering the material parameter of the metal sheet to be processed,
(3) comparing the material parameters in the relational database with the material parameter of the metal sheet to be processed which is obtained by the reverse-engineering,
if a reference material parameter, between which and the material parameter of the metal sheet to be processed an error is less than a second threshold value, exists in the relational database, performing a bending operation, and
if a reference material parameter, between which and the material parameter of the metal sheet to be processed an error is less than a second threshold value, does not exist in the relational database, like in the establishing the relational database, simulating the bending process using the material parameter of the metal sheet to be processed which is obtained by the reverse-engineering, adding a relationship which is obtained by the simulation among the material parameter of the metal sheet to be processed, a forming angle, an amount of springback, and an amount of press of the upper die to the relational database, making the material parameter of the metal sheet to be processed which is obtained by the reverse-engineering become the reference material parameter of the metal sheet to be processed in the relational database, and subsequently performing the bending operation; and
(4) performing the bending operation, the performing including
inputting a bending angle, and
calculating a needed amount of press of the upper die based on a formula representing a relation between the forming angle corresponding to the reference material parameter and the amount of press of the upper die of the die of a bending machine for performing the bending operation, sending the needed amount of press of the upper die to the bending machine, and controlling the bending machine in a way that the bending machine bends the blank.

2 . The method for controlling bending of a metal sheet according to claim 1 , wherein the structure parameter of the die used for the bending process includes a draw radius of the upper die and an opening of a lower die in the die.

3 . The method for controlling bending of a metal sheet according to claim 1 , wherein
in order to establish the finite element simulation model for the forming, an actual amount of springback of the metal sheet for the simulation is obtained by performing a bending test, and a difference between the actual amount of springback and the simulated amount of springback is calculated, and if the difference is greater than a first threshold value, the simulation is repeatedly performed by refining a grid size of the finite element simulation model for the forming until the difference becomes less than the first threshold value.

4 . The method for controlling bending of a metal sheet according to claim 1 , wherein each material parameter used to establish the relational database on the relationship among the material parameters, the forming angles, the amounts of springback, and the amounts of press of an upper die includes a performance parameter and a flow stress curve of a material measured by a tensile test for detecting the material.

5 . The method for controlling bending of a metal sheet according to claim 1 , wherein the first threshold value is 2%.

6 . The method for controlling bending of a metal sheet according to claim 1 , wherein
the bending process is simulated, and a relationship between a different bending angle θ′ and an amount ΔH of press is recorded, subsequently, an amount Δθ of springback corresponding to the different bending angle θ′ is predicted using the finite element simulation model, and a relationship between the different bending angle θ′ and the amount Δθ of springback is obtained, and based on θ=θ′+Δθ representing a relationship among a forming angle θ, the bending angle θ′ and the amount Δθ of springback, a relationship between the forming angle θ and the amount ΔH of press is obtained

7 . The method for controlling bending of a metal sheet according to claim 1 , wherein the second threshold value is 1%.

8 . The method for controlling bending of a metal sheet according to claim 7 , wherein
if the reference material parameter, between which and the material parameter of the metal sheet to be processed an error is less than the second threshold value, does not exist in the relational database, the bending process is simulated by inputting the material parameter of the metal sheet to be processed, which is obtained by the reverse-engineering, into the finite element simulation model, thereby, a relationship between a forming angle θ of the metal sheet to be processed and an amount ΔH of press is obtained, and the relationship between the forming angle θ of the metal sheet to be processed and the amount ΔH of press is sent to the relational database.

Assignees

• Univ Shanghai Jiaotong
• Hitachi Ltd

Inventors

• Zhao Zhen
• Zhuang Xincun
• Zhao Xingfeng
• Tanaka Hideaki

Classifications

• G01N2203/0216

  Finite elements · CPC title

• G01N2203/0282

  Two dimensional, e.g. tapes, webs, sheets, strips, disks or membranes · CPC title

• G01N2203/0218

  Calculations based on experimental data · CPC title

• G06F30/20

  Design optimisation, verification or simulation (optimisation, verification or simulation of circuit designs G06F30/30) · CPC title

• G06F30/23

  using finite element methods [FEM] or finite difference methods [FDM] · CPC title