Method of bending workpiece to target bending angle accurately and press brake for use in the same method

• US 5,857,366 A
• Filed: 01/08/1997
• Issued: 01/12/1999
• Est. Priority Date: 07/08/1994
• Status: Expired due to Fees

• Current Assignee: Amada Company Limited
• Original Assignee: Amada Company Limited
• Inventors: Koyama, Junichi
• Primary Examiner(s): JONES, DAVID B
• Application Number:
  US08/765,170
• Time in Patent Office: 734 Days
• Field of Search: 72/17.3, 72/31.1, 72/21.5, 72/702, 72/389.3, 72/389.5
• US Class Current: 72/31.1
• CPC Class Codes: B21D 5/004 with program control
• CPC Class Codes: B21D 5/02 on press brakes without making use of clamping means
• CPC Class Codes: G05B 19/404 characterised by control arrangements for compensation, e.g. for backlash, overshoot, tool offset, tool wear, temperature, machine construction errors, load, inertia G05B19/19, G05B19/41 take precedence
• CPC Class Codes: G05B 2219/37205 Compare measured, vision data with computer model, cad data
• CPC Class Codes: G05B 2219/37357 Force, pressure, weight or deflection
• CPC Class Codes: G05B 2219/37403 Bending, springback angle
• CPC Class Codes: G05B 2219/45143 Press-brake, bending machine
• CPC Class Codes: G05B 2219/50063 Probe, measure, verify workpiece, feedback measured values

Abstract

A press brake for bending a sheet-shaped work between an upper tool and a lower die and a method of bending the work are provided. In the method, at first, bending angles at plural positions of the work are measured by a trial bending. Next, based on the bending angles obtained, an engagement positional relation between the upper tool and the lower die is corrected to achieve accurate bending of the work at a target bending angle in order to carry out the method, the press brake includes a control unit for calculating a D value of a distance from a bottom of the lower die to a tip of the upper tool.

Claims

1. A method of bending a sheet-shaped workpiece using a press brake in which said workpiece is pinched between an upper tool and a lower die while an engagement positional relationship between said upper tool and said lower die is controlled, said press brake further including an upper apron having said upper tool installed thereon, a lower apron having said lower die installed thereon and drive means for driving either one of said upper and lower aprons close to or apart from the other of said upper and lower aprons, and method comprising:

(a) calculating a theoretical D value indicating a theoretical engagement positional relationship between said upper tool and said lower die that corresponds to a target bending angle, according to workpiece information, die information and bending information;

(b) bending said workpiece while controlling said engagement positional relationship between said upper tool and said lower die, according to said theoretical D value;

(c) measuring bending angles of said workpiece at a plurality of positions after said bending and calculating a mean value of said bending angles;

(d) calculating a theoretical load value for bending said workpiece according to said mean value of said bending angles and calculating a theoretical mechanical deflection value based on said theoretical load value;

(e) detecting actual pressure applied on said drive means during said bending of said workpiece;

(f) calculating an actual mechanical deflection value based on said actual pressure;

(g) calculating a correction value for said D value according to a difference between said theoretical mechanical deflection value and said actual mechanical deflection value;

(h) correcting said engagement positional relationship between said upper tool and said lower die by adding said correction value to said D value and performing said bending of said workpiece again;

(i) repeating the above steps (c)-(h) until said mean bending angle of said workpiece reaches a value within a predetermined tolerance of said target bending angle;

(j) controlling said engagement positional relationship between said upper tool and said lower die such that said engagement positional relationship remains constant after said bending angle of said workpiece reaches said value constant after said bending angle of said workpiece reaches said value and repeating said bending a predetermined number of times in accordance with a quality of workpieces.

2. The method of bending a sheet-shaped workpiece using a press brake according to claim 1, wherein said drive means comprises a pair of hydraulic cylinders arranged on both sides of said lower apron, for driving said lower apron.

3. A method of bending a workpiece using a press brake while an engagement positional relationship between an upper tool and a lower die is controlled, said press brake further including an upper apron having said upper tool installed thereon, a lower apron having said lower die installed thereon, drive means for driving either one of said upper and lower aprons close to or apart from the other of said upper and lower aprons and crowning cylinders arranged under said lower apron to compensate for a downward curve during said bending, said method comprising:

calculating a theoretical D value indicating a theoretical engagement positional relationship between said upper tool and said lower die that corresponds to a target bending angle, according to workpiece information, die information and bending information;

bending said workpiece while controlling said engagement positional relationship between said upper tool and said lower die, according to said theoretical D value;

measuring bending angles of said workpiece at a plurality of positions after said bending and calculating a mean value of said bending angles;

calculating a theoretical load value for bending said workpiece according to said mean value of said bending angles and calculating a theoretical mechanical deflection value based on said theoretical load value;

detecting actual pressure applied on said drive means during said bending of said workpiece;

calculating an actual mechanical deflection value based on said actual pressure;

calculating a difference between said theoretical mechanical deflection value and said actual mechanical deflection value;

calculating an amount of deflection at a plurality of positions in a longitudinal direction of said lower apron in said press brake according to said difference between said theoretical deflection value and said actual mechanical deflection value and said bending angles of said workpiece at said plurality of positions, and converting said amount of deflection at said plurality of positions in said longitudinal direction to calculate bending angles at a plurality of corresponding positions of said workpiece;

calculating pressure to be applied on said crowning cylinders in said lower apron according to said calculated bending angles at said plurality of corresponding positions; and

curving said lower apron upward by applying said calculated pressures on said crowning cylinders to perform said bending of said workpiece with said upper tool and said lower die.

4. A method of bending a workpiece using a press brake while an engagement positional relationship between an upper tool and a lower die is controlled, said press brake further including an upper apron having said upper tool installed thereon, a lower apron having said lower die installed thereon, drive means for driving either one of said upper and lower aprons close to or apart from the other of said upper and lower aprons and crowning cylinders arranged under said lower apron to compensate for a downward curve during said bending, said method comprising;

calculating a theoretical D value indicating a theoretical engagement positional relationship between said upper tool and said lower die that corresponds to a target bending angle, according to workpiece information, die information and bending information;

bending said workpiece while controlling said engagement positional relationship between said upper tool and said lower die, according to said theoretical D value;

measuring bending angles of said workpiece at a plurality of positions after said bending and calculating a mean value of said bending angles;

calculating a theoretical load value for bending said workpiece according to said mean value of said bending angles and calculating a theoretical mechanical deflection value based on said theoretical load value;

detecting actual pressure applied on said drive means during said bending of said workpiece;

calculating an actual mechanical deflection value based on said actual pressure;

calculating a difference between said theoretical mechanical deflection value and said actual mechanical deflection value;

calculating an amount of deflection at a plurality of positions in a longitudinal direction of said lower apron in said press brake according to said difference between said theoretical deflection value and said actual mechanical deflection value and said bending angles of said workpiece at said plurality of positions, and converting said amount of deflection at said plurality of positions in said longitudinal direction to calculate bending angles at a plurality of corresponding positions of said workpiece;

calculating pressure to be applied on said crowning cylinders in said lower apron according to said calculated bending angles at said plurality of corresponding positions;

calculating bending angles of both sides of said workpiece which are bent by applying said calculated pressures on said crowning cylinders, and calculating an amount of correction for said D value according to said calculated bending angles; and

calculating an instructive value according to a correction amount for said D value and said theoretical D value and controlling said upper tool and said lower die according to said instructive values to perform said bending of said workpiece.

5. A method of bending a sheet-shaped workpiece using a press brake in which said workpiece is pinched between an upper tool and a lower die while an engagement positional relationship between said upper tool and said lower die is controlled, said press brake further including an upper apron having said upper tool installed thereon, a lower apron having said lower die installed thereon and drive means for driving either one of said upper and lower aprons close to or apart from the other of said upper and lower aprons, said method comprising:

(a) calculating a theoretical D value indicating a theoretical engagement positional relationship between said upper tool and said lower die that corresponds to a target bending angle, according to workpiece information, die information and bending information;

(b) calculating a theoretical load value according to said workpiece information, said die information and said bending information, and calculating a theoretical mechanical deflection value according to said theoretical load value;

(c) calculating an instructive D value indicating said engagement positional relationship between said upper tool and said lower die according to said theoretical D value and said theoretical mechanical deflection value and performing bending of said workpiece according to said instructive D value;

(d) measuring bending angles of said workpiece at a plurality of positions after said bending and calculating a mean value of said bending angles;

(e) calculating a theoretical load value for bending said workpiece according to said mean value of said bending angles and calculating a theoretical mechanical deflection value based on said theoretical load value;

(f) detecting actual pressure applied on said drive means during said bending of said workpiece;

(g) calculating an actual mechanical deflection value based on said actual pressure;

(h) calculating a correction value for said instructive D value according to a difference between said theoretical mechanical deflection value and said actual mechanical deflection value;

(i) correcting said engagement positional relationship between said upper tool and said lower die by adding said correction value to said D value and performing said bending of said workpiece again;

(j) repeating the above steps (d)-(i) until said mean value of said bending angle of said workpiece reaches an acceptable value within a predetermined tolerance of said target bending angle;

(k) controlling said engagement positional relationship between said upper tool and said lower die such that said engagement positional relationship remains constant after said mean value of said bending angle of said workpiece reaches said acceptable value and repeating said bending in accordance with a predetermined quantity of workpieces.

6. A press brake in which a sheet-shaped workpiece is pinched between an upper tool and a lower die while an engagement positional relationship between said upper tool and said lower die is controlled to perform bending of said workpiece, said press brake comprising:

means for calculating a theoretical D value indicating a theoretical engagement positional relationship between said upper tool and said lower die that corresponds to a target bending angle, according to workpiece information, die information and bending information;

means for bending said workpiece while controlling said engagement positional relationship between said upper tool and said lower die, according to said theoretical D value;

means for measuring bending angles of said workpiece at a plurality of positions after said bending and calculating a mean value of said bending angles;

means for calculating a theoretical load value for bending said workpiece at said mean value of said bending angles and calculating a theoretical mechanical deflection value based on said theoretical load value; and

means for calculating a correction value for said theoretical D value according to said theoretical mechanical deflection value.

7. A press brake in which a sheet-shaped workpiece is pinched between an upper tool and a lower die while an engagement positional relationship between said upper tool and said lower die is controlled to perform bending of said workpiece, said press brake comprising:

an upper apron having said upper tool installed thereon;

a lower apron having said lower die installed thereon;

drive means for driving either one of said upper and lower aprons close to or apart from the other of said upper and lower aprons;

means for calculating a theoretical D value indicating a theoretical engagement positional relationship between said upper tool and said lower die that corresponds to a target bending angle according to workpiece infomation, die information, and bending information;

means for bending said workpiece while controlling said engagement positional relationship between said upper tool and said lower die according to said theoretical D value;

means for measuring bending angles of said workpiece at a plurality of positions after said bending and calculating a mean value of said bending angles;

means for calculating a theoretical load value for bending said workpiece at said mean value of said bending angles and calculating a theoretical mechanical deflection value based on said theoretical load value;

means for detecting actual pressures applied on said drive means during said bending of said workpiece;

means for calculating an actual mechanical deflection value based on said actual pressure; and

means for calculating a correction value for said theoretical D value according to a difference between said theoretical mechanical deflection value and said actual mechanical deflection value.

8. A press brake for bending a workpiece by controlling an engagement positional relationship between an upper tool and a lower die, said press brake comprising;

an upper apron having said upper tool installed thereon;

a lower apron having said lower die installed thereon;

drive means for driving either one of said upper and lower aprons close to or apart from the other of said upper and lower aprons;

crowning cylinders arranged under said lower apron to compensate for a downward curve during said bending,

means for calculating a theoretical D value indicating a theoretical engagement positional relationship between said upper tool and said lower die that corresponds to a target bending angle according to workpiece information, die information and bending information;

means for bending said workpiece while controlling said engagement positional relationship between said upper tool and said lower die according to said theoretical D value;

means for measuring bending angles of said workpiece at a plurality of positions after said bending and calculating a mean value of said bending angles;

means for calculating a theoretical load value for bending said workpiece at said mean value of said bending angles and calculating a theoretical mechanical deflection value based on said theoretical load value;

means for detecting actual pressure applied on said drive means during said bending of said workpiece;

means for calculating an actual mechanical deflection value based on said actual pressure;

means for calculating a difference between said theoretical mechanical deflection value and said actual mechanical deflection value;

means for calculating an amount of deflection at a plurality of positions in a longitudinal direction of said lower apron in said press brake and converting said amount of deflection at said plurality of positions bending angles at a plurality of corresponding positions of said workpiece;

means for calculating pressures to be applied on said crowning cylinders in said lower apron according to said calculated bending angles at said plurality of corresponding positions;

means for calculating bending angles of both sides of said workpiece which are bent by applying said calculated pressure to said crowning cylinders and calculating a correction value for said D value according to said calculated bending angles; and

means for calculating an instructive value according to said correction value for said theoretical D value and said theoretical D value and controlling said engagement positional relationship between said upper tool and said lower die according to said instructive value to perform said bending of said workpiece.

9. A press brake in which a sheet-shaped workpiece is pinched between an upper tool and a lower die while an engagement positional relationship between said upper tool and said lower die is controlled to perform bending said workpiece, said press brake comprising:

an upper apron having said upper tool installed thereon;

a lower apron having said lower die installed thereon;

drive means for driving either one of said upper and lower aprons close to or apart from the other of said upper and lower aprons;

means for calculating a theoretical D value indicating a theoretical engagement positional relationship between said upper tool and said lower die that corresponds to a target bending angle according to workpiece information, die information and bending information;

means for calculating a theoretical load value according to said workpiece information, die information and bending information and calculating a theoretical mechanical deflection value according to said theoretical load value;

means for calculating an instructive D value indicating said engagement positional relationship between said upper tool and said lower die according to said theoretical D value and a theoretical mechanical deflection value and performing bending said workpiece according to said instructive D value;

means for measuring bending angles of said workpiece at a plurality of positions after said bending and calculating a mean value of said bending angles;

means for calculating a theoretical load value for bending said workpiece according to said mean value of said bending angles and calculating a theoretical mechanical deflection value based on said theoretical load value;

means for detecting actual pressure applied on said drive means during said bending of said workpiece;

means for calculating an actual mechanical deflection value based on said actual pressure;

means for calculating a correction value for said theoretical D value according to a difference between said theoretical mechanical deflection value and said actual mechanical deflection value; and

means for correcting said engagement positional relationship between said upper tool and said lower die by adding said correction value to said instructive D value and performing said bending said workpiece again.

10. A press brake for bending a workpiece between a punch and a die by reciprocating at least one of an upper table and a lower table, said punch being provided on a bottom of said upper table and said die being provided on a top of said lower table and having a V-shaped groove, said press brake including a control unit for calculating and controlling a distance D from a bottom of said die to a tip of said punch, said control unit of said press brake comprising:

means for inputting bending information relating to said punch, said die and said workpiece;

means for determining whether said workpiece is winding around said tip of said punch in accordance with said bending information inputted into said input means;

means for calculating an amount of spring-back of said workpiece in accordance with a result by said workpiece winding determination means;

air bend/bottoming determination means for determining whether said workpiece is bent under air-bend condition or bottoming condition by said amount of spring-back and a target angle;

means for calculating a workpiece pinching angle when said air bend/bottoming determination means determines bending under said air-bend condition;

means for calculating pressure to be applied at said workpiece pinching angle calculated by said workpiece pinching angle calculating means; and

means for calculating a position of one of said upper table and said lower table to be moved when said workpiece is pinched at said workpiece pinching angle.

11. The press brake according to claim 10, further comprising:

means for calculating a mechanical deflection of said press brake according to said pressure applied at said workpiece pinching angle; and

means for calculating a final table position according to said position of said one of said upper table and said lower table to be moved and said mechanical deflection.

12. A press brake for bending a workpiece between a punch and a die by reciprocating at least one of an upper table and said lower table, said punch being provided on a top of said lower table and having a V-shaped groove, said press brake including a control unit for calculating and controlling a distance D from a bottom of said die to a tip of said punch, said control unit of said press brake comprising:

means for inputting bending information relating to said punch, said die and said workpiece;

means for determining whether said workpiece is winding around said tip of said punch in accordance with said bending information inputted into said input means;

means for calculating an amount of spring-back of said workpiece in accordance with a result by said workpiece winding determination means;

air bend/bottoming determination means for determining whether said workpiece is bent under air/bend condition or bottoming condition by said amount of spring-back and a target angle;

means for calculating a workpiece pinching angle when said air bend/bottoming determination means determines bending under said bottoming condition;

means for calculating pressure to be applied at said workpiece pinching angle calculated by said workpiece pinching angle calculating means;

means for calculating a first boundary load value between a bottoming area where said workpiece is bent under said bottoming condition and an air bend area where said workpiece is bent under said air bend condition, said first boundary load value existing on the side of said bottoming area;

means for calculating a second boundary load value between said bottoming area and said air bend area, said second boundary load value existing on the side of said air bend area;

means for calculating a load value required for said bottoming by shifting said first boundary load value to said boundary load value; and

means for calculating a position of one of said upper table and said lower table to be moved when said workpiece is pinched at said workpiece pinching angle.

13. The press brake according to claim 12, further comprising:

means for calculating a mechanical deflection of said press brake according to said pressure applied at said workpiece pinching angle;

means for calculating a final table position according to said position of said one of said upper table and said lower table to be moved and said mechanical deflection.