Bending angle correction method and press brake

• US 6,189,364 B1
• Filed: 04/20/1999
• Issued: 02/20/2001
• Est. Priority Date: 10/29/1996
• Status: Expired due to Fees

• Current Assignee: Komatsu Industries Corporation (Komatsu Ltd.), Komatsu Ltd.
• Original Assignee: Komatsu Ltd.
• Inventors: Takada, Masaaki
• Primary Examiner(s): JONES, DAVID B
• Application Number:
  US09/284,772
• Time in Patent Office: 672 Days
• Field of Search: 72/311, 72/311.1, 72/311.2, 723/893, 723/894, 723/895, 727/02
• US Class Current: 72/702
• CPC Class Codes: B21D 5/02 on press brakes without making use of clamping means
• CPC Class Codes: B30B 1/186 Control arrangements
• CPC Class Codes: G05B 19/41 characterised by interpolation, e.g. the computation of intermediate points between programmed end points to define the path to be followed and the rate of travel along that path G05B19/25, G05B19/31, G05B19/37, G05B19/39, G05B19/40 take precedence
• CPC Class Codes: G05B 2219/36486 Memorize workpiece deviations as function of angle, compensate, extra feed
• CPC Class Codes: G05B 2219/37582 Position, angle of workpiece surface
• CPC Class Codes: G05B 2219/45143 Press-brake, bending machine

Abstract

A bend angle correction method directed to carrying out simple and accurate penetration of a movable die into a fixed die to produce a uniform angle throughout the length of a workpiece, being unaffected by material variations. When bending a sheet-like workpiece to a desired angle by the cooperative movement of a movable punch driven by three or more drive shafts and a fixed die disposed in an opposing relationship with the movable die, the bend angle of the workpiece is measured during bending operation and the difference between the measured bend angle and a target angle is obtained, at at least three points which are the ends and center of the workpiece. Based on the differences, correction amounts for the penetration of the movable die are obtained on a shaft-load imposed point basis.

Claims

1. A bend angle correction method for correcting a bend angle when bending a workpiece by the cooperative movement of a movable die and a fixed die, the movable die being driven at shaft-load imposed points, for penetration, by three or more drive shafts, and the fixed die being disposed in an opposing relationship with the movable die, comprising:

(a) providing memory means, and storing in said memory means workpiece bending conditions, workpiece target bend angle to springback angle relationship data and workpiece bend angle to movable die penetration amount relationship data;

(b) providing measuring means and measuring the bend angle of the workpiece during bending operation and obtaining the difference between a target bend angle and the measured bend angle at at least three points, that are, each end and a center of the workpiece;

(c) providing calculating means, and calculating with said calculating means, a provisional penetration point of the movable die associated with each drive shaft, based on the workpiece bending conditions and the workpiece target bend angle to springback angle relationship data which are stored in the memory means, and calculating a corrective penetration amount of the movable die associated with each angle measuring point, based on the bend angle of the work piece measured by the bend angle measuring means when each provisional penetration point has been reached and based on the workpiece target bend angle to springback angle relationship data and the workpiece bend angle to movable die penetration amount relationship data which are stored in the memory means;

(d) providing interpolating means and obtaining, by interpolation, a final penetration point of the movable die associated with each shaft-load imposed point of the movable die, from the corrective penetration amounts calculated by the calculating means; and

(e) driving the movable die, with use of the die driving means, until each shaft-load imposed point of the movable die reaches its final penetration point, after driving it until each shaft-load imposed point reaches its provisional penetration point.

2. A press brake for bending a workpiece by the cooperative movement of a movable die and a fixed die, the movable die being driven at shaft-load imposed points, for penetration, by three or more drive shafts, and the fixed die being disposed in an opposing relationship with the movable die, the press brake comprising:

(a) memory means for storing workpiece bending conditions, workpiece target bend angle to springback angle relationship data and workpiece bend angle to movable die penetration amount relationship data;

(b) bend angle measuring means for measuring, during bending operation, the bend angle of the workpiece at at least three points that are located along the length of the workpiece;

(c) calculating means for calculating a provisional penetration point of the movable die associated with each drive shaft based on the workpiece bending conditions and the workpiece target bend angle to springback angle relationship data which are stored in the memory means, and for calculating a corrective penetration amount of the movable die associated with each angle measuring point, based on the bend angle of the workpiece measured by the bend angle measuring means when each provisional penetration point has been reached and based on the workpiece target bend angle to springback angle relationship data and the workpiece bend angle to movable die penetration amount relationship data which are stored in the memory means;

(d) interpolating means for obtaining, by interpolation, a final penetration point of the movable die associated with each shaft-load imposed point of the movable die, from the corrective penetration amounts calculated by the calculating means; and

(e) die driving means for driving the movable die until each shaft-load imposed point of the movable die reaches its final penetration point, after driving it until each shaft-load imposed point reaches its provisional penetration point.

3. A press brake according to claim 2, wherein said interpolating means calculates the final penetration point associated with each shaft-load imposed point, based on a crowning correction value and an inclination correction value,

said crowning correction value being obtained from a deflection difference of a bed for supporting the fixed die, the deflection difference being the difference in deflection between the bed position corresponding to a center of the workpiece and a line connecting bed positions that correspond to ends of the workpiece,

said inclination correction value being obtained from the crowning correction value and the difference in deflection between the bed positions corresponding to the ends of the workpiece.

4. A press brake according to claim 3, wherein said bend angle measuring means is so mounted as to be movable along rails in a lengthwise direction of the bed, said rails being laid on a front face and/or a back face of the bed for supporting the fixed die.

5. A bend angle correction method for correcting a bend angle when bending a short workpiece with the length of bend much shorter than the length of a bending machine, by the cooperative movement of a movable die and a fixed die, the movable die being driven at shaft-load imposed points, for penetration, by three or more drive shafts, and the fixed die being disposed in an opposing relationship with the movable die, comprising

(a) providing memory means, and storing in said memory means, workpiece bending conditions, workpiece target bend angle to springback angle relationship data and workpiece bend angle to movable die penetration amount relationship data;

(b) providing measuring means and measuring the bend angle of the workpiece during bending operation and obtaining the difference between a target bend angle and the measured bend angle, at at least one point located along the length of the workpiece;

(c) providing calculating means, and calculating with said calculating means, a provisional penetration point of the movable die associated with each drive shaft, based on the workpiece bending conditions and the workpiece target bend angle to springback angle relationship data which are stored in the memory means, and calculating a corrective penetration amount of the movable die associated with each angle measuring point, based on the bend angle of the workpiece measured by the bend angle measuring means when each provisional penetration point has been reached and based on the workpiece target bend angle to springback angle relationship data and the workpiece bend angle to movable die penetration amount relationship data which are stored in the memory means;

(d) providing interpolating means, and obtaining by interpolation, a final penetration point of the movable die associated with each shaft-load imposed point of the movable die, from the corrective penetration amounts calculated by the calculating means; and

(e) driving the movable die, with use of the die driving means, until each shaft-load imposed point of the movable die reaches its final penetration point, after driving it until each shaft-load imposed point reaches its provisional penetration point.

6. A press brake for bending a short workpiece with the length of bend much shorter than the length of the press brake, by the cooperative movement of a movable die and a fixed die, the movable die being driven at shaft-load imposed points, for penetration, by three or more drive shafts, and the fixed die being disposed in an opposing relationship with the movable die, the press brake comprising:

(a) memory means for storing workpiece bending conditions, workpiece target bend angle to springback angle relationship data and workpiece bend angle to movable die penetration amount relationship data;

(b) bend angle measuring means for measuring, during bending operation, the bend angle of the workpiece at at least one point that is located along the length of the workpiece;

(c) calculating means for calculating a provisional penetration point of the movable die associated with each drive shaft based on the workpiece bending conditions and the workpiece target bend angle to springback angle relationship data which are stored in the memory means, and for calculating a corrective penetration amount of the movable die associated with each angle measuring point, based on the bend angle of the workpiece measured by the bend angle measuring means when each provisional penetration point has been reached and based on the workpiece target bend angle to springback angle relationship data and the workpiece bend angle to movable die penetration amount relationship data which are stored in the memory means;

(d) interpolating means for obtaining, by interpolation, a final penetration point of the movable die associated with each shaft-load imposed point of the movable die, from the corrective penetration amounts calculated by the calculating means; and

(e) die driving means for driving the movable die until each shaft-load imposed point of the movable die reaches its final penetration point, after driving it until each shaft-load imposed point reaches its provisional penetration point.

7. A press brake according to claim 6, wherein said interpolating means calculates the final penetration point for each shaft-load imposed point, by linear interpolation of the corrective penetration amounts of the movable die associated with the angle measuring points located at ends of the workpiece.

8. A press brake according to claim 6 or 7, wherein said bend angle measuring means is so mounted as to be movable along rails in a lengthwise direction of a bed for supporting the fixed die, said rails being laid on a front face and/or a back face of the bed for supporting the fixed die.