Metal deforming – With indication of condition or position of work – product,... – Work drawn or extruded through die
Patent
1996-09-12
1998-11-24
Jones, David
Metal deforming
With indication of condition or position of work, product,...
Work drawn or extruded through die
72 3111, 723893, 72702, B21D 502
Patent
active
058393102
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a press brake for bending a workpiece with an upper die and a lower die that is arranged in opposing relationship with the upper die, and more particularly to a press brake designed to measure the bending angles of a workpiece during a bending process so as to achieve high-accuracy bending work.
BACKGROUND ART
In a known press brake for performing V-shaped bending with an upper die (i.e., punch) and lower die (i.e., die) which press a sheet-like workpiece held between them, the amount of driving either the upper or lower die is controlled by an NC device according to information on the material and thickness of a workpiece being processed and on die conditions. It is difficult for such a punch press to accurately control the driving amount because of variations in the thickness and/or properties of material of the workpiece processed. To solve this problem, it has been proposed to measure the bending angles of the workpiece during a bending process to provide a feedback for modifying a subsequent driving amount for either of the dies to be driven (hereinafter referred to as "movable die") so that increased accuracy can be ensured in bending operation. In this case, the angle of springback (return to an original shape due to resilience) of the workpiece varies depending on the material and thickness of the workpiece, die conditions and the like, and it is therefore necessary to measure the springback angle by in-line processing.
In this respect, there have been made many attempts to achieve accurate computation of a final driving amount for the movable die. One example is set out in Japanese Patent Laid-Open Publication No. 1-228612 (1989) in which the amount of springback necessary for determining a final drive end for the movable die is automatically measured for every workpiece and the final drive end is calculated based on the measured amount of springback, a target bending angle and an actual bending angle.
Japanese Patent Laid-Open Publication No. 3-71922 (1991) discloses another example in which the workpiece is unloaded after it has been bent to a provisional drive end and a final drive end is calculated from changes in the pressure exerted on the workpiece during the unloading process.
These publications both require complicated arrangements for controlling the movable die and therefore the ram. in order to make springback angle measurements and this results in an extended processing period and less productivity.
Accordingly, the invention has been made with the purpose of overcoming the foregoing drawbacks and one of the objects of the invention is therefore to provide a press brake capable of bending sheet-like workpieces with high accuracy in a short time.
DISCLOSURE OF THE INVENTION
We have studied extensively with a view to solving the problems described earlier and finally come to the invention with the founding in which the springback angles of workpieces do not vary so much between lots and can be estimated with high accuracy by utilizing classification according to the material and thickness of workpieces, etc.
In one aspect, the invention (the principle of which is illustrated in FIG. 1) aims to provide a press brake for bending a workpiece with an upper die and a lower die that is arranged in opposing relationship with the upper die, the press brake comprising: conditions for the workpiece, (ii) the relationship between the target bending angle for the workpiece and the springback angle of the workpiece and (iii) the relationship between the bending angle of the workpiece and the amount of driving either movable one 1 (hereinafter referred to as "movable di( 1") of the upper and lower dies; workpiece during a bending process; the movable die 1 based on the information stored in the memory means 2 and for computing a final drive end for the movable die 1 based on the bending angle of the workpiece measured at the provisional drive end by the bending angle measuring means 3 and on the information stored in the memory means 2; and end
REFERENCES:
patent: 4430879 (1984-02-01), Rolland
patent: 4864509 (1989-09-01), Somerville et al.
patent: 5148693 (1992-09-01), Sartorio et al.
patent: 5285668 (1994-02-01), Tokai
patent: 5497647 (1996-03-01), Nagakura
Takada Masaaki
Tokai Shigeru
Jones David
Komatsu Ltd.
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