US 2004/0111177 A1Published application

Method for setting the travel of a press brake

AssigneeBystronic Laser AG

InventorsGerrit Gerritsen, Piero Papi

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Abstract

The invention relates to a method for setting the travel of a press brake comprising at least one sensor, which measures a physical parameter (p) that varies with the force exerted by the punch on a piece of sheet metal placed on the die, and an electronic device that controls the displacement of the mobile apron between a top dead center and a bottom dead center (BDC). Said electronic device is provided with computing means for correcting the bottom dead center value according to the measurement taken for said displacement and for the physical parameter (p). The difference in thickness between the real thickness of the sheet metal and the set value (e) for the sheet metal thickness is measured during bending; instantaneous bending angle α under the load of the piece is calculated as a function of the displacement, taking account of said difference in thickness and the geometric parameters of the punch and the die; the bearing force (f) of the punch on the piece is calculated using the value of the physical parameter (p); the sequence of values for the instantaneous bending angle/bearing force pair (α, f) is taken and compared to a reference curve (α, f)ref which is pre-recorded during a bending operation involving the same material, and the electronic control device calculates a bottom dead center correction taking account of the deviation between the (α, f) pairs and reference curve (α, f)ref, said difference in thickness and the deformations in the press.

A method for adjusting the stroke of a press brake comprising a fixed table (1) carrying a die (2), a moving beam (3) carrying a punch (4), means (5, 5′) of moving the moving beam, the said movement means bearing on uprights (6, 6′) fixed to the fixed table, measuring rules (9, 9′) for measuring the movement (d) of the moving beam with respect to the uprights, at least one sensor (8, 8′) measuring a physical parameter (p) varying according to the force exerted by the said punch on a piece placed on the said die, and an electronic control device (7) controlling the movement of the moving beam between a top dead centre and a bottom dead centre (BDC), provided with means of acquiring the movement measurements (d) and the physical parameter (p), and calculation means for correcting the value of the said bottom dead centre according to the measurements of the said movement and the said physical parameter, characterised in that the difference in thickness between the actual thickness of the piece and the nominal thickness (e) of the piece is calculated by comparing the actual position of the movement of the punch at which there occurs a predetermined variation Δp in the said physical parameter (p) with the theoretical position of the said movement where this variation Δp should occur, in that the electronic control device processes the measurements of the said movement (d) and the said physical parameter (p), during the plastic deformation phase of the piece during bending, so as to compare them and determine their differences with the data recorded during a reference bending operation which made it possible to obtain the set value αc of the bending angle after release of the force exerted by the punch and to determine a reference value of the spring effect correction, and in that the electronic control device calculates a correction to the bottom dead centre according to the said reference correction of the spring effect and the said differences with the reference recording data.

Abstract

Claims9