Method for correcting a folding operation and folding press

A method of correcting a bending operation performed by a press brake comprising the steps of

• providing two side frames integral with a fixed beam, a movable beam, and with displacement means for displacing the movable beam resting on said two side frames, and sensors, fixed respectively to the two side frames,
• measuring forces exerted by said displacement means on the said side frames,
• providing deformation compensation cylinders associated with one of the two beams, and an electronic control device for controlling the displacement of the movable beam between a top dead centre and a bottom dead centre,
• pre-recording a calibration diagram in a memory of the electronic control device using calibration pieces of lengths shorter than 10% of the length between two said cylinders, the said diagram establishing a correspondence between forces measured by the sensors associated with the side frames and pressures that can be applied to said compensation cylinders of the beam carrying them, in order to keep the said beam substantially straight, and
• applying pressures during a subsequent bending operation to the said compensation cylinders corresponding to the forces measured at the said sensors according to said diagram,
• making a correction to a depth of penetration of the punch into the die by recalculating a bottom dead centre of the press according to characteristics of a piece to be bent and values measured by the sensors fixed to the side frames, and
• applying the foregoing steps to a short piece to be bent, wherein a correction to the bottom dead centre is calculated by means of the formula
• ΔZ=(F.l2al2b)/(3.E.I.l)
• in which:
• F is the local load on the short piece (in newtons)
• l is the distance between the side frames
• la and lb are the respective distances from the centre of the piece to the side frames
• E is the modulus of elasticity of the top beam (in N/mm2)
• I is axial moment of inertia of the beam (in mm4).

A method of correcting a bending operation performed by a press brake comprising the steps of

• providing two side frames integral with a fixed beam, a movable beam, and with displacement means for displacing the movable beam resting on said two side frames, and sensors, fixed respectively to the two side frames,
• measuring forces exerted by said displacement means on the said side frames,
• providing deformation compensation cylinders associated with one of the two beams, and an electronic control device for controlling the displacement of the movable beam between a top dead centre and a bottom dead centre,
• pre-recording a calibration diagram in a memory of the electronic control device using calibration pieces of lengths shorter than 10% of the length between two said cylinders, the said diagram establishing a correspondence between forces measured by the sensors associated with the side frames and pressures that can be applied to said compensation cylinders of the beam carrying them, in order to keep the said beam substantially straight, and
• applying pressure during a subsequent bending operation, the said compensation cylinders pressures corresponding to the forces measured at the said sensors according to said diagram,
• making a correction to a depth of penetration of the punch into the die by recalculating a bottom dead centre of the press according to characteristics of a piece to be bent and values measured by the sensors fixed to the side frames, and
• applying the foregoing steps to a long piece to be bent, wherein a correction ΔZ′ to the bottom dead centre is applied to the travel of the movable beam calculated by means of the formula
• ΔZ′=(5.Q.I4)/(384000.E.I)
• in which:
• Q designates the load per unit length on the piece (in N/m)
• E is the modulus of elasticity of the top beam (in N/mm2)
• I is the axial moment of inertia of the beam (in mm4).

A press brake comprising a fixed beam, a movable beam, two side frames integral with the fixed beam, displacement means for displacing the movable beam resting on said two side frames sensors, fixed respectively to the two side frames, measuring forces exerted by the said displacement means on the said side frames, deformation compensation cylinders associated with the bottom beam, and an electronic control device controlling a displacement of the movable beam between a top dead centre and a bottom dead centre, wherein the said electronic control device is programmed for controlling the displacement of the movable beam between a top dead centre and a bottom dead centre, wherein a calibration diagram is pre-recorded in a memory of the electronic control device using calibration pieces of lengths shorter than 10% of the length between two said cylinders, the said diagram establishing a correspondence between forces measured by the sensors associated with the side frames and pressures that can be applied to said compensation cylinders of the beam carrying them, in order to keep the said beam substantially straight, and wherein, during a subsequent bending operation, are applied to the said compensation cylinders pressures corresponding to the forces measured at the said sensors according to said diagram, and wherein a correction to a depth of penetration of the punch into the die is made by recalculating a bottom dead centre of the press according to characteristics of a piece to be bent and values measured by the sensors fixed to the side frames, wherein said method is applied to a short piece to be bent, and wherein a correction to the bottom dead centre is calculated by means of the formula

• ΔZ=(F.l2a.l2b)/(3.E.I.l)
• in which:
• F is the local load on the short piece (in newtons)
• l is the distance between the side frames
• la and lb are the respective distances from the centre of the piece to the side frames
• E is the modulus of elasticity of the top beam (in N/mm2)
• I is axial moment of inertia of the beam (in mm4).

A press brake comprising a fixed beam, a movable beam, two side frames integral with the fixed beam, displacement means for displacing the movable beam resting on said two side frames sensors, fixed respectively to the two side frames, measuring forces exerted by the said displacement means on the said side frames, deformation compensation cylinders associated with the bottom beam, and an electronic control device controlling a displacement of the movable beam between a top dead centre and a bottom dead centre, wherein the said electronic control device is programmed for controlling the displacement of the movable beam between a top dead centre and a bottom dead centre, wherein a calibration diagram is pre-recorded in a memory of the electronic control device using calibration pieces of lengths shorter than 10% of the length between two said cylinders, the said diagram establishing a correspondence between forces measured by the sensors associated with the side frames and pressures that can be applied to said compensation cylinders of the beam carrying them, in order to keep the said beam substantially straight, and wherein, during a subsequent bending operation, are applied to the said compensation cylinders pressures corresponding to the forces measured at the said sensors according to said diagram, and wherein a correction to a depth of penetration of the punch into the die is made by recalculating a bottom dead centre of the press according to characteristics of a piece to be bent and values measured by the sensors fixed to the side frames, wherein said method is applied to a lone piece to be bent, and wherein a correction ΔZ′ to the bottom dead centre is applied to the travel of the movable beam calculated by means of the formula

• ΔZ′=(5.Q.I4)/(384000.E.I)
• in which:
• Q designates the load per unit length on the piece (in N/m)
• E is the modulus of elasticity of the top beam (in N/mm2)
• I is the axial moment of inertia of the beam (in mm4).