Summary
Press-brakes are machines for bending sheet-metal. These machines are generally built up
out of a stationary lower beam and a vertically moving upper beam connected by a frame.
Conventional press-brakes are driven using one hydraulic cylinder at each end of the moving
upper beam. Because the workpiece is made between these actuators, both beams are exposed
to three-point bending. Deflection of the beams lead to unwanted variations in the bendangle
along the length of the workpiece. To reduce this deflection, SAFAN has introduced
a patented pulley and belt drive system for the upper beam. The actuators now create a
distributed load rather than two local forces, reducing the deflection to 2% of the original
situation. This report concentrates on improving the lower beam.
After analyzing the behavior of the lower beam, it was replaced by an assembly of a subframe
with a new lower beam stacked on top. This allows the lower beam to be supported directly
beneath the workpiece, preventing part of the bending. By making the supports between the
subframe and the lower beam moveable, the lower beam can be optimally supported for every
different workpiece.
Due to the difference in bending-shape between the subframe and the lower beam, the supports
need to allow rotation while transducing the maximum load of 200 ton. Several possible
solutions are offered for the supports. Attention is also paid to improving the stiffness of
the subframe and lower beam and the positioning of the supports. The benefit gained from
all suggested design-changes is quantified using simulations and shows great promise. The
concept of moveable supports in a press-brake lower beam assembly has been patented.
SummaryPress-brakes are machines for bending sheet-metal. These machines are generally built upout of a stationary lower beam and a vertically moving upper beam connected by a frame.Conventional press-brakes are driven using one hydraulic cylinder at each end of the movingupper beam. Because the workpiece is made between these actuators, both beams are exposedto three-point bending. Deflection of the beams lead to unwanted variations in the bendanglealong the length of the workpiece. To reduce this deflection, SAFAN has introduceda patented pulley and belt drive system for the upper beam. The actuators now create adistributed load rather than two local forces, reducing the deflection to 2% of the originalsituation. This report concentrates on improving the lower beam.After analyzing the behavior of the lower beam, it was replaced by an assembly of a subframewith a new lower beam stacked on top. This allows the lower beam to be supported directlybeneath the workpiece, preventing part of the bending. By making the supports between thesubframe and the lower beam moveable, the lower beam can be optimally supported for everydifferent workpiece.Due to the difference in bending-shape between the subframe and the lower beam, the supportsneed to allow rotation while transducing the maximum load of 200 ton. Several possiblesolutions are offered for the supports. Attention is also paid to improving the stiffness ofthe subframe and lower beam and the positioning of the supports. The benefit gained from
all suggested design-changes is quantified using simulations and shows great promise. The
concept of moveable supports in a press-brake lower beam assembly has been patented.
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