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To use nonmandrel bending successfully, machine function and rigidity must be considered. The most widely used form of machine is the CNC rotary draw bender, although nonmandrel tooling will also perform satisfactorily on a press bender.
As a minimum requirement, the bending machined should have a traveling pressure die. A more desirable feature would be a machine-controlled pressure die assist that works in conjunction with a machine-controlled tube boost. The boost can be through the carriage itself or a separate unit.
The timing and control of the boost and the powered pressure die necessitates that they be programmed from a single control.
Power and rigidity are also machine requirements for nonmandrel bending. Usually , machine capacity is rated by a material designation along with a maximum outside diameter (OD) and wall thickness. In some instances, machine capacity may even be listed as a section-modulas capacity. In general terms, capacity can be thought of as the ability to pull a bend.
While bending with a shaped tube groove will fall into the same basic limits, the power and rigidity needed to resize and reshape the tube during bending affect the situation.
This is because the machine's pressure die bolster must have the power to close the pressure die with the bend die. The pressure die bolster must also have the rigidity to maintain cavity control throughout the bend.