STEP #4:  PRESSURE DIE ASSIST SETTING

Like the wiper, pressure die assist is not necessary if there are no flaws for it to fix.  In this case, if there is no terminal hump on the outside radius and the flattening is acceptable, you do not need pressure die assist.  Turn it off or set it to a neutral pressure (depending upon your machine), and your set-up is complete.  Otherwise start from a neutral pressure setting and increase the assist until the flaws disappear. 

Keep in mind that many newer CNC tube-bending machine have both “assist” pressure and “boost” pressure.  The term “boost” generally means a type of axial pressure applied during the bend to the entire circumference of the tube by means of clamps behind the pressure die.  Using this type of pressure forces material through the line of tangency to feed both the intrados and the extrados.  Assist, on the other hand, feeds material only into the extrados which is useful in decreasing flattening and wall-thinning.