Up acting press brakes are designed such that the lower beam lifts the die into the punch. The upper beam stays fixed during the operation. This design may not seem intuitive but it does have some advantages. Since the ram sits on the cam instead of hanging on it, as the bearings and cam wear down the motion of the ram stays consistent. This also eliminates vibration in the machine and it can be argued that it increases the life of the brake. Because the operator has to move with the ram it requires that they be more conscious of their actions, possibly reducing the risk of injury. Te most noted advantage though is that in the case of a mechanical or electrical failure the press brake will fall away from the closed position meaning that there is less of a chance for injury for the operator.
The up acting press brake is more susceptible to deflation across the tool length because the lower beam is typically driven up from the center. This puts more pressure on both the lower and upper beams in the center which leads to decreased tonnage as you move further to each side. This deflection also makes an up acting press brake less ideal for staging multiple dies across the length of the beam. When bending on an up acting press brake keep your work in the center of the brake to avoid tilting the ram to one side. The up acting design is also less common than down acting, therefore there may be a learning curve for new operators who are accustomed to down acting brakes. It takes more skill to keep the sheet metal set against the back gauge when moving with the part, this can lead to inaccuracy in the finished bend. More operator movement is involved possibly affecting the ergonomics of the work. When operators aren’t involved and the positioning of the work piece is automated the upwards motion makes it more technically challenging as the programming must incorporate the vertical movement with the lower beam as well as the normal bending of the work piece.