The design principle for both machines is different, it results in the different synchronous structures on both sides of the ram. NC press brake adopts torsion shaft to connect the both sides of the ram and force the ram to move up and down synchronously, in this way, NC press brake uses the compulsive synchronous way mechanically, so the ram parallelism cannot be check and adjust by itself. For the CNC Press brake, two linear encoders are installed on the machine both sides and the CNC controller can analyze the synchronous condition on both sides of the ram by the feedback from both linear encoders. If there is some error, the controller will make the adjustment by the proportional valve to keep the synchronization of the ram. CNC controller, hydraulic system and the linear encodes consist of the closed loop control system.
The ram parallelism will affect the workpiece accuracy. The NC Press brake synchronization is kept mechanically and it has no real time feedback for the error, what is more, it can not adjust by itself and will cause the low bending accuracy. On NC press brake, both cylinders are forced to move up and down synchronously by the torsion-bar. If the partial load exists for long time, it will cause the deformation for the torsion-bar. For CNC Press brake, the controller will control the synchronization of the ram by both proportional valve and the linear encoder will send back the feedback for the error to the controller, if there is some error, the linear encoder will send the feedback and the controller will send the signal to the proportional to make the adjustment and keep the ram synchronous and improve the bending accuracy.
For the press brake, we are always talking about three speeds: Down speed, working speed and return speed. For NC Press brake, it will us 6:1 or 8:1 cylinder, for the CNC Press brake, it will use 13:1 or 15:1 cylinder, so CNC press brake will work faster than NC press brake. When NC press brake ram comes down, its down speed is around 80mm/s, the backgauge moving speed is around 100mm/s. But for CNC Press brake, its ram down speed will be up to 200mm/s and it can move very fluently during the speed change point. Its backgauge speed can be up to 400mm/s and it will improve the working efficiency obviously.
Because of its design, NC press brake can not bend by partial load. If it is working like this for long time, the torsion-bar will deform easily. It will not happen on the CNC press brake, both Y1 and Y2 Axes will work independently and it can work by partial load.
Closed loop system
For most of NC press brake, it will not come with crowning system as standard. The operator needs to adjust the bending angle manually before bending the official product. It will take long time and waste material; it will also be difficult to make the product in very precision way.
Sometimes, the customer will also add the manual crowning system as optional part for his press brake, considering the manual operating method, we also cannot compare it with CNC press brake. Because on CNC Press brake, the crowning system will be controlled by the Controller and it will adjust the crowning system according to the bending parameters. It can improve the working efficiency and accuracy.
NC press brake normally can only control X and Y axis, but for CNC Press brake, it can control at least 3+1 axis. Other options can be like 4+1 axis, 5+1 axis, 6+1 axis, 7+1 axis, 8+1 axis and so on. It can work for more complicated product bending.
We will use mechanical fast clamp, manual crowning system, manual height adjustment Z stopper, ball screw and linear guide, oil cooler, light curtain for the NC press brake, but on CNC press brake, apart from these optional configurations on the NC press brake, we can also choose TYOKKO or AMADA type double-face clamp, hydraulic clamp, robotic arm, sheet follower, laser protection, laser angle measurement, servo pump unit.