CNC vs NC Press Brake: Key Differences Explained
In this article, I will explore the key differences between CNC and NC press brakes. As I delve into the intricacies of each system, you’ll gain a clearer understanding of their functionalities and advantages. Whether you’re considering upgrading your equipment or simply want to enhance your knowledge, recognizing the distinctions between CNC vs NC press brake systems is essential. Join me as we break down the features, benefits, and ideal applications of these vital machines in the sheet metal industry.
Overview
When someone wants to purchase press brake, sometimes he will be confused with CNC press brake and NC press brake. Actually there are many differences between these two press brake machines. Today we will share some main important tips about how to distinguish CNC press brake and NC press brake. Hope it will give you some helps when you start your business. Actually, we will name torsion-bar type press brake “NC Press brake” and name Electro-hydraulic type press brake “CNC press brake”.
CNC Press Brake
Nc Press Brake
Difference
Structure
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.
 Torsion-bar |  Linear encoder |
Accuracy
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.
Working speed
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.
Mechanic rigidity
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.
 Torsion-bar structure |  Closed loop system |
Crowning 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.
CNC Axis
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.
Optional configurations
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.
Conclusion
| No. | Item | Difference | |
| CNC press brake | NC press brake | ||
| 1 | Ram synchronization | Stable synchronous performance, better flexibility. CNC controller can detect and correct ram inclination. | Torsion rod ensures the ram synchronization mechanically |
| 2 | Bending angle calculation | Bending angle can be figured out automatically by inputting press brake tooling angle, opening, radium and metal sheet thickness through CNC controller. | / |
| 3 | Feedback of bending depth | Linear encoder can detect the position of both sides of the ram and has the crowning structure of throat deformation, which can ensure the same angle in the line of the bending channel. | / |
| 4 | Worktable crowning | CNC controller can figure out required crowning force for the worktable deformation during bending process automatically, which can ensure the uniformity of bending angle in whole length and improve the linearity of the work-piece. | / |
| 5 | Angular correction | If the programming angle differs from the actual bending angle, CNC controller can automatically correct the angle once the user inputs the error value. | / |
| 6 | Back gauge position | System can figure out the position of each back-gauge axis automatically according to the bending height, moving and correcting quickly. | Back gauge can only move back and front by manually inputting value |
| 7 | Programming method | Date or graph programming, easy program modification and editing. | Program cylinder stroke and back gauge movement |
| 8 | Unfolding length | CNC Controller can calculate the unfolding length by graphic programming of interior or exterior size. (DA-58T, DA-66T, DA-69T) | / |
| 9 | Interference calculation | CNC controller can automatically determine the reasonable bending sequence according to the programmable graph, punch and die, machine outline, and alert in the case of bending interference. Bending sequence can also be confirmed by manual modification. | / |
| 10 | Ram down speed | 160-180mm/s | 80-100mm/s |
| 12 | Bending angle accuracy | ≤18’ | ≤30’ |
| 13 | Back gauge axis | Several CNC axes for optional | Only X axis(back and front) |
Price comparision
Actually, If the machine capacity is less than 200tons, the price for CNC press brake will be more than 2 times higher than NC press brake. If the press brake capacity is more than 200tons, the price for CNC press brake will be less than 2 times than NC press brake. In this way, if the bending machine capacity is higher, it will be better to choose CNC Press brake machine.
