Before buying the bending machine, we will come into contact with the term digital control system. The common ones are CNC, NC, and PLC, so what do they mean?
CNC Bending Machine
CNC plate rolling machine is the abbreviation of Computer Numerical Control Machine Tool, which is an automatic rolling plate machine tool controlled by a program. The control system can logically process the program specified by the control code or other symbolic instructions, and decode it through the computer so that the machine tool can execute the specified action.
CNC belongs to the category of mechanical numerical control processing. For precise processing, it is usually necessary to control mechanical quantities such as position, angle, and speed, and switch quantities related to the flow of mechanical energy. The generation of numerical control depends on the appearance of data carriers and binary data operations.
NC: (Numerical Control) digital control, which means numerical control, NC is the old generation of the numerical control system, electronic equipment built with circuit boards, uses discrete digital information to control the operation of machinery and other devices, and can only be programmed by the operator himself, compared with the function of the computer, the gap is very large, and it is not convenient to develop.
Now the newer bending machine tools are generally CNC bending machine tools and no longer use NC control. There is a special corresponding CNC programming language control, but in terms of driver development, it is still in the NC digital control mode, which controls the operation of the motor through digital information.
PLC Bending Machine
PLC programmable logic controller is an electronic device specially designed for digital operation in an industrial environment. PLC mainly adopts the scanning working mode. The working mode of sequential scanning is simple and intuitive, which simplifies the program design and provides a strong guarantee for the reliable operation of the PLC. Nowadays, more and more plate rolling machines and angle roll tools are controlled by PLC. Using PLC control can simplify the circuit and make the design simpler, safer, and more reliable. Some advanced PLCs have various interfaces to realize the functions of connecting machines and networking.
In actual application, only the 4-roller plate rolling machine can be controlled by CNC, which is determined by its working principle. In the aspect of section bending machines, BIT’s PBA series aluminum profile bending machine and PBH 4-roll angle roll adopt CNC control, here because the PBA aluminum bending machine uses some servo motor as power, so it can use CNC, while PBH 4-roll angle roll because of the 4roller structure, the working principle is the same as that of the 4-roller plate rolling machine, which can also be controlled by CNC.
PLC and CNC
PLC is more suitable for general control tasks, while CNC is more focused on processing
The control accuracy of ordinary PLC is not as high as that of CNC, and the overall solution of high-end PLC with motion control is higher than the total cost of CNC, although the cost of ordinary PLC is lower. After comparing the overall PLC solution and CNC, many users are more optimistic about using CNC, because of the two characteristics of high overall reliability and low total cost.
The higher degree of integration and modularity of CNCs enables cost savings in specific processes, staff training, equipment maintenance, etc., resulting in a higher return on long-term investment. And many operators are specialized in CNC machine tools, not automation programmers. They all want to focus on technology, mass production, and customized processing instead of general logic programming.
The advantage of PLC is that it is much easier to find a skilled PLC programmer than a CNC engineer, with shorter training cycles and more technical support.
On the factory floor, when there are a large number of complex tasks and simple actions or processes at the same time, CNC and PLC can work together to complete the process requirements.
Difference between CNC and PLC
A CNC system in a narrow sense is a functional unit that provides users with an interactive interface and realizes position control. It consists of three parts, MMI (Man Machine Interface) human-computer interaction unit, NCK (Numerical Control Kernel) numerical control core unit, and PLC (Programmable Logic Controller) programmable controller.
- NCK is the core part of CNC. The analysis of the G code and the implementation of the interpolation algorithm are all completed in NCK.
The role of PLC in CNC is mainly to control the tool change of the machine tool, the speed of the spindle, and other places that servo control cannot reach, and play an auxiliary role. In fact, the PLC itself is quite a computer, and it can also realize the motion control function.
- CNC and PLC have different development histories, both of which appear to solve practical problems, and are aimed at different applications.
- In the CNC system, some auxiliary functions are handed over to PLC for processing, and PLC also has the opportunity to display its talents. In addition to auxiliary functions, it also realizes complex motion control functions.
- CNC and PLC have their own programming languages and user interfaces and cooperate with each other when completing large tasks, and each has the same division of labor
- Technology continues to cross the border, the edges are gradually blurred and the edges and corners are relatively clear. In the future, CNC and PLC will have their own characteristics in continuous integration.
- However, in CNC machine tools, NCK+ servo motors can better complete motion control, so PLC generally does not participate in motion control.
The motion control of the bending machine mainly involves the control of stepper motors and servo motors. The control structure mode is generally: control device + driver + (stepper or servo) motor.
The control device can be a PLC system or a dedicated automation device (such as a motion controller, or motion control card).
When the PLC system is used as a control device, although it has the flexibility and certain versatility of the PLC system, it is difficult to achieve or program very difficult for the requirements of high precision (such as interpolation control) and sensitive response, and the cost may be high.
With the advancement of technology and the accumulation of technology, the motion controller came into being. It solidifies some general and special motion control functions (such as interpolation instructions) in it. Users only need to configure and call these function blocks or instructions. , which reduces the difficulty of programming, and also has advantages in performance and cost.
- It controls position, speed and torque, usually not used independently, but can be controlled by PLC and CNC
- The use of PLC is not limited to CNC but is a common motion control device. A motion controller is a special PLC dedicated to motion control.
- The motion control device of CNC is basically PLC in the past, but most high-performance CNCs use motion controllers.