How to choose CNC machine tools

Three aspects can be considered when purchasing CNC machine tools

The first is whether the machine body can meet its own processing requirements, and the quality of the machine tool.

The second is the CNC system. There are many types of CNC systems. Choosing the right system is the key to purchasing CNC machine tools.

The latter is the drive unit, which is also the key to machine tool control. Different drive units can achieve different machining accuracy. When selecting a drive unit, it is necessary to select an appropriate drive unit according to the accuracy requirements of the workpiece to be processed.

The CNC system is the control center of the CNC machine tool, known as the "brain" of the machine tool. The machine tool equipped with the CNC system greatly improves the precision, speed and efficiency of parts processing.

The function of the CNC system is undoubtedly an important limiting factor for the design and selection of CNC machine tools.

The following important factors must be considered when choosing a CNC system:

1. Driving ability

2. Full closed-loop demand and dual-drive demand

3.five-axis control requirements

4.RTCP, the choice will be relatively large. At the same time, the CNC system suppliers that may be involved in the five-axis function must also seriously consider export licenses, after-sales services, etc.

The following is an analysis of the numerical control system

Optional CNC system

The numerical control system is the "brain" of the numerical control machine tool, which operates and processes the control information of the machine tool. According to the principle of numerical control system, it can be divided into two categories: economical numerical control system and standard numerical control system.

1. Economical numerical control system Economical numerical control system generally refers to open-loop numerical control system from the point of view of control method, which has the advantages of simple structure, low cost, convenient maintenance and debugging, low operation and maintenance cost, etc. Accuracy, feed speed and torque are mutually restricted, and the improvement of performance is limited. Economical CNC systems are often used in CNC wire cutting and some economical CNC lathes and milling machines that do not require high speed and precision, and are also widely used in the CNC transformation of ordinary machine tools. The open-loop numerical control system means that the index control system itself does not have a position detection device. The numerical control system sends out a certain number and frequency of command pulses, and the drive unit performs the machine tool positioning. When the open-loop system is affected by external factors, the machine tool does not move or does not move in place, but when the system has reached the designated position, the machining accuracy of the machine tool will be greatly reduced. However, because of its simple structure, rapid response, stable and reliable operation, convenient debugging and maintenance, and very low price, it still has a large market in China.

2. Standard CNC system

Standard CNC systems include semi-closed-loop CNC systems and fully-closed-loop CNC systems.

The semi-closed-loop CNC system generally refers to the position signal (photoelectric encoder) of the servo motor of the machine tool fed back to the CNC system. The system can automatically perform position detection and error comparison, and can compensate and control part of the error, so its control accuracy is higher than that of the open-loop CNC system. Higher, but lower than the fully closed-loop CNC system.

In addition to the position feedback of the servo motor of the machine tool, the fully closed-loop numerical control system also has the position signal of the position detection device (usually a grating ruler) of the machine tool worktable fed back to the system, thereby forming all position follow-up control, and the system is in the processing process. All position errors are automatically detected and compensated.

The machining accuracy of the fully closed-loop CNC system is high, but the debugging and maintenance of this system is extremely difficult, and the price of the system is very high, which is only suitable for medium and medium CNC machine tools.

Because the price of the open-loop control system is much lower than that of the closed-loop control system, when choosing a CNC system, the proportion of the price and cost of the CNC system to the entire CNC machine tool should be considered, and then according to the configuration of the machine tool and the requirements of the machine tool itself, the middle , Low-grade machine tools use open-loop control system, medium and low-grade machine too.