Intrinsic Characteristics of CNC System

The following are some basic CNC characteristics in the current mold machining process:

1. The non-uniform rational B-spline (NURBS) interpolation of curves and surfaces of CNC

This technology uses interpolation along the curve instead of using a series of short straight lines to fit the curve. The application of this technology has become quite common. Many CAM software currently used in the mold industry provides an option, which is to generate parts programs in NURBS interpolation format. At the same time, the powerful CNC also provides five-axis interpolation function and related properties. These properties improve the quality of surface finishing, improve the smoothness of motor operation, increase the cutting speed, and make the parts program smaller.

2. The smaller instruction unit of CNC

Most CNC systems transmit motion and positioning instructions to the main shaft of a machine tool with a unit not less than 1 micron. After making full use of the CPU processing power to improve this advantage, the smallest instruction unit of some CNC systems can even reach 1 nanometer (0.000001mm). After the instruction unit is reduced by 1000 times, higher machining accuracy can be obtained, and the motor can run more smoothly. The stable operation of the motor allows some machine tools to run at higher accelerations without increasing the vibration of the machine tool.

3. Bell-shaped curve acceleration/deceleration

It is also called S-curve acceleration/deceleration, or creep control. Compared with the linear acceleration method, this method allows the machine tool to obtain a better acceleration effect. Compared with other acceleration methods, it also includes straight-line method and exponential method. The bell-shaped curve method can be used to obtain smaller positioning error.

4. Machining track monitoring

This technology has been widely used. The technology has many performance differences that distinguish its working mode in low-end control systems from that in high-end control systems. Generally speaking, CNC realizes the preprocessing of the program by monitoring the machining track, so as to ensure that it can obtain more excellent acceleration/deceleration control. According to the performance of different CNC, the number of program blocks required for monitoring the machining track varies from two to hundreds, which is mainly determined by the shortest machining time of the part program and the time constant of acceleration/deceleration. Generally speaking, in order to meet the machining requirements, at least fifteen program blocks for machining track monitoring are required.

5. Digital servo control

The development of digital servo system is so rapid that most machine tool manufacturers choose this system as the servo control system of machine tool. After using this system, CNC can control the servo system more timely, and the CNC control of the machine tool has become more precise.

6. Linear motor

In recent years, the performance and popularity of linear motors have been significantly improved, so many machining centers have adopted this device. The application of other advanced technologies has reduced the size, weight, and improved the cooling efficiency of the machine tool. All these technological advancements make linear motors have stronger advantages when compared with rotating motors: higher acceleration/deceleration rate; more accurate positioning control, higher rigidity; higher reliability; internal dynamic braking.