1. Non-uniform rational B- spline (nurbs) interpolation of curves and surfaces This technique uses interpolation along the curve, rather than using a series of short straight lines to fit the curve. The application of this technology is quite common. The cam software used by many mold industries provides an option to generate part programs in nurbs interpolation format. At the same time, the powerful cnc also provides five-axis interpolation function and related features. These properties improve the quality of surface finishing, improve the smoothness of motor operation, increase the cutting speed, and make the part processing program smaller.
2. Smaller command units Most CNC systems transmit motion and positioning commands to the machine spindle in units not less than 1 micron. After taking full advantage of the CPU processing power to improve this advantage, some CNC systems can even reach the minimum instruction unit of 1 nanometer (0.000001mm). After the command unit is reduced by 1000 times, higher machining accuracy can be obtained, and the motor can run more smoothly. The smooth operation of the motor enables some machine tools to run at a higher acceleration without increasing the vibration of the bed.
The bell curve acceleration/deceleration is also known as the s-curve acceleration/deceleration, or creep control. Compared with the use of linear acceleration, this method can make the machine tool to obtain better acceleration effect. Compared with other acceleration modes, including linear mode and exponential mode, the bell curve mode can obtain smaller positioning error.
4. The technology of monitoring the trajectory to be processed has been widely used. The technology has many performance differences, which distinguish the working mode in the low-end control system from the working mode in the high-end control system. Generally speaking, cnc is to realize the pre-processing of the program through the monitoring of the machining trajectory, so as to ensure that better acceleration/deceleration control can be obtained. According to the performance of different cnc, the number of program blocks required for the monitoring of the processing trajectory varies from two to hundreds, which mainly depends on the minimum processing time of the part program and the time constant of acceleration/deceleration. Generally speaking, in order to meet the processing requirements, at least fifteen to-be-processed track monitoring program blocks 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 tools. After using this system, CNC can control the servo system more timely, and CNC control of the machine tool becomes more accurate.
The role of the digital servo system is as follows:
1) The sampling speed of the current loop will be increased, coupled with the improvement of the current loop control, thereby reducing the temperature rise of the motor. In this way, not only the life of the motor can be extended, but also the heat transferred to the ball screw can be reduced, thereby improving the accuracy of the screw. In addition, the increase in sampling speed can also increase the gain of the speed loop, which helps to improve the overall performance of the machine tool.
2) Since many new cnc's use high-speed sequences to connect with the servo loop, through the communication link, cnc can obtain more working information of the motor and drive device. This can improve the maintenance performance of the machine tool.
3) Continuous position feedback allows high-precision processing with high-speed feed. The acceleration of cnc operation speed makes the rate of position feedback become the bottleneck of machine tool running speed. In the conventional feedback manner, as the sampling speed of the cnc and the external encoder of the electronic device changes, the feedback speed is restricted by the type of signal. Using serial feedback, this problem will be solved well. Precise feedback accuracy is achieved even when the machine runs at very high speeds.
The working performance and popularity of linear motors have been significantly improved, so many machining centers have adopted this device. Some advanced technology makes the maximum output force of the linear motor on the machine tool is 15,500n and the maximum acceleration is 30g. The application of other advanced technologies has reduced the size of the machine tool, reduced the weight, and greatly improved the cooling efficiency. All these technological advances give linear motors an advantage over rotary motors: higher acceleration/deceleration rates; more accurate positioning control, higher stiffness; higher reliability; and internal dynamic braking.