The exclusive function of the exclusive planning CNC system Beijiafanake Electromechanical Co., Ltd. (100085) Li Jiate With the development of the L technology, the functions of the CNC system are constantly developing. These functions are mainly reflected in the following aspects: high-precision idle speed, 5-axis linkage, error compensation, networking, and security.

High-precision, high-speed machining technology is the development of traditional CNC machining technology, and it has no essential difference from traditional CNC machining. For 篼 、, high-speed CNC machining, the goal of CNC machine tools is to require high-precision parts to be machined at high speed. In order to perform high-speed machining on the basis of accuracy, there are three important factors: mechanical systems, CNC controls and drives.

Regarding the requirements for high-speed machining on machinery, I will not go into details here. It is important to note that high speed and high precision machining requires the machine to have a heel stiffness and a light moving part, especially the feed and spindle sections.

This is followed by the CNC system, which is the unit that issues speed and position commands. First, the command is required to be transmitted accurately and quickly. After processing, a position command is issued for each coordinate axis, and the servo system must drive the tool to move accurately according to the command.

The CNC system converts the input part program into the shape trajectory to be machined, the feedrate and other command information, and continuously sends the position command to each servo axis. In order to obtain idle speed and high precision, the CNC must select the optimum feed rate according to the shape trajectory of the part machining, and generate the position command with the highest possible feed rate within the allowable precision. Beyond the corners and small radii, the CNC should be able to determine how much the machining speed will affect the accuracy, and automatically reduce the tangential speed of the tool before the tool reaches such a point. For mold processing, the general program segment is small, but the program is very long, so it is necessary to use special control methods to achieve boring and high-speed machining. The servo system requires accurate and fast driving to machine high-precision mechanical parts at an idle speed. For this reason, the servo system must have the ability to respond quickly, suppress the disturbance, and require the servo system to not generate vibration and eliminate resonance with the machine.

Idle machining requires a high-speed spindle unit and an idle machine feed drive unit. The feed rate of 篼 also requires the acceleration of 篼. For example, the stroke of a high-speed machine tool is usually between 500-1000mm. In such a short distance, the feed rate of the machine tool increases from zero to 40m/min, and the feed acceleration value of the machine tool should exceed 9.8m/s2. . Feed acceleration is more important when machining curved surfaces. Its addition is proportional to the square of the feed rate. If a servo motor does not produce a sufficiently high speed, it cannot process at high speed and with high precision. At present, the spindle unit mainly uses a vector-controlled AC asynchronous motor due to the heating of the rotor of the asynchronous motor. The internal cooling idle spindle motor is also used now; the structure of the synchronous motor is also studied. In order to achieve a large feed addition (decrease) speed, linear motors have been increasingly used. Safety issues are important when machining at high speeds. Because the chips in high-speed machining are shot like bullets, the safety requirements for the system are very slim.

The requirements of CNC for high-speed machining and high-speed machining can be 1/=: It can process and control the suffocation flow quickly and accurately. Its processing error is controlled to a minimum.

It can minimize the impact of the machine and make the machine move smoothly.

Have enough capacity to allow high-volume machining programs to run at high speeds or have the ability to transfer large amounts of data over a network.

Servo motor, spindle motor, and I sensor with high resolution and high speed operation.

Reliability and safety are important because they are processed at idle speeds.

The functions of idle speed and high precision mainly include the following aspects: feed rate control and addition (subtraction) speed processing function (including corner deceleration processing): the error in high speed machining is mainly due to the hysteresis and servo of the control system plus (decrease) speed. Caused by the lag of the system. Therefore, the control system should try to reduce the error in these two aspects. For example, feedforward control is used to reduce the error caused by servo lag. Improve servo control with digital servo technology. Thanks to the digital servo technology, the speed gain and position gain of the servo system can be improved, thus reducing the error caused by the servo lag. Reduce the error caused by the addition (decrement) speed lag. In idle machining, the addition (deceleration) speed and feed rate are the most important parameters. Only when the machining shape is strictly controlled, the addition (deceleration) speed and feed rate can be used to achieve high-speed machining. Large feed rates can cause large errors during system transitions, such as corners. In order to achieve high speed machining, the feed rate must be controlled. In addition, the use of the addition (decrease) speed before interpolation can also reduce the error caused by the addition (decrement) speed lag.

The feed rate and acceleration and deceleration are pre-calculated in the shape of the workpiece, so that the numerical control system pre-calculates the motion trajectory and motion speed of each program segment after programming and before execution; that is, pre-processing the program to be run, according to the above The control feed rate and the acceleration and deceleration methods mentioned. The feed rate and the acceleration and deceleration of some blocks are calculated in advance, and then the geometrical trajectory of the movement is sent to the multi-segment buffer. When running, the tool moves at a high speed at a certain speed, but the error of the machining shape is Still small. This is the principle of "forward-looking control", sometimes referred to as "advance control" and "forward control."

With the remote buffer and the idle distribution of the DNC operation, it is necessary to quickly transfer the program from the input to the CNC system for machining a large number of program parts. After the CNC reads a program, it calculates the data of the program, generates a distribution pulse for each axis, and transmits it to the servo system to operate the servo motor. The time at which the dispense pulse is generated (the time the block is processed) is an important factor in the performance of the CNC. For a block, the operation of the idle DNC allows the time required to generate the dispensed pulses (using the remote buffer) to be greatly reduced. This function shortens the distribution pulse that generates a block, thus ensuring that a program consisting of a small block does not pause between blocks. For example, when performing a DNC operation, a program consisting of a system of I1mm blocks (3-axis linear interpolation) can operate at a speed of 60 m/min without interrupting the execution of the allocation. Thanks to the function of the remote buffer, high-speed input of data is realized, thus ensuring the progress of idle processing.

Improve system resolution, for example, nano-interpolation, which uses a processor with an idle RISC. Machining with nanometer-based interpolation allows the machine to match the machining performance at the optimum feed rate.

The control of jerk, when moving in the shape of the curve, the change of acceleration may cause mechanical vibration. The control of jerk is to automatically measure such movement to reduce the speed and reduce the mechanical impact to reduce the roughness of the machined surface.

NURBS interpolation: When designing molds using CAD, NURBS waves are widely used to represent free curves. Compared with general CNC, NURBS has higher transfer rate and shorter program. The mechanical parts that are machined at the same time are closer to the geometry of the dry CAD design.

For high-speed, high-precision machining functions, when selecting, it is also necessary to select the function based on the machining speed or the machining accuracy.

The shape of a general mechanical part is essentially a two-dimensional surface. However, the three-dimensional simultaneous processing of the two-dimensional surface is not optimal from the processing effect, and the efficiency is low and the surface roughness value is high. The 5-axis linkage is not only efficient, but also greatly improved in roughness. 5-axis linkage allows cutting with the best shape. Off-line programming is typically used for the 5-axis machining of rotating coordinate systems. The type, radius and length of the tool are required to be constant during CNC programming, which makes it difficult to modify the program and the tool. In order to solve this difficulty, a coordinate transformation method is provided in the CNC system, so that some programming and tool correction are performed directly in the machine without repeating the post processing. This can be achieved by defining a new workpiece coordinate system, which is converted by the CNC system to the coordinates of the corresponding axis.

The position of the tool can be changed by the position of the rotation 4, the direction vector of the tool, and the PRY. The function is also heavy for the manual mode. For example, when the tool is broken, the tool needs to be moved.

When a 5-axis machine tool uses a ball cutter for 3-axis simultaneous machining, only a part of the potential for milling can be used to achieve higher productivity only when machining with a cylindrical or spiral cutter. However, in order to ensure that the cylindrical knife or the exclusive planning of the spiral cutter tool moves along the required path, usually the 5-axis programming of the tool requires a large number of intermediate cutting points to be inserted in the middle. The 5-axis transformation uses the handheld control unit to dynamically adjust the rake angle to ensure that the tool tip remains stable. The length of the tool can be corrected by the sub-CNC, so during the machining process, in order to react to the event of the tool break and to compensate for the wear of the tool, the tool can be measured directly on the machine when needed. These features allow the machine to run unattended at night. The CNC is linked to the laser measurement system and automatically provides the corresponding measurement cycle for tool set and breakage monitoring. Since different tool geometries can be corrected, such as cylindrical, spiral and conical spiral tools, the same procedure can use different tools. Currently, high-end CNC systems can perform 5-axis machining. The main functions are as follows: (1) It is suitable for different machine configuration 5-axis machining functions. It can be adapted to different machine configurations, including tool tilt type, table tilt type and composite type. The offset between the first and second rotating shafts due to the machine or the offset between the tool shaft and the rotating shaft can also be considered in the system. It can compensate for tool length in the direction of the tool axis. Even if the direction of the tool axis rotates with the rotary axis, it can be compensated in the direction of the tool axis. Control of the tool center point Even if the direction of the tool axis changes, the tool center can still be controlled to follow the determined line. 5-axis machining tool radius compensation: Tool radius compensation can be performed on a plane perpendicular to a tilting tool or leading edge offset. 5-axis machining circular interpolation, which can define the arc on the inclined plane. Inclined plane machining instructions: It is convenient to make a part program in the case of oblique plane machining, and the rotary axis can be controlled so that the tool is perpendicular to the inclined plane. 5-axis machining Manual feed moves the tool along the inclined workpiece plane, or it can be manually moved along the axial direction of the skew tool. (2) Complex machining function 5-axis machining tool center point control, cylindrical cutting interpolation machining cutting point compensation, AI 篼 fine contour control / AI nano high-precision contour control, 5-axis machining tool radius compensation, 5-axis machining manual feed Features. It can be turned on, CNC and 5-axis on one CNC.

In order to ensure that the machining error of the idle system is small, the system needs to have an error compensation device. These compensations include: full-stroke linear compensation and nonlinear bending compensation, pitch compensation, clearance compensation, over-quadrant compensation, tool offset and thermal expansion, static friction, dynamic rubbing compensation, etc.

With a wide range of network functions and software packages, you can build the best system for your machine. (1) Centralized management, one computer can be used to control multiple machine tools, which is convenient for monitoring, operation and processing and NC program transmission and management = (2) remote support and service.

In the future, the numerical control is at a high speed, so the reliability requirements are very slim. The double check function is an important measure to ensure the safe operation of the CNC system.

(Finish)

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