how to choose cnc system

Numerical control system includes numerical control device, feed drive (feed speed control unit and servo motor), spindle drive (spindle speed control unit and spindle motor) and detection element. The above contents should be included when selecting a numerical control system.
1, the choice of numerical control device
(1) Type selection
According to the type of CNC machine tool to choose the corresponding CNC device, in general, CNC device is suitable for car, drilling, boring, milling, grinding, stamping, EDM cutting and other processing types, should be targeted to choose.
(2) Selection of performance
Different CNC devices, its performance is very different, the number of control axes have single axis, 2 axis, 3 axis, 4 axis, 5 axis, and even more than 10 axis, 20 axis; Linkage axle count more than 2 or 3 axis, the highest feed speed with 10 m/min, 15 m/min, 24 m/min, 240 m/min. The resolution is 0.01mm,0.001mm,0.0001mm. These indicators are different, the price is also different, should be based on the actual needs of the machine tool, such as general turning processing use 2 axis or 4 axis (double tool holder) control, plane parts processing use more than 3 axis linkage. Don't go for the latest and highest level, choose reasonably.
(3) Selection of functions
A numerical control system has many functions, including basic functions ---- essential functions of numerical control device; Select function - a function for the user to select. Some select functions to solve different processing objects, some to improve processing quality, some to facilitate programming, and some to improve operation and maintenance performance. Some of the selection functions are related, and to select this, you must also select another item. Therefore, it is necessary to choose according to the design requirements of the machine tool, do not choose too many steps without analysis, and miss the relevant functions, so that the function of the CNC machine tool is reduced, causing unnecessary losses.
The programmable controller in the selection function has two types: built-in and independent. It is best to choose the built-in type, it has different models, first of all, according to the input and output signal points between the CNC device and the machine tool to choose. The number of points selected should be slightly more than the number of practical points, and a cup may be added and change the control performance needs. The next step is to estimate the sequential program size and select storage capacity. The program scale increases with the complexity of the machine tool, and the storage capacity also increases, which should be selected reasonably according to the specific situation. There are also technical specifications such as processing time, instruction function, timer, counter, and internal relay, and the quantity should also meet the design requirements.
(4) The choice of price
Different countries, different CNC device manufacturers, the production of different specifications of products, the price is very different, should meet the control type, performance, function on the basis of the selection, comprehensive analysis of the performance price ratio, choose the high performance price ratio of CNC devices, in order to reduce costs.
(5) The choice of technical services
When choosing a CNC device that meets the technical requirements, it is necessary to take into account the reputation of the manufacturer, whether the documentation such as the product instructions is complete, and whether it can train the user in programming, operation and maintenance personnel. There is no special technical service department to provide long-term spare parts and timely maintenance services to benefit the technical and economic benefits.
2, feed drive selection
(1) The AC servo motor is preferred, because compared with the DC motor, the rotor inertia is small, the dynamic response is good, the output power is large, the speed is high, the structure is simple, the cost is low, the application environment is not limited.
(2) By correctly calculating the load conditions added to the motor shaft to select the appropriate specifications of the servo motor.
(3) The feed drive manufacturer provides a series of complete sets of products for the feed speed control unit and servo motor, so after the servo motor is selected, the corresponding speed control unit is selected by the product manual.
3, the choice of spindle drive
(1) The mainstream spindle motor is preferred, because it does not have the restriction of commutation, high speed and large capacity like the DC spindle motor, the constant power speed regulation range is large, the noise is low, and the price is cheap. At present, 85% of CNC machine tools in the world use AC spindle drive.
(2) Select the spindle motor according to the following principles:
(1) According to different machine tools to calculate the cutting power, the selected motor should meet this requirement; ② According to the required spindle acceleration and deceleration time, the motor power should not exceed the maximum output power of the motor; (3) In the case of requiring frequent spindle starting and braking, the average power must be calculated, and its value cannot exceed the continuous rated output power of the motor; (4) In the case that the constant surface is required to be controlled, the sum of the cutting power and acceleration power required for the constant surface speed control should be within the power range that the motor can provide.
(3) The spindle drive manufacturer provides a series of complete sets of products for the production of the spindle speed control unit and the spindle motor, so after the spindle motor is selected, the corresponding spindle speed control unit is selected by the product manual.
(4) When the spindle is required for orientation control, the position encoder or magnetic sensor is selected to achieve the orientation control of the spindle according to the actual situation of the machine tool.
4, the selection of detection components
(1) According to the position control scheme of the numerical control system, the linear displacement of the machine tool is measured directly or indirectly, and the linear or rotating detection elements are selected. At present, semi-closed loop control is widely used in CNC machine tools, and rotary Angle measuring elements (rotary transformer, pulse encoder) are selected.
(2) According to the requirements of the CNC machine tool to detect accuracy or speed, choose the position or speed detection element (test generator, pulse encoder). In general, large machine tools are mainly to meet the speed requirements, high-precision, small and medium-sized machine tools are mainly to meet the accuracy. The resolution of the selected detection element is generally an order of magnitude higher than the machining accuracy.
(3) At present, the most commonly used detection element of CNC machine tools is the photoelectric pulse encoder, which selects the corresponding specification pulse encoder according to the ball screw pitch of CNC machine tools, the minimum movement of the CNC system, the command ratio and the detection ratio.
(4) When selecting detection components, it is necessary to take into account that the numerical control device has the corresponding interface circuit.