- Input: The input of part program and control parameters, compensation amount and other data can be in various forms such as photoelectric readers, keyboards, disks, DNC interfaces connected to upper-level computers, and networks. The CNC device usually completes invalid code deletion, code verification and code conversion during the input process.
- Decoding: Regardless of whether the system is working in MDI mode or memory mode, the part program is processed in a block unit, and various part contour information (such as start point, end point, straight line or arc, etc.) is processed. Machining speed information (F code) and other auxiliary information (M, S, T code, etc.) are interpreted into a data form that can be recognized by the computer according to certain grammatical rules, and stored in a designated memory dedicated unit in a certain data format. During the decoding process, the grammar check of the program segment must be completed. If a grammatical error is found, the alarm will be immediately reported.
- Tool compensation: Tool compensation includes tool length compensation and tool radius compensation. Usually the part program of CNC device is programmed with part contour trajectory, and the function of tool compensation is to convert the part contour trajectory into the tool center trajectory. In a better CNC device, the workpiece for tool compensation also includes automatic transfer between program segments and over-cutting discrimination, which is the so-called C tool compensation.
- Feed speed machining: The tool movement speed given by programming is the speed in the composite direction of each coordinate. The first work to be done in speed machining is to calculate the sub-velocities of each motion coordinate according to the composite speed. In some CNC devices, the minimum speed and maximum speed allowed by the machine tool, and the automatic acceleration and deceleration of the software are also handled here.
- Interpolation: The task of interpolation is to “densify data points” on a curve with a given start point and end point. The interpolation program runs once in each interpolation cycle, and in each interpolation cycle, a tiny linear data segment is calculated according to the commanded feedrate. Usually, after a number of interpolation cycles, the interpolation process completes a block trajectory, that is, the “data point densification” work from the start of the block to the end of the block is completed.
- Position control: Position control is located on the position loop of the servo loop. This part of the work can be implemented by software or hardware. Its main task is to compare the theoretical position with the actual feedback position in each sampling period, and use the difference to control the servo motor. In position control, it is usually necessary to complete the gain adjustment of the position loop, the pitch error compensation of each coordinate direction and the backlash compensation to improve the positioning accuracy of the machine tool.
- I/O machining: I/O machining mainly deals with CNC device panel switch signals, input, output and control of machine tool electrical signals (such as tool change, gear shift, cooling, etc.).
- Display: The display of the CNC device is mainly used for the convenience of the operator. It is usually used for the display of part programs, parameter display, tool position display, machine tool status display, alarm display, etc. Some CNC devices also have static and dynamic graphics display of the tool machining path.
- Diagnosis: Check and locate abnormal situations in the system, including online diagnosis and offline diagnosis.
Link to this article：The Work Process Of CNC System
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