Here, we mainly summarize the functions to be achieved by the aforementioned CNC tasks in order to further analyze and integrate the hardware and software architecture of the CNC controller.
The functions of the CNC controller usually include basic functions and selection functions. Basic functions are essential functions of the CNC system, and selection functions are functions that users can choose according to the characteristics and uses of the machine tool. CNC usually has the following main functions:
1. Axis control function: This function refers to the number of axes that the CNC can control and control simultaneously. For the axes of motion of CNC machine tools, there are moving axes and rotary axes, basic axes and additional axes. Generally, CNC lathes only need 2 axes to be controlled simultaneously. CNC milling machines, CNC boring machines and machining centers require 3 or more control axes. The number of axes that can be controlled simultaneously can be 2 axes or 3 axes, etc., depending on the purpose. CNC machine tools that process spatial surfaces require more than 3 axes to be controlled simultaneously. The more control axes there are, especially the more simultaneous control axes there are, the more complex the CNC controller is, and the more difficult it is to compile multi-axis linkage part programs. 2. Preparation function: The preparation function is also called G function, which is used to instruct the machine tool movement mode, including basic movement, plane selection, coordinate setting, tool compensation, fixed cycle, meter-inch conversion and other instructions. It is expressed by G and the two digits behind it. 3. Interpolation function: CNC realizes the trajectory of tool movement through software interpolation. Due to the strong real-time performance during continuous contour control, the calculation speed of software interpolation is difficult to meet the requirements of CNC machine tools for feed speed and resolution, and requires CNC to continuously expand other functions to reduce the CPU time occupied by interpolation calculation. Therefore, the interpolation function of CNC is actually divided into coarse interpolation and fine interpolation. The software interpolates a small line segment data each time, which is called coarse interpolation. The private service interface divides the small line segment into a single pulse output according to the result of coarse interpolation, which is called fine interpolation.
The shapes of parts to be contoured are mostly composed of straight lines and arcs, and some are composed of more complex curves. Therefore, there are straight line, arc, parabola, sine, cylinder, and spline interpolation. The methods for implementing interpolation operations include point-by-point comparison method, digital integration method, direct function operation method, etc. Feed function. According to the requirements of mechanical processing technology, the feed function of CNC uses F to directly command the feed speed of each axis of the CNC machine tool.
