CNC machining refers to the processing that the control system issues commands to make the tool perform various movements that meet the requirements, and express the shape and size of the workpiece in the form of numbers and letters. It generally refers to the process of machining parts on CNC machine tools.
A CNC machine tool is a machine tool controlled by a computer. The computer used to control the machine tool, whether it is a dedicated computer or a general-purpose computer, is collectively referred to as a numerical control system. The movement and auxiliary actions of CNC machine tools are controlled by the commands issued by the CNC system. The instructions of the CNC system are compiled by the programmer according to the material of the workpiece, the processing requirements, the characteristics of the machine tool and the instruction format (NC language or symbols) specified by the system. The numerical control system sends out operation or interruption information to the servo device and other functional components according to the program instructions to control various movements of the machine tool. When the machining program of the part ends, the machine will automatically stop. For any kind of CNC machine tool, if there is no program command input in its CNC system, the CNC machine tool cannot work. The controlled actions of the machine tool roughly include the start and stop of the machine tool; the start and stop of the spindle, the change of the rotation direction and speed; the direction, speed and mode of the feed movement; the selection of the CNC machine tools materials, the compensation of the length and radius; the replacement of the tool, the cooling Liquid opening and closing, etc.
In NC programming, the dimensions and positions of all points, lines and surfaces are based on the programming origin. Therefore, it is best to give the coordinate dimensions directly on the part drawing, or try to mark the dimensions with the same datum.
In programming, programmers must fully grasp the geometric element parameters that constitute the part outline and the relationship between the geometric elements. Because all geometric elements of the part contour need to be defined during automatic programming, and the coordinates of each node need to be calculated during manual programming, no matter which point is unclear or uncertain, programming cannot be performed. However, due to the lack of consideration or neglect by the part designers in the design for CNC machining process, the parameters are often incomplete or unclear, such as whether the arc and the straight line, the arc and the arc are tangent, intersecting or separating. Therefore, when reviewing and analyzing the drawings, you must be careful and contact the designer in time if you find any problems.
In machining CNC technology, the machining process is often concentrated, and it is very important to locate with the same reference. Therefore, it is often necessary to set some auxiliary datums or add some process bosses to the blank.
The shape and inner cavity of the part should preferably adopt a unified geometric type or size, which can reduce the number of tool changes, and may also apply control programs or special programs to shorten the program length. The shape of the part is as symmetrical as possible to facilitate programming with the mirror machining function of CNC machining to save programming time.