The tool position point position and tool position vector determination of the NC program depend on the position of the machining coordinate system. Therefore, the exact position of the machining coordinate system or the programming coordinate system must be determined before machining the part.
When machining workpieces on ordinary equipment, the operator usually uses the edge or edge of the tool to determine the edge position of the workpiece as the zero point of machining, and then uses the scale value of the machine tool dial or the reading displayed on the digital display through simple mathematical operations. Determine the zero point of the working coordinate system, and use this point as the reference point for all positions, which is the origin of the machining coordinate system.
The working principle of CNC milling machine and ordinary milling machine is the same: the position of the workpiece on the machine tool must be determined before processing, or the part can be positioned with the dial value or the value of the position digital display. Then, the operator establishes the machining coordinate system, also known as the zero point, by pressing the buttons on the control panel of the CNC machine. It's just that the position of the zero point is determined by the operation inside the control system of the numerical control equipment.
The establishment of the machining coordinate system of the workpiece on the CNC milling machine is to determine the exact position of the workpiece in the machining coordinate system. First, you should understand the concept of two zero points, which are the origin of the machine tool coordinate system and the origin of the machining coordinate system.
CNC milling machines all have a reference point, which is usually referred to as the origin of the machine tool coordinate system or the initial position of the machine tool. It is a fixed reference position set on the machine tool by the machine tool manufacturer and established by limit switches or sensors. The function is to synchronize the machine tool with the control system and establish the starting point for measuring the movement of the machine tool. In a practical sense, the machine zero is fixed, usually at the top right of the machine. When the machine tool is started, the machine tool must execute the canned cycle program that returns to the machine tool zero point, that is, the initialization program, and then automatically store the offset value between the machine tool reference point and the machine tool origin in the machine control unit MCU (Machine Control Unit).
For NC programming and NC machining, another important origin is the program origin, which is the geometric reference point defined by the programmer during NC programming, and this point is used as the origin of the machining coordinate system, which is commonly referred to as the workpiece. origin. The workpiece coordinate system is the machining coordinate system determined when the part is NC programming.