Analysis of the principle and method of tool alignment of CNC lathe

The meaning of the knife is that before the CNC lathe is working normally, the position of each tool must be determined first, so as to ensure the quality of the lathe’s work. When determining the position, the tool offset value is required, that is, the specific tool position is determined in the workpiece coordinate system and the CNC lathe coordinate system, which requires selecting a suitable CNC lathe reference point and doing a series of related work.
1. The basic principle of tool alignment of CNC lathes
We take a flat-bed CNC lathe as an example to discuss the basic concepts and principles of lathe tool alignment. The O marked in the figure is the origin of the flat-bed machine tool, OP is the origin of the workpiece, B is the starting point, T is the reference point for the tool, L0 is the thickness of the chuck, L is the length of the workpiece extending out of the chuck, d is the diameter of the bar, (X0, Z0) is the coordinate value of the starting point B relative to the OP point.
Under normal circumstances, the origin of the machine tool is adjusted by the manufacturer before the machine leaves the factory, and the original point of the machine tool cannot be changed at will during use.The selection of the coordinate system of CNC machine tools is based on the origin of the machine tool as the origin of the coordinate system, which is generally located at the intersection of the front end of the chuck and the center line of the spindle.The reference point of a CNC lathe usually refers to a fixed point on the tool holder. R is used instead of R in the figure. This is the point where the reference point T and point O of the tool are the farthest away. This point is also debugged by the manufacturer and does not need to be changed in use.Before the CNC machine tool performs tool alignment, all the tool holders must be returned to the reference point for operation.The selection of the specific location of the reference point R should be determined according to the passage of the mechanical stop on the machine tool.
The determination of the workpiece coordinate system and the starting point is also very important.Under normal circumstances, the origin of the workpiece coordinate system can also be arbitrarily selected, but for the convenience of programming, it is generally selected at the intersection of the right end face of the workpiece or the left end face and the center line.The starting point B is also called the starting point of the program, that is, the position of the tool site A and the origin of the workpiece OP.After the coordinate system of the workpiece is established, it will not conflict with the coordinate system of the CNC machine tool, and the two are independent of each other.The selection of the tool reference point T is an important step before the CNC machine tool is processed. The selection of this point should be fixed so that the movement effect of each tool can be better controlled.Reasonable setting of the knife offset value is also particularly critical, and the process of setting it is actually the process of knife operation.Before the CNC lathe is in normal operation, the size value of the tool position relative to the origin of the workpiece should be determined according to the programming requirements, and then the starting position of the tool should be determined based on this size value.Bias compensation of tool position is a frequent measure to be taken.When many knives process one part at the same time, all tool tips must be moved to the reference point of the same coordinate system when programming. At this time, tool position compensation needs to be used.If a tool is used in the processing process, and it must be installed back to its original position after being replaced or polished, some errors will inevitably occur, which requires tool position compensation to reduce the error.

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