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How does the CNC machining center perform tool compensation?

Time:2021-03-29 Views:173

 CNC machining centers are used to process parts with complex shapes, multiple processes, and high precision requirements. Therefore, a few or a dozen tools or more are needed to process a part. Since the diameter and length of each tool are different, after determining the zero point of the workpiece coordinate system for the processed part, it is necessary to introduce the tool compensation function to ensure that each tool is lowered to the correct height during the machining process. The tool path for cutting processing.


   Tool compensation can be divided into tool length compensation and tool radius compensation. Length compensation refers to the compensation in the axial direction of the spindle, that is, the compensation in the axial direction of the milling cutter, and the compensation in the radial direction of the milling cutter, that is, the diameter of each milling cutter is different, and the compensation in the diameter direction is called radius compensation.


  How does the CNC machining center perform tool compensation?


   1. Tool radius compensation


   1. Significance of tool radius compensation


   The CNC machining center regards the tool as a point for path movement when the program is running. For example, when using the tool R3 to mill a square boss with a side length of 100, the program is input according to a square size with a side length of 100, and the path of the tool axis is a square with a side length of 106, then the workpiece is milled on the workpiece to be a 100 square with the drawing size . If the tool radius compensation function is not used, the path of the tool axis during machining is a square with a side length of 100, and the workpiece milled out is a square boss with a side length of 94, which does not meet the requirements of the drawing size.


  2. Command format


   G17/G18/G19 G00/G01 G41/G42 IP_D_


   G41: Tool radius left compensation


   G42: Tool radius right compensation


   Radius compensation can only be performed in the specified coordinate plane. Use the plane selection command G17, G18 or G19 to select the XY, ZX or YZ plane as the compensation plane respectively. The radius compensation must specify the compensation number, and the tool radius value is stored by the compensation number D. When the above command is executed, the tool can automatically shift to the left (G41) or right (G42) by a tool radius compensation value. Since the creation of tool compensation must be completed in the block containing motion, G00 (or G01) is also written in the above format. The compensation should be cancelled before the end of the procedure.


   3. Application of tool radius compensation


   Tool radius compensation has two types of compensation: B function and C function. Since the tool radius compensation of the B function only calculates the tool compensation according to this program, it cannot solve the transition problem between the program segments. The workpiece contour is required to be processed into a round transition, so the workmanship at the sharp corners of the workpiece is not good; the C function tool radius Compensation can automatically process the transfer of the tool center trajectory between the two program segments, and can be programmed completely according to the contour of the workpiece. Therefore, almost all modern CNC machine tools adopt C function tool radius compensation.


   How to judge the direction of tool radius compensation? Judgment method: "Follow the direction of tool movement", the tool is left compensation on the left side of the workpiece, and the tool is right compensation on the right side of the workpiece. The compensation can be "negative". When the tool radius compensation takes a negative value, the functions of G41 and G42 are interchanged.

 How does the CNC machining center perform tool compensation?(图1)

The radius value of the tool is pre-stored in the memory Dxx. xx is the memory number. When a program needs several tools, it is recommended that the tool number Txx corresponds to the memory Dxx, that is, the radius compensation value of the T1 tool uses the D01 memory accordingly , So it is not easy to make mistakes during processing. After executing the tool radius compensation, the CNC system automatically calculates and makes the tool automatically compensate according to the calculation result. In the process of processing, if there is a difference between the part outline size and the drawing size, you can modify the radius compensation value in the memory Dxx, and then re-run the program to meet the requirements. Use G40 to cancel tool radius compensation, or use D00 to cancel tool radius compensation.


Note during use: When creating and canceling tool compensation, G41, G42, G40 instructions must be in the same segment with G00 or G01 instructions, that is, G00 or G01 instructions must be used at the same time in the block that uses G41, G42, G40 instructions, but not at the same time Use G02 or G03, and the length of the linear segment that runs when creating or canceling tool compensation is greater than the radius of the tool to be compensated, otherwise the compensation function will not work; and in the compensation mode, writing 2 or more tools does not work. The moving block (auxiliary function, pause, etc.), the tool will produce overcutting or undercutting.

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