Factors affecting the dimensional accuracy of CNC machining

- Feb 15, 2019-

First, factors that can avoid the dimensional accuracy of CNC machining


Processing technology


In most of the actual machining errors are caused by unreasonable machining processes, in the basic processing technology (such as milling CNC machining, "first coarse after finishing, first face back hole, first large face small face" or fixture use" On the basis of reducing the number of clamping, try to use the basic machining process details such as the combination fixture, try to reduce the machining error caused by the iron filings on the aluminum parts, because the aluminum parts are very soft, and the excluded iron filings can easily cause the machining errors of the aluminum parts. . For example, in the FANUC or Central China Machining Center, the deep hole should be used as much as possible with the G83 command, so that the iron filings can be discharged instead of the G73 command.


2. Numerical calculation in manual programming and automatic programming


3. Cutting three elements: cutting speed vc, feed rate f, cutting depth ap and tool compensation


In this case, in simple terms, under the premise of ensuring the processing quality and tool wear, the adjustment parameters fully exert the cutting performance of the tool, so that the cutting efficiency is the highest and the processing cost is the lowest.


In the CNC lathe, there are also factors such as the wear compensation of the cutter head. Since I have not touched the lathe for a long time, I dare not go down to the details.


4. For the knife, the inaccurate tool is also a factor that causes dimensional error. Therefore, try to choose a good edge finder. If the machine has an automatic tool setter, it would be better.


Second, irresistible factors:


1. Cooling deformation after workpiece processing


This is basically unavoidable. Pay attention to the use of coolant during processing and pay attention to the deformation of the workpiece after cooling.


2. The stability of the machine itself


If it is not a new machine tool or the machine tool has undergone a lot of machining without debugging, the dimensional error caused by the machine itself may occur. There are several factors that cause the machine tool itself to have errors:


Mechanical aspects:


a. Loose between the servo motor and the lead screw


b. Ball screw bearing or nut wear


c. Insufficient lubrication between the screw and the nut


Electrical aspects:


a. Servo motor failure


b. There is dirt inside the grating scale


c. Servo amplifier failure


PMC recovery is possible in terms of system parameters, so it is omitted.


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