Factors affecting dimensional accuracy of CNC machining

I. Avoidable factors affecting dimensional accuracy of CNC machining

Processing technology

Most of the actual machining errors are caused by the irrational processing technology. In ensuring the basic processing technology (such as "roughness first, then precision, first surface then hole, first large surface, then small surface" or fixture use " Reduce the number of clamping, try to use the combination of fixtures and other basic processing details ", to minimize the processing errors caused by iron filings on aluminum parts, because aluminum parts are very soft, and the excluded iron filings can easily cause processing errors on aluminum parts. . For example, in FANUC or Central China machining centers, use the G83 command to make deep holes as much as possible so that iron filings can be discharged instead of the G73 command.

2. Numerical calculation in manual programming and automatic programming

3. Three elements of cutting: cutting speed vc, feed amount f, cutting depth ap and tool compensation

In simple terms, it is to adjust the parameters to give full play to the cutting performance of the tool under the premise of ensuring the processing quality and tool wear, so that the cutting efficiency is the highest and the processing cost is the lowest.

In CNC lathes, there are also elements such as tool head wear compensation. Since I have not touched the lathe for a long time, I dare not go into details, please ask the owner to search by themselves.

4. Tool setting, inaccurate tool setting is also a factor that causes dimensional error, so try to choose a good edge finder, if the machine tool has an automatic tool setting, it is even better

2. Irresistible factors:

1. Workpiece cooling deformation

This is basically unavoidable. Pay attention to the use of coolant when processing, and pay attention to the deformation of the cooled workpiece when performing in-situ measurements.

2. Stability of the machine tool itself

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

Mechanical aspects:

a. Looseness between servo motor and lead screw

b. Worn ball screw bearings or nuts

c. Insufficient lubrication between screw and nut

Electrical aspects:

a. Servo motor failure

b. Dirt inside the scale

c. Servo amplifier failure

PMC recovery can be performed on system parameters, so it is omitted.