The first piece machining accuracy of CNC drilling and milli
When using CNC drilling and milling machines, it is common to encounter situations where the machining accuracy of the parts cannot meet expectations when starting up early in the morning; After a long holiday, the precision of the parts that are started for processing is often unstable, and the probability of failure during high-precision processing is high, especially in terms of positional accuracy.
Factories without precision machining experience often attribute the cause to equipment quality issues. And factories with precision machining experience will consider the thermal balance between environmental temperature and machine tools. They are very clear that even high-precision machine tools can only achieve stable machining accuracy in a stable temperature environment and thermal equilibrium state.
Usually, we do first piece machining to verify the correctness of the part machining program and to verify whether the dimensions after machining meet the requirements of the drawing. At the same time, it is also to verify whether the selected tool, cutting amount, and set tool compensation value are appropriate during programming. However, we cannot ignore the influence of thermal characteristics of CNC drilling and milling machines on machining accuracy.
The thermal characteristics of CNC drilling and milling machines have an impact on machining accuracy, accounting for almost half of the machining accuracy. The spindle and XYZ motion axis components of the machine tool, such as the guide rails and screws, will undergo heating and deformation due to load and friction during motion. However, in the thermal deformation error chain, the displacement of the spindle and XYZ motion axis components relative to the workbench affects the machining accuracy. There is a significant difference in machining accuracy between the equipment in a long-term shutdown state and a thermal equilibrium state, mainly because the temperature of the spindle and various motion axes of the CNC machine tool will remain relatively fixed after running for a period of time. Moreover, as the machining time changes, the thermal accuracy of the CNC drilling and milling machine tends to stabilize, indicating that preheating the spindle and moving parts before machining is very necessary.
If the machine tool has been left idle for more than several days, we recommend preheating for at least 30 minutes before high-precision machining; If the idle state is only a few hours, we suggest preheating for 5-10 minutes before high-precision machining.
In fact, the preheating process involves involving the CNC drilling and milling machine in the repeated movement of the machining axis, performing multi axis linkage, such as moving the XYZ axis from the bottom left corner of the coordinate system to the top right corner, and repeatedly walking diagonally. When executing, we can write a macro program on the machine tool to repeatedly perform the preheating action.
After sufficient preheating of the CNC drilling and milling machine, it can be put into high-precision machining production.
