The factory uses precision CNC machine tools (machining centers, EDM, slow wire-traveling machine tools, etc.) for high-precision processing. Do you have this experience: when the machine is started for processing every morning, the processing accuracy of the first piece is often not good enough; if the machine is started for processing after a long holiday, The accuracy of the first batch of parts is often very unstable, and the probability of failure is extremely high during high-precision processing, especially position accuracy.
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Factories without precision machining experience often blame equipment quality issues for this unstable accuracy. Factories with precision machining experience will attach great importance to the thermal balance between ambient temperature and machine tools. They know very well that even high-precision machine tools can only obtain stable processing accuracy in a stable temperature environment and thermal equilibrium state. When high-precision machining is about to begin after the machine is turned on, preheating the machine tool is the most basic precision machining common sense.
1. Why is it necessary to preheat the machine tool?
The thermal characteristics of CNC machine tools have an important impact on machining accuracy, accounting for almost more than half of the machining accuracy.
The spindle of the machine tool, the guide rails, screws and other components used in the XYZ motion axis will all heat up and deform due to load and friction during movement. However, it is the relative relationship between the spindle and the XYZ motion axis component that ultimately affects the machining accuracy in the thermal deformation error chain. Displacement of the workbench.
The machining accuracy of the machine tool is significantly different between the long-term stop operation state and the thermal equilibrium state. The reason is that the temperature of the spindle and each motion axis of the CNC machine tool is relatively maintained at a certain fixed level after running for a period of time, and As the processing time changes, the thermal accuracy of CNC machine tools tends to be stable, which shows that it is very necessary to preheat the spindle and moving parts before processing.
However, the "warm-up exercise" preparation of machine tools is ignored or unknown to many factories.
2. How to preheat the machine tool?
If the machine tool is idle for more than several days, it is recommended to preheat for more than 30 minutes before high-precision machining; if the machine tool is idle for only a few hours, it is recommended to preheat for 5-10 minutes before high-precision machining.
The preheating process is to allow the machine tool to participate in the repeated movement of the processing axis. It is best to perform multi-axis linkage, such as moving the XYZ axis from the lower left corner to the upper right corner of the coordinate system, and repeatedly moving diagonally.
During execution, you can write a macro program on the machine tool to let the machine tool repeatedly perform the preheating action. For example, when a CNC machine tool stops running for a long time or before processing high-precision parts, based on the mathematical 3D elliptical parameter curve and the preheated machine tool space range, with t as the independent variable and the coordinates of the three motion axes of XYZ as parameters, according to A certain incremental step takes the specified maximum range of the XYZ motion axis as the boundary condition of the parameter curve, and associates the spindle speed and XYZ motion axis feed speed with the independent variable t, allowing them to continuously change within the specified range to generate CNC programs that can be recognized by CNC machine tools are used to drive each motion axis of the machine tool to produce synchronous no-load motion, and are accompanied by the control transformation of the spindle speed and feed speed during the motion process.
After the machine tool is fully warmed up, the energetic machine tool can be put into high-precision machining production. You will obtain stable and consistent machining accuracy.
