​The machining accuracy is unqualified? The forgotten "machine warm-up"!

The machining accuracy is unqualified? The forgotten "machine warm-up"!

The factory uses precision CNC machine tools (machining centers, EDM, slow wire and other machine tools) for high-precision machining. Do you have any experience: When you turn on the machine every morning for machining, the machining accuracy of the first part is often not good enough; The accuracy of the first batch of parts is often very unstable, and the probability of failure in high-precision machining is extremely high, especially the position accuracy.

Factories without precision machining experience often attribute the instability of accuracy to equipment quality problems. And factories with precision machining experience will pay great attention to the environmental temperature and the heat balance of the machine tool. They know very well that even high-precision machine tools can only obtain stable machining accuracy under a stable temperature environment and thermal equilibrium. In the case of high-precision machining and production after the machine is turned on, preheating the machine tool is the most basic common sense of precision machining.

01

Why do we need to warm up the machine?

The thermal characteristics of CNC machine tools have an important impact on machining accuracy, accounting for almost half of the machining accuracy. The main shaft of the machine tool, the guide rails used by the XYZ motion axis, the lead screw and other components will be heated and deformed due to load and friction during the movement. However, in the thermal deformation error chain, the final influence on the machining accuracy is the displacement of the spindle and XYZ motion axis components relative to the worktable.

The machining accuracy of the machine tool in the state of long-term shutdown and the state of thermal equilibrium is quite different. 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 With the change of processing time, the thermal accuracy of CNC machine tools tends to be stable, which indicates that preheating of the spindle and moving parts before processing is very necessary.

However, the preparatory part of the "warm-up exercise" of the machine tool is ignored or unknown by many factories.

02

How to warm up the machine?

If the machine is left for more than a few days, it is recommended to preheat for more than 30 minutes before high-precision machining; if the machine is left 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 machining axis. It is best to perform multi-axis linkage, such as moving the XYZ axis from the lower left corner of the coordinate system to the upper right corner, and repeating the diagonal line.

When executing, you can write a macro program on the machine tool to allow the machine tool to repeatedly perform the preheating action.

After the machine is fully warmed up, the energetic machine tool can be put into high-precision processing and production, and you will obtain stable and consistent processing accuracy.