Is It Necessary To Warm Up The CNC Machine Every Morning?

Factories use precision CNC machine tools (machining centers, electric sparks, slow wire and other machine tools) for high-precision machining. Do you have such an experience: Turn on the machine every morning for processing, and the machining accuracy of the first part is often not good enough; And after vacation, 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 with insufficient precision machining experience often attribute this unstable accuracy to equipment quality problems. For factories with rich experience in precision machining, they attach great importance to the environmental temperature and the thermal 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.

1. Why do we need to warm up the machine tool?

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 in the XYZ motion axis, the lead screw and other components will be heated and deformed due to load and friction during the movement, but the main shaft and the XYZ motion axis components in the thermal deformation error chain ultimately affect the machining accuracy.

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.

2. How to preheat the machine tool?

If the machine is left for more than several 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.

When executing, you can write a macro program on the machine tool to allow the machine tool to repeatedly perform the preheating action. For example, when the CNC machine tool is stopped for a long time or before high-precision parts processing, according to the mathematical 3D elliptic parameter curve and the preheated machine space range, t is the independent variable, and the coordinates of the three motion axes of XYZ are used as the parameter. With a certain incremental step, the maximum range of the specified XYZ motion axis is used as the boundary condition of the parameter curve, and the spindle speed and the feed speed of the XYZ motion axis are associated with the independent variable t, so that it can continuously change within the specified range, and generate The recognizable numerical control program of the numerical control machine tool is used to drive each movement axis of the machine tool to produce synchronous no-load movement, and is accompanied by the control transformation of the spindle speed and the feed speed during the movement.

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