Failed machining accuracy? The forgotten "machine warm-up"!

2021/08/09


Factories use precision CNC machine tools (machining centers, EDM, slow-walking machines, etc.) for high precision machining, do you have this experience: every morning when you start the machine for machining, the machining accuracy of the first part is often not good enough; the first parts that start after a long holiday are often very unstable in terms of accuracy, and the probability of failure is very high in high precision machining, especially in terms of positional accuracy.

Factories without experience in precision machining often blame the quality of equipment for this unstable accuracy. Factories with experience in precision machining, on the other hand, pay great attention to the ambient 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 balance. In the case of high precision machining production after the machine is turned on, it is the most basic common sense of precision machining to warm up the machine.

Why do you 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. Machine tool spindle, XYZ motion axis parts used in the guide, screw and other components will be in motion due to load and friction and warming deformation, but the thermal deformation error chain ultimately affects the machining accuracy is the spindle and XYZ motion axis parts relative to the table displacement.
Machine tool in a long time stop running state and thermal equilibrium state of processing accuracy differences, the reason for this is because the CNC machine tool spindle and each axis of motion in the operation of a period of time, the temperature is relatively maintained at a fixed level, and with the change in processing time, the thermal accuracy of CNC machine tools tend to stabilize, which shows the processing of the spindle and moving parts before the warm-up is very necessary.
However, the machine tool "warm-up" this preparation is ignored by many factories or do not know.

How to warm up a machine
If the machine has been on hold for more than a few days, it is recommended that it be warmed up for 30 minutes or more before high precision machining; if it has been on hold for only a few hours, it is recommended that it be warmed up for 5-10 minutes before high precision machining.
The warm-up process is to involve the machine tool in the repeated movement of the machining axes, preferably in a multi-axis linkage, such as having the XYZ axis move from the lower left corner position of the coordinate system to the upper right corner position, repeatedly going diagonally.
The execution can be done by writing a macro program on the machine tool to allow the machine tool to repeatedly perform the warm-up action.
After the machine is sufficiently warmed up, the vibrant machine is ready for high precision machining production and you will get consistent and uniform machining accuracy.