The factory uses precision CNC machine tools (machining centers, electric sparks, slow wire, etc.) for high-precision machining. Do you have such experience: every morning when the machine is turned on for machining, the machining accuracy of the first piece is often not good enough; The accuracy of the first batch of parts is often very unstable, and the probability of failure is extremely high during high-precision machining, especially the positional accuracy.
Add pictures to WeChat: Yuki7557 to send 10G CNC tutorial
Factories without experience in precision machining often attribute the instability of precision to equipment quality problems. And factories with experience in precision machining will attach great importance to the thermal balance of ambient temperature and machine tools.
They are very clear that even high-precision machine tools can only obtain stable machining accuracy in a stable temperature environment and thermal equilibrium state. In the case of high-precision machining production after starting up, preheating the machine tool is the most basic precision machining common sense.
1. Why do we need to preheat 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 and the guide rails and lead screws used in the X, Y, and Z motion axes will all heat up and deform due to load and friction during motion, but the main shaft and X , Y, Z The relative displacement of the moving axis components of the workbench.
The machining accuracy of the machine tool in the state of long-term stop operation and the state of thermal equilibrium is quite different. The reason is that the temperature of the spindle and each movement axis of the CNC machine tool is relatively maintained at a certain 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 shows that it is very necessary to preheat the spindle and moving parts before processing.
However, the preparation link of "warm-up exercise" of machine tools is ignored by many factories.
2. How to preheat the machine tool?
If the machine tool has been left on hold 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 on hold for only a few hours, it is recommended to preheat for 5 to 10 minutes before high-precision machining.
The warm-up 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 X, Y, and Z axes from the lower left corner of the coordinate system to the upper right corner, and repeatedly walking diagonally.
When executing, you can write a macro program on the machine tool to let the machine tool repeatedly perform the warm-up action. For example, when the CNC machine tool stops running for a long time or before processing high-precision parts, according to the mathematical 3D ellipse parameter curve and the preheated machine space range, take t as the independent variable, and the coordinates of the three motion axes of X, Y, and Z as the Parameter variable, according to a certain incremental step, the maximum range of the specified X, Y, Z motion axis is used as the boundary condition of the parameter curve, and the spindle speed and the feed speed of the X, Y, Z motion axis are related to the independent variable t Correlation, let it change continuously within the specified range, generate a CNC program that can be recognized by the CNC machine tool, and use it to drive the movement axes of the machine tool to produce synchronous no-load motion, and during the motion process, it is accompanied by the control transformation of the spindle speed and feed speed.
After the machine tool is fully warmed up, the vigorous machine tool can be put into high-precision machining production!
