The factory uses precision CNC machine tools (machining centers, EDM, slow wire moving machine tools, etc.) for high precision processing. Do you have this experience: When the machine is started for processing every morning, the machining precision of the. the first piece is often not good enough; when the machine is started for processing after a long vacation. 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.
Factories without experience in precision machining often attribute this unstable precision to equipment quality problems. Factories with experience in precision machining will place great importance on the thermal balance between ambient temperature and machine tools. They know very well that even high-precision machine tools can only achieve stable processing precision under a stable temperature environment and thermal equilibrium state. When high-precision machining is about to start after the machine is powered on, preheating the machine tool is the most basic common sense in precision machining.
1. Why is it necessary to preheat the machine tool?
The thermal characteristics of CNC machine tools have a significant impact on machining accuracy, accounting for almost half of the machining accuracy.
The machine tool spindle, guide rails, screws and other components used in XYZ movement axis components will heat and deform due to load and friction during movement. However, the final impact on machining accuracy is the chain of thermal distortion errors. is the relative relationship between the spindle and the components of the XYZ axis of motion. Moving the workbench.
The machining accuracy of the machine tool is significantly different between the long-term shutdown operating state and the thermal equilibrium state. The reason is that the temperature of the spindle and each axis of movement of the CNC machine tool is relatively maintained at a certain fixed level. after running for a while, 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 the treatment.
However, the preparation of machine tools by “warm-up exercise” is ignored or unknown in 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 unused for only a few hours, it is recommended to preheat for 5-10 minutes; before high precision machining.
The preheating process aims to enable the machine tool to participate in the repeated movement of the processing axis. It is best to perform multi-axis linking, for example by moving the XYZ axis from the lower left corner to the upper right corner of the coordinate system. , and moving diagonally several times.
During execution, you can write a macro program on the machine tool to allow the machine tool to repeatedly perform the preheating action. For example, when a CNC machine tool stops for a long time or before processing high-precision parts, based on the mathematical curve of 3D elliptical parameters and the range of machine space- preheated tool, with t as the independent variable and the coordinates of the three motion axes of XYZ as parameters, according to a certain incremental step, taking the maximum range of the specified XYZ motion axis as the parameter The boundary condition of the curve, and combines speed of spindle and the feedrate of the XYZ movement axis to the independent variable t, allowing them to change continuously within the specified range, generates a CNC program that can be recognized by the CNC machine tool, and is used to drive each axis of movement of the machine tool to generate synchronous space. The movement of the load is accompanied by the control transformation of the spindle speed and feed speed during the movement.
After the machine tool is fully warmed up, the energetic machine tool can be put into high-precision machining production. You will get stable and consistent machining accuracy.
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