What guarantees the machining accuracy of machine tools?

2、 Practical application

1. Full closed loop control system

In theory, the closer to the drive axis (lead screw pair), the more accurate the measurement is. Due to the limitation of structure space, there are only two ways to install the grating ruler, one is near the side of the lead screw, the other is installed outside the guide rail. It is recommended to select the first installation method as far as possible, but it is not convenient to repair and maintain. On the contrary, the grating ruler with high precision is selected, but the accuracy required by CNC machine tool is not achieved. Even in the first case, the installation position of the grating ruler is close to the drive axis, but there is a certain distance between the installation position and the driving axis. The combination of this distance and the swing of the object during driving brings great trouble to the detection and control of the grating ruler. When the driving object swings to the installation side of the grating ruler, the grating ruler mistakenly thinks that the moving speed is insufficient, and the system gives acceleration signal, and the driven object immediately swings to the other side. When the grating ruler is detected, it mistakenly thinks that the moving speed is too fast, and the system will give a deceleration signal. In this way, the control of each linear coordinate axis of CNC machine tool is not improved It aggravates the vibration of the driving object, which leads to the strange phenomenon that the full closed-loop is inferior to the semi-closed-loop.

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