Thermal Expansion Control of Composite Machining Centers

Since it is a composite machining center, every part of the machine tool must ensure high precision, so that high precision can be achieved during use.

The accuracy of machine tools is mainly divided into three parts: static accuracy, such as: straightness, flatness, concentricity and other geometric accuracy tests.

Dynamic accuracy such as: positioning accuracy, repeat positioning accuracy, spindle runout, vertical and horizontal conversion repeat positioning accuracy, and motion stability (no crawling).

Thermal balance accuracy: During the high-speed machining process of the machine tool, each friction part, each moving part, motor, and electrical parts will generate heat, causing thermal expansion of all parts.

Therefore, all means must be taken to prevent heat generation, reduce heat generation and use forced cooling to make thermal expansion develop in a controlled direction.

Synchronous motors are used. Since synchronous motors do not cut magnetic lines of force, they do not produce electrical losses and thus do not generate heat, such as spindle motors and servo motors for each axis.

Reducing wear system: If the guide rail adopts linear rolling guide rail, its friction coefficient is greatly reduced, which also reduces heat generation.

Forced cooling method is adopted: the ball screw, spindle and all servo motors are liquid-cooled, and these coolants are equipped with a forced cooling system to ensure that the spindle, ball screw servo motors work at a constant temperature: the workpiece is processed and cooled in time, and the lubricant is also kept at a constant temperature This technology prevents the temperature from affecting the machine bed, and at the same time improves the cutting conditions.

Thermal compensation method is adopted: For example, the temperature sensor on the spindle will perform thermal compensation on the nose of the spindle as the temperature changes during use: four thermal sensors are installed throughout all linear axes to perform real-time monitoring of the linear axes. Thermal compensation.

In order to ensure the high rigidity and high dynamics of the machine tool, the bed adopts a wall structure (Figure 1), and there are two guide rails on the X-axis to ensure the high rigidity of the spindle in the Z-axis direction. Compared with the moving column machine tool , its static mass is doubled and its moving weight is reduced by 50%. The bed is made of GGG-60 (equivalent to QT600-3 ductile iron, cutting technology website note) castings, and has undergone snow-covered aging treatment to ensure that the machine tool has high rigidity and vibration absorption. The Y-axis guide rail adopts a 35° inclination angle (Figure 2), which makes it difficult for iron chips to accumulate on it, and the spiral chip conveyor is separated from the bed (Figure 3), so that the heat and vibration of the iron chips and coolant will not affect the bed The spindle is equipped with a vibration sensor to prevent the spindle from being processed in the resonance area.

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