Product knowledge

Introduction to the speed change mode and maintenance method

Source:未知Author:hyzc Addtime:2022-09-22 Click:
CNC machine tools generally use DC or AC spindle servo motors to achieve infinitely variable speed of the spindle.​​
 
AC spindle motor and AC variable frequency drive device (cage induction AC motor is equipped with vector conversion variable frequency speed regulation system), because there is no brush and no spark, so the service life is long, and the performance has reached the level of DC drive system, even in noise. aspect has been reduced. Therefore, it is widely used at present.
 
The relationship between the power or torque transmitted by the spindle and the rotational speed. When the machine tool is in continuous operation, the spindle speed is in the range of 437~3500r/min, and the spindle transmits the full power of the motor 11kW, which is the constant power area II of the spindle (solid line). In this area, the maximum output torque of the spindle (245N.m) decreases with the increase of the spindle speed. When the spindle speed is in the range of 35~437r/min, the output torque of the spindle does not change, which is called the constant torque area I of the spindle (solid line). In this region, the power that the spindle can transmit decreases as the spindle speed decreases. The dotted line in the figure shows the constant power area and constant torque area when the motor is overloaded (allowed to be overloaded for 30min). The overload power of the motor is 15kW, and the maximum output torque of the overload is 334N.m.

Stepless speed change
In actual production of CNC machine tools, it is not necessary to have constant power in the entire variable speed range. Generally, it is required to use constant power transmission in the middle and high speed sections, and constant torque transmission in the low speed section. In order to ensure that the spindle of the CNC machine tool has a large torque at low speed and the speed change range of the spindle is as large as possible, some CNC machine tools are equipped with a gear speed change on the basis of the AC or DC motor stepless speed change, making it a stepless speed change.

Mechanical Spindle Maintenance
Lubricating oil is often used to reduce the working temperature of the bearing. There are two types of lubrication: oil-air lubrication and oil-circulating lubrication. When using these two methods, pay attention to the following points:
1. When using oil circulation lubrication, it is necessary to ensure that the amount of oil in the constant temperature oil tank of the spindle is sufficient. ​​
2. The oil-air lubrication method is just the opposite of the oil-liquid circulation lubrication. It only needs to fill 100% of the bearing space capacity. ​​
The advantage of circulating lubrication is that, under the condition of satisfying lubrication, it can reduce friction and heat generation, and can absorb part of the heat of the main shaft assembly. ​​
There are also two types of lubrication for the spindle: oil mist lubrication and injection lubrication.



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