With the advancement of science and technology, the improvement of product performance and the improvement of user requirements for product experience, products require higher and higher precision for machine tool equipment processing. For the current 3C parts, drilling and tapping machines are mainly used when processing. The drilling and tapping machines can not only perform high-speed drilling, tapping and milling, but also perform continuous smooth curve processing, with the characteristics of high speed, high precision and high efficiency.
The spindle is an important part of a drilling and tapping machine. Such spindles generally operate at high speeds in both domestic and overseas machines. Rapid shaft rotation raises spindle temperature, and temperature changes directly affect machining dimensional accuracy and surface quality. Spindle bearings are critical to rotational accuracy. During high-speed operation, bearing friction generates substantial heat, making it a major source of spindle heating.
In the spindle temperature rise solution, the system's adaptive thermal compensation and other measures are used to ensure the machine's processing accuracy. The subsequent remedial measures for the spindle temperature rise do not solve the machining errors caused by the spindle heating at the source.
Effect of temperature rise
As the 3C industry's first choice, the drilling and tapping machine is a high-precision processing equipment that combines speed and accuracy. The spindle is the core component of the drilling and tapping machine that provides the main power for processing. Research shows that the proportion of spindle thermal error to the total error of machine tools can reach 70% at most. Among them, the thermal elongation of the spindle is particularly prominent. This error is along the axis of the spindle, and the drilling and tapping machine is in the Z direction, which is also the sensitive direction of machining errors. The accuracy of the spindle has a very important impact on the accuracy of the entire machine tool.
This article tests the thermal elongation of the spindle, and the data is shown in Figure 1.
According to the above values, it can be seen that when the spindle temperature changes between room temperature and 95℃, the spindle thermal elongation value fluctuates to 0.024mm, and the change is most obvious when the temperature is between 45℃~75℃. During the processing of the drilling and tapping machine, the thermal elongation of the spindle affects the change of its Z value. As the processing time increases, the greater the thermal elongation value, the more it affects the processing accuracy of the processed parts.
In addition to the influence of the spindle temperature rise on the machining accuracy, since the load on the bearing will increase with the temperature rise of the spindle, the service life of the bearing will decrease with the increase of temperature, and the higher the temperature, the greater the gradient of decrease.
Measures to reduce spindle temperature rise
(1) Optimize the assembly method of the spindle;
(2) Select the appropriate cooling method;
(3) Select moderate processing parameters.
(Source: Laoqu, who is engaged in the machine)