Optimum Structure Design of CNC Lathe Spindle


With the rapid development of science and technology, the processing precision of mechanical equipment is getting higher and higher, and the mass production of processed parts is achieved in the high-efficiency and high-precision CNC machine tools in the machining industry such as electronics, automobiles, washing machines and medical equipment. widely used.

China's preliminary understanding of CNC machine tools in the 1980s, and now the demand for CNC machine tools in various machining industries, can be said to be the world's largest manufacturer and use of CNC machine tools, especially for small and medium-sized CNC machine tools. The number of companies producing such CNC machine tools has increased dramatically. However, most CNC machine tools produced in China have relatively poor machining accuracy and high maintenance rate, which can not meet the requirements of processing high-precision mechanical parts. Had to rely on imported machine tools.

From the current view of CNC machine tool control system, in addition to some well-known foreign brands, the performance of CNC system developed in China is basically stable and reliable, and the control accuracy is relatively high. The main reason for the low precision, poor stability and high maintenance rate of some CNC machine tools is the unreasonable design of the machine tool structure, the low precision of machining parts of the machine tool, and the assembly process. Compared with similar foreign machine tools, there is a big gap.

CNC lathes account for the main proportion of CNC machine tools. Small and medium-sized CNC lathes with the largest diameter below φ360 are used the most. Most of these CNC lathes use the variable frequency motor stepless speed regulation to directly drive the lathe spindle for cutting. In order to improve the machining accuracy of lathes, in addition to improving the accuracy of the bed, saddle, ball screw and other components, the spindle part of the lathe is a key component to improve the machining accuracy and service life of the lathe. After more than ten years of analysis and research on the spindle structure of medium and small CNC lathes, an ideal spindle structure has been designed. The spindle structure has high speed, high precision, long service life, simple assembly, convenient maintenance and good waterproof performance.

The structure and characteristics of the spindle are analyzed below. The structure of the spindle is shown in Figure 1.

First, the spindle structure analysis

A pair of angular contact series bearings and a single angular contact bearing are used at the front end of the main shaft to form an angular contact bearing pair. A separate angular contact bearing locks the bearing through a lock nut. A pair of angular contact back-to-back combined bearings are used at the rear end of the spindle. The bearing is locked by a lock nut through a bearing pad. The five-bearing support structure adopts a pair of series angular contact bearings at the front end, and is equipped with a single angular contact bearing, which has the characteristics of high rotation speed, high precision and high rigidity.

Second, the main features of the spindle structure

1. There are two sinks on the main shaft. A water stop is formed on the front flange, and a water hole is opened in the lower part of the flange. Once the coolant liquid enters from the gap between the main shaft and the front flange, the coolant falls into the front flange retaining tank due to the centrifugal force due to the high-speed rotation of the spindle, and is discharged from the lower flow hole. A sink was designed on the bearing pad to achieve the purpose of secondary waterproofing. The rear bearing part is also designed with the same waterproof structure as the front end. Its waterproof structure is very effective, ensuring that the coolant cannot enter the bearing and the bearing is damaged.

2. The main shaft can be used as a component. In addition to the pulley, the entire bearing and bearing pad are installed first. And adjust the bearing clearance, and then fit into the hole of the front box body, and lock the front flange screw. There is a bearing inner and outer ring adjustment pad between the front end series bearings, and the bearing and bearing clearance can be adjusted by grinding the adjustment pad on the tooling in advance. Mounting the bearing on the spindle tightens the front and rear lock nuts to the tightest extent without damaging the bearings because they are too tight. Excluding the ordinary spindle structure, the spindle bearing is too tight or too loose due to insufficient assembly experience by adjusting the spindle tail lock nut to directly adjust the spindle bearing clearance. When the bearing is used for a certain period of time, bearing wear occurs. It is also possible to re-adjust the bearing clearance by grinding the inner pad of the bearing to restore the spindle rotation accuracy.

3. The rear bearing hole of the front box is no stepped hole. When the length of the thermal expansion and contraction changes due to the running of the main shaft, the outer ring of the rear bearing will move slightly in the bearing hole to ensure the precision of the spindle rotation and increase the service life of the bearing. .

4. Maintenance and disassembly is very convenient. When it is necessary to disassemble the spindle, first remove the spindle pulley, then remove the fastening screw on the front flange, and directly push the spindle and all the spindle bearings together from the front housing from the rear of the spindle. Due to the small diameter of the inner ring of the bearing, it is not easy to disassemble the bearing. In order to facilitate the removal of the inner ring of the bearing without breaking the outer ring of the bearing to damage the bearing, a bearing pad for the bearing is designed, so that the bearing can be easily removed from the main shaft.

The above analysis of the main features of this CNC lathe optimization spindle structure for peer reference. All in all, the spindle part of CNC machine tools plays an important role in CNC machine tools, which is related to the performance, accuracy and service life of CNC machine tools. For CNC machine tool manufacturers, whether there is a good CNC product is related to whether their own CNC machine tool products can be recognized and welcomed by the majority of users. In the highly competitive CNC machine tool market, you can get a place in the main factor. For CNC machine tool users, there are excellent CNC machine tools that create more benefits for the company, which is the dream of many entrepreneurs. For the country, the quality and development of CNC machine tools has been freed from the blockade of some countries in the field of numerical control technology. It has promoted the development of China's military, medical, aerospace and other industries.