Performance Analysis of Bearing for Punch Spindle

High-speed punching machine tool spindle technology in recent years is an important trend. Rolling bearings are one of the most important mechanical supports in high-speed rotary motion, and they are also important bases for military and civilian industries. As the mechanical products continue to high-precision, high-speed and high degree of automation of the direction of development, a variety of equipment working speed continues to increase, making the corresponding value (bearing diameter and speed of the product) has reached 300 million, and trying to simply improve the rolling bearing Structure and lubrication conditions to improve the value has far can not meet this requirement. In order to solve this problem, the speed can be increased by about 40% from the case of structural parameters, poor ball quality, such as ball bearings (ball diameter smaller than the average bearing) while maintaining other conditions unchanged. The other is to change the bearing material (such as the use of ceramic ball bearings) because the ceramic material used in the hope that the team 3 balls, the density of only 40% of steel, while the ceramic ball diameter of the small use, Can further reduce the quality of the ball, punch to further improve the speed, especially for ultra-high-speed machine tool spindle.

Ceramic ball bearings have a variety of forms, the machine is commonly used in hybrid ceramic ball bearings, its inner and outer rings are still producing bearing steel, but the ball is used for engineering ceramic materials, known as ceramic ball bearings. Compared with the traditional bearing steel, engineering ceramics materials have many excellent physical and mechanical properties: wear-resistant, high temperature, corrosion-resistant, non-magnetic, insulation low density (about 40%) electrical and thermal expansion coefficient small (25% Modulus (150%), etc., can play an important role in rolling bearings, greatly improving the bearing fatigue life.

In this paper, some important characteristics of ceramic ball bearings for high-speed machine tool spindle are analyzed, and the experimental results of hot-pressed silicon nitride are introduced.

1 ceramic ball bearings rated static load in the design and selection of the most important foundation is the rated static load and rated dynamic load. The former is the largest static load the bearing can withstand, which involves the rolling bearing fatigue life. In the international standard 76 defined in the static load rating of the rolling bearing is the rolling element static load and the rolling contact bearing the maximum contact stress of the total plastic deformation, which is 1/10000 of the rolling element diameter. Static load is too large, the plastic deformation of bearing steel will affect the normal use, therefore, the above definition of bearing steel is appropriate, but under static load plastic deformation behavior of 34 ceramic compared to steel, punch small to almost negligible , Ceramic ball bearings still use the method defined static load is clearly not appropriate. Therefore, the 4 standard provides the general ball bearing rated static load bearing maximum rolling contact with the ring roller contact stress calculation centers 4200 static load ceramic ball bearings more appropriate agitation, the bearing steel is still applicable.

On this basis, we analyze and compare the bearing capacity of steel bearings and ceramic ball bearings under static load.

Is a method of measuring the breaking load of a ball, specified in Japanese Industrial Standard 1501, and comparing the values ​​of 3 ceramic balls and steel balls obtained by this method. It can be seen that with the crushing load compared to the minimum crushing load of the material ball about 1/21 of the steel balls / 3. However, according to the above two criteria, the limit of the static load of the ball used in the bearing is much lower than the crushing load. The limit of static load of ball bearing is controlled by plastic deformation. When the maximum contact stress of ball ring raceway exceeds 4200, the total plasticity of the maximum rolling element and ring rolling contact bearing is reduced by more than ten thousandths of the sphere diameter Therefore, the maximum contact stress of steel ball bearings can not exceed this value. The static load limit of the ceramic ball bearing is controlled by the maximum contact stress between the ball and the bearing roller, and there is almost no plastic deformation due to the plastic deformation of the 34 ceramic. Based on the value of the punch can be calculated by the maximum contact stress failure is defined in the 4 standard ball bearing internal maximum contact force of engineering ceramics is basically a brittle material. When the load is greater than the ultimate load of a brittle fracture of broken ceramic ball. However, due to the development of materials industry, the strength and toughness of ceramic materials has been greatly improved. At present, the ceramic ball bearings of the material in the normal working load does not occur brittle failure, but with the steel bearing has the same failure mode.

Thrust ball bearing fatigue testing machine and Japan Koyo Seiko Toshiba as shown in Table 1 test conditions. Under these conditions, the specimen 34 balls and Table 1 were lubricated under the experimental conditions 1200 / hr 60, and the spindle oil ball 3 ball diameter 9 was loaded at 4,000. First, the silicon ceramic than the high carbon chromium bearing steel rolling fatigue life long. Small, so the contact state better. As the ceramic mark density is only deep groove ball or angular contact ball bearings, the fatigue life with the ball and ring rolling the maximum contact stress. This contact stress on the one hand, from the normal working load, on the other hand, from the heart of the rolling body. When the bearing is running at high speed, the centrifugal force load of the rolling element 10 is equivalent to the additional attack 10. Because of the density of the steel of about 34% of the 34 ceramics, the number of stress cycles under high-speed conditions / the administrator should use the rolling fatigue life of the ceramic ball bearings to significantly reduce the contact stress between the silicon nitride balls and the raceway rollers , Thereby extending the service life of the bearing.

3 ceramic ball bearings in the case of high-speed operation, high-speed operation, the ball and the inner and outer ring rolling control is assumed that the outer rolling contact ball occurs in the pure rolling, rolling contact in the inner ring , Rotational angular velocity and rotational angular velocity ratio are revolutionary. The slew ratio can be used to measure the rolling contact state of the bearing, and the 16 / min value of the smaller, weekly ceramic ball bearing and ball bearing in the ball bearing steel is 40%. In the case of high-speed operation. While the ceramic ball size of the centrifugal force is only about 40 percent of the steel ball, so the ceramic ball bearing inner and outer contact angle difference is smaller than the ball bearing, and thus smaller than the spherical roller bearing (as shown).

Through the ceramic ball and steel ball angular contact ball bearing roller than the calculated results can be drawn, bearing steel ball rolling ceramic ball bearings 50% higher. This shows that the high-speed friction in the temperature Sheng-Jun ceramic ball bearings than steel bearings, especially in the harsh environment of lubrication, the advantages of ceramic ball bearings is more prominent.

4 ceramic ball bearings, corrosion-resistant, insulating and non-magnetic ceramic corrosion resistance is much better than steel, which makes ceramic ball bearings for special environments, such as sea water. However, the corrosion resistance of 4 ceramics can be significantly different from the raw materials, the quality and the sintering additives and sintering conditions. In the curves of the ratio, respectively!

The weight loss rate of three different 4 materials at 90 ° is shown as 30% hydrochloric acid. Therefore, the corrosion resistance of ceramic ball bearings in the process, need to pay attention to the corrosion resistance of silicon nitride. And additives.

Another advantage of the ceramic ball bearing is that it can be used in applications where complete insulation is required. The resistivity of the steel ranges from 108 to 104 ° C. , While the ceramic is above 16. It can be seen that the insulating properties of ceramic materials is much better than steel.

In the strong magnetic field environment, the use of steel bearings, bearing wear powder adsorption between the rolling element and the rolling surface, early bearing damage spalling, the main reason for increased noise, because the ceramic ball bearings are completely non-magnetic, and with normal capacity, so Requires a completely non-magnetic bearing of the occasion.

As a result of the use of silicon nitride ceramic materials 5 Conclusion, ceramic ball bearings can withstand static load than steel bearings, and have a longer rolling fatigue life. As the ceramic ball bearing roller bearing roller pen pen bearing small, ceramic ball bearings in high-speed friction and temperature rise is less than bearing steel. From the perspective of the material itself, punch silicon nitride ceramics have excellent corrosion resistance, insulation, non-magnetic mechanical and physical properties, so the use of non-metallic materials as rolling bearing rolling system is particularly suitable for some steel bearings can not adapt to special environments.

Spin-Rolled Spin / Roller Bearing Friction Heat and Bend Strength and Fracture Toughness of Ceramic Materials (Continued from page 46) Performance improvements, better performance ceramic materials have received increasing attention, but also make it as a rolling bearing For example, when the spool moves 0.2 position, the hydraulic pump, the high pressure oil enters the valve port, the valve port type liquid pressure is made = 3. The outlet hydraulic fluid is output Of the = 1.5 particles attached to the fixed wall to meet the non-slip bar.

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