In the industrial field of small piece parts, the term "precision bearing" may refer to ultra-precision ball bearings, precision angular contact bearings, super precision ball bearings, or other bearing products designed with high accuracy and great precision quality. The ball bearing commonly used in mechanical engineering is a type of rolling element bearing that contains balls to support the separation between the bearing races. This is essential for the entire precision bearing operation process. In other words, the main purpose of ball precision bearings is to reduce rotational friction, while precision bearings’ radial and axial loads during operation.
In fact, the ball precision bearings can use at least three races to accommodate the balls to achieve the purpose of reducing friction and loads, and can transmit the loads through the ball units with the precision bearings.
In most applications, one race is fixed, while the other race is fixed to the rotating component. When one of the precision bearings’ races rotates, it will cause the balls to rotate. Compared with the sliding of two flat surfaces, the friction coefficient of balls rolling is much lower.
In applications, precision bearings are a useful tool that can help maintain the smooth operation of the machine and reduce failures. The development of the precision bearings’ concept can be traced back to the middle Ages. One of the earliest versions of bearing design was a rolling element bearing, which was a wooden ball precision bearings’ model used to support a rotating table. During the Renaissance, an artist used drawings of ball precision bearings in his design for helicopter in 16th century. Later, many European experts devoted themselves to the development of bearing structure in mechanical design, hoping to use it to make the mechanical operation smooth and reduce friction. Bearings used in modern industry have more functions and features, and are more versatile. Therefore, operation and calculation are much more complicated.
Due to the smaller contact areas between the balls and the race, the load capacity of the ball bearing is often lower than that of other types of rolling-element bearings during operation. However, they can tolerate certain deviations of the inner and outer races. Like any other mechanical devices that involves friction and motion, ball bearings must be equipped with an appropriate lubrication mechanism to work properly. Usually, it uses oil or grease-based lubricants to achieve elasto-hydrodynamic effect. Dry lubricated bearings can also work at extreme temperatures. If the bearing device is expected to have its nominal life under its maximum load, the bearing must be lubricated with a lubricant with at least a minimum dynamic viscosity.
The term dynamic viscosity is a word derived from bearing design. Use the dynamic viscosity recommended by the bearing manufacturer to be in the correct ratio to the diameter of the bearing. At this point, to be precise, the correct dynamic viscosity will decrease with rotating frequency to an appropriate value. The calculation is very complicated but critical. Engineers must correctly set all influencing factors to make the device operate normally.
Throughout history, the application of bearings has been extensive and long. In the field of machine tools, there are many items that cannot work without the help of bearing devices. As mentioned above, the machine tool spindle is one of the important components of modern machine tools. The spindle has a variety of designs, and different designs are based on its driving mechanism and power sources.
In terms of spindle classification, there are belt driven, motorized, gear driven, direct driven, motor built in, etc. Among all drive mechanisms, the direct driven spindle has greater torque power, faster and more accurate activation, and larger area coverage. The speed of the spindle is a key parameter that determines the performance of the machining center. The spindle speed RPM (revolutions per minute) standard varies from region to region, and there is no such a common definition. Although manufacturers in Europe, Japan, and Taiwan have a certain consensus on RPM standards, regional differences are still significant.
In the metalworking sector, a turn and mill machine is also known as a CNC turning center. This is a machine tool with both turning and milling functions, and can rotate the work piece on the rotating axis to perform various machining operations. Traditionally, a machine tool can contain several spindles, such as headstock and tailstock spindles on a bench lathe machine. Among several spindles on a machine, the primary spindle is usually is the biggest one. If the spindle is referenced without further qualification, it usually refers to the primary spindle. This is because, in today's industry, there will be many available components that can be combined.
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