How to choose bearings at both ends of ball screw?

Among the loads borne by ball screw, both radial load and axial load exist at the same time, which should be considered when selecting bearings. Common bearings that can bear the above load at the same time are angular contact bearing and tapered roller bearing. The former focuses on light load and high speed occasions, while the latter focuses on heavy load and low speed occasions. It should be noted that the above two kinds of bearings are generally used in pairs, and they are relatively installed (face to face or back to back), which can limit the axial movement of the lead screw.

The early form of linear motion bearing is to put a row of wooden sticks under a row of pry plates. Modern linear motion bearings use the same working principle, but sometimes balls are used instead of rollers. The simplest rotary bearing is a sleeve bearing, which is just a bushing sandwiched between the wheel and the axle. This design was later replaced by rolling bearings, that is, many cylindrical rollers were used instead of the original bushings, and each roller was like an independent wheel.

An early example of ball bearing was found on an ancient Roman ship built in Lake Nano, Italy in 40 BC: a wooden ball bearing was used to support a rotating desktop. It is said that Leonardo da Vinci once described a ball bearing with a ratio of 1500. Among all kinds of immature factors of ball bearings, it is very important that the balls will collide and produce extra friction. But putting the ball in a small cage can prevent this phenomenon. /kloc-in the 0/7th century, Galileo first described the "cage ball" ball bearing. /kloc-At the end of 0/7th century, C. Wallow in Britain designed and manufactured ball bearings, and put them on a mail truck for trial use. P. Worth in Britain obtained a patent for ball bearings. The earliest practical rolling bearing with cage was invented by watchmaker john harrison in 1760 for making H3 chronograph. /kloc-at the end of the 8th century, H.R. Hertz of Germany published a paper on contact stress of ball bearings. On the basis of Hertz's achievements, R. Striebeck of Germany and A. Parmgren of Sweden carried out a lot of experiments, which contributed to the development of design theory and fatigue life calculation of rolling bearings. Subsequently, N.P. Petrov of Russia applied Newton's viscosity law to calculate bearing friction. The first patent on fairway was obtained by Philip Vaughan of Carmarthen in 1794.

1883, Friedrich Fisher put forward the idea of grinding steel balls with the same size and accurate roundness with suitable production machines, which laid the foundation for bearing industry. O. Reynolds of Britain made a mathematical analysis of Thor's discovery and derived Reynolds equation, which laid the foundation of hydrodynamic lubrication theory.