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The difference between planetary roller screw and ball screw

Views:2     Author:Site Editor     Publish Time: 2021-02-08      Origin:Site

Difference

The difference between planetary roller screw and ball screw

The structure of the planetary roller screw is similar to that of the ball screw. The difference is that the load transfer element of the planetary roller screw is a threaded roller, which is a typical line contact; while the load transfer element of the ball screw is a ball, which is a point contact. The main advantage is that there are numerous contact points to support the load. Threaded rollers instead of balls will allow the load to be quickly released through numerous contact points, which can have higher impact resistance.

Bearing capacity life

The advantage of planetary roller screws compared with ball screws is that they can provide higher rated dynamic and static loads than ball screws. Threaded rollers instead of balls will allow the load to be quickly released through numerous contact lines, which can have higher impact resistance.

Both planetary roller screws and ball screws apply to Hertz's law

According to Hertz's pressure law, we can conclude that the static load of the planetary roller screw is 3 times that of the ball screw, and the life is 15 times that of the ball screw.

Speed and acceleration

Planetary roller screw can provide higher rotation speed and higher acceleration. The rollers in the planetary roller screw design mechanism of the RGT and RGTB series are non-circulating, while the balls in the ball screw mechanism are cyclic, which will make the rotation speed of the planetary roller screw the ball screw 2 times, the acceleration will reach 3g.

Lead and pitch

The lead of the planetary roller screw can be smaller than that of the ball screw.

Since the lead of the planetary roller screw is a function of the pitch, the lead can be less than 0.5mm or less. The lead of the planetary roller screw can be designed and calculated as an integer or a decimal (for example: 3.32mm per revolution). There will be no need for reduction gears to match. The change of lead will not bring any geometrical changes to the screw shaft and nut.

The lead of the ball screw is limited by the diameter of the ball, so the lead will be standard.

Stiffness and strength

The numerous contact lines of the planetary roller screw will greatly improve the rigidity and impact resistance.


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