The structure of a ball screw is similar to that of a planetary roller screw. The difference is that the load transfer element of a planetary roller screw is a threaded roller, which is a typical linear contact, while the load transfer element of a ball screw is a ball, which is a point contact, with the main advantage of having numerous contact points to support the load. The planetary roller screw is a mechanism that converts rotary motion into linear motion. The rolling element in the middle of the nut and the screw is a threaded roller, and the numerous contact lines make the planetary roller screw have a very high load carrying capacity.
Planetary Roller Screws & Precision Ball Screw
So what are the specific differences between planetary roller screw and ball screw?
1.Speed and Acceleration
Planetary roller screws can provide higher rotational speed and higher acceleration. The CHR and CHRC series planetary roller screw design mechanism has a non-circulating type of roller, while the ball screw mechanism has a circulating type of ball, which will enable the planetary roller screw to rotate twice as fast as the ball screw, and the acceleration will reach 3g.
2、Guidance and Pitch
The lead of planetary roller screw can be smaller than that manufactured by ball screw. Since the lead of a planetary roller screw is a function of pitch, the lead can be less than 0.5mm or smaller. The lead of a planetary roller screw can be designed to be calculated as an integer or a fractional number and will not require a reduction gear to be proportioned. The change in lead does not bring any geometric change to the screw shaft and nut. In contrast, the lead of ball screw is limited by the diameter of ball, thus the lead will be standard.
3、Load Capacity Life
The advantage of planetary roller screw versus ball screw is that it can provide higher dynamic and static load ratings than ball screw. The threaded roller instead of ball will enable the load to be released quickly through numerous contact lines, thus enabling higher impact resistance.
Both planetary roller screws and ball screws are subject to Hertz's Law. From Hertz's Law of Pressure, we can conclude that a planetary roller screw can withstand 3 times the static load of a ball screw and 15 times the life of a ball screw.
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Post time: Sep-27-2022
