Why Is The Load-bearing Capacity of Planetary Screw More Than That of Ball Screw?
Publish Time: 2026-10-08 Origin: Site
The carrying capacity of planetary roller screw (PRS) is significantly higher than that of traditional ball screw (typically 3-10 times that of ball screw), mainly due to its line contact structure, multi-roller load-sharing design, and optimized force distribution. The specific reasons are as follows:
1. Contact mode: Line contact replaces point contact, and the contact area is significantly increased.
1.1. In ball screw, the contact is point contact (steel balls are in point contact with the raceway), with a small contact area and high local contact stress, which is prone to surface fatigue wear due to stress concentration, limiting the ultimate carrying capacity.
1.2. In planetary roller screw, the contact is line contact (the threads of the screw and nut are in line contact), with a significantly increased contact area, which can more effectively distribute the load and significantly reduce local contact stress, thereby enhancing the overall carrying capacity.
2. Structural layout: Multiple rollers for load sharing, more uniform force distribution
2.1. The carrying capacity of ball screw is limited by the number of balls in the nut and the size of the circulating raceway, with the load mainly concentrated at a limited number of contact points.
2.2. The planetary roller screw uses multiple (usually 6-12) threaded rollers arranged around the planetary gear to mesh with the screw and nut simultaneously, forming a multi-point/multi-line load-bearing structure. This design rapidly releases the load through numerous contact lines, with a more uniform force distribution and higher impact resistance.
3. Stress distribution and fatigue life: Low contact stress, strong anti-fatigue ability
Due to the line contact and load-sharing design, in the same load, each rolling element in the planetary roller screw bears much lower stress than in the ball screw, reducing material fatigue wear, making it less prone to plastic deformation under heavy load conditions, and significantly increasing the carrying capacity limits for both static and dynamic loads.
In summary, the planetary roller screw achieves higher force transmission efficiency and ultimate carrying capacity in the same volume through the reduction of dimensional contact and the mechanical design of multiple points for load sharing, outperforming ball screw in heavy-load and high-impact conditions.