Low Cost Automation Tutorial

#135 Mastering Ball Screws - 5 : Noise Reduction of Ball Screws

Category : Linear Motion Components

November 2, 2012

Increased demand for the ball screw noise reduction is due to, not only to the conventional production factory environments, but increased ball screw applications in quiet environments (low noise levels) such as offices, hospitals, and food production lines. Furthermore, ball screw noise reduction links to improved functionalities such as energy savings and extended operational life, thus it is inevitable for performance increase.

(1) About ball screw noise reduction

Comparisons are made below between the construction and noise generating conditions of rolling ball bearings, rolling ball bearing style linear guides, and ball screws.

Structural differences

(2) Noise source (= vibration source) of ball screws

Ball screw noise source (= vibration source) is due to the following structural problems.

Ball screw noise source (= vibration source)	Type of noise
a) Complex ball recirculation paths	Ball collision noises
b) Screw shaft groove surface roughness and surface waviness	Chattering sounds
c) Shaft vibrations from bending and concentricity errors	Squeaking noises by abnormal steel ball sliding
d) Groove shape accuracy (bending, unevenness of groove shape)	Squeaking noises by abnormal steel ball sliding
e) Screw shaft and nut installation errors	Squeaking noises by abnormal steel ball sliding

Ball screw noise is generally defined with an empirical formula: Noise is proportional to the Log of the product of ball diameter dm and screw shaft rotation n. Therefore, the principle measures are reducing the ball diameter and reducing the operational speeds.

For this reason, using large screw leads to lower the rotational speeds can effectively reduce the ball screw noises even at high linear speed operations.

(3) Noise reduction measures as a mechanical system

-	Since the ball screws are installed as components on automation machinery, the noise level is determined by the countermeasures applied to the entire automated machine system. By this countermeasure, the overall noise reduction effect can be obtained.
-	The following items can be listed as the representative factors of mechanical system noise. (1) Lack of mechanical system rigidity (static and dynamic) (2) Structural characteristics such as sound trapping covers (3) Lack of countermeasures on individual vibration source adding up to enhanced vibration transmission and resonaces.

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