HOME  > Low Cost Automation Tutorial  > #009 Linear Guide Mechanism other than Shafts
Low Cost Automation Tutorial

#009 Linear Guide Mechanism other than Shafts

Category : Linear Motion Components
August28, 2009

Combinations of shafts and linear bushings (or oil-less bushings) as rails and sliders are the simplest form of linear guide mechanism.

(1)Shortcomings of linear guide with shafts and bushings.

Following shortcomings can be noted.

Shortcomings of Shafts and BushingsCountermeasuresEvolution of linear guide mechanisms
Linear bushings cannot be used for rotary motion along the shaft circumference.Two shafts are used to constrict the rotary motionBall spline + Spline shaft configuration.
End supported shafts configuration does not provide enough rigidity against high downward loads.Use of larger diameter shaft and double linear bushings.Shaft guide rails + shafts + linear bushings

(2)Advances in linear motion guide devices

Simplified depiction of the advancements is as follows.


Explained by simplified pictorial

a)A ball spline has ball rolling grooves on the shaft, and free to move only in linear direction. (See [Fig.1])
Fig.1] Ball spline

b)A guide rail support is provided under the entire length of the shaft, increasing the shaft rigidity. Mating linear bushing has a lower section removed to account for the guide rail. (See [Fig.2])
Fig.2] Linear guide unit

c)Since a free moving ball retainer is the bearing element, no movement restrictions in either rotation or linear.

d)Principally similar in construction to b), but ball rolling grooves are provided on the rail to increase bearing contact surfaces for high load capability.
[Fig.3] Higher rigidity and long life design of Slide Gides