Linear Motion

Linear motion guides find use in a variety of precision linear motion applications, from machine tools to medical equipment. They come in two basic types: plain bearing and rolling element. Rolling-element types are further categorized as recirculating ball bearing and guide wheel.

Recirculating linear motion types support loads with a continuous stream of bearing balls that move in and out of contact with a guide rail. The bearings are made to follow straight sections with radii at their ends. This causes balls to vibrate and make noise as they accelerate from the straight to curved sections. The use of polymer cages that separate balls lowers, but does not eliminate, ball-bearing noise in square-rail designs.

Guide wheels, in contrast, react loads through wheels that run on triangular-profile rails. Guide wheels can lower noise levels by 20% compared with square-rail linear motion systems, because the ball-bearing raceway path is a constant radius.

Guide wheels are also more forgiving of mounting-surface irregularities than recirculating linear motion designs. Parallel-track guide wheel systems work fine when mounted on surfaces flat to ±0.004 in. For comparison, mounting surfaces for square rails are typically held to ±0.001 in., which can substantially raise installation costs. Still, be sure to carefully prepare surfaces for parallel-track systems needing high accuracy and repeatability.

Off-the-shelf linear motion guide-wheel systems have a positioning accuracy of about ±0.005 in. depending on the accuracy of the track-mounting surface. Tracks made of drawn steel that is hardened and ground can push that number down to about ±0.001 in.

The operating environment is another important consideration with linear motion. Guide wheels better tolerate contamination than recirculating designs and don't need protective covers on track ways.

 

Characteristic	Guide Wheels	Round Rail	Square Rail	Teflon Bushing
Antifriction	Yes	Yes	Yes	No
High Speed	Excellent	Good	Good	Excellent
High Load	Good	Good	Excellent	Good
Accuracy	Good	Good	Excellent	Fair
High Temperature	Excellent	Good	Poor	Poor
Dirty Environment	Excellent	Poor	Poor	Good
Clean Environment	Good	Good	Good	Poor
Ease of Assembly	Excellent	Good	Good	Good
Noise	Excellent	Good	Good	Excellent
Long Lengths	Excellent	Good	Poor	Good
Rotary Capability	Yes	No	No	No
Compliance	Excellent	Good	Poor	Fair
Rigidity	Good	Good	Excellent	Fair
Low Profile	Excellent	Poor	Excellent	Fair
Cost	Excellent	Good	Poor	Excellent

Learn More about DualVee Technology:

Overview
Harsh Environments
Smooth Motion
Low Noise
Long Lengths
Clean Room
High Temperature
Rotary Motion
Best Practices

DualVee product information