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Zero Backlash Linear Motion

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Zero Backlash Linear Motion Fluid Power/Power Transmission LINEAR MOTION Bearing & roller Zero Backlash Linear Motion Roller pinion system produces high-speed, Rollers in opposition long-life, precision motion option Unique tooth profile BY AL PRESHER, CONTRIBUTING EDITOR SOURCE: NEXEN GROUP INC. pplications requiring high speed, tially maximize motion across the surfaces, The roller pinion system maximizes motion precision and zero backlash can with the bearing-supported roller and across the surfaces because the bearing- be a challenge to implement for pinion always rolling across the surface,” supported roller and pinion are always roll- A ing across the surface. Smooth operation system designers using conventional rack Weiss says. “There is never a point when is achieved using a unique tooth profi le and pinion or long travel ball screw sys- the roller stops rolling across the tooth, so design which never creates a point where tems. But these applications are a great system operation is very smooth.” the roller stops rolling across the tooth. target for a unique roller pinion system Because Nexen’s RPS systems are pre- (RPS). Using a design that delivers more loaded by applying a small load (0.0005- where the pinion is cut in half, and one than 99-percent effi ciency in converting to 0.0010-inch interference), two of the of the pinions in the same axis as the rotary to linear motion, RPS technology rollers are always in opposing contact on gearhead or motor is preloaded against from Nexen Group Inc. reduces wear and several teeth. The result is that the system the other. But often these confi gurations achieves longer service life at high speeds never stops rolling as the pinion is going degrade the performance of the system. up to 11 m/sec (36.1 ft/sec). through its motion. Motion is smooth, With a new line of integration solu- “Compared to a conventional rack quiet and achieves high effi ciency by tions for ISO 9409 fl anged gearheads, and pinion which is designed to mini- reducing friction. the RPS system is said to be easier to mize sliding of the surfaces, our rack Weiss says that in order to eliminate install in a broad range of linear motion is designed to force sliding all of the backlash, traditional systems commonly applications. Flange mount pinions time,” says Kevin Weiss, chief engineer at use a dual-pinion set-up where there are can be directly mounted to a fl anged Nexen Group. “With a typical involute two pinions running on one rack. The gearhead (no shaft bushing required) system, there is a point at the pitch circle two pinions are pre-loaded either elec- and a pinion pre-loader system includes diameter where the gearing is basically tronically or with a spring, causing one everything needed to properly integrate pivoting on the surfaces.” pinion to work against the other. Some the RPS into a machine design (fasteners, “With the roller pinion system, we essen- solutions use a split-pinion arrangement adjustment device, drawings, etc.). All components are pre-selected to work How Roller Pinion Achieves Zero Backlash together, and the integrator-focused design reduces components and simpli- Rollers in fi es proper application. The RPS rack P opposition is available in standard segmented lengths of one-meter and half -meter increments and can be custom cut as P' required, allowing unlimited run SOURCE: NEXEN GROUP INC. lengths and accommodating diverse application requirements. A cutaway diagram highlights elements of Nexen’s rack and pinion system (RPS). The pinion consists of bearing-supported rollers that smoothly roll across a unique tooth profi le. Unlike traditional rack and pinion, the system is designed to run with interfer- For more information: ence, allowing two rollers to remain preloaded (in opposition) at all times. This elimi- Nexen Group Inc.: nates backlash and allows for smooth, fl uid motion at near 99-percent effi ciency. http://www.nexengroup.com/rps/ F12 FLUID POWER/POWER TRANSMISSION / A SUPPLEMENT TO DESIGN NEWS MAY 2010 [www.designnews.com] DNX100501_Roller_ID.indd 12 5/4/2010 1:58:19 PM.
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