Nexen Linear Drive
Linear Drive For Gantry-based Cutting Systems

The Application

Gantry cutting systems are used to cut precise shapes from large sheets of metal using laser, plasma or water jet technologies. They consist of a CNC controlled X&Y axis system, suspended above the work piece, that supports the plasma cutter head. This allows the rapid production of parts and quick change overs. Each axis is driven by a servomotor that typically uses ballscrews or traditional rack and pinion to create the linear motion.

 

The Problem

Machines with longer runs have to use traditional rack and pinion due to length limitations of ballscrews. This makes maintaining high accuracy a problem due to inherent backlash. To overcome this short coming, split or dual pinions can be used, but they greatly increase the drive system cost and increases wear. For maximum accuracy, linear encoders are needed since both technologies suffer from backlash, cumulative error and thermal creep. These technologies also have high maintenance needs and are very susceptible to environmental and process generated contaminates that accelerate wear and reduce precision and life.

The Nexen Advantage

Nexen has a new revolutionary linear drive concept that provides the best attributes of both of these older technologies while eliminating their short comings. The roller pinion system (RPS) utilizes a pinion consisting of bearing supported rollers that engage a patented tooth profile. This innovative design provides many advantages including: zero backlash, no cumulative error regardless of the distance, unlimited lengths, accuracy of ±20 micrometers, speeds up to 11 m/s (36.1 ft/s), modular rack for immediate availability and individual segment replaceability, 99% efficient, quiet operation, low or no maintenance, hardened wear surfaces, corrosion resistant finish, much longer life, and price competitive with precision ground ball screws.

This amazing set of features allows higher machine speeds, less maintenance and repair expense, while improving accuracy. Often linear encoders can be avoided and the servo encoder relied on for accurate position feedback. In dirty environments, the RPS system can often run lube free -- preventing abrasive build up on the rack or eliminating lube throw off.