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The Axtrusion Linear Motion System

Roger Cortesi (


The Axtrusion is a new linear motion element developed by Professor Alexander Slocum and Roger Cortesi of the Massachusetts Institute of Technology’s Mechanical Engineering Department Precision Engineering Research Group. It is an easy to manufacture non-contact linear motion system. The prototype uses porous graphite air bearings and an open face permanent magnet linear motor to support and propel the carriage. Since there is no contact between the carriage and the way, the Axtrusion is ideal for high speed applications where reliability is at a premium. Initial testing of the prototype carriage indicates that it has the following performance specifications: a vertical load capacity of 2000 N (450 lbs); horizontal load capacity of 4000 N (900 lbs); a carriage pitch error of 12 micro-radians (2.5 arc seconds); a yaw error of 7.7 micro-radians (1.6 arc seconds); a vertical straightness at the center of the carriage of 0.3 microns (0.000012 inches); and a vertical stiffness of the carriage of 422 Newtons per micron (2,400,000 lbs/in).


Download the Thesis (PDF files)

Video Clips of the Axtrusion in Action (.mpg files)!!!

An Overview of the Axtrusion Concepts and Prototype

A Detailed Presentation of the Data from the Prototype

Animated Results of the Modal Analysis

Photos of the Bearing Replication Sequence

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The prototype Axtrusion undergoing pitch testing at Dover Instruments.

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Roger replicating the airbearings in to the prototype carriage.