Rotary-linear axes for high speed machining

This thesis presents the design, analysis, fabrication, and control of a rotary-linear axis; this axis is a key subsystem for high speed, 5-axis machine tools intended for fabricating centimeter-scale parts. The rotary-linear axis is a cylinder driven independently in rotation and translation. This hybridization minimizes machine inertias and thereby maximizes accelerations allowing for the production of parts with complex surfaces rapidly and accurately. Such parts might include dental restorations, molds, dies, and turbine blades. The hybrid rotary and linear motion provides special challenges for precision actuation and sensing. Our prototype rotary-linear axis consists of a central shaft, 3/4 inch (1.91 cm) in diameter and 15 inches (38.10 cm) long, supported by two cylindrical air bearings. The axis has one inch (2.54 cm) of linear travel and unlimited rotary travel. Two frameless permanent magnet motors respectively provide up to 41 N continuous force and 0.45 N-m continuous torque. The rotary motor is composed of commercially available parts; the tubular linear motor is completely custom-built. The prototype axis achieves a linear acceleration of 3 g's and a rotary acceleration of 1,300 rad/s2. With higher power current amplifiers and reduced sensor inertia, we predict the axis could attain peak accelerations of 12 g's and 17,500 rad/s2 at low duty cycles. This thesis also examines several concepts for developing a precision rotary-linear sensor that can tolerate axial translation.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2001

Author dc:creator

• Liebman, Michael Kevin, 1974-

Advisor dc:contributor.advisor

• David L. Trumper.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/8218

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/8218