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Proceedings Paper

New low-cost dimensionally stable composite linear absolute position encoder scale
Author(s): William L. Hassler; Robert K. Nakayama
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Paper Abstract

A major problem in the use of standard linear position encoders is that the etched glass scales they use have a coefficient of thermal expansion (C. T. E. ) of about 1 1 . Oppm/ C. This means that their position measurements drift with changes in environmental temperature proportional to their C. T. E. . A new low cost dimensionally stable composite scale was made for use in a new absolute linear position encoder. The unidirectional Polyphenylene Sulfide/AS4 carbon fiber composite material that this scale is made of was tested for dimensional stability with respect to changes in temperature humidity and creep. The C. T. E. of the scale material was measured to be nominally 0. 29 ppm/ C with a standard deviation of 0. 12 over the operating temperature range of -2 to 62 C. The overall displacement strain due to 98 moisture absorption relative to 0 moisture absorption was measured to be 9 ppm. The strain due to stress-relief creep was found to be a maximum of 3 ppm over a period of 173 days. These results show that a linear position encoder scale made of this material is superior to those made of the standard glass currently being used and more cost effective than fused silica for most applications. 1.

Paper Details

Date Published: 1 November 1990
PDF: 12 pages
Proc. SPIE 1335, Dimensional Stability, (1 November 1990); doi: 10.1117/12.22867
Show Author Affiliations
William L. Hassler, Parker Hannifin Corp. (United States)
Robert K. Nakayama, Parker Hannifin Corp. (United States)

Published in SPIE Proceedings Vol. 1335:
Dimensional Stability
Roger A. Paquin, Editor(s)

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