FOR IMMEDIATE RELEASE:             NIST 94-10
April 5, 1994

Contact:  Mark Bello, NIST         COLLABORATION ON TARGET,
          (301) 975-3776           NIST INVENTION HEADS FOR
                                   THE FACTORY
          James Richter, NCMS
          (313) 995-0300

          E.B. Schenk, Giddings & Lewis
          (313) 293-3000

     A computer model developed by National Institute of
Standards and Technology researchers can substantially improve
the cutting accuracy of a piston-turning machine used by U.S.
automakers, according to results of recent tests conducted at
NIST for Giddings & Lewis--maker of the high-precision machine
tool--General Motors Corp., Ford Motor Co., and the National
Center for Manufacturing Sciences, which managed and funded the
collaboration.

     Improved accuracy will translate into higher productivity
and higher precision in the manufacture of automobile-engine
pistons.  Because it eliminates the need to warm up machines
before production begins, the technology also is expected to
generate energy savings for engine makers.

     The successfully completed tests conclude a 13-month phase
of the NCMS-organized collaboration.  The industrial partners now
will focus on steps to incorporate the NIST-developed technology
into new Giddings & Lewis machines for GM and Ford.

     "This project perfectly fits our mission of improving U.S.
manufacturing productivity as well as enhancing the competitive
position of the U.S. machine-tool industry," says Jay Nilsson,
NCMS project manager.

     During several days of testing at the NIST facility,
aluminum piston billets were machined over six-hour periods.  
In an attempt to simulate actual production conditions, certain
environmental conditions were varied and production stoppages
corresponding to plant coffee breaks and lunch hours were
incorporated into the testing periods.  Results showed
significant improvements in the billets machined with the NIST
temperature-compensation technology as compared with those
machined without it.  On the basis of these results, NIST experts
believe that as much as an 80 percent reduction in the variation
of piston size could be achieved.
                                     
     In practical terms, this means that the unmodified machine, 
which Giddings & Lewis introduced commercially in mid-1992,
already can cut automobile-engine pistons so precisely that the
dimensions vary by less than half the diameter of a human hair. 
With the NIST software, which compensates for temperature-caused
changes and other sources of "errors" that limit accuracy,
dimensional variation in the slightly oval parts can be reduced
to far less than one-tenth the diameter of a human hair.

     For engine builders, hair-splitting differences are not
trivial.  "Now, a manufacturer may make one size of pistons for
an hour or so and then switch to another size class," explains
Ken Drew, Giddings & Lewis project engineer.  "With the computer
model you can go a step farther and make any size class on
demand."

     Martin Suchoski, a senior project engineer at the GM
Technical Center in Warren, Mich., expects additional payoffs:
reduced machine "dead" time, less scrap and higher productivity. 

     Because the software corrects for expansion and contraction
as the machine warms and cools, he says, the equipment need not
run idle for about an hour until attaining a steady operating
temperature for production.  It also eliminates the need for
relief help when operators take a break because the machine can
be shut off and restarted without harming its performance.

     Although logistics and details are now being worked out,
says Giddings & Lewis's Drew, "the model will definitely be put
into the machine."  He adds that Giddings & Lewis intends to
pursue other potential performance enhancements identified during
the collaboration.

     "This is a well-focused project," says GM's Suchoski. "We
have usable results and they are going to be applied."

     Earlier consultations between NIST and Giddings & Lewis
researchers led to modifications in the machine's final design. 
Those changes helped to create stable temperature patterns inside
the machine, reducing irregularities that can distort the
geometry of machine components and, as a result, impair
performance.

     The idea of using software-based methods to improve the
performance of machine tools and coordinate measuring machines
was pioneered at NIST's Manufacturing Engineering Laboratory.

     "The underlying concept is that the accuracy of machine
tools is limited--to a significant extent--by geometric
imperfections and non-random irregularities, or errors such as
thermal deformations," explains Alkan Donmez, who led the NIST
side of the collaboration with Giddings & Lewis, GM and Ford. 
"Because these errors are often very repeatable, they also are
predictable, which means you can build predictive computer models
for real-time error compensation."
                                     
     Brown & Sharpe and Sheffield Measurement (now part of
Giddings & Lewis) were among the first to adopt the approach,
applying it commercially to coordinate measuring machines, which
are used to inspect the dimensions of parts.  Donmez and his
colleagues are continuing to refine approaches to enhancing
machine-tool accuracy and to extend the range of applications.

     "This successful project is another example of the
laboratory's mission, namely to apply our expertise in
collaborating with industry to solve meaningful technical
problems that affect U.S. competitiveness," says Dr. Michael J.
Wozny, the director of the Manufacturing Engineering Laboratory.

     A non-regulatory agency in the Commerce Department's
Technology Administration, NIST promotes economic growth by
working with industry to develop and apply technology,
measurements and standards.

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