Lisa M. Gill
James J. Filliben
Raghu Kacker
Statistical Engineering Division, CAML
Said Jahanmir
Lewis Ives
Ceramics Division, MATLS
In July of 1992, a research program on ceramic machining was initiated by the Materials
Science and Engineering Laboratory prompted by the results of a comprehensive survey of
U.S. Industry which confirmed that the primary impediment to the widespread use of
advanced ceramics is the high cost of machining. In order to be competitive, both nationally
and internationally, advanced machining operations of ceramics needed to be better
understood and more efficiently carried out. The program was lead by and continues under
the direction of Said Jahanmir of the Ceramics Division. The mission of the program is to
assist U.S. Industry in the development of precision machining for the manufacturing of cost-
effective advanced ceramic products. The goal is to develop measurement methods, produce
and collect data, and produce reference materials and databases to assess the influence of
machining properties and performance on advanced ceramics.
To assure that industry needs were properly addressed and to take advantage of expertise
existing at other research institutions, NIST established a consortium with members from
industry, academia, and government. The role of the consortium members is vital to the
success of the program; they participate in the research projects by providing materials,
testing, technical advice, and other in-kind contributions. Currently, the 21 members actively
involved are:
| Ceradyne Inc. |
General Electric Co. |
Tech. Assessment & Transfer |
| Cercom, Inc. |
General Motors Corp. |
Torrington Co. |
| Cincinnati Milacron, Inc. |
Georgia Inst. of Tech. |
Univ. of Delaware |
| Corning Inc. |
Kansas State Univ. |
Univ. of Maryland |
| Dow Chemical Co. |
Landis/Western Atlas Corp. |
Univ. of Massachusetts |
| Eaton Corp. |
Lehigh Univ. |
Univ. of Rochester |
| Ford Motor Co. |
Stevens Institute of Tech. |
West Advanced Ceramics, Inc. |
A primary goal of the consortium is to collect and analyze data on the effect of grinding
parameters on ceramic properties/performance. Of particular interest is how the strength and
surface integrity vary with the grinding parameters, and the determination of grinding
conditions that result in high material-removal rates. These data and other evaluated data
gathered from the literature and consortium members are being assembled in a computerized
database. This Ceramic Machinability Database will provide access to data for different types
of ceramics and will help users, such as manufacturing engineers, tooling managers, and
machinists, develop machining plans for the cost-effective production of ceramic parts.
One project in the program evaluates the feasibility of several non-destructive methods (such
as ultrasonics and thermal wave measurement methods) to detect and characterize the
machining damage in ceramics. In addition, the generation of reliable surfaces is an
important issue; hence, another project seeks to determine the effects of grinding conditions in
the "ductile regime" grinding process to establish the role of microstructure and grinding
parameters in obtaining damage-free surfaces and the fundamental mechanisms involved in
the material-removal process during grinding of silicon nitrides. The purpose is to determine
the influence of grinding parameters, such as down feed, wheel grit size, and table speed, on
machinability and ceramic strength, and to determine optimal settings. Further, an exploration
of the relationship between ceramic microstructure and ceramic properties (e.g., grain size,
distribution of second phases, hardness, and fracture toughness) is underway.
The Statistical Engineering Division has played a critical role from the beginning. In
particular, for the silicon nitride project, it was recognized that the conclusions regarding
important grinding parameters may potentially be contaminated by other factors such as
laboratory, batch, etc. This large-scale multi-laboratory experiment thus required a careful
experiment design to assure the validity of the conclusions. Early on in this multi-year
project, SED members Raghu Kacker and Lisa Gill provided the expertise in constructing an
experiment design with enough scope that project goals were efficiently and unambiguously
achieved. More recently, after the experimental data was collected, SED members Lisa Gill
and James Filliben provided the data analysis expertise in ascertaining important grinding
factors, uncovering significant non-grinding factors, identifying interactions, and establishing
optimal settings. At each of the semi-annual meetings, Lisa Gill provided to consortium
members well-received detailed presentations of such conclusions along with the supporting
data analysis methodology (a few representative analysis graphics from the talks are provided
below). A jointly co-authored paper entitled "Effects of Grinding on Strength of Sintered
Reaction Bonded Silicon Nitride" will be presented at the Second International Conference on
Machining of Advanced Materials (September 30, 1996, Eurograss Aachen, Germany).
Figure 19: Probability Plot Correlation Coefficient Plot (SRBSN, Longitudinal, Batch 1): The character
of the plot is the lab identification number. The 3-Parameter Weibull is the best distribution
overall, but the 2-Parameter Weibull and Normal distributions still do a reasonable job
representing the distribution of the data. The Lognormal distribution does not do so well.
Date created: 7/20/2001
Last updated: 7/20/2001
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