Precision Engineering

We have extended our atomistic molecular dynamics modeling of precision machin ing processes to the tens-of-nanometers scale attainable in experimental studies of single-point diamond turning. Our calculated cutting forces agree remarkably well with the experimental measurements, and the simulations suggests a possible mechanism for the formation of segmented chips during high speed machining. We have also extended our modeling capabilities to three spatial dimensions. We find a rather interesting result—dislocation motion is not an efficient mechanism for accommodating strain due to point indentations on the nanometer scale in three dimensions.

The Combined Bibliography assembles in one document the 1970-1989 reports, conference proceedings, and publications authored by members of the Engineering Directorate - Materials Fabrication Division and the Precision Engineering Program. It was prepared from data recovered from the LLNL Library's and report database and from DOE's Energy Database using Pro-Cite.

The use of industrial X-ray computed tomography (CT) for dimensional metrology has become an important aspect of modern quality control [1, 2, 3]. The CT technique presently contributes to geometric dimensioning and tolerancing of mechanical parts (and other device components) for technology and manufacturing companies. It is used as a tool for nondestructive dimensional quality control in various industries, such as automotive, aerospace, electronics assembly and packaging, medical devices, injection molding, casting, and additive manufacturing. However, even under optimal measurement conditions, the technologies for CT dimensional metrology have traditionally been limited to spatial resolutions no better than 3-10 μm. This leads to several challenges for measuring samples of small dimensions (with volumes in the order of a few mm 3)-e.g., low signal-to-noise ratio in the CT data, and limited detection of contrast changes and spatial details. To overcome these challenges, the authors of this paper have developed a package-a solution consisting of hardware and software-for performing high-precision metrology using the high-resolution capabilities of ZEISS Xradia Versa 3D X-ray microscopes (XRM, or sub-micron CT systems), which can attain spatial resolutions better than 1 μm (e.g., 0.5 μm with the Versa 620 model). This new package, Metrology Extension (MTX) for Xradia Versa, includes a workflow designed to adjust and calibrate the XRM system to perform metrology tasks. Once the MTX calibration workflow is executed, the system can be used to measure small volumes, in the order of (5 mm) 3 or less, with high dimensional accuracy. The main purpose of this paper is to present, evaluate, and analyze, the experimental results of several measurement tests to verify the metrological performance of several XRM systems after calibration (and pre-setting of the instrument's work zone) with MTX. In addition, examples of industrial measurement applications that use the MTX workflow are presented. FIGURE 1. Two-stage magnification architecture of the ZEISS Xradia Versa 3D X-ray microscopes. The combination of both geometric and optical magnification enables high-resolution capabilities.

The three-probe method for separating the spindle rotation error and the specimen form error is extensively described in the literature. An attractive feature is its application in in-process measurement. However, the resulting uncertainty is studied far less extensively. In this paper, an evaluation and propagation method for the uncertainty, as well as for an uncertainty reduction, is given based on the system transfer function (S-function). First, based on the Laplace transform, the measurement system model is developed and expressed by an S-function. Second, the propagation laws of input uncertainties are analytically deduced by computing the partial derivatives of the S-function of roundness. Then, the laws are numerically validated by Monte Carlo simulations. The uncertainty propagation laws show that the uncertainties propagate with varying amplification over the harmonic domain, and moreover, they enable the quantification of roundness uncertainty. Taking the roundness uncer...

Machining with single-point diamond tools is an area of increasing interest in the manufacture of optics, lens moulds, hard discs and other products Although many materials have been machined with impressive results, questions remain regarding the science of ...