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Divisions
PED
MMD
ISD
MSID
MEL
Postdoc
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Gaithersburg, Maryland
U.S. citizenship is required
Condition Monitoring and Condition Based Maintenance of Machine Tools 50.82.21.B5194
Donmez, Mehmet Alkan (301) 975-6618
alkan@nist.gov
Quality and equipment utilization requirements (e.g., just-in-time scheduling) are placing more pressure on the reliability of machine tools and ancillary equipment. Preventive maintenance by performing routine tasks at predetermined intervals is commonly used, but rarely optimized according to actual equipment reliability data. Very few computerized maintenance systems track equipment condition on a real-time basis, offer on-line problem diagnosis, or provide advice and/or self-correcting solutions. The information available in modern machine tool controllers, augmented with targeted sensor applications, provides opportunities to improve the maintenance and reliability machine tools by enabling the early detection, prediction, and remote diagnosis of component failures.
We perform research on key enablers for successful condition monitoring and condition based maintenance of machine tools including (1) identification of and models for failure modes of key machine components; (2) identification of suitable measurements that correlate with a developing fault of abnormal machine behavior; (3) advanced signal analysis techniques applicable to the nonlinear, nonstationary, and multiple-source environment encountered in machine tools; (4) the ability to diagnose the condition of machine components (and the machining process); (5) the ability to predict the remaining life of the equipment and provide advice and/or self-correcting solutions; (6) networked smart sensor technology and Internet technologies for remote monitoring and diagnosis; and (7) definitions and (test) methods for the specification of the mean time between failure (MTBF) as a component of standards for machine tool performance.
Available resources include a variety of CNC machine tools, instrumented testbed for key machine tool components (currently used for condition monitoring of linear motor drive), instrumented testbed for machine tool condition monitoring, extensive library of advanced signal processing algorithms, infrastructure for remote monitoring of machine tool controller and sensor data, and a large variety of sensors and instruments for data acquisition.
Metrology for Meso-scale Machine Tools 50.82.21.B5196
Donmez, Mehmet Alkan (301) 975-6618
alkan@nist.gov
This program will explore the challenges and opportunities of metrology for new generation mesoscale machine tools. Metrology challenges include (1) the required dramatic improvements in machining accuracy; (2) the lack of space for metrology components; (3) the difficult application of process-intermittent inspection as a result of the small feature sizes; and (4) the difficulties in achieving repeatable part fixturing, requiring multiple operations in one setup. The small work volume required by the machining applications also presents unique opportunities for the application of superior metrology concepts that radically depart from classical machine tool metrology. One example involves the metrology frame: the separation of the metrology loop from the load bearing structure. The accuracy of the resulting machine tool would then only be affected by the accuracy of the metrology system and the resolution of the actuators. Thus, the effects of the traditional machine tool error sources such as wear, and thermal and mechanical loads are either eliminated or dramatically reduced.
Our major activities will focus on investigating alternative meso-machine design and analyzing design concepts from the points of view of machined part accuracy, sensitivity to individual machine component errors, sensitivity to environmental factors, integration of small-scale non-intrusive metrology sensors, and other performance parameters. A test platform will also be developed to conduct metrology and cutting experiments to fabricate mesoscale parts.
Available equipment includes laser interferometer systems; two-dimensional grid encoders; high-precision displacement transducers; linear motor drive systems; CNC controllers; dynamic signal analyzers; a variety of temperature, vibration, and force sensors; powerful computational platforms for modeling and analysis; high-speed air bearing spindles; and air bearing slide systems.
Microforce Realization and Measurement 50.82.21.B4782
Jon Pratt (301) 975-5470
jon.pratt@nist.gov
Research focuses on developing a novel laboratory and instrumentation to produce, measure, and disseminate forces in the range between 10-8 N and 10-2 N in a fashion traceable to the International System of Units (SI). The quantitative measurement of such forces is of increasing importance in the study of micromechanical materials properties, fatigue and fracture testing of thin films and MEMS structures, and basic experimental studies of molecular bonds and protein formation. At present, we are developing a primary electrostatic force balance that can be probed to ascertain a calibrated contact force. We envision using this balance to calibrate a variety of secondary artifacts, such as piezoresistive silicon cantilevers, MEMS load cells, and solid-state laser load cells. We welcome research in precision engineering and instrumentation, experimental physics, and in the development and evaluation of small force measuring devices. The laboratory has PC's for data acquisition and computation, access to both an instrumented indentation machine and a molecular force probe, a cleanroom/sample preparation area, an electric, acoustic, and vibration isolated room where force measurements can be made, a variety of optical and mechanical stages, fixtures, and tables, laser interferometers, and various electronic instrumentation and data acquisition equipment geared toward the design, fabrication, and testing of precision instruments.
Intrinsic Force Standards Based on Atomic and Molecular Interactions 50.82.41.B6736
Jon Pratt (301) 975-5470
jon.pratt@nist.gov
The intrinsic forces project aims to establish the capability to traceably measure picoforces using intrinsic molecular forces obviating the need for calibration of transfer artifacts. In the realm of piconewton to nanonewton forces, there are a handful of phenomena already referred to as "force standards" in the single-molecule, bioforce literature. We intend to put these phenomena to the test; measuring and assigning SI values to a selection of atomic and molecular forces that are archetypes of the various interactions (bonding, binding, and conformation change). We are installing a UHV cryogenic AFM/STM equipped with a tuning fork style probe for dynamic force spectroscopy. This system will be used to explore single atom break junctions where we attempt to accurately measure the rupture force of a single gold atomic bond. A high resolution force sensor is being developed that can mount as a sample in the UHV environment to serve as a calibration reference for the experiment. Along with atomic bond rupture, we are exploring DNA as a metrology standard for force measurements. The overstretching-induced conformation of DNA occurs under a tensile force level of approximately 65 pN, as measured using both SPM and optical trapping instruments, and we are seeking to develop procedures for traceably recording this force interaction using a general purpose AFM that we will equip with a custom force sensor, such as a focus ion beam milled micro cantilever.
Wet Chemical Nanomanufacturing 50.82.41.B6737
Jon Pratt (301) 975-5470
jon.pratt@nist.gov
A host of wet chemical processes are used to manufacture nanoscale objects, however most of the techniques capable of extracting local information on the resulting nanoscale processes and products involve high-vacuum environments. NIST is creating a new class of nanoscale analytical methods designed to interrogate wet chemical nanomanufacturing environments, the scanning probe electrochemical interfacial electrophoresis system (SPECIES). This platform will enable localized machining as well as chemical, electrical, and mechanical characterization of nanoscale manufactured objects in a wet chemical process environment. To do this, the scanning probe paradigm is being integrated with radio-frequency electrochemistry and in-situ electrophoresis to construct a complete picture of the wet chemical processing of manufactured nanostructures. The available facilities will include precision electrochemical and separations instrumentation, an atomic force microscope, a nanoindenter, high-bandwidth electrical test equipment, motion control hardware, optical microscopy, a fume hood, wet chemistry facilities, and data acquisition hardware and software.
Smart Sensors, Interfaces, and Networks for Metrology and Manufacturing 50.82.21.B3904
Kang Lee (301) 975-6604
Kang.lee@nist.gov
This program focuses on the development of advanced smart sensors, communication protocols and networking technologies for improving remote metrology and manufacturing operations. Smart sensor development efforts include, but are not limited to, the research, development, and application of wireless, micro-electromechanical system (MEMS), low-power, simple and efficient security protocol, power-scavenging sensor-enabled RFID (Radio Frequency Identification), and networking technologies. The program also encompasses the development of interfaces and networking schemes for the connectivity of a large number of smart sensors and actuators for closed-loop manufacturing applications. Other areas of research interest include the modeling and studying of the behavior of large sensor networks consisting of hundreds or even thousands of sensors and actuators, and the use of the Intranet and Internet as a delivery mechanism for sensor data and information, as well as for machine tool and machining process monitoring, diagnostic, and control. Research and development of frameworks, communication protocols, and standards for Intranet and Internet-based distributed measurement and control applications using networked sensors and actuators is in progress.
Equipment and facility, available for use at NIST include embedded microprocessor development systems. UML modeling tools, off-the-shelf software development tools, wireless sensor networks, logic analyzers, spectrum analyzers, an electronic laboratory facility, and networked computers for developing smart sensors and Internet-based embedded applications for networked smart transducer appliances.
Closed Loop Manufacturing 50.82.21.B1580
Donmez, Mehmet Alkan (301) 975-6618
alkan@nist.gov
This program consists of experimental and theoretical efforts to characterize and improve machine tool performance, including sensor-based closed loop control of entire machining process. Particular problems include fast characterization of geometric, thermal, and dynamic machine tool errors; characterization and improvement of machine tool components; process characterization; development of on-machine part inspection and analysis; development and implementation of multilayer adaptive control architectures with temperature, torque, vibration, and force sensing; and development of post-process inspection and analysis techniques to continuously improve the machine and process parameters used in an automated manufacturing system. We are interested in studying the transferability of thermal models from one machine to another within the same product line and in improving the robustness of these models over a product line and over a period of time.
Available equipment includes laser interferometer systems; laser ball bar; telescoping ball bars; two-dimensional grid encoder; high precision displacement transducers; dynamic signal analyzers; a variety of temperature, vibration, and force sensors; machine tools; powerful computational platforms; and a number of CNC machining and turning centers, and coordinating measuring machines.
Virtual Machine Tools
50.82.21.B4016 Donmez, Mehmet Alkan (301) 975-6618
alkan@nist.gov
This research focuses on developing an electronic representation of machine tool performance characteristics and software tools to predict and visualize the outcome of machining processes. Of particular interest are the predicted tolerances of machined parts. Virtual machine tools will be building blocks for the virtual manufacturing environment of the future. They allow manufacturers to test and optimize manufacturing plans before any machining resources are committed and before any costly scraps are generated.
The specific research areas include (1) models for machine performance; (2) integration of performance data into these models; (3) tools for simulation of machining; and (4) data structures, formats, and dictionaries to communicate and store performance data of machine tools. The mathematical models to describe uncertainties in the error sources of machine tools and propagations of these uncertainties to the statistical process parameters are important components of this research program. The simulations of machine operations will include the effect of environmental factors as well as other sources of uncertainties in the real manufacturing environment. The research also addresses solid modeling problems in representing machined parts while visualizing small errors in dimensions and form over the nominal geometry.
Available equipment and computing resources include (1) Windows workstations; (2) various CNC machine tools; (3) a variety of measurement equipment for machine tool performance evaluation such as laser interferometers, telescoping ball bars, and high precision displacement transducers; and (4) CAD/CAM/CAE and FEM software such as COSMOS, ProE, N-See, and mathematical analysis and modeling tools such as Matlab.
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Force Measurement 50.82.21.B1586
Zeina Jabbour (301) 975-4468
zeina.jabbour@nist.gov
NIST provides static calibration of force transducers over the load range from 0.5 kN–4.448 MN (10 pounds force–12 million pounds force). Efforts are under way to further enhance the accuracy of calibrations, and to provide additional services. The six overlapping areas of study include machine-sensor interactions, temporal effects, environmental effects, electrical characterization, data analysis and error assessment, and development of optimal calibration and characterization procedures. A corollary activity is the development, for use as a transfer standard, of a modern force transducer that will be much superior to available transducers in terms of stability, freedom from thermoelastic effects and hysteresis, freedom from environmental influences, and freedom from errors that are due to off-axis loading. NIST is also interested in extending its single-axis, static-calibration service to include calibration of multiaxis force sensors and also dynamic force calibrations. Available equipment includes six deadweight machines capable of applying forces in ascending and descending fashion in both compression and tension. These machines have been fully automated, except for the 27 kN deadweight machine that is still operated manually. The forces over the entire range from 0.4 kN to 448 MN are known to within 5 ppm. In addition, MMD maintains environmental chambers and extensive electrical equipment.
Acoustic Measurement and Analysis 50.82.21.B1588
Victor Nedzelnitsky (301) 975-6638
vnedzel@nist.gov
NIST continually updates its airborne acoustical measurement, calibration, and analysis capabilities to extend the range of acoustic pressures or frequencies, to improve accuracy, to provide additional capabilities, and to automate measurement procedures. Current and planned research areas included (1) extension of pressure calibration capability down to frequencies of 1 Hz; (2) extension of free-fluid reciprocity calibration capability up to frequencies of 100 kHz; (3) extension of pressure calibration capability to include phase response; (4) development of procedures for absolute calibration of acoustic intensity transducers; (5) development of improved techniques for detection and recognition of extremely low-level sound pressure signals; (6) development of automated systems for calibration of microphones, sound level meters, and noise dosimeters; (7) development of improved measurement procedures for audiometry, hearing aids, and hearing protectors; (8) development of improved procedures for accurate measurement of radiated sound power; and (9) establishment of a reference sound-source calibration service. Available facilities included a 450-cubic meter anechoic chamber, several smaller chambers, and extensive acoustical instrumentation.
Mass 50.82.21.B3905
Zeina Jabbour (301) 975-4468
zeina.jabbour@nist.gov
NIST maintains and disseminates the unit of mass —the kilogram— to the U.S. government, industry, and academia. We disseminate the unit of mass in the range from 1 mg to 27000 kg. Continous research efforts focus on methods for improving the mass measurements capabilities by developing new and improved measurement procedures, automating equipment, improving statistical process control techniques, and investigating alternative materials for mass standards. This program focuses on the characterization of the surfaces of mass standards and the behavior of mass standards under controlled atmospheres. The purpose of this program is to shed light on the stability of the mass unit, a problem that has become apparent in the last few years and to support the ongoing "Electronic Kilogram" effort a EEEL, a research effort to replace the last remaining artifact-based SI unit with an invariant of nature.
Development of Improved Accelerometer Calibration Capability 50.82.21.B3906
Donmez, Mehmet Alkan (301) 975-6618
alkan@nist.gov
In many applications the absolute sensitivity (voltage output per unit of acceleration) of the accelerometer used in a vibration measurement is required. The sensitivity of an accelerometer is most often determined by subjecting the accelerometer to a known uniaxial sinusoidal acceleration over the range of motional excitation frequencies of interest and measuring the accelerometer output at each frequency. Depending on the application, the motional frequencies of interest cover a range of at least 2 Hz to 20 kHz. The uncertainty of the measurement of accelerometer sensitivity if affected strongly by two factors: the imperfection or distortion of the applied motion from the desired purely sinusoidal motion and by the presence of motion transverse to the intended axis of uniaxial motion. Two methods for the absolute determination of accelerometer sensitivity have been developed. The interferometric method (fringe-counting a lower frequencies and fringe-disappearance at higher frequencies) uses the wavelength of a He-Ne laser light as the reference standard for displacement. The other absolute method , the reciprocity method, uses a set of masses as a mechanical reference standard and the application of the electromechanical theory of reciprocity to determine accelerometer sensitivity. The uncertainty in the determination of accelerometer sensitivity routinely available is 1% to 4% depending on frequency.
An increasing demand for lower uncertainty in the measurement of accelerometer sensitivity has motivated the development of a new prototype electrodynamic shaker which permits the calibration of accelerometers by two independent and absolute methods using the same shaker.
It is designed to minimize cross-axis motion and the distortion of the motional waveform.
It is also designed with a very large mechanical impedance between the moving element on
which the accelerometer is mounted and the components of the interferometer.
It is equipped with dual coils and two retractable magnets to provide for reciprocity
measurements without attaching a second source of vibration to the shaker. In initial testing,
this prototype has shown much lower uncertainties at selected frequencies. We invite
interested applicants to join us in developing improved or new mechanical, electromechanical,
and optical techniques so that the planned system will be capable of determining accelerometer
sensitivity with greatly improved uncertainty over the entire range of frequencies of interest.
Manufacturing Process Characterization Models 50.82.61.B3916
Rob Ivester (301) 975-8324
rob.ivester@nist.gov
This research focuses on the development of models to characterize material removal manufacturing processes to allow companies to understand the capabilities of their processes. This will allow them to make more informed decisions about what types of specifications they can reasonably expect from their processes. These models will be based on well-proven theories and techniques, including analytically derived relationships, dynamic equations, empirical correlations, and statistical inferencing.
In addition to the development of characterization models, research would also involve techniques for interfacing this information with a language for specifying the flow of processes. These characterization models would be directly accessible from manufacturing software tools that represent and manipulate manufacturing process information.
This research is part of a larger effort to develop and validate standard specifications and characterizations of manufacturing process information to allow companies to better document, understand, and optimize their processes as well as to facilitate the exchange of process information among different functions within their organization and among partnering organizations.
Metrology for the Development of Machining Process Models 50.82.41.B6738
Rob Ivester (301) 975-8324
rob.ivester@nist.gov
Developing a machining process can be a complex task requiring considerable resources and expertise. The selection of process parameters such as tool geometry, tool material, cooling strategy, depth of cut, feedrate, and cutting speed affects important outcomes of the machining process, including product dimensions, surface quality, residual stresses, cutting forces, tool life, chatter, chip morphology, and machining time. The respective relations result from complex physical and chemical phenomena in the cutting zone, an environment of extreme strains and strain rates, high temperatures, and rapid temperature changes. Computer simulation of the cutting process (e.g., using the Finite Element Method [FEM] is becoming a valuable tool for the development, validation, and optimization of demanding machining applications. It allows for the evaluation of "what-if" scenarios and parameter optimization in the virtual domain, enabling first-part-correct manufacturing and streamlining the design of parts and manufacturing processes. The quality and application range of the obtained simulation results depend on the availability of: reliable material data for conditions encountered during cutting; information on friction, material separation criteria, and tool-workpiece dynamics; and models and computational methods for predicting process behavior.
We conduct research to improve industrial capability for physics-based modeling and optimization of metal cutting processes. Our focus is on practical methods to obtain the required material data and model parameters, including associated uncertainties and their effects. Furthermore, we develop and apply new techniques to observe phenomena at the cutting edge to improve models and simulation tools. Our facilities include pulse-heated split-Hopkinson bar for material testing; a testbed for high-speed micro-videography in both infrared and visible spectra of chip formation during cutting, dynamometers, instrumented hammers, and accelerometers; FEM-based simulation and analysis software; and (high-speed) precision and ultra-precision machine tools. Through collaboration with other NIST laboratories, we also have access to a full spectrum of techniques for material and geometry characterization at the micro and macro scales.
Quadrature Laser Interferometry for Dynamic Displacement Measurements 50.82.21.B5896
Donmez, Mehmet Alkan (301) 975-6618
alkan@nist.gov
Quadrature laser interferometry (QLI) for measuring dynamic displacements has many advantages over a conventional Michelson interferometer. One main problem of conventional laser interferometry in measuring dynamic displacements is tht at high frequencies of vibration displacements are too small to create a fringe. Therefore, instead of counting fringes, the measurement must determine what fraction of a fringe the motion represents. QLI is one solution to improve sensitivity of displacement measurements within sub fringe. QLI's most significant advantage is that it provides a means of absolute phase calibration. Phase shift of the measured voltage of vibration transducer relative to applied motion is important in shock metrology, modal analysis, studies of complex structures, and in mathematical modeling. However, there are many challenges associated with QLI including optical design, ultra highspeed data acquisition, and signal processing and associated uncertainties. Our focus is both in the analytical and experimental aspects of this metrology method.
Available equipment and computing resources include variety of highly characterized vibration exciters, laser interferometers, optical and electronic breadboards, high-speed high-resolution data acquisition systems, mathematical analysis and modeling tools.
Nano-structured optics metrology
Griesmann, Ulf (301) 975-4929
ulf.griesmann@nist.gov
Modern nano-fabrication technology has enabled the precise fabrication of parts and structures with dimensions comparable to the wavelength of light or smaller. This, in turn, opens up new ways to engineer the phase and amplitude of light waves to create light-waves with unique properties. An entirely new class of optics has been created which is often referred to as "diffractive optics" to emphasize that their function is achieved through the diffraction of light-waves at microscopic structures with dimensions comparable to the wavelength of light. Diffractive optical elements (DoEs) have properties which are impossible to achieve with traditionally polished refractive optics. For example, a diffractive lens can be designed which focuses a light-wave at several points in space simultaneously. DoEs are, therefore, important components in many novel optics products and have become a vibrant field of research.
Progress in the application and manufacture of advanced optical elements depends on the ability to measure their performance. This requires traceable metrology for optical figure and wave-front, sometimes with uncertainties at the sub-nanometer level for example for semiconductor lithography optics. The primary goal of our researcy is the development of improved methods for the measurement of precision optics.
Diffractive optical elements, or nano-structured optics, have properties that traditionally polished optics cannot achieve. The NIST Nanofab facility has extensive resources that can be applied to fabricate customized nano-structured optical elements. This provides research opportunities into metrology methods for these nano-structured optical components and their application to measuring the optical figure of aspheric optical elements, optical meta-materials, polarization sensitive nano-structured optics, digital holography, and other areas. Other facilities available for research include: ulticonfiguration XCALIBIR, a phase-shifting interferometer with an aperture of 300 mm; a commercial phase-shifting interferometer with 150 mm aperture; an infrared interferometer; GEMM, an experimental system for the measurement of free-form optical surfaces based on local curvature; an ultra-precision coordinate measuring machine' polishing machines; and a fringe-projection system for three-dimensional form metrology.
Metrology for Precision optics
Griesmann, Ulf (301) 975-4929
ulf.griesmann@nist.gov
Progress in the application and manufacture of advanced optical elements depends on the ability to measure their performance. This requires traceable metrology for optical figure and wave-front, with uncertainties at the sub-nanometer level for high-impact applications such as semiconductor lithography. The primary goal of our research is the development of improved interferometric methods for the measurement of precision optics and the characterization of the measurement uncertainty of these methods. Interferometers usually require calibrated reference surfaces, and we develop and refine (absolute) calibration procedures for the flat and spherical reference surfaces commonly found in commercial interferometers. In recent years, advances in the fabrication of aspheric and free-form optical surfaces are leading to their increased use in optical systems because of the reduction in size, complexity, and cost. The measurement of aspheric surfaces, however, poses a very formidable problem, especially for precision optics. We are developing, characterizing, and comparing methods for the measurement of precision aspheric surfaces such as interferometry with computer generated holograms and stitching interferometry. Research opportunities exists to develop, improve, or characterize metrology methods for precision optics. Facilities available for research include: multi-configuration XCALIBIR, a phase-shifting interferometer with an aperture of 300 mm; a commercial phase-shifting interferometer with 150 mm aperture; an infrared interferometer; GEMM, an experimental system for the measurement of free-form optical surfaces based on local curvature; an ultra-precision coordinate measuring machine; polishing machines; and a fringe-projection system for three-dimensional form metrology.
melwebmaster@nist.gov
Last updated:
May. 06, 2008
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