15 research outputs found
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STATS SRS v11.0
The objective of this project is the delivery of an application that will provide a unified, web-based system for collecting, verifying and analyzing the achievements for Laboratory employees. The application will enable individual Directorates to manage and report achievement record data for their employees using an LLNL standard web browser. In addition, cross directorate data reporting and analysis will be available for such organizations as LSTO and programmatic directorates. This system is intended to store reference data and metadata for employee achievements. Abstracts and entire publications will not be stored in this system.Directorates are expected to use this system at all levels of management in preparing for Annual Self-Assessments, peer reviews, LDRD reviews, work force reviews, performance appraisals, and requests from sponsors. This document represents the primary deliverable for the Requirements Definition stage of system development. As part of a successful Requirements Definition, this document provides the development staff, the project sponsor, and the user community with a clear understanding of the product's operational, data, and other requirements. With this understanding, the development staff will take the opportunity to refine estimates regarding the cost, schedule, and deliverables reflected in it
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Investigation of acoustic emission for use as a wheel-to-workpiece proximity sensor in fixed-abrasive grinding
This paper reports on the feasibility of using Acoustic Emission (AE) for sensing the proximity of a grinding wheel to a glass workpiece, both prior to contact and in the early stages of contact. Our measured AE signals indicate that we can track the position of the grinding wheel as it approaches the workpiece through the turbulent coolant layer and than as contact initiates with a workpiece during spherical generation. Our data for the initial contact region is dominated by cyclical bursts of AE that appear to correspond to tool spindle motion errors. Our principal goal is to minimize the time required to {open_quote}find the part{close_quote} without damaging the surface of a brittle workmaterial, i.e. during the transition from a fast approach to the much slower final in-feed required for the grinding operation. Our results also suggest that AE is useful as a gauging signal in determining the position of the grinding wheel with respect to the machine tool
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Implementation of an acoustic emission proximity detector for use in generating glass optics
We are using the approach acoustic emission (AE) signal during a grinding operation to detect the proximity of the grinding wheel relative to a brittle material workpiece and are using this detection as a feed- back control signal in our CNC. The repeatability of the AE signal during the wheel approach is the key that allows AE to be used as a proximity detector and is demonstrated at LLNL to be about mm. We noted significant changes of the AE signal as process parameters are modified, but conclude that with a quick CNC calibration routine and holding the parameters constant during a given operation, the AE system can be successfully used to sense pre- contact wheel- to- workpiece separation. Additionally, the AE sensing system allows real- time monitoring during grinding to provide in- process information. The first prototype of an AE system on a commercially available generator is currently be tested at the Center for Optics Manufacturing
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Performance evaluation of bound diamond ring tools
LLNL is collaborating with the Center for Optics Manufacturing (COM) and the American Precision Optics Manufacturers Association (APOMA) to optimize bound diamond ring tools for the spherical generation of high quality optical surfaces. An important element of this work is establishing an experimentally-verified link between tooling properties and workpiece quality indicators such as roughness, subsurface damage and removal rate. In this paper, we report on a standardized methodology for assessing ring tool performance and its preliminary application to a set of commercially-available wheels. Our goals are to (1) assist optics manufacturers (users of the ring tools) in evaluating tools and in assessing their applicability for a given operation, and (2) provide performance feedback to wheel manufacturers to help optimize tooling for the optics industry. Our paper includes measurements of wheel performance for three 2-4 micron diamond bronze-bond wheels that were supplied by different manufacturers to nominally- identical specifications. Preliminary data suggests that the difference in performance levels among the wheels were small
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In-process EDM truing to generate complex contours on metal-bond, superabrasive grinding wheels for precision grinding structural ceramics
The demand and use of precision grinding of structural ceramics continue to increase as the worldwide advanced ceramic industry surpasses $20 billion is sales. Included in this industry are engineering structural ceramics, electronic ceramics, bioceramics and others. These materials are used in applications such as engine components, casting and extrusion dies, bearings, medical implants, nozzles, thermal insulators, and more. Along with the variety of ceramic applications comes a broad range of precision requirements, which in turn leads to various required processes to accommodate a spectrum of specifications. A process for grinding ceramic components to micrometer tolerances was employed and further developed at Lawrence Livermore National Laboratory for two separate grinding projects
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Use of in-process EDM truing to generate complex contours on metal-bond, superabrasive grinding wheels for precision grinding structural ceramics
This paper presents recent work performed at Lawrence Livermore National Laboratory to develop cost-effective, versatile and robust manufacturing methods for grinding precision features in structural ceramics using metal-bond, superabrasive grinding wheels. The developed processes include utilizing specialized, on-machine hardware to generate precision profiles onto grinding wheels using electrical-discharge machining (EDM) and a contoured rotating electrode. The production grinding processes are described, which were developed and used to grind various precision details into a host of structural ceramics such as Al{sub 2}O{sub 3}, Si{sub 3}N{sub 4}, and BeO. The methodologies, hardware and results of both creep-feed and cylindrical grinding are described. A discussion of imparted grinding damage and wheel wear is also presented
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Applied grinding wheel performance evaluation for optical fabrication
We are collaborating with the Center for Optics Manufacturing (Rochester NY) to develop fine diamond grinding wheels for spherical grinding of glass optics. A standardized method for evaluating wheel performance includes in-process acoustic emission (AE). This paper includes recent AE measurements taken during the evaluation of several fine diamond grinding wheels and discusses how this new information might relate to the physical performance of the wheels. An interesting observation is also reported on the surface topography of worn bronze wheels using an interferometric profiler
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Process diagnostics for precision grinding brittle materials in a production environment
Precision grinding processes are steadily migrating from research laboratory environments into manufacturing production lines as precision machines and processes become increasingly more commonplace throughout industry. Low-roughness, low-damage precision grinding is gaining widespread commercial acceptance for a host of brittle materials including advanced structural ceramics. The development of these processes is often problematic and requires diagnostic information and analysis to harden the processes for manufacturing. This paper presents a series of practical precision grinding tests developed and practiced at Lawrence Livermore National Laboratory that yield important information to help move a new process idea into production
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Precision grinding process development for brittle materials
High performance, brittle materials are the materials of choice for many of today's engineering applications. This paper describes three separate precision grinding processes developed at Lawrence Liver-more National Laboratory to machine precision ceramic components. Included in the discussion of the precision processes is a variety of grinding wheel dressing, truing and profiling techniques
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Working with the superabrasives industry to optimize tooling for grinding brittle materials
The optics manufacturing industry is undertaking a significant modernization, as computer-numeric-controlled (CNC) equipment is joining or replacing open-loop equipment and hand lapping/polishing on the shop floor. Several prototype CNC lens grinding platforms employing ring tools are undergoing development and demonstration at the Center for Optics Manufacturing in Rochester, NY, and several machine tool companies have CNC product lines aimed at the optics industry. Benefits to using CNC ring tool grinding equipment include: essentially unlimited flexibility in selecting radii of curvature without special radiused tooling, the potential for CIM linkages to CAD workstations, and the cultural shift from craftsmen with undocumented procedures to CNC machine operators employing computerized routines for process control. In recent years, these developments, have inspired a number of US optics companies to invest in CNC equipment and participate in process development activities involving bound diamond tooling. This modernization process,extends beyond large optics companies that have historically embraced advanced equipment, to also include smaller optical shops where a shift to CNC equipment requires a significant company commitment. This paper addresses our efforts to optimize fine grinding wheels to support the new generation of CNC equipment. We begin with a discussion of how fine grinding fits into the optical production process, and then describe an initiative for improving the linkage between optics industry and the grinding wheel industry. For the purposes of this paper, we define fine wheels to have diamond sizes below 20 micrometers, which includes wheels used for what is sometimes called medium grinding (e.g. 10-20 micrometers diamond) and for fine grinding (e.g. 2-4 micrometers diamond)