Robert W. Ivester

Assessment of machining models: Progress report

Abstract Progress in developing and assessing predictive modeling of machining processes has been hindered by the extremely localized nonlinear physical phenomena that occur in machining and the many different types of models ranging from theoretical to empirical. The difficulty in assessing models has been cited by industry as the major barrier to use of modern machining models. Current practice in industry is to machine and change tools conservatively, or to conduct costly empirical studies for a limited selection of tools and coolants. The Assessment of Machining Models project will assess the ability of modern machining models to predict the outputs of machining processes based upon a consistent, well measured calibration data set. The data set is nearly complete and is to be used in benchmarking the predictive capability of machining models in blind tests. This paper presents the project motivation, goals, and representative calibration data set results. The next steps in the effort include release of the calibration data, solicitation and collection of predictions, and evaluation and reporting of results.

An Analysis of Existing Ontological Systems for Applications in Manufacturing and Healthcare

The objective of the work described in this paper is to move closer to the ultimate goal of seamless system integration using the principle behind ontological engineering to unambiguously define domain-specific concepts. A major challenge facing industry today is the lack of interoperability between heterogeneous systems. This challenge is apparent in many sectors, including both healthcare and manufacturing. Current integration efforts are usually based solely on how information is represented (the syntax) without a description of what the information means (the semantics). With the growing complexity of information and the increasing need to completely and correctly exchange information among different systems, the need for precise and unambiguous capture of the meaning of concepts within a given system is becoming apparent.

Simultaneous visible and thermal imaging of metals during machining

In order to investigate temperatures reached during orthogonal metal cutting, a novel approach for measuring temperatures at the tool-chip interface has been developed based on high-speed thermography. A thermal infrared camera and a visible camera combined through a dichroic beam splitter form the basis for a synchronized visible and infrared imaging system. Pairing the infrared camera with a higher speed visible camera allows for assessment of thermal images with aberrant chip flow or an obstructed view of the tool/chip interface. This feature facilitates the use of the apparatus in machining environments where machining chips or other debris fly about. The measurement setup also includes a force dynamometer, custom timing circuitry, and a high-speed digital oscilloscope to enable timing of frames together with force measurements so that analysis of the infrared images can be compared against the energy levels measured through the cutting forces. The resulting infrared images were converted to radiance temperatures through comparison to a NIST calibrated blackbody. Emissivity was measured by thermally imaging the machining chips heated to known temperatures. Machining experiments were performed at various cutting speeds and at two different infrared wavelengths. Analysis of these experiments gives insight into the relationships between emissivity, temperature, surface condition, infrared wavelength and motion blur. The analysis shows that using the visible, thermal and force data together is a significant improvement over any of these alone. These insights lead to practical guidance for use of infrared imaging systems to image rapidly moving objects.

Smart machining systems: issues and research trends

Smart Machining Systems (SMS) are an important part of Life Cycle Engineering (LCE) since its capabilities include: producing the first and every product correct; improving the response of the production system to changes in demand (just in time); realizing rapid manufacturing; and, providing data on an as needed basis. Thereby, SMS improve the performance of production systems and reduce production costs. In addition, an SMS not only has to improve a particular machining process, but it also has to determine the best optimized solution to produce the part faster, better, at lower cost, and with a minimum impact on the environment. In addition, new software tools are required to facilitate the improvement of a machining system, characterized by a high level of expertise or heuristic methods. A global approach requires integrating knowledge/information about the product design, production equipment, and machining process. This paper first discusses the main characteristics and components that are envisioned to be part of SMS. Then, uncertainties associated with models and data and the optimization tasks in SMS are discussed. Robust Optimization is an approach for coping with such uncertainties in SMS. Current use of machining models by production engineers and associated problems are discussed. Finally, the paper discusses interoperability needs for integrating SMS into the product life cycle, as well as the need for knowledge-based systems. The paper ends with a description of future research trends and work plans.

Serrated Chip Morphology and Comparison with Finite Element Simulations

ABSTRACT The complexity of chip formation in machining processes stems from the confluence of several physical phenomena - mechanical, thermal, and chemical - occurring at very high strain rate. The prediction of chip morphology depends on a fundamental understanding of these phenomena and is of industrial importance for cutting force prediction and surface integrity control. Within this framework, our paper focuses on the modelling of serrated-chip formation (saw-tooth shape chip) and on the physical phenomena accompanying the serrated-chip formation according to the variation of feed rate. In the first part, bibliography review and experimental study on chip formation is made. The experimental study, based on metallographic analysis of chip morphology, focuses on the machining of an American Iron and Steel Institute (AISI) 4340 steel alloy work material. The second part of the paper deals with the FEM model to simulate cutting processes using the Abaqus explicit code and Third Wave Systems Advantedge software. The simulations utilize plasticity models for material behaviour and damage to predict chip morphology. The third section proposes a comparison of simulations results with experimental observations. Experimental results support the results of the simulations for various cutting parameters. We end the paper with some concluding remarks.

Robust Optimization for Smart Machining Systems: An Enabler for Agile Manufacturing

This paper reports our efforts towards developing a mathematical and information framework for optimization of machining processes within a Smart Machining System (SMS). An SMS uses diverse integrated technologies that enable an enterprise to: (1) produce the first and every product correct; (2) improve the response of the production system to changes in demand (just in time); (3) realize rapid and agile manufacturing; and (4) provide data to the rest of the enterprise as needed. Optimization of machining processes is an important component of an SMS and contributes to realizing these capabilities. Based on a prototype, we demonstrate the concepts for robust optimization within an SMS and develop requirements and challenges for robust optimization in an SMS.

ACCELERATED WEAR TESTS FOR THE ASSESSMENT OF MACHINING MODELS CALIBRATION DATA

This paper documents the release of the accelerated wear tests for the Assessment of Machining Models (AMM) calibration data set, including some brief background material and a summary of previously published results. Measurements and results for the accelerated wear tests are summarized and a representative plot is given. Sources of uncertainty associated with the accelerated wear test measurements are discussed. The paper closes with a brief discussion of the wear test data and the complete data files, which are available through the project web site athttp://www.nist.gov/amm/. *Official contribution of the National Institute of Standards and Technology; not subject to copyright in the United States.

Detection of Cutting Phenomena Using Sensor Fusion

This paper presents an investigation of the application of a suite of sensors for simultaneous in-situ measurements of machining processes. While not every individual sensor responds to all machining phenomena, the suite of sensors together responds to many machining phenomena of interest, including chip segmentation, chip breakage, and vibrations. The simultaneous use of a suite of sensors with modest data-acquisition equipment and the use of careful preliminary laboratory testing for optimizing sensor performance distinguishes this present proof-of-concept work from prior process monitoring efforts using individual sensors. This paper includes a discussion of pre-deployment laboratory measurements and a full description of the instrumented tool holder, associated circuitry, and data analysis methods. The deployment of multiple sensors of varying sophistication and cost lays a technical foundation for the ultimate objective of industrially practical measurement and monitoring systems for metal cutting processes.Copyright

Analysis of Orthogonal Cutting Experiments Using Diamond-Coated Tools with Force and Temperature Measurements

Two dimensional (2D) orthogonal cutting experiments using diamond-coated tools were conducted with forces and tool-tip temperatures measured by dynamometry and infrared thermography, respectively. The objective of this study was to analyze cutting parameter effects on process behavior in diamond-coated tool machining. Special cutting tools and workpieces were prepared to realize orthogonal cutting. The specific cutting energy and the ratio of forces in the normal and cutting directions increased with decreasing uncut chip thickness. The tool temperatures generally increase with the uncut chip thickness. The specific cutting energy decreases slightly with the increase of the cutting speed. The tool temperatures increase significantly with the cutting speed, but level off at a higher cutting speed, 5 m/s. The effect of increasing the edge radius was to increase the specific cutting energy and the force ratio. The tool temperatures were lowest at the middle edge radius value and increase at both the smaller and larger edge radii.