Mahesh Mani

Discrete event simulation to generate requirements specification for sustainable manufacturing systems design

A sustainable manufacturing systems design using processes, methodologies, and technologies that are energy efficient and environmental friendly is desirable and essential for sustainable development of products and services. Efforts must be made to create and maintain such sustainable manufacturing systems. Discrete Event Simulation (DES) in combination with Life Cycle Assessment (LCA) system can be utilized to evaluate a manufacturing system performance taking into account environmental measures before actual construction or use of the manufacturing system. In this paper, we present a case study to show how DES can be utilized to generate requirements specification for manufacturing systems in the early stages of the design phase. Requirement specification denotes the description of the behavior of the system to be developed. The case study incorporates use of LCA data in combination with DES. Data for the model in the case study is partly provided through the format supported by the Core Manufacturing Simulation Data (CMSD) standardization effort. The case study develops a prototype paint shop model, and incorporates alternate decisions on energy use, choice of machines, and environmental bottleneck detection. The study results indicate the potential use of utilizing DES in combination with LCA data to generate requirements specification for designing sustainable manufacturing systems.

Sustainability characterisation for manufacturing processes

Manufacturing industries lack the measurement science and the needed information base to measure and effectively compare environmental performances of manufacturing processes, across resources and associated services with respect to sustainability. The current use of ad hoc methods and tools to assess and describe sustainability of manufactured products does not necessarily account for manufacturing processes explicitly, and hence results in inaccurate and ambiguous comparisons. Such comparisons do not proactively contribute to sustainability improvement. Further, we identified that there are no formal methods for acquiring and exchanging information that help establish a consolidated sustainability information base. Our ultimate goal is to develop the needed measurement science and methodology to evaluate sustainability of fundamental manufacturing processes to ensure reliable and consistent comparisons. As a precursor, based on a literature study, this paper identifies the required elements to evaluate sustainability performance for manufacturing with a focus on the environmental impact. Societal and economic impacts, although equally important, are beyond the scope of discussion in this paper. In this paper, we first discuss identified manufacturing process classifications, sustainable manufacturing indicators and computable metrics, relevant information models and software tools, a conceptual model for sustainability characterisation, and finally, conclude with an overview of the future research directions.

Sustainability Characterization for Additive Manufacturing

Additive manufacturing (AM) has the potential to create geometrically complex parts that require a high degree of customization, using less material and producing less waste. Recent studies have shown that AM can be an economically viable option for use by the industry, yet there are some inherent challenges associated with AM for wider acceptance. The lack of standards in AM impedes its use for parts production since industries primarily depend on established standards in processes and material selection to ensure the consistency and quality. Inability to compare AM performance against traditional manufacturing methods can be a barrier for implementing AM processes. AM process sustainability has become a driver due to growing environmental concerns for manufacturing. This has reinforced the importance to understand and characterize AM processes for sustainability. Process characterization for sustainability will help close the gaps for comparing AM performance to traditional manufacturing methods. Based on a literature review, this paper first examines the potential environmental impacts of AM. A methodology for sustainability characterization of AM is then proposed to serve as a resource for the community to benchmark AM processes for sustainability. Next, research perspectives are discussed along with relevant standardization efforts.

Carbon weight analysis for machining operation and allocation for redesign

The objective of this research paper is to explore and develop a new methodology for computing carbon weight (CW) – often referred to as carbon footprint, in manufacturing processes from part level to assembly level. In this initial study, we focused on machining operations, specifically turning and milling, for computing CW. Our initial study demonstrates that CW can be computed using either actual measured data from process level information or from initial material and manufacturing process information. In mechanical design, tolerance analysis principles extend from design to manufacturing and tolerances accumulate for parts and processes. By extending this notion to CW, we apply mechanical tolerancing principles for computing worst case and statistical case CW of a product. We call this the CW tolerance approach (CWTA). Two case studies demonstrate the computation of CW. Based on the tolerance allocation concepts; CW allocation is also demonstrated through specific redesign examples. CWTA helps in identifying carbon intensive parts/processes and can be used to make appropriate design decisions.

Extending the notion of quality from physical metrology to information and sustainability

In this paper we intend to demonstrate the need for extending the notion of quality from the physical domain to information and, more comprehensively, to sustainability. In physical metrology there are well established principles such as fundamental units, precision, accuracy, traceability and uncertainty. In order to understand and define quality for information and sustainability we need to develop metrological concepts similar to those of physical metrology. Research efforts related to information quality (IQ) are scattered. IQ is primarily defined in terms of several characteristics (dimensions) which lack consensus definitions and are sometimes subjective. However, the notion of IQ is currently in practice and has provided some useful insights towards defining formal approaches to IQ. In order to extend the notion of quality to sustainability we need, as in the case of information, a well defined metrology similar to physical metrology. Sustainability is currently getting attention in many areas of human endeavor. One proposal is to measure sustainability in terms of a triple bottom line, namely social, economical and environmental aspects of human endeavor. Sustainability metrics are continuously evolving and their clear definition is fundamental to the understanding of the notion of sustainability quality. As an example we consider evaluation of carbon footprint, as a metric towards sustainability, for manufacturing a simple turned part. After analyzing the current literature, we identify the following needs for characterizing the notion of sustainability quality: (a) standardized terminology of terms and concepts, (b) metrics and metrology, (c) harmonization and extension of standards, (d) conformance testbeds for standards and (e) development of information models that support sustainability.

Characterizing Energy Consumption of the Injection Molding Process

ABSTRACT Presently available systems for sustainability assessment do not fully account for aspects related to a product’s manufacturing. In an effort to make more sustainable decisions, today’s industry seeks reliable methods to assess and compare sustainability for manufacturing. As part of the Sustainable Manufacturing program at the National Institute of Standards and Technology (NIST), one of our objectives is to help develop the needed measurement science, standards and methodologies to evaluate and improve sustainability of manufacturing processes. As a first step towards developing standard reference sustainability characterization methodologies for unit manufacturing processes, in this paper we focus on injection molding with energy as the sustainability indicator. We present a science-based guideline to characterize energy consumption for a part manufactured using the injection molding process. Based on the study, we discuss the selection of process parameters and manufacturing resources, determination of cycle time, theoretical minimum energy computations, and estimated energy computations for characterizing the injection molding process.

A review on measurement science needs for real-time control of additive manufacturing metal powder bed fusion processes

Additive manufacturing technologies are increasingly used in the development of new products. However, variations in part quality in terms of material properties, dimensional tolerances, surface roughness and defects limit its broader acceptance. Process control today based on heuristics and experimental data yields limited improvement in part quality. In an effort to identify the needed measurement science for real-time closed-loop control of additive manufacturing (AM) processes, this paper presents a literature review on the current AM control schemes, process measurements and modelling and simulation methods as it applies to the powder bed fusion process, though results from other processes are reviewed where applicable. We present our research findings to identify the correlations between process parameters, process signatures and product quality. We also present research recommendations on the key control issues to serve as a technical basis for standards development in this area. Complimentary details to this paper with summary tables, range of values, preliminary correlations and correlation figures can be accessed from a National Institute of Standards and Technology Report (http://nvlpubs.nist.gov/nistpubs/ir/2015/NIST.IR.8036.pdf). This paper is developed based on the report.

Impact of Energy Measurements in Machining Operations

Over the past years, institutions in general are increasingly interested and involved in sustainability and social responsibility. In addition, social and political pressures have lead to the creation of new regulations and policies that support new business opportunities around global sustainability. Considering sustainable manufacturing, a number of indicators have been proposed and currently being researched. The aim of this paper is to explore and discuss the impact of energy measurements as an indicator for sustainable manufacturing. The main question to be asked is that can energy measurement be used for process optimization in machining level. Based on energy monitoring during two Computer Numerical Control (NC) machining case studies, the significance of energy cost based on different CNC machining strategies and parameter settings is examined and discussed. The preliminary results from the energy measurements on the case studies indicate that potential cost savings in energy will be minimal in CNC operations. Based on the case studies, the potential energy savings in monetary value do not necessarily justify a companys investment in implementing real time energy tracking technologies the results were limited in scope with regards measuring energy as indicator for evaluating other performance outcomes.

Simulation and analysis for sustainable product development

PurposeSimulation plays a critical role in the design of products, materials, and manufacturing processes. However, there are gaps in the simulation tools used by industry to provide reliable results from which effective decisions can be made about environmental impacts at different stages of product life cycle. A holistic and systems approach to predicting impacts via sustainable manufacturing planning and simulation (SMPS) is presented in an effort to incorporate sustainability aspects across a product life cycle.MethodsIncreasingly, simulation is replacing physical tests to ensure product reliability and quality, thereby facilitating steady reductions in design and manufacturing cycles. For SMPS, we propose to extend an earlier framework developed in the Systems Integration for Manufacturing Applications (SIMA) program at the National Institute of Standards and Technology. SMPS framework has four phases, viz. design product, engineer manufacturing, engineer production system, and produce products. Each phase has its inputs, outputs, phase level activities, and sustainability-related data, metrics and tools.Results and discussionAn automotive manufacturing scenario that highlights the potential of utilizing SMPS framework to facilitate decision making across different phases of product life cycle is presented. Various research opportunities are discussed for the SMPS framework and corresponding information models.ConclusionsThe SMPS framework built on the SIMA model has potential in aiding sustainable product development.

Characterizing Sustainability for Manufacturing Performance Assessment

Manufacturing industries lack the measurement science and the needed information base to measure and effectively compare performance of manufacturing processes, resources and associated services with respect to sustainability. The current use of ad-hoc methods and tools to assess and describe sustainability of manufactured products do not account for manufacturing processes explicitly and hence results in inaccurate and ambiguous comparisons. Further, there are no formal methods for acquiring and exchanging information that help establish a consolidated sustainability information base. Our goal is to develop the needed measurement science and methodology that will enable manufacturers to evaluate sustainability performance of fundamental manufacturing processes ensuring reliable and consistent comparisons. In this paper, we propose and discuss a methodology for sustainability characterization to bridge the measurement science and the needed information base for sustainable manufacturing. This will set the stage for manufacturers to objectively assess and compare different manufacturing processes for sustainability.Copyright