Shaw C. Feng

A Model for Capturing Product Assembly Information

The important issue of mechanical assemblies has been a subject of intense research over the past several years. Most electromechanical products are assemblies of several components, for various technical as well as economic reasons. This paper provides an object-oriented definition of an assembly model called the Open Assembly Model (OAM) and defines an extension to the NIST Core Product Model (NIST-CPM). The assembly model represents the function, form, and behavior of the assembly and defines both a system level conceptual model and associated hierarchical relationships. The model provides a way for tolerance representation and propagation, kinematics representation, and engineering analysis at the system level. The assembly model is open so as to enable plug-and-play with various applications, such as analysis (FEM, tolerance, assembly), process planning, and virtual assembly (using VR techniques). With the advent of the Internet more and more products are designed and manufactured globally in a distributed and collaborative environment. The class structure defined in OAM can be used by designers to collaborate in such an environment. The proposed model includes both assembly as a concept and assembly as a data structure. For the latter it uses STEP. The OAM together with CPM can be used to capture the assembly evolution from the conceptual to the detailed design stages. It is expected that the proposed OAM will enhance the assembly information content in the STEP standard. A case study example is discussed to explain the Usecase analysis of the assembly model.

Object-oriented representation of electro-mechanical assemblies using UML

The important issue of representing mechanical assemblies has been a subject of intense research over the past several years. Most electromechanical products are assemblies of several components. This paper presents an object-oriented definition of an assembly model called Open Assembly Model (OAM). The assembly model has function, form, and behavior. It defines both a system level conceptual model and the associated hierarchical relationships. The model provides a way for representing tolerance representation and propagation, kinematics representation, and engineering analysis at the system level. The assembly model is open so as to enable plug-and-play with various analysis and applications modules. A case study example is discussed to explain the Usecase analysis of the assembly model.

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.

Unified functional tolerancing approach for precision cylindrical components

Current geometric dimensioning and tolerancing (GD&T) standards dictate that the geometry of a cylindrical manufactured part should be characterized in terms of its roundness, straightness, cylindricity and diameter. However, standards define the form errors using maximum peak-to-valley values – a very simplistic geometric description. As a result, measurements based on GD&T definitions for manufactured parts are ineffective for identifying and diagnosing error sources in a manufacturing process. This paper introduces a new tolerancing scheme for cylindrical parts and its application to functional tolerancing for diesel engine components. The new tolerance definition method is based on Legendre and Fourier polynomials for modelling and characterizing typical geometric errors found in machined cylindrical parts. As the tolerance parameters in the new tolerancing scheme represents the whole profile characteristics of the part geometry, they provide a direct link to part function and error sources of manufacturing processes. This paper describes the Legendre and Fourier polynomials-based tolerancing method. Typical machining errors of cylindrical parts in precision turning and grinding processes are analysed and modelled using the new tolerancing method. Application of the new tolerancing method is illustrated with an example of functional tolerancing a production diesel engine component, which shows that the new tolerancing method is effective for the specification and control of fuel leakage variation in diesel engine component design and manufacturing.

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.

Introducing Sustainability Early into Manufacturing Process Planning

In response to the global trend towards implementing sustainable manufacturing practices, we put forth an exploratory approach that uses energy monitoring as a means to introduce sustainability criteria early into manufacturing process planning. Typically cost, quality and time are the indices for manufacturability assessment in generating manufacturing process plans. In this paper, we propose the idea of introducing sustainability to complement cost, quality and time to arrive at alternative sustainable plans in identified manufacturing processes. To be sustainable, it is pertinent that manufacturing firms understand the energy consumption of different manufacturing equipment used to produce products. This will enable industry to implement energy reduction processes in a more effective manner and pave the way for improved and alternate manufacturing solutions. The paper presents the potential utility of energy usage readings in the interest of continuing dialogue and collaboration.

Characterization of Probe Dynamic Behaviors in Critical Dimension Atomic Force Microscopy

This paper describes a detailed computational model of the interaction between an atomic force microscope probe tip and a sample surface. The model provides analyses of dynamic behaviors of the tip to estimate the probe deflections due to surface intermittent contact and the resulting dimensional biases and uncertainties. Probe tip and cantilever beam responses to intermittent contact between the probe tip and sample surface are computed using the finite element method. Intermittent contacts with a wall and a horizontal surface are computed and modeled, respectively. Using a 75 nm Critical Dimension (CD) tip as an example, the responses of the probe to interaction forces between the sample surface and the probe tip are shown in both time and frequency domains. In particular, interaction forces between the tip and both a vertical wall and a horizontal surface of a silicon sample are modeled using Lennard-Jones theory. The Snap-in and Snap-out of the probe tip in surface scanning are calculated and shown in the time domain. Based on the given tip-sample interaction force model, the calculation includes the compliance of the probe and dynamic forces generated by an excitation. Cantilever and probe tip deflections versus interaction forces in the time domain can be derived for both vertical contact with a plateau and horizontal contact with a side wall. Dynamic analysis using the finite element method and Lennard-Jones model provide a unique means to analyze the interaction of the probe and sample, including calculation of the deflection and the gap between the probe tip and the measured sample surface.

TOWARDS KNOWLEDGE MANAGEMENT FOR SMART MANUFACTURING

The need for capturing knowledge in the digital form in design, process planning, production, and inspection has increasingly become an issue in manufacturing industries as the variety and complexity of product lifecycle applications increase. Both knowledge and data need to be well managed for quality assurance, lifecycle-impact assessment, and design improvement. Some technical barriers exist today that inhibit industry from fully utilizing design, planning, processing, and inspection knowledge. The primary barrier is a lack of a well-accepted mechanism that enables users to integrate data and knowledge. This paper prescribes knowledge management to address a lack of mechanisms for integrating, sharing, and updating domain-specific knowledge in smart manufacturing. Aspects of the knowledge constructs include conceptual design, detailed design, process planning, material property, production, and inspection. The main contribution of this paper is to provide a methodology on what knowledge manufacturing organizations access, update, and archive in the context of smart manufacturing. The case study in this paper provides some example knowledge objects to enable smart manufacturing.

Towards a Multi-View Semantic Model for Product Feature Description

Multiple perspectives need to be included in a product development process. Engineers from different departments usually have different views on a product design. It is hence necessary to define information structures that support multiple views. This paper provides an analysis and approach to develop a multi-view semantic model of three levels to describe product features. We base our analysis on a three-level conceptulization of engineering design features. The base level is substance, the intermediate level is view, and the top level is purpose. A multi-view semantic model will enhance semantic integrity of feature information throughout the product development for sharing information, such as design intent, manufacturing capability, and quality requirements.

Disassembly Process Information Model for Remanufacturing

Abstract Disassembly is essential to dismantle a product for remanufacturing during maintenance or at the end of service life. The National Institute of Standards and Technology has developed an information model for describing disassembly processes. A disassembly process includes many subprocesses, such as separation, cleaning, repair, replacement, and inspection. This paper describes a disassembly process information model with the following key components: workpiece, material content, equipment, and workflow. The workflow aspect supports the modeling of operations, operation sequences, decision making, branching an operation into multiple ones, and joining multiple operations into one. The model provides a foundation for computer-aided disassembly software systems development.