A.Y.C. Nee

Multi‐objective optimization of part‐ building orientation in stereolithography

In rapid prototyping, such as SLA (stereolithography apparatus) and FDM (fused deposition modelling), the orientation of the part during fabrication is critical as it can affect part accuracy, reduce the production time, and minimize the requirement for supports and, thus, the cost of building the model. Presents a multi‐objective approach for determining the optimal part‐building orientation. Considers different objectives such as part accuracy and building time. Objective functions have been developed based on known sources of errors affecting part accuracy and the requirements of good orientations during the building of a model. The objective functions employ weights assigned to various surface types affecting part accuracy. The primary objective is to attain the specified accuracy achievable with the process. The secondary objective is to minimize the building time. Gives examples to illustrate the algorithm for deriving the optimal orientation which can assure better part quality and higher building efficiency.

Hybrid genetic algorithm and simulated annealing approach for the optimization of process plans for prismatic parts

For a CAPP system in a dynamic workshop environment, the activities of selecting machining resources, determining set-up plans and sequencing machining operations should be considered simultaneously to achieve the global lowest machining cost. Optimizing process plans for a prismatic part usually suffer from complex technological requirements and geometric relationships between features in the part. Here, process planning is modelled as a combinatorial optimization problem with constraints, and a hybrid genetic algorithm (GA) and simulated annealing (SA) approach has been developed to solve it. The evaluation criterion of machining cost comes from the combined strengths of machine costs, cutting tool costs, machine changes, tool changes and set-ups. The GA is carried out in the first stage to generate some initially good process plans. Based on a few selective plans with Hamming distances between each other, the SA algorithm is employed to search for alternative optimal or near-optimal process plans. In the GA and SA algorithms, some preliminarily defined precedence constraints between features and operations are manipulated. A case study and the comparisons with the single GA and SA approaches show that this hybrid approach can achieve highly satisfactory results.

Methods for in-field user calibration of an inertial measurement unit without external equipment

This paper presents methods to calibrate and compensate for non-zero biases, non-unit scale factors, axis misalignments and cross-axis sensitivities of both the tri-axial accelerometer and gyroscopic setups in a micro-electro-mechanical systems (MEMS) based inertial measurement unit (IMU). These methods depend on the Earths gravity as a stable physical calibration standard. Specifically, the calibration of gyroscopes is significantly improved by comparing the outputs of the accelerometer and the IMU orientation integration algorithm, after arbitrary motions. The derived property and proposed cost function allow the gyroscopes to be calibrated without external equipment, such as a turntable, or requiring precise maneuvers. Both factors allow the IMU to be easily calibrated by the user in the field so that it can function as an accurate orientation sensor. A custom-made prototype IMU is used to demonstrate the effectiveness of the proposed methods, with data that are carefully obtained using prescribed motions, as well as those less rigorously collected from the IMU when it is mounted on the head of a user or held in hands with brief random movements. With calibration, the observed average static angular error is less than a quarter of a degree and the dynamic angular error is reduced by a factor of 2 to 5.

Augmented reality applications in manufacturing: a survey

Augmented reality (AR) is a novel human–machine interaction that overlays virtual computer-generated information on a real world environment. It has found good potential applications in many fields, such as military training, surgery, entertainment, maintenance, assembly, product design and other manufacturing operations in the last ten years. This paper provides a comprehensive survey of developed and demonstrated AR applications in manufacturing activities. The intention of this survey is to provide researchers, students, and engineers, who use or plan to use AR as a tool in manufacturing research, a useful insight on the state-of-the-art AR applications and developments.

Using genetic algorithms in process planning for job shop machining

This paper presents a novel computer-aided process planning model for machined parts to be made in a job shop manufacturing environment. The approach deals with process planning problems in a concurrent manner in generating the entire solution space by considering the multiple decision-making activities, i.e., operation selection, machine selection, setup selection, cutting tool selection, and operations sequencing, simultaneously. Genetic algorithms (GAs) were selected due to their flexible representation scheme. The developed GA is able to achieve a near-optimal process plan through specially designed crossover and mutation operators. Flexible criteria are provided for plan evaluation. This technique was implemented and its performance is illustrated in a case study. A space search method is used for comparison.

Advanced manufacturing systems: socialization characteristics and trends

Since 1960s, with the development of societal and related technologies, many advanced manufacturing systems (AMSs) and modes have been put forward, and they have attracted the attention of a large number of researchers in manufacturing, information and management fields. However, existing studies are mainly focused on the specific theoretical research of each AMS, and the horizontal comparison of the difference and evolution of these AMSs are not significant. Furthermore, most of the existing studies try to realize concrete technical implementation, and discussions on the relationship among these AMSs and social factors are relatively rare. Therefore, this paper aims to address this issue, and a brief overview of the development process of AMSs is first presented. Next, a tri-view model is established to analyze the evolution and socialization characteristics of AMSs. It is found that the sharing of manufacturing resources and capabilities, the value creation carriers, the value measuring criteria, the composition of the value chain and enterprise collaboration, and the user participation in manufacturing are all moving towards socialization. It is essential that the evolution and development of AMSs should also adapt this trend towards socialization in order to achieve better sharing of limited resources and efficient adding of value.

Feature-based design in a distributed and collaborative environment

Abstract In this paper, a client/server framework has been developed to enable a dispersed team to accomplish a feature-based design task collaboratively. A manipulation client+modelling server infrastructure has been proposed to facilitate consistent primary information modelling for multiple users and adaptability of the system. Based on feature-to-feature relationships, a distributed feature manipulation mechanism has been proposed to filter the varied information of a working part during a co-design activity to avoid unnecessary re-transferring of the complete large-size CAD files each time when any interactive operation is imposed on the model by a client. In the distributed environment, a design task and the engaged clients are organised and connected through working sessions generated and maintained dynamically with a collaborative server. The environment is open to downstream manufacturing analysis modules to achieve distributed concurrent engineering.

Virtual and Augmented Reality Applications in Manufacturing

Abstract Augmented Reality (AR) is a fast rising technology and it has been applied in many fields such as gaming, learning, entertainment, medical, military, sports, etc. This paper reviews some of the academic studies of AR applications in manufacturing operations. Comparatively, it is lesser addressed due to stringent requirements of high accuracy, fast response and the desirable alignment with industrial standards and practices such that the users will not find drastic transition when adopting this new technology. This paper looks into common manufacturing activities such as product design, robotics, facilities layout planning, maintenance, CNC machining simulation and assembly planning. Some of the issues and future trends of AR technology are also addressed.

Undercut feature recognition in an injection mould design system

In the design of plastic injection moulds, the presence of undercut features would affect mould cost and structure. In this paper, the definition, classification of undercut features and the related notions to identify them are presented. Based on the proposed undercut feature definition and taxonomy, the relationships between the undercut features and their mouldability are described. The definition of undercut feature parameters and the computational methodologies to determine them are proposed. The undercut feature draw range and directions are introduced based on the V-maps of undercut features. The recognition criteria from which the undercut features can be identified are presented. In consideration of blending surfaces, two pairs of notions, viz. actual and virtual first adjacent surfaces, actual and virtual edges are proposed. As undercut features can be consistently recognized, the identification criteria for undercut features are given. The industrial case studies show that the methodologies developed are efficient in recognition and extraction of undercut features in complex injection moulded parts.

A distributed multi-agent environment for product design and manufacturing planning

This paper describes a multi-agent approach to the integration of product design, manufacturability analysis, and process planning in a distributed manner. The objective is to develop a distributed concurrent engineering system to allow geographically dispersed entities to work cooperatively towards overall system goals. In the paper, an agent-based concurrent engineering system concerning product design and manufacturing planning, and its fundamental framework and functions are presented. The proposed model considers constraints and requirements from the different product development cycles in the early development phases and fully supports the concept of design-for-manufacturability. This methodology uses conflict resolution (CR) techniques and design-improvement suggestions to refine the initial product design. The model comprises a facilitator agent, a console agent and six service agents. Each service agent is used to model different product development phases, and the console agent acts as an interacting interface between designers and the system, while the facilitator is responsible for the decomposition and dispatch of tasks, and resolving conflicts of poor designs. A prototype system for part design, manufacturability analysis, and process planning has been implemented. The performance of the prototype system shows that it could be extended to include other service agents, such as assemblability analysis, to become a comprehensive distributed concurrent engineering system for geographically dispersed customers and suppliers.