Optimal wafer site selection using forward selection component analysis

Reducing wafer metrology continues to be a major target in semiconductor manufacturing efficiency initiatives due to it being a high cost, non-value added operation that impacts on cycle-time and throughput. However, metrology cannot be eliminated completely given the important role it plays in process monitoring and advanced process control. To achieve the required manufacturing precision, measurements are typically taken at multiple sites across a wafer. The selection of these sites is usually based on a priori knowledge of wafer failure patterns and spatial variability with additional sites added over time in response to process issues. As a result, it is often the case that in mature processes significant redundancy can exist in wafer measurement plans. This paper proposes a novel methodology based on Forward Selection Component Analysis (FSCA) for analyzing historical metrology data in order to determine the minimum set of wafer sites needed for process monitoring. The paper also introduces a virtual metrology (VM) based approach for reconstructing the complete wafer profile from the optimal sites identified by FSCA. The proposed methodology is tested and validated on a wafer manufacturing metrology dataset. © 2012 IEEE.

"Lazarillo de Tormes": melhoria da mobilidade em Salamanca

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Civil na Área de Especialização de Vias de Comunicação e Transportes

Optimização do processo de fabrico de componentes para a indústria automóvel

A qualidade é um factor-chave na indústria automóvel. Todos os fornecedores de componentes para a indústria automóvel estão sujeitos a qualificações e auditorias sistemáticas, com vista a melhorar os processos e verificar a sua rastreabilidade. Quando os processos assentam essencialmente em mão-de-obra intensiva, torna-se muito mais difícil atingir a ambicionada meta dos zero-defeitos, e a garantia da qualidade pode ficar comprometida, sendo necessário instalar procedimentos de controlo mais apurados. No entanto, se o processo ou processos forem convenientemente definidos, e se optar por capital intensivo em detrimento da mão-de-obra intensiva, a garantia da qualidade pode ser uma realidade, podendo ser fortemente minimizadas as operações de controlo da qualidade. Este trabalho teve por base a necessidade de reduzir fortemente, ou eliminar mesmo, o aparecimento de defeitos de montagem num sistema designado por remachado. Após cuidada análise do processo instalado, já parcialmente automatizado, mas ainda fortemente dependente de mão-de-obra, procedeu-se ao projecto de um equipamento capaz de reproduzir o mesmo efeito, mas que acomodasse alguns possíveis defeitos oriundos dos fornecedores dos componentes que são inseridos neste conjunto, colocados a montante na cadeia de fornecimento do produto. O equipamento resultante deste trabalho permitiu baixar o tempo de ciclo, acomodar a variabilidade dimensional detectada nos componentes que constituem o conjunto e reduzir drasticamente o número de não-conformidades.

Melhoria/simplificação ergonómica de linhas de montagem

Hoje em dia, com os avanços constantes na indústria, novas áreas começam cada vez mais a ser foco de atenção por parte das organizações. Motivados pela procura de melhores condições para os seus colaboradores e por todos os benefícios que este tipo de intervenção oferece, tanto a curto, como principalmente a médio e longo prazo, a Grohe Portugal, mais especificamente o seu departamento de montagem, achou relevante potenciar a aplicação da Ergonomia nos seus postos de trabalho. Posto isto, esta dissertação pretende apresentar o trabalho desenvolvido junto da organização que teve como objetivo projetar e executar uma linha de montagem que tivesse em consideração os seguintes aspetos: • Ergonomia; • Automatização ou semi-automatização de operações; • Simplificação de aspetos operacionais; • Sistemas de abastecimento mais robustos e de fácil uso; • Simplificação de setups; • Definição de dimensões normalizadas para futuros projetos. As soluções encontradas tiveram como objetivo primordial satisfazer o maior número possível de colaboradores, sendo que para tal foram utilizados dados referentes a antropometria da população Portuguesa. Para a realização e conclusão deste projeto, o trabalho foi decomposto em varias etapas, de entre as quais se destacam: • Analise e estudo dos métodos de montagem; • Levantamento de todos os componentes e operações que constituem o processo de fabrico das diversas famílias onde foram implementados novos projetos; • Definição e uniformização da estrutura das novas linhas de montagem; • Estudo e definição da disposição dos componentes na nova linha, bem como da sua forma de abastecimento; • Projeto da linha de montagem em 3D com recurso ao software SolidWorks (DassaultSystemes, 2014); • Montagem final da linha, bem como o acompanhamento da sua fase de arranque. Durante o estagio foi ainda pensado e implementado um projeto paralelo com vista a constante manutenção e melhoria do departamento de montagem cujo objetivo, através de “plant walks”, e detetar de entre outras, situações de falta de identificação de componentes ou equipamentos, degradação de ferramentas, fugas ou derrames nas linhas, etc. O balanco final do trabalho foi bastante positivo, tendo-se alcançado melhorias em alguns índices de qualidade, tempos de abastecimento e condições ergonómicas dos postos de trabalho que sofreram intervenção, tendo essas melhorias resultado numa avaliação positiva por parte dos colaboradores que integram essas mesmas linhas.

Benefits of Implementing Lean Practices and the Impact of the Lean Aerospace Initiative in the Defense Aerospace Industry and Government Agencies

In the 1980’s, many United States industrial organizations started developing new production processes to improve quality, reduce cost, and better respond to customer needs and the pressures of global competition. This new paradigm was coined Lean Production (or simply “Lean”) in the book The Machine That Changed The World published in 1990 by researchers from MIT’s International Motor Vehicle Program. In 1993, a consortium of US defense aerospace firms and the USAF Aeronautical Systems Center, together with the AFRL Materials and Manufacturing Directorate, started the Lean Aircraft Initiative (LAI) at MIT. With expansion in 1998 to include government space products, the program was renamed the Lean Aerospace Initiative. LAI’s vision is to “Significantly reduce the cost and cycle time for military aerospace products throughout the entire value chain while continuing to improve product performance.” By late 1998, 23 industry and 13 government organizations with paying memberships, along with MIT and the UAW were participating in the LAI.

Markov Process Modeling of A System Under WIPLOAD Control

This paper analyzes a proposed release controlmethodology, WIPLOAD Control (WIPLCtrl), using a transfer line case modeled by Markov process modeling methodology. The performance of WIPLCtrl is compared with that of CONWIP under 13 system configurations in terms of throughput, average inventory level, as well as average cycle time. As a supplement to the analytical model, a simulation model of the transfer line is used to observe the performance of the release control methodologies on the standard deviation of cycle time. From the analysis, we identify the system configurations in which the advantages of WIPLCtrl could be observed.

Applying the Lessons of “Lean Now” to Transform the US Aerospace Enterprise

Lean is common sense and good business sense. As organizations grow and become more successful, they begin to lose insight into the basic truths of what made them successful. Organizations have to deal with more and more issues that may not have anything to do with directly providing products or services to their customers. Lean is a holistic management approach that brings the focus of the organization back to providing value to the customer. In August 2002, Mrs. Darleen Druyun, the Principal Deputy to the Assistant Secretary of the Air Force for Acquisition and government co-chairperson of the Lean Aerospace Initiative (LAI), decided it was time for Air Force acquisitions to embrace the concepts of lean. At her request, the LAI Executive Board developed a concept and methodology to employ lean into the Air Force’s acquisition culture and processes. This was the birth of the “Lean Now” initiative. An enterprise-wide approach was used, involving Air Force System Program Offices (SPOs), aerospace industry, and several Department of Defense agencies. The aim of Lean Now was to focus on the process interfaces between these “enterprise” stakeholders to eliminate barriers that impede progress. Any best practices developed would be institutionalized throughout the Air Force and the Department of Defense (DoD). The industry members of LAI agreed to help accelerate the government-industry transformation by donating lean Subject Matter Experts (SMEs) to mentor, train, and facilitate the lean events of each enterprise. Currently, the industry SMEs and the Massachusetts Institute of Technology are working together to help the Air Force develop its own lean infrastructure of training courses and Air Force lean SMEs. The first Lean Now programs were the F/A-22, Global Hawk, and F-16. Each program focused on specific acquisition processes. The F/A-22 focused on the Test and Evaluation process; the Global Hawk focused on Evolutionary Acquisitions; and the F-16 focused on improving the Contract Closeout process. Through lean, each enterprise made many significant improvements. The F/A-22 was able to reduce its Operational Flight Plan (OFP) Preparation and Load process time of 2 to 3 months down to 7 hours. The Global Hawk developed a new production plan that increases the annual production of its Integrated Sensor Suite from 3 per year to 6 per year. The F-16 enterprise generated and is working 12 initiatives that could result in a contract closeout cycle time reduction of 3 to 7 years. Each enterprise continues to generate more lean initiatives that focus on other areas and processes within their respective enterprises.

Implementation of global make to inventory strategy at BASF SE

La optimización y armonización son factores clave para tener un buen desempeño en la industria química. BASF ha desarrollado un proyecto llamada acelerador. El objetivo de este proyecto ha sido la armonización y la integración de los procesos de la cadena de suministro a nivel mundial. El proceso básico de manejo de inventarios se quedó fuera del proyecto y debía ser analizado. El departamento de manejo de inventarios en BASF SE ha estado desarrollando su propia estrategia para la definición de procesos globales de manufactura. En este trabajo se presentará un informe de las fases de la formulación de la estrategia y establecer algunas pautas para la fase de implementación que está teniendo lugar en 2012 y 2013.

The effect of thermal conductivity of RIM moulds in kinetics cure

Reaction Injection Moulding (RIM) is a moulding technology used for the production of large size and complex plastic parts. The RIM process is characterized essentially by the injection of a highly reactive chemical system (usually polyurethane) and fast cure, in a mould properly closed and thermally controlled. Several studies show that rapid manufacturing moulds obtained in epoxy resins for Thermoplastic Injection Moulding (TIM) affect the moulding process and the final properties of parts. The cycle time and mechanical properties of final parts are reduced, due to a low thermal conductivity of epoxy materials. In contrast, the low conductivity of materials usually applied for the rapid manufacturing of RIM moulds, increase the mechanical properties of final injected parts and reduce the cycle time. This study shows the effect of the rapid manufacturing moulds material during the RIM process. Several materials have been tested for rapid manufacturing of RIM moulds and the analysis of both, temperature profile of moulded parts during injection and the cure data experimentally obtained in a mixing and reaction cell, allow to determine and model the real effect of the mould material on the RIM process.

Mechanism for synchronized motion between two humans in mutual tapping experiments: Transition from alternative mode to synchronization mode

We performed mutual tapping experiments between two humans to investigate the conditions required for synchronized motion. A transition from an alternative mode to a synchronization mode was discovered under the same conditions when a subject changed from a reactive mode to an anticipation mode in single tapping experiments. Experimental results suggest that the cycle time for each tapping motion is tuned by a proportional control that is based on synchronization errors and cycle time errors. As the tapping frequency increases, the mathematical model based on the feedback control in the sensory-motor closed loop predicts a discrete mode transition as the gain factors of the proportional control decease. The conditions of the synchronization were shown as a consequence of the coupled dynamics based on the subsequent feedback loop in the sensory-motor system.

The effect of rapid changes in ionospheric flow on velocity vectors deduced from radar beam-swinging experiments

The effects on the horizontal ionospheric velocity vectors deduced from radar beam-swinging experiments, which occur when changes in the flow take place on short time scales compared with the experiment cycle time, are analysed in detail. The further complications which arise in the interpretation of beam-swinging data, due to longitudinal gradients in the flow and to field-aligned flows, are also considered. It is concluded that these effects are unlikely to seriously compromise statistical determinations of the response time of the flow, e.g. to changes in the north-south component of the IMF, such as have been recently reported by Etemadiet al. (1988, Planet. Space Sci.36, 471), using EISCAT ‘Polar’ data.

Simulation-based support tool for operator performance in batch manufacturing

In industry, the workload and utilization of shop floor operators is often misunderstood. In this paper, we will present several real case studies, using Discrete Event Simulation (DES) models, which allow us to better understand operators in a batch manufacturing environment. The first study investigates labour in a machining plant consisting of multiple identical CNC machines that batch produce parts. The second study investigates labour in an eight station, gravity die casting rotary table. The results from these studies have shown that there can be potential improvements made by the production planners in the current labour configuration. In the first case study, a matrix is produced that estimates what the operator's utilization levels will be for various configurations. From this, the preferred operator to machine ratio over a range of cycle times is presented. In the second study, the results have shown that by reducing the casting cycle time, the operator would be overloaded. A discrete event simulation of these two cases highlighted areas that were misunderstood by plant management, and provided them with a useful decision support tool for production planning.

Kanban devs modelling, simulation and verification

Kanban Control Systems (KCS) have become a widely accepted form of inventory and production control. The creation of realistic Discrete Events Simulation (DES) models of KCS require specification of both information and material flow. There are several commercially available simulation packages that are able to model these systems although the use of an application specific modelling language provides means for rapid model development. A new Kanban specific simulation language as well as a high-speed execution engine is verified in this paper through the simulation of a single stage single part type production line. A single stage single part KCS is modelled with exhaustive enumeration of the decision variables of container sizes and number of Kanbans. Several performance measures were used; 95% Confidence Interval (CI) of container Flow Time (FT), mean line throughput as well as the Coefficient of Variance (CV) of FT and Cycle Time were used to determine the robustness of the control system.

Linear-motor based five-axis parallel machine for effective material processing

The aim of the work was to reduce the cost and improve the performance of five-axis machines. The main performance criteria were motion cycle-time and positioning accuracy/precision. A novel machine that utilizes the concept of parallel-kinematics and linear motor technology is proposed, designed, built and controlled for this sake.

Automation of a complex transfer operation using a polar manipulator

Purpose – The objective of this paper included developing a polar robot (SPBot) for rotating and transferring car engine block (CEB) around and along two different axes in a confined workspace envelope.

Design/methodology/approach – The complex transfer operations of the CEB requires sweeping complete surface of the half sphere, and thus a polar robot is best suited to such a task in a confined space. Considering the limited space for this operation, a specially designed manipulator is built comprising 2 degrees of freedom driven by electrical servo motors. Also due to the special form of CEB, an especially designed pneumatic gripper is developed. Kinematics models, static and dynamic equations, together with trajectory planning for such a manipulator are described.

Findings – The high-speed complex transfer in a limited environment is successfully implemented.

Originality/value – The developed polar robot provides for complex transfer operations that significantly increases the speed of the product line and thus reducing the cycle time from 60?s using manpower to just 20?s using the robot.