Modelo híbrido Pull y Push en el sector de las telecomunicaciones (un estudio de caso) empleando dinámica de sistemas

Trabajo de investigaciónA través de esta investigación se establece la importancia de la aplicación del estudio del comportamiento de los niveles de inventarios, específicamente en el sector de las telecomunicaciones (Caso de estudio Claro Colombia), teniendo en cuenta su complejidad y la relación que existe entre la determinación de los niveles de inventarios con respecto a las fluctuaciones de la demanda de equipos, por lo cual se aborda el problema por medio de dinámica de sistemas. De acuerdo con lo anterior se elaboró un modelo empleando dinámica de sistemas que permite determinar los niveles de inventarios en cada una de las etapas de almacenaje de equipos requeridos para la operación, que responde a los cambios de la demanda, buscando los niveles mínimos de inventario.MaestríaMagister en Ingeniería Industria

On the meaning of ConWIP cards:an assessment by simulation

The simplicity of Constant Work-In-Process (ConWIP) makes it one of the most widely adopted card-based production control solutions. Its simplicity, however, also limits the opportunities that are available to improve the concept. There are arguably only two major search directions: (i) to alter the meaning of cards away from controlling jobs; and (ii) to adopt alternative, more sophisticated backlog sequencing rules. In this study, we outline a simple, practical load-based ConWIP system that changes the meaning of cards. Rather than controlling the number of jobs, cards are associated with a certain amount of workload. Simulation results demonstrate the positive performance impact of limiting the total shop load. The Workload Control literature advocates the use of a corrected load measure as it better represents the direct load queuing at a station; but this worsens performance when compared to a shop load measure in the context of ConWIP

Centralised vs. decentralised control decision in card-based control systems:comparing kanban systems and COBACABANA

Kanban systems are simple yet effective means of controlling production. Production control is decentralised or exercised locally on the shop floor, i.e. a downstream station signals to an upstream station that an item is needed. If items are always the same and known, then demands can be satisfied instantaneously from stock; but if items differ and are unknown, demands must first be propagated backwards from station to station before being satisfied. The former is defined as an inventory control problem and the latter as an order control problem. Handling the order control problem via kanban involves a decentralised card acquisition process (during which information is propagated from station to station) that is separated from the actual production process. COBACABANA (control of balance by card-based navigation), an alternative card-based solution, shares kanban’s control structure but centralises the card acquisition process. Evaluating the two systems therefore provides a unique opportunity to compare decentralised and centralised control. Using simulation, we demonstrate that it is specifically the centralised card acquisition process that allows COBACABANA to balance the workload across resources and thus to outperform kanban in an order control problem. This has major implications for research and practice

A Quantitative Evaluation of the Productivity of the Mercedes-Benz Production System

Productivity of automotive manufacturing production systems have been an area of study among researchers since the industrial revolution. Automotive manufacturing production systems that are implemented properly increase productivity in production environments. Researchers have demonstrated that productivity can be improved through modeling the Toyota production system. However, researchers have not established how implementing Mercedes Benz production system (MBPS) impacted Mercedes-Benz cars\u27 productivity between 1999 and 2017. The purpose of this quantitative research study was to examine the effect of implementing the Mercedes-Benz Production System (MBPS). A survey was administered to 35 Mercedes-Benz employees that consisted of operation managers, plant managers, manufacturing engineers, and shop workers. The study used Spearman\u27s correlations to analyze the strength of the associations between the dependent variable of productivity and the three independent variables of cycle-time variation, employee-headcount variation, and key performance indicators. The results showed no statistically significant relationship, supporting that implementing the MBPS was not sufficient enough to reject the null hypothesis the research questions. The social change implications for this research may promote positive social change by its emphasis on the implementation of manufacturing production systems. Such implementations may then stimulate increased economic efficiencies, quality, and profitability for society

A DESIGN SCIENCE ENABLED ORGANIZATIONAL CAPABILITY STATE MEASUREMENT APPROACH

Organizational capability plays a critical role in creating and maintaining an organization's competitive advantage. It enables organizations to develop and implement organizational strategies and business models. However, the measurement of the organizational capability to assist the prediction of organizational performance remains a challenging task. It is especially challenging for organizations with limited resources, such as monetary resources, time and the expertise to organizational capability and instrument for measuring organizational capability. The challenge is two-fold. Firstly, organizational capability measurement aims to predict organizational performance rooted in individual performance. However, it is challenging to find a practical framework that links individual performance with organizational performance and guides the organizational capability measurement by considering the individual factors. Secondly, the questionnaire is widely used for measuring individual knowledge, attitudes, emotion and perceptions. However, questionnaire design methods are still very ill-defined processes that the generation of items heavily relies on the experience of experts or the questionnaires designed by other researchers about a similar topic. This research aims to provide an organizational capability state (OCS) model and develop a framework for questionnaire design using a design methodology — Environment Based Design (EBD). The primitive factors for OCS are organizational members’ knowledge, skills and the perception of workload and affect. The questionnaire design framework achieves the OCS measurement by developing a questionnaire for assessing organizational members’ knowledge, skills, perception, affect and goal. With two case studies, the framework of questionnaire design is proved to be effective in questionnaire design. The combination of the OCS model and questionnaire design framework enables a cost-effective and less expert-dependent measurement of organizational capability

Performance analysis and development of pull-type production control strategies for evolutionary optimisation of closed-loop supply chains

The objective of this thesis is to establish a Closed-Loop Supply Chain (CLSC) design that is analysed through a series of simulation models, aimed at defining the highest performing production control strategy, whilst considering multiple related variables on both the forward and reverse flow of materials in manufacturing environments. Due to its stochastic nature, the reverse logistics side of the CLSC represents an increased source of variance for the inventory management and control strategies as it implies the erratic supply of returned materials, in addition to the very random customer demand, hence with highly variable inputs on both sides of the productive system, intrinsically inherent to this line of research. To test the operational performance of several pull-type production control strategies, a simulation-based research method was designed. The strategies experimented were: Hybrid Extended Kanban CONWIP special case (HEKC-II), Hybrid Kanban CONWIP (HKC), Dynamic Allocation Hybrid Extended Kanban CONWIP special case (DNC HEKC-II) and Dynamic Allocation Hybrid Kanban CONWIP (DNC HKC). All were tested in scenarios with high and low processing time variability and with 90% returned products and 40% returns from an open market system, therefore totaling 16 simulation models. Multi-objective evolutionary algorithms were utilised to generate the Pareto-optimum performance frontier with the objective of simultaneously minimising both performance metrics: The overall average work in progress (WIP) and the average backlog queue length (BL) for the entire CLSC. Processes used in the recovery and recycling of end of life manufactured goods were examined. This research method structures leading factors towards improved economic viability and sustainability of technologies required for the effective implementation of inventory control strategies on highly complex closed-loop supply chains with the focus on the performance metrics and optimum utilisation of resources available for the industry. The dynamic allocation strategies proved significant performance improvement, shifting the entire Pareto frontier forward with major advances on both metrics. Furthermore, it happened on all scenarios tested. The modified HEKC-II, with an optimisable parameter that enables it to be overwritten in a way that it can match the well-established HKC, also performed as originally intended and had better results than HKC in some cases, especially with the higher variability level. It also provided grounds for the suggested improvements and flexibilisation of the HEKC strategy. A major contribution of this thesis was the successful implementation of another advanced control methodology, entitled here the Intelligent Self-Designing Production Control Strategy, which provided maximum control performance. It consisted essentially of DNC HEKC-II with the following modifications: I) Extensive increase of dynamically allocated authorisation cards; II) Further anticipation of the time to trigger the change in the number of cards according to the finished goods buffer level, plus an acceleration/deceleration factor of this change; III) The capability of downsizing itself to become similar to HKC in an optimisation process if diverse production system conditions and variability would require. It displayed a very significant shift of the performance frontier

Dynamic card control strategy in pull manufacturing systems

The dynamic control of cards in pull systems can improve the performance of a manufacturing system in a turbulent demand condition. The traditional fixed card approach can reduce the performance of a system in some cases. This article presents a dynamic card control methodology in order to keep a high level of performance measures. The proposed methodology is based on the observation of customer demand in order to detect the fluctuations and adjust the number of cards. The demand fluctuations is evaluated based on two moving average: the first on a medium horizon and the second on a short horizon. The comparison between the two moving averages is the signal of the controller developed. A simulation environment has been developed to test the proposed methodology in both kanban and Constant Work In Process (CONWIP) systems. The simulations conducted in several scenarios highlight the better performance obtained using the controller. The main performance measures investigated are: the throughput, the queue of orders waiting to be processed, the throughput time of the orders, the number of cards used and the orders delayed. The benefits are more relevant in the case reliability reduction of the manufacturing system