1,721,159 research outputs found
Integrated Quality and Production Logistics Analysis of Asynchronous Manufacturing Lines With Deteriorating Machines Monitored by SPC.
No full textQuality, maintenance and production logistics aspects have been traditionally treated by scientist and industrialists almost in isolation, i.e. with relative attention to their mutual relation. However, recent works show that a strong relation between equipment availability, product quality and system productivity do exist. This paper presents for the first time a general decomposition method able to study the integrated quality and production logistics performance of production systems where machines are subject to progressive deterioration states. The partially observable degrading process is considered to be monitored by statistical control charts that may activate preventive maintenance procedures. The proposed method is based on a completely new idea of decomposition approach that applies to general multiple-up and multiple-down state machines. The development of such integrated performance evaluation framework paves the way to the development of a coupled evaluation / optimization procedure to jointly determine the cost optimal design of quality control tools, maintenance policies and production system parameters
Performance evaluation of two-stage buffered production systems with discrete general Markovian machines
No full textThis paper presents an exact analytical method for the performance evaluation of buffered two-stage production systems where machines are modeled as generally complex discrete time Markov reward models. The method is based on the exact solution of the difference equation describing the dynamics of the system in the internal states. Then, a unique solution is obtained by imposing boundary conditions at the limiting buffer levels. The method results to be computationally stable and efficient even for large number of machine states. The generality of the model allows evaluating a wide set of previously uninvestigated systems. For example, systems with machines having generally distributed failure and repair times, systems with quality deteriorating machines or with flexible machines processing multiple part-types can be modeled. Furthermore, the developed model can be used as a building block to extend the analysis to generally long production lines via system decomposition. © IFAC
A decomposition method for the analysis of long buffered production systems with discrete general Markovian machines
No full textThis paper presents a new decomposition method for the approximate performance evaluation of buffered multi-stage production systems where machines are modeled as generally complex discrete time Markov chains with reward. The method is based on the exact solution of smaller two-machine sub-systems, also referred as building blocks, with machines that also feature such general characteristics. A decomposition approach is developed that propagates all the possible interruptions of flow due to starvation and blocking conditions throughout the pseudo-machines of each building block. In order to deal with such general settings, new decomposition equations are developed. A new algorithm is proposed for solving these decomposition equations. The proposed method proves to be very fast and accurate over a wide range of test cases, partly reported in this paper. To prove the generality of the framework, reported cases are focused on systems with generally distributed up and down times and systems with degrading machines. This method paves the way to the analysis of a wider class of previously un-investigated systems. © IFAC
Joint Design of Quality and Production Control in Multi-Stage Asynchronous Manufacturing Systems
No full textThis paper proposes an analytical method for the joint design of quality and production control parameters in unreliable asynchronous multi-stage lines. Classical statistical quality control charts are typically designed without taking into consideration the logistic performance of multi-stage systems. Similarly, production control parameters, such as the number of kanban cards at any stage of a kanban controlled system, are typically designed without taking into consideration the impact of this decision on the product quality. By doing so, it is implicitly assumed that the two controllers act as independent. However, the dynamics of real systems show that this is not true. Specifically, the proposed method optimally sets the sample size, the sampling frequency and the position of the control limits of the quality control charts as well as the number of kanban cards at any stage of production, by jointly considering the mutual relations between the controllers. Numerical results compare the solution of this integrated design with the configurations obtained by solving the two problems in isolation with existing techniques. They show that great benefits can be achieved by the proposed integrated design of the quality and production control parameters, since it fully captures the interaction between the dynamics of the two controllers
Integrated production and reconfiguration planning in modular plug-and-produce production systems
Full text linkModular plug-and-produce production systems have been proposed as promising architectures to face the challenge of evolving market requirements, large product variety and small lots. These systems enable fast reconfiguration through on-line production modules substitution. However, such capability poses challenges at planning level, as the sequencing of lots and the selection of production modules need to be performed simultaneously. This paper proposes an integrated method for production and reconfiguration planning combining stochastic lot completion time distribution analysis and lot sequence optimization to maximize the system service level. The approach is validated in a real industrial system producing hydraulic valves
Integrated Analysis of Quality and Production Logistics Performance in Asynchronous Manufacturing Lines
No full textAnalysis of the Lead Time Distribution in multi-product systems with dedicated buffers
Full text linkPerishable products that deteriorate before leaving the production system are common in industry. The most classic example is the food industry but several cases can be found in semiconductor manufacturing, and in polymers forming processes. These systems often require the scrapping of parts whose lead-time has exceeded a certain threshold. Previous works have considered single-product systems and have shown that the size of the buffers and actions dedicated to improve the machine availability may strongly affect the percentage of scrapped parts. In this paper, we model the dynamics of this phenomenon in a multi-product system composed of two machines that are connected through dedicated buffers. Furthermore, the model allows the use of three different policies for the mixing of products. The main contribution is a method for the calculation of the lead time distribution of each product that can be used to determine the effective throughput of the system. The relevance of the method is shown by means of numerical results that provide important insights on the problem and show counterintuitive behaviors
A Decomposition Approach for the Approximate Evaluation of the Output Variability in Multi-Stage Production Lines
No full textThe evaluation of the average performance of manufacturing systems has been widely investigated in the manufacturing system engineering literature. However, there is industrial evidence that production variability due to random disturbances causes the observed production rate to be different from its average value. In this paper, a fast and accurate approximate analytical method for the evaluation of the output variability in capacitated multi-stage production lines where machines are prone to random failures is proposed. The method decomposes the production line into two-machine one-buffer subsystems and propagates the first two asymptotic moments of the output throughout the production line. Numerical results show that the proposed method has good accuracy if compared with discrete event simulation and outperforms existing methods for the output variance estimation. The industrial benefits derived by the use of this method are shown through application to real manufacturing contexts
Issues in the modeling and design of material recycling systems
No full textInterest in recycling has surged in recent years due to increasing primary material costs, environmental concerns over material production and disposal, and laws in many countries designed to improve material recycling rates. In response, recycling systems are becoming more complex as increasing material recovery is
required from products with complicated material mixtures such as WEEE (Waste Electric and Electronic Equipment) and ELVs (End-of-Life Vehicles). To increase separation system performance and to process complex material mixtures, separation systems are typically organized as highly integrated multi-stage systems. In spite of their cost, the problem of estimating the performance and designing multi-stage separation
systems has rarely been tackled from a systems engineering perspective, resulting in poor integration and sub-optimal configuration of industrial multi-stage separation systems. This paper presents a new approach to modeling and analyzing the performance in terms of recovery and grade of multi-stage material separation systems. Individual comminution and separation processes are modeled and integrated into a separation network model that can be studied with analytical techniques. This model can be used to evaluate the performance
of multi-stage separation systems under varying operating conditions, supporting decisions related to system configurations. Several basic examples demonstrate the utility of this model for design purposes. Furthermore, several open research challenges in this new research area are highlighted
Performance Evaluation of Selective and Adaptive Assembly Systems
No full textSelective assembly systems are found in several manufacturing contexts, above all automotive and mechanical components manufacturing, where the tolerances imposed on the assembled product is much tighter than the tolerance imposed on the sub-components. Selective assembly consists in measuring the key quality characteristics of each sub-component after the machining/forming process and sorting the components into quality classes according to the measurement outcome. In order to improve the product quality, the assembly station is allowed to assemble only components from matching quality classes. By employing selective assembly, high precision assemblies can be produced from low precision components, at the cost of increasing the complexity of the system management and of decreasing the total production rate of the system. Therefore, an integrated quality and production logistics analysis of this system is needed, to correctly and profitably manage such trade-off. In this paper, a decomposition method is developed that allows predicting the integrated quality and production logistics performance of these complex systems
- …
