1,720,988 research outputs found
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
Analysis 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
Calculating the joint distribution of n batch delivery spans in a stochastic permutation flow shop
Full text linkProduction quality performance in manufacturing systems processing deteriorating products
Full text linkIn several manufacturing contexts including food industry, semiconductor manufacturing, and polymers forming, the product quality deteriorates during production by prolonged exposure to the air caused by excessive lead times. Buffers increase the system throughput while also increasing the production lead time, consequently affecting the product quality. This paper proposes a theory and methodology to predict the lead time distribution in multi-stage manufacturing systems with unreliable machines. The method allows to optimally set inventory levels to achieve target production quality performance in these systems. The industrial benefits are demonstrated in a real manufacturing system producing micro-catheters for medical applications
Lead Time Dependent Product Deterioration in Manufacturing Systems with Serial, Assembly and Closed-Loop Layout
No full textIn several manufacturing systems found in the automotive, food and semiconductor industries, product
quality or value deterioration due to excessive residence time in the system are observed. This phenomenon
generates defective or low value products, thus undermining the performance of these systems. In this paper,
a method to compute the lead time distribution under a wide set of system architectures is proposed. The
method is based on the analysis of the probability that a part enters the system in a certain position in the
buffer and on the calculation of the distribution of the time to absorption of a Markov chain representing the
states of the downstream portion of system. Then, considering a function that expresses how the product
deteriorates with the residence time in the system, the main performance measures are derived. Numerical
results show previously uninvestigated behaviors of manufacturing systems under lead time constraints and
provide insights on the design of these complex systems. In particular, the method supports the optimal
selection of buffer sizes to achieve the target effective throughput in these systems
Equipment selection and evaluation approach for an adaptable assembly line
No full textIn an evolving manufacturing sector, decisions about production systems design, reconfiguration and management are critical tasks. In addition, the rapid evolution and underlying uncertainty of market conditions, make these decisions more important and capital intensive. In this paper, we focus our attention on the equipment selection in an adaptable assembly cell where different easy-changeable hardware modules can be arranged around a skeleton architecture to provide different assembly technologies with different execution modes and performances. In this paper we present the architectural framework of a procedure defining the different sequencing of the tasks in relation to alternative execution modes, a possible skeleton architecture and a procedure that, given the selection of the equipment, provides the evaluation of the associated performance to be compared against the capability requests, expressed in terms of volumes and mix of the products. The modularity provided by the considered architecture is also exploited through the possibility of a fast setup of the assembly line, thus allowing the rearrangement and substitution of the different hardware modules to cope with the production of different parts. Both equipment cost and performance are taken into consideration to identify the most promising configurations. A testing of the approach through the application to a realistic case is also provided
Impact of Preventive Maintenance on the Service Level of Multi-stage Manufacturing Systems with Degrading Machines
No full textIn manufacturing systems, preventive maintenance plays a fundamental role in keeping and improving the operational condition of machines and the output product quality. However, preventive maintenance policies affect the available productive time of the system. This directly influences the lot completion time and delivery dates of customer orders. Therefore the choice of preventive maintenance policies needs to be taken by jointly considering the actual condition of machines and the impact of these policies on the service level of the system. This paper proposes an analytical approach for the analysis of the impact of preventive maintenance on the service level of manufacturing systems characterized by degrading machines. The actual degradation state of critical machines is inferred from condition monitoring information gathered by sensor networks. The results obtained from the application of the method to a real industrial case in the aeronautics industry show that the decisions on the optimal maintenance policies depend on both the actual status of machines and the target lot completion time, thus paving the way to new service level oriented maintenance policies
Analysis of the Lead Time Distribution in Closed Loop Manufacturing Systems
No full textIn several manufacturing systems found in the automotive, food and semiconductor industries, product quality or value deterioration due to excessive residence time in the system are observed. This phenomenon generates defective or low value products, thus undermining the performance of these systems. In this paper, we develop an exact analytical method for calculating the lead time distribution of closed loop systems and present an heuristic to predict the peaks of this distribution. Numerical results show previously uninvestigated behavior of closed loop manufacturing systems under lead time constraints and provide insights on the design of these complex systems
Impact of condition based maintenance policies on the service level of multi-stage manufacturing systems
Full text linkPreventive maintenance is crucial for keeping the operational condition of machines but it affects the available productive time of the system. This influences the lot completion time and the delivery dates. Therefore the choice of preventive maintenance policies needs to be taken by jointly considering the actual condition of machines and the service level of the system. In this context, the main contribution of this paper consists in showing how the completion time of a lot is significantly affected by the preventive maintenance policy. This is done by means of numerical illustrations obtained by using both ad-hoc models and a real industrial case. The second contribution relies in the presented methodology that allows the modeling of general synchronous production lines and, given a lot size, the computation of their corresponding service level. The methodology is described in such a way that its extension to different scenarios (such as different system layout and asynchronous machines) is fairly straightforward
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