Optimizing the integrated economic production quantity for a stochastically deteriorating production system under condition-based maintenance

This paper proposes a new integrated economic production quantity (EPQ) and condition-based maintenance (CBM) model for a stochastically deteriorating production system. Inspections are performed periodically to measure the real time degradation. The system fails (out-of-control) whenever its degradation is beyond a critical threshold level. In the out-of-control state, a proportion of nonconforming items are produced. To assess the degradation of the system and to increase the production of conforming items, preventive maintenance (PM) actions are carried out. An integrated EPQ and CBM optimization model that minimizes the total expected cost rate over an infinite time horizon is developed. The objective is to determine a joint optimal EPQ and PM strategy minimizing the sum of inspection/maintenance and setup costs, cost of nonconforming items in addition to inventory holding cost. Numerical experiments are provided to illustrate the proposed approach

Integrated production quality and condition-based maintenance optimisation for a stochastically deteriorating manufacturing system

This paper investigates the problem of optimally integrating production quality and condition-based maintenance in a stochastically deteriorating single- product, single-machine production system. Inspections are periodically performed on the system to assess its actual degradation status. The system is considered to be in ‘fail mode’ whenever its degradation level exceeds a predetermined threshold. The proportion of non-conforming items, those that are produced during the time interval where the degradation is beyond the specification threshold, are replaced either via overtime production or spot market purchases. To optimise preventive maintenance costs and at the same time reduce production of non-conforming items, the degradation of the system must be optimally monitored so that preventive maintenance is carried out at appropriate time intervals. In this paper, an integrated optimisation model is developed to determine the optimal inspection cycle and the degradation threshold level, beyond which preventive maintenance should be carried out, while minimising the sum of inspection and maintenance costs, in addition to the production of non-conforming items and inventory costs. An expression for the total expected cost rate over an infinite time horizon is developed and solution method for the resulting model is discussed. Numerical experiments are provided to illustrate the proposed approach

Optimal scope of supply chain network & operations design

The increasingly complex supply chain networks and operations call for the development of decision support systems and optimization techniques that take a holistic view of supply chain issues and provide support for integrated decision-making. The economic impacts of optimized supply chain are significant and that has attracted considerable research attention since the late 1990s. This doctoral thesis focuses on developing manageable and realistic optimization models for solving four contemporary and interrelated supply chain network and operations design problems. Each requires an integrated decision-making approach for advancing supply chain effectiveness and efficiency. The first model formulates the strategic robust downsizing of a global supply chain network, which requires an integrated decision-making on resource allocation and network reconfiguration, given certain financial constraints. The second model also looks at the strategic supply chain downsizing problem but extends the first model to include product portfolio selection as a downsizing decision. The third model concerns the redesign of a warranty distribution network, which requires an integrated decision-making on strategic network redesign and tactical recovery process redesign. The fourth model simultaneously determines the operational-level decisions on job assignment and process sequence in order to improve the total throughput of a production facility unit

Production and Warranty Optimal Period in Deteriorating Production Systems by Considering Inspection of both Manufacturing Equipment and Products Simultaneously

Traditionally high share of production-distribution costs to inventory and supply policy dedicated. The production model of politics is important for a system of distribution, taking into account the actual conditions of production and optimal production parameters influenced. One of these conditions is that the production equipment during production turned out of control and produce defective products. It is possible to change the mode in real terms, and then significantly increase the amount of defective products. Despite these conditions, one of the parameters affecting the demand for products and sales, and consequently the amount of corporate profits is the product warranty. The after-sales service product parameter influencing the willingness of consumers to buy the product. In this work, it consider the potential failure of production equipment, as well as the product warranty, mathematical models of inventory control policy, based on actual production conditions for the production units. This model is aimed at achieving the optimal length of time in each period and for optimum product warranty with respect to maximizing profits per unit of time. In other words, the goal is create an optimal balance between product sales revenue and costs incurred during the period of warranty for the product. In fact, in this article will discuss this model and its resolution

Revenue management for multiple product recovery options : a triangulation approach

In recent times large numbers of end-of-use/end-of-life returns have been the result of the increasing pressure from environmental legislations, particularly the directive on Waste Electrical and Electronic Equipment (WEEE) in the European Union. These returns incur acquisition costs and take-back operation costs regarded as a sunk cost by many industries. Thus, returned/recovered product valuation and marketing issues become crucial factors for survival and profitability of many firms in various sectors in today’s competitive world. The research undertaken is relevant as pricing and revenue management for recovered products. Indeed, this theme is considered as a niche research and the fifth phase (prices and markets) of the evolution of closed loop supply chain research. Hence, it has been noted as one of the most critical research areas in quantitative modelling for reverse logistics and closed loop supply chain management studies. The research area is in its early stage because it can be seen that only a handful of articles have been published in peer reviewed international journals, exploring a pricing and marketing decision of recovered products. Hence, there are significant opportunities to conduct pricing and revenue management research in reverse logistics, particularly with regard to multiple recovery options.The primary objective of this research work is to formulate three pricing models by using a non-linear programming approach to determine optimal profit-maximising acquisition prices and selling prices, together with UK-based case studies in the mobile phone and computer recycling businesses. Moreover, this research aims to formulate two simulation models based on these case companies by investigating the impact of the uncertainty element in terms of return quantity and reprocessing time on firm’s profit. The triangulation approach is employed, specifically the multilevel model comprising case studies, questionnaire survey, and empirical quantitative models in order to address the principal research questions i.e. “What are optimal acquisition prices of received mobile phones and optimal selling prices of reprocessed handsets?”, “What are optimal selling prices of reprocessed computers?”, and based on the total profit, “What if the model's parameters change?”The contribution of this research covers the generation of pricing and simulation models that are suitable for the recycled mobile phone and computer sector. The literature review discovers that the research on this subject lacks considerations of multiple recovery options, return rate and demand rate as exponential functions, recovery capacity limitation, product substitution policy, the element of uncertainty in terms of return quantity and reprocessing time, and multiple time periods. Hence, this research fulfils six main research gaps in academic literature as follows. First, this study takes multiple recovery options into account. Second, return and demand rate are modelled as an exponential function. Third, pricing and simulation models cope with a limit to recovery capacity. Fourth, models with product substitution policy are investigated. Fifth, the element of uncertainty in terms of return quantity and reprocessing time is added into proposed models. Finally, this study proposes models with multiple time periods.The results from this research work support current pricing and revenue management research and most importantly, the results generated from these proposed models can enhance managers’ decision making in recovery operations and reverse logistics

A Framework for Reverse Logistics

Reverse Logistics has been stretching out worldwide, involving all the layers of supply chains in various industry sectors. While some actors in the chain have been forced to take products back, others have pro-actively done so, attracted by the value in used products One way or the other, Reverse Logistics has become a key competence in modern supply chains. In this paper, we present a content analysis of reverse logistics issues. To do so, we propose a content framework focusing on the following questions with respect to reverse logistics: why? what? how?; and, who?, i.e. driving forces and return reasons, what type of products are streaming back, how are they being recovered, and who is executing and managing the various operations. These four basic characteristics are interrelated and their combination determines to a large extent the type of issues arising from the resulting reverse logistics system.supply chain management;reverse logistics;content analysis;theory;framework

COORDINATED INVENTORY PLANNING FOR NEW AND OLD PRODUCTS UNDER WARRANTY

This paper is motivated by the inventory planning issues faced by a manufacturer of a digital projector. The seller faces demand from two sources: new demand, and demand to replace failed items under warranty. We model this setting as a multi-period single product inventory problem where the new demand in different periods are independent and the demand for replacing failed items under warranty is proportional to the number of items under warranty. We assume linear procurement, penalty and holding costs. We consider backlogging and emergency supply cases, and study both discounted cost and average cost cases. We prove the optimality of the w-dependent base stock ordering policy where the base stock level is a function of w, the number of items currently under warranty. For the special case, where the demand for new products is stationary, we prove the optimality of a stationary w-dependent base stock policy for the fi nite horizon discounted and the in finite horizon discounted and average cost cases. In our computational study, we fi nd that such an integrated policy can lead to 31% average improvement in expected costs when compared to a policy that neglects warranty repairs

Reverse logistics

This paper gives an overview of scientific literature that describes and discusses cases of reverse logistics activities in practice. Over sixty case studies are considered. Based on these studies we are able to indicate critical factors for the practice of reverse logistics. In addition we compare practice with theoretical models and point out research opportunities in the field