Zied Hajej

Modelling and analysis for sequentially optimising production, maintenance and delivery activities taking into account product returns

This paper develops and analyses a stochastic optimisation problem with a service level constraint for generating a sequentially optimal plan of production, maintenance and delivery activities in a deteriorating manufacturing system. Stochastic demand along with product returns are both assumed the latter of which allows for restocking products returned by the customer which are still new and thus in saleable condition. A constrained production/maintenance/delivery problem with service level, stochastic demand, delivery time, failure rate and product returned is formulated based on quadratic model. This quadratic formulation is adapted to provide an inventory, delivery, production and maintenance policies. The objective of this paper is to study the delivery time influence on the planning of the production, maintenance and delivery activities. Finally, we present simulation results to illustrate the exploitation of the proposed approach.

Forecasting and maintenance problem under subcontracting constraint with transportation delay

In this paper, a forecasting production/maintenance optimization problem has been proposed with a random demand and single machine M1 on a finite horizon. The function rate of the machine M1 is depending on the production rate for each period of the forecasting horizon. In order to satisfy the customer, a subcontracting assures the rest of the production through machine M2 with transportation delay. An analytic formulation of the problem has been proposed using a sequential computation of the optimal production plan for which an optimal preventive maintenance policy has been calculated based on minimal repair. Firstly, we find, the optimal production plans of principal and subcontracting machines, which minimises the total production and inventory cost for the cases without and with returned products under service level and subcontracting transportation delay. Secondly, we determine a joint effective maintenance policy with the optimal production plan, which integrates the various constraints for the production rates, the transportation delay and the returned production deadline. Numerical results are presented to highlight the application of the developed approach and sensitivity analysis shows the robustness of the model.

Improved preventive maintenance in the framework of forecasting problem under subcontractor constraint

The paper presents a new improved preventive maintenance strategy for a forecasting problem of production and maintenance optimisation under subcontractor constraint. In order to satisfy the customer, the manufacturing system consists of a principal machine M1 and called upon subcontractor machine Ms. Knowing that both machines are subjected to random failures, failure rate of main machine increases with time and according to production rates. An improved preventive maintenance strategy is used for control of the machine M1, whereas subcontractor machine Ms is uncontrollable from preventive maintenance point of view. An analytic formulation of problem has been proposed in order to determine the economical production plans for M1 and Ms. An improved maintenance strategy (IMS) is developed in order to minimise the total production loss, when the subcontractor machine is unavailable. It consists of determining the best time to perform preventive maintenance actions taking into account production rates, history of M1 and the state of subcontractor machine Ms. Numerical results and sensitivity analysis are presented to highlight the performance measure and the usefulness of the IMS.

Joint Optimization Approach of Maintenance and Production Planning for a Multiple-Product Manufacturing System

This paper deals with the problem of maintenance and production planning for randomly failing multiple-product manufacturing system. The latter consists of one machine which produces several types of products in order to satisfy random demands corresponding to every type of product. At any given time, the machine can only produce one type of product and then switches to another one. The purpose of this study is to establish sequentially an economical production plan and an optimal maintenance strategy, taking into account the influence of the production rate on the system’s degradation. Analytical models are developed in order to find the production plan and the preventive maintenance strategy which minimizes sequentially the total production/inventory cost and then the total maintenance cost. Finally, a numerical example is presented to illustrate the usefulness of the proposed approach.

A decision optimization model for leased manufacturing equipment with warranty under forecasting production/maintenance problem

Due to the expensive production equipment, many manufacturers usually lease production equipment with a warranty period during a finite leasing horizon, rather than purchasing them. The lease contract contains the possibility of obtaining an extended warranty for a given additional cost. In this paper, based on the forecasting production/maintenance optimization problem, we develop a mathematical model to study the lease contract with basic and extended warranty based on win-win relationship between the lessee and the lessor. The influence of the production rates in the equipment degradation consequently on the total cost by each side during the finite leasing horizon is stated in order to determine a theoretical condition under which a compromise-pricing zone exists under different possibilities of maintenance policies.

Solving the Production and Maintenance Optimization Problem by a Global Approach

This paper concerns the combined production and maintenance plans for a manufacturing system satisfying a random demand. We propose a new optimization model transformed from the production policy model and a global approach for finding the optimal production/maintenance schedule. The numerical experiments illustrate the efficiency of our proposed model and a global method by comparing with the result of the literature works.

Quality issue in forecasting problem of production and maintenance policy for production unit

In this study, we consider an unreliable deteriorating production system that produces conforming and non-conforming products to satisfy a random demand under a given service level and during a finite horizon. The production system is subjected to a failure-prone machine. The quality of the produced products is affected by the machine deterioration since the rate of defectives increases as the deterioration increases. Preventive maintenance actions can be piloted on the production system to reduce the influence of deterioration and the defective rate. A joint control policy is based on a stochastic production and maintenance planning problem with goals to determine, firstly, the economic plan of production and secondly, the optimal maintenance strategy. The proposed jointly optimisation minimises the total cost of production, inventory, maintenance and defectives. A failure rate and quality relationship are defined to show the influence of the production rates variation on the failures rate as well as on the defective rate. A numerical example and an industrial case study are adopted to illustrate the proposed approach and a sensitivity analysis to validate the jointly optimisation.

Impact of the Corrective Maintenance Cost on Manufacturing Remanufacturing System Performance

This paper studies a manufacturing remanufacturing system composed by two parallel machines, a serviceable inventory, a remanufacturing inventory and a customer which demands a constant quantity of part. Taking into account the return of the used part and the maintenance action, discrete flow model is used to model and to simulate the system. The goal of this work is to evaluate the optimal serviceable inventory level which allows minimizing the sum of inventory, lost sales costs and the corrective maintenance cost. Numerical results are presented to show the impact of the corrective maintenance cost on the optimal serviceable inventory level.

An optimal integrated maintenance for multi parallel workstations under returned products

This paper treaties an integrated maintenance problem of manufacturing system with considering a returned products and leasing constraints. We have established an economical production policy and an optimal maintenance strategy for a production system composed by numerous parallels workstations. The system contains a numerous machines to meet a random demands, respecting a certain service level and with considering the returned product (withdrawal right). Firstly, to obtain an economical production planning, we minimize the total production cost. Secondly, according to obtained production plan, we determine the optimal maintenance strategy for different leased machines. The main is to show the impact of the returned products on the production plan and the production rates on the degradation degree of machines.