Nagen Nagarur

A multicriteria approach to the selection of preventive maintenance intervals

Abstract This paper discusses the problem of determining optimal preventive-maintenance intervals for components in a production system. The maintenance planning of a paper factory is taken as a case study. The traditional approach of a single objective function for this type of a problem is described, and some of the disadvantages of taking such a single objective are discussed. The paper proposes a new model incorporating multiple criteria. For the case study, two criteria, expected costs and reliability, are taken into consideration. The MCDM method PROMETHEE is used to solve the problem. Sensitivity analysis is carried out for the variations in the subjective weights assigned to the criteria.

Some performance measures of flexible manufacturing systems

The diffusion of flexible manufacturing systems (FMS) has not only invigorated production systems, but has also given considerable impetus to relevant analytical fields like scheduling theory and adaptive controls. The classical concepts and models may not be adequate to address the issues pertaining to FMS and they may have to be either modified or replaced. One of the important issues in this regard is the performance measures for these systems. These measures are needed for economic appraisals and for system design. Two such existing measures, flexibility and reliability, are re-examined in this paper. A new performance measure, producibility, is introduced here, which is defined as the extent to which a system fulfils its purpose. Appropriate mathematical models are developed to compute this measure for a system. Individual and combined effects of flexibility and reliability on a multi-component, multi-product system are analysed under the framework of producibility.

Component part standardization: A way to reduce the life-cycle costs of products

Abstract This paper studies the effects of component part standardization on life-cycle costs. Three possible situations for component standardization are discussed. A summary is presented of various costs in different phases of the product life cycle and how they are shared among the manufacturer, user, and society. Then, we explain how the component standardization reduces the costs of different phases of the product life cycle. Finally, we point out some of the possible disadvantages of component standardization.

Case study: RCM – yes, no or maybe?

The basic research question of this paper is how to determine the optimum maintenance concept for an industrial installation in a practical, i.e. with a reasonable input effort, way. The paper starts out with a critical review of maintenance concepts available from literature. These concepts are considered for use in a specific case, i.e. a paint spraying robot in an automobile manufacturing plant, and it is decided to implement a RCM‐like approach. The original RCM concept is modified in order to better fit the specific needs in terms of technical and organizational requirements of the company in question. The paper concludes with some general thoughts on the applicability of such an RCM‐like concept for the company in question.

An object‐oriented decision support system for maintenance management

As the world approaches a new millennium, more and more industrial and manufacturing processes are being computerized and rapid retrieval and use of necessary information is vital if an organization is to remain competitive. The present work develops a computerized decision support system to assist in maintenance planning. The system design and analysis, and the decision support system design and development are all developed in an object‐oriented environment. The support system is driven by maintenance performance indices. Both object‐oriented databases and relational databases are used, for transient and permanent entities respectively. A knowledge base with if‐then rules is developed for fault diagnosis and repair. The methodology was applied to a powder coating plant to develop its maintenance decision support system.

Production planning and scheduling for injection moulding of pipe fittings A case study

Abstract The present study considers the development of a production planning and scheduling model for injection moulding of PVC pipe fittings in a local factory. The objective is to minimize the total costs of production, inventory, and shortages. A three-stage sequential procedure is used to solve the problem. The total problem domain is divided into three subproblems by mould-machine grouping. Each subproblem is then solved as a single-machine, multi-product, capacity lot-sizing problem, with a three-month planning horizon. A linear, zero-one goal programming approach is used to generate the solution. Finally, the production plan of the first month is decomposed and scheduling for each individual machine is carried out by a heuristic procedure. Comparison of the results show that the new procedure can substantially reduce both shortage and inventory costs.

Impact of commonality and flexibility on manufacturing performance: A simulation study

Abstract To keep the manufacturing operations at a high level of efficiency, in the presence of a large product variety, companies resort to certain strategies, important of which are product component standardization and machine flexibility. Standardization or part commonality can greatly reduce the complexity of a manufacturing system and improve its performance. Similarly machine flexibility would enable the machine process different operations and components, to keep a low machine idle time. This study looks at the impact of commonality on such performance criteria as makespan, machine utilization, and factor productivity. A case study is analyzed using the simulation tool SIMPLE++.

A Computer‐based Inventory Management System for Spare Parts

Describes the design and analysis of a computer‐based information system for inventory management in a computer service company. Studies the existing manual system for possible adaptation and necessary modifications and identifies the requirements of the users and the components of the system. To facilitate control, the parts are classified into four categories. Various quantitative models for demand forecast, economic order quantity, and safety stock are considered, and for each part type, an appropriate set of models is used depending on the relative importance of its category. The information system so designed is implemented in a modular form. The database for this application is implemented in dBASE III PLUS while the control programs are written in CLIPPER tools. Extensive user interface is provided for user‐friendliness.

A production order quantity model with stochastic demand for a chocolate milk manufacturer

Abstract A production planning model with stochastic demand, constant defective rate and capacity constraint is developed to analyse the production problem of a chocolate milk manufacturer. The model is proven to possess an optimal solution under the given conditions. An optimal production plan is established for the firm, which is shown to be superior to the present production plan. The sensitivity analysis performed on the optimal solution provides useful insights on the inventory control and capacity requirement decisions of the firm.

An integrated decision support system for FMS: using intelligent simulation

Abstract In the present study, an integrated decision support system is presented for a manufacturing system, considering a three-level interdependent planning hierarchy. Decision making processes are identified for all the management planning levels. Master production schedule, bill of materials, and inventory records generate the material requirement plan, and in turn the schedule of arrival of the parts in the shop. The DSS so designed is capable of supporting various kinds of decisions at all levels using simulation as the main technique. A generic simulation model is developed for the flexible manufacturing systems. Simulation is designed to be an intelligent simulation system for proper integration.