Discrete production workstation with two types of imperfect items: determining the optimal promise time

Abstract

This paper presents a discrete production system where units are manufactured and reworked, if needed, one at a time using the same resources. Examples of these systems include products that involve extensive manual operations such as welding or manual assembly of intricate items. This industrial setting is not discussed in the literature. The major difficulty in studying these systems is the huge number of possible sequences of conforming and non-conforming units. This paper presents a very efficient approach to analyse these systems. We generate the system statistics for short production periods. In order to study the long-term behaviour of system statistics, we introduce renewal cycles. A major issue facing a manufacturer using these systems is determining the time it takes to produce a given customer order which is called promise time. This paper aims to find the optimal promise time that maximises the expected profit. Numerical experiments show that the expected profit is inversely proportional to the processing times. In addition, the expected profit is sensitive to the parameters; a change of ± 0.05 in the probability of having a conforming unit may result in a 25% change in the expected profit.

KEYWORDS:

• Random production output
• discrete production system
• imperfect production
• renewal cycles
• asynchronous rework
• promise time

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The authors confirm that the data used and analysed in this study are available within the article.

Additional information

Notes on contributors

Omar G. Alsawafy

Omar Alsawafy is a Visiting Assistant Professor in the Industrial and Systems Engineering Department at King Fahd University of Petroleum and Minerals (KFUPM). In addition, he is a member of the Interdisciplinary Research Center for Intelligent Manufacturing & Robotics at the same university. He received the PhD. and MSc. Degrees in Industrial and systems engineering from KFUPM in 2018 and 2012, respectively. His BSc. In Industrial Engineering was earned from An-Najah National University, 2009. His research interests cover areas in optimization, simulation, production planning and inventory control, supply chain management, and maintenance management.

Shokri Z. Selim

Shokri Selim has a BS in Production Engineering, Cairo University, 1970, and a PhD in Operations Research, Georgia Institute of Technology, 1979. He joined King Fahd University of Petroleum & Minerals in 1979 as an assistant professor and retired in 2021 as a professor. He was an area editor for AJSE and an associate editor for Pattern Recognition. He published 97 journal and conference papers and three registered patents. Currently he conducts research in imperfect discrete production systems, location of sensors on pipelines, location of base stations and interdependent infrastructure networks.