On the meaning of ConWIP cards: an assessment by simulation

ABSTRACT

The simplicity of Constant Work-In-Process (ConWIP) makes it one of the most widely adopted card-based production control solutions. Its simplicity, however, also limits the opportunities that are available to improve the concept. There are arguably only two major search directions: (i) to alter the meaning of cards away from controlling jobs; and (ii) to adopt alternative, more sophisticated backlog sequencing rules. In this study, we outline a simple, practical load-based ConWIP system that changes the meaning of cards. Rather than controlling the number of jobs, cards are associated with a certain amount of workload. Simulation results demonstrate the positive performance impact of limiting the total shop load. The Workload Control literature advocates the use of a corrected load measure as it better represents the direct load queuing at a station; but this worsens performance when compared to a shop load measure in the context of ConWIP.

KEYWORDS:

• Order release
• production control
• ConWIP (constant work-in-process)

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [grant number 71750410694], [grant number 71872072]; FCT – Fundação para a Ciência e Tecnologia of Portugal under the project PEst2015-2020: UID/CEC/00319/2013; Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme 2017.

Notes on contributors

Matthias Thürer

Matthias Thürer is Distinguished Professor in Management Science and Engineering at the Institute of Physical Internet, Jinan University (Zhuhai, PR China). Before getting involved in academia, Matthias worked in several companies, did an apprenticeship and became a master craftsman (“Meister”). Simple control for complex shops is one of Matthias’ main research interests. He has published widely on production control systems and is a leading expert on Workload Control, COBACABANA (Control of Balance by Card Based Navigation) and Lean Work Design.

Nuno O. Fernandes

Nuno O. Fernandes is currently working as adjunct Professor at the Department of Electrical and Industrial Engineering at the Polytechnic Institute of Castelo Branco, Portugal. He received his PhD degree in Production and Systems Engineering from the University of Minho, Portugal, in 2007. His research interests are in production planning and control (PPC) and simulation. He has published on these subjects in several international journals.

Nick Ziengs

Nick Ziengs is Lecturer at the Hanze University of Applied Sciences Groningen, The Netherlands. He received his PhD degree from the University of Groningen. His research interests are unit-based pull systems and he has published on this subject in several international journals.

Mark Stevenson

Mark Stevenson is a Professor of Operations Management at Lancaster University Management School (LUMS), Lancaster University, UK. He has published on a range of topics, including production planning and control in low-volume high-variety contexts. His work has appeared in leading operations and supply chain management journals, including the International Journal of Operations and Production Management, Production and Operations Management, Supply Chain Management: An International Journal, the International Journal of Production Economics, the International Journal of Production Research, and Production Planning and Control. Mark regularly attends the European Operations Management Association (EurOMA) conference and is a fellow of both the Chartered Management Institute (CMI) and the Higher Education Academy (HEA).