Decision Sciences Journal
Volume 29, Number 1
Winter 1998

Planned Lead Times in Multistage Systems

Ram P. Mohan
Adapta Solutions, Inc., 22 Saw Mill River Road, Hawthorne, NY 10532, email: ram_mohan@adaptasolutions.com

Larry P. Ritzman
Operations and Strategic Management, Boston College, Chestnut Hill, MA 02167, email: ritzman@bc.edu

Abstract: This study investigates the impact of planned lead times on performance in multistage manufacturing where material requirements planning is used in a make-to-stock environment. We simulate a variety of different operating environments and find: (1) planned lead times are important to customer service levels under all operating environments examined, but have a smaller impact on inventory investment; (2) tight due dates introduced by short planned lead times hurt customer service without saving much inventory; (3) small increases to tight planned lead times improve customer service substantially with small inventory increases; (4) co-component inventories change with planned lead times, and disparity between such inventories is a sign of poor timing coordination; (5) the fixed order quantity rule performs better than the periodic order quantity rule; and (6) tall product structure and large lot sizes require particular attention to planned lead times. The findings also extend the current understanding of planned lead times by including uncertainties such as forecast error, yield loss, and equipment reliability. The study concludes with a way to diagnose and improve poorly set planned lead times.

Subject Areas: Inventory Management, Material Requirements Planning, Production and Inventory Control Systems, and Simulation.