MANUFACTURING & SERVICE OPERATIONS MANAGEMENT Vol. 00, No. 0, Xxxxx 2006, pp. 1–22 issn 1523-4614  eissn 1526-5498  06  0000  0001 inf orms ® doi 10.1287/msom.1060.0118 © 2006 INFORMS Performance Evaluation of an Automatic Transfer Line with WIP Scrapping During Long Failures George Liberopoulos, George Kozanidis Department of Mechanical and Industrial Engineering, University of Thessaly, 38334 Volos, Greece {glib@uth.gr, gkoz@uth.gr} Panagiotis Tsarouhas Department of Informatics and Computer Technology, Technological Education Institute of Lamia, 35100 Lamia, Greece, ptsarouh@teilam.gr W e develop a model of a failure-prone, bufferless, paced, automatic transfer line in which material flows through a number of workstations in series, receiving continuous processing along each workstation. When a workstation fails, it stops operating, and so do all the other workstations upstream of it. The quality of the material trapped in the stopped workstations deteriorates with time. If this material remains immobilized beyond a certain critical time, its quality becomes unacceptable and it must be scrapped. We develop analytical expressions for important system performance measures for two cases. In the first case, the in-process material has no memory of the quality deterioration that it experienced during previous stoppages, whereas in the second case it has. In both cases, we assume that the workstation uptimes and downtimes follow memoryless distributions. We use the analytical expressions to numerically study the effect of system parameters on system performance. To evaluate the memoryless assumption, we compare the performance of the original model to that of a modified model in which the workstation downtimes do not follow memoryless distributions. The performance of the modified model is obtained via simulation. Key words : transfer line; material scrapping; performance evaluation History : Received: December 20, 2005; accepted: June 2, 2006. 1. Introduction A traditional, widespread way of organizing high- volume, low-variety production is the manufactur- ing flow line, production line, or transfer line. Transfer lines require all material to visit workstations in the same sequence, thus simplifying material handling. Transfer lines are common in both discrete-parts and continuous-processing manufacturing. Discrete-parts manufacturing is characterized by individual parts that are clearly distinguishable and is often encoun- tered in the industries of computer and electronic products, electrical equipment and appliances, trans- port equipment, machinery, fabricated metal, wood, furniture products, etc. Process industries, on the other hand, operate on material that is continually flowing, as is the case with petroleum and coal products, metallurgical products, nonmetallic mineral products (e.g., ceramics, glass, and cement), basic chemicals, food and beverage products, paper prod- ucts, etc. Mass production of discrete parts shares many of the characteristics of the process industries. Con- versely, sometimes in process industries, fluids are processed in distinct batches that can be viewed as discrete parts. Generally, process industries are cap- ital intensive and are concerned with capacity. With increasing production volume, it becomes economi- cally attractive to automate individual workstations, integrate them into one system by a common auto- mated transfer mechanism and a common control system, and link them with synchronized material movement so they can begin their tasks simultane- ously. Transfer lines with these characteristics are often referred to as synchronized or paced automatic transfer lines. The literature on transfer lines is vast. The earli- est papers on transfer lines appeared in the 1950s and ’60s. Notable examples of such research are Vladzievskii (1950–1951), Koenigsberg (1959), Zim- mern (1956), Sevastyanov (1962), Freeman (1967), 1