Self-Buffering, Self-Balancing, Self-Flushing Production Lines

Abstract

This research addresses a system of flexible worker assignments in a setting where there are more workers than machines. When organized using this system, a production line balances itself by shifting the workloads continuously and automatically in response to changes in the state of the system. The system is, in effect, buffering itself against variation by altering the work assignments on the fly. This allows the system to operate with very low levels of work-in-process inventory (WIP). In this paper, the workers (rather than machines) are the factor that limits the rate of output. We also assume that the line has a "U" shape, but many of the results do not depend on this topology. An industrial example is described. The system has some interesting and counter-intuitive properties which we demonstrate under a variety of circumstances through an exploratory approach that uses both Markovian and simulation models. Several different policies are compared under conditions of processing time uncertainty. We demonstrate that a flexible assignment system can outperform fixed assignments in a variety of circumstances. Of particular interest is the near absence of balance delay, even when the tasks cannot be divided equally among the workers.work sharing, line balancing, low WIP, on-the-fly assignment, U-shaped

A Little Flexibility Is All You Need: On the Asymptotic Value of Flexible Capacity in Parallel Queuing Systems

“…This is easily seen for the single-type system and may extend to N types. Another measure that would be worth investigating would be throughput (see, for instance, Ostolaza et al 1990, Zavadlav et al 1996, Andradóttir et al 2001, Van Oyen et al 2001. Another alternative to our cost-based approach is in Iravani et al (2005Iravani et al ( , 2011 which use structural and capacity flexibility methods, respectively, to rank different flexibility configurations.…”

Compensating for Failures with Flexible Servers

“…Andradóttir et al (2001) and Andradóttir and Ayhan (2005) examine tandem lines with limited buffers under manufacturing blocking. Bischak (1996), Zavadlav et al (1996), andOstolaza et al (1990) study the throughput of systems where flexibility occurs across different zones, showing that high utilization is possible even with small buffer sizes. Ahn et al (1999) examine the problem of minimizing the expected holding cost in a system with no exogenous arrivals, two parallel queues, one flexible server, and one fixed server.…”

Throughput Maximization for Tandem Lines with Two Stations and Flexible Servers

“…Other research on dynamic server assignment policies includes the work of Ostalaza, McClain, and Thomas [14], McClain, Thomas, and Sox [13], and Zavadlav, McClain, and Thomas [21] on dynamic line balancing. In particular, Ostalaza, McClain, and Thomas [14] and McClain, Thomas, and Sox [13] study dynamic line balancing in tandem queues with shared tasks that can be performed at either of two successive stations.…”

“…In particular, Ostalaza, McClain, and Thomas [14] and McClain, Thomas, and Sox [13] study dynamic line balancing in tandem queues with shared tasks that can be performed at either of two successive stations. This work was continued by Zavadlav, McClain, and Thomas [21], who study several server assignment policies for systems with fewer servers than stations, in which all servers trained to work at a particular station have the same capabilities at that station. Moreover, assuming that each server has a service rate that does not depend on the task (s)he is working on, Bartholdi and Eisenstein [6] define the "bucket brigades" server assignment policy and show that under this policy, a stable partition of work will emerge yielding optimal throughput.…”