Presentations at Conference

The Chair of Production Management participated in 29. Workshop der Quantitativen Betriebs­wirtschafts­lehre, Schloss Hirschberg, Germany

Presented topics were:

Biondi, M. and R. Stolletz (2019): Maintenance and production scheduling for a single machine with maintenance mode selection. 

Preventive maintenance on manufacturing units are necessary to maintain the ma-chines in a condition to produce and to execute the required tasks. A maintenance typically allows the machine to work for a certain amount of time before it is re-quired for the machine to be taken off-line again for the next maintenance. In some situations, more than one maintenance modes can be selected for a maintenance occurrence, i.e. the machine can be taken off-line for a longer time therewith allow-ing the machine to work uninterrupted for a longer time afterwards. In this work, we detail a new optimization problem for the integrated scheduling of mainte-nance and production on a single machine with maintenance mode selection. Structural properties of the optimal solution will then be introduced and solution methods discussed.

Foroughi, A. and R. Stolletz (2019): Performance evaluation of time-dependent bulk queues.

Bulk queues are a special class of queueing systems, where jobs arrive in batches or they are served in batches. They have many applications in production and ser-vice systems. For example, appointment systems in healthcare can be considered as bulk queueing systems with scheduled arrivals. We study a time-dependent bulk queue with deterministic timedependent batch arrival but generally distributed processing time. We present a new approximation approach for the expected wait-ing time of such a time-dependent $D^{X(t)}\G\1$ queue. The proposed approxi-mation method can evaluate underloaded, overloaded, and critically loaded sys-tems.
First numerical examples assess the accuracy of the proposed approximation ap-proach by comparison to a simulation and a Fluid approximation.

Zenouzzadeh, S. M. and R. Stolletz (2019): Shift Scheduling in Multi-stage Systems

Many production and service systems consist of serial stages operated by (partly) multi-skill workers. These systems face time-dependent demand and the workload of each stage is not determined in advance, but rather obtained from the output of the predecessor stage. We present a mixed-integer linear model for daily shift scheduling of multi-skill workers in multi-stage systems considering such interde-pendencies among the stages. Numerical examples based on realistic data from a warehouse illustrate the performance of the proposed model.