Research
As part of the research at the Chair of Operations Management practically relevant questions in the field of Operations management and Supply Chain Management are investigated. The focus of the scientific work at the chair is the analysis and optimization of complex processes, where problems are not limited to manufacturing companies. Considering innovative technological possibilities, new planning and control approaches are developed which take account of particular uncertainties. Based on realistic modeling, new solution methods and algorithms are designed and developed. The following research priorities are currently being treated at the chair:
Design and Analysis of Manufacturing Systems
Contact: Prof. Dr. Gudrun Kiesmüller, Chair of Operations Management
The design of a manufacturing system is essential for its performance. Even a few design improvements can increase production output or maintain throughput at a lower cost, consequently increasing the revenue of a company. In a discrete part production line throughput is influenced by variable processing times or unexpected machine failures, amongst other reasons. One possible way of mitigating the effects of these uncertainties is by installing buffers between the machines such that the machines are decoupled, meaning they are less affected by each other and can continue producing while another machine is under repair or when processing is slow. In this research project it is investigated how the throughput of a manufacturing system can be increased by smart spare parts planning.
Selected publications:
G.P. Kiesmüller, J. Zimmermann. The influence of spare parts provisioning on buffer size in a tandem system. IISE Transactions (2018), 50 (5), 1-14.
Maintenance and Reliability
Contact: Prof. Dr. Gudrun Kiesmüller, Chair of Operations Management
Advanced technical systems (e.g. power generators, manufacturing systems, computer networks, medical systems, material handling systems, defense systems) serve for primary operations in our society. They must be kept up and running for operational continuity in power plants, factories, banks, hospital, airports, warehouses, etc. Interruptions of these systems lead to significant losses and therefore companies try to avoid downtimes by smart maintenance activities which have to be planned and integrated in production schedules. Another possibility to improve the availability of a system is a reliability improvement program and a redesign of components. In this research project we study joint reliability and spare parts planning and joint production and maintenance planning.
Selected publications:
W. von Hoyningen-Huene, G. P Kiesmüller. Evaluation of the Expected Makespan of a Set of Non-Resumable Jobs on Parallel Machines with Stochastic Failures. European Journal of Operational Research (2015), 240, 439-446.
K. Öner, G.P. Kiesmüller, G.J. van Houtum. On the Upgrading Policy After the Redesign of a Component for Reliability Improvement. European Journal of Operational Research (2015), 244, 867-880.
K. Öner, G.P. Kiesmüller, G.J. van Houtum. Optimization of component reliability in the design phase of capital goods. European Journal of Operational Research (2010), 205, 615-624.
Optimal safety stocks in Supply Chains
Contact: Prof. Dr. Gudrun Kiesmüller, Chair of Operations Management
Despite careful planning, it may be useful due to unforeseen events, to keep safety stocks in a supply chain. Then the question raises, at which place the safety stocks need to be hold and which quantity is required. Especially in complex networks and under uncertain customer demand, planning safety stocks is an important component in the design of efficient processes. In one of the current research projects uncertain demand and supply are considered simultaneously. Especially the influence of random production yield on safety stocks is investigated.
Selected publications:
D. Sonntag, G.P. Kiesmüller. The influence of quality inspections on the optimal safety stock level. Production and Operations Management (2017), 26 (7), 1284-1298.
K. Inderfurth, G.P. Kiesmüller. Exact and heuristic linear-inflation policies for an inventory model with random yield and arbitrary lead times. European Journal of Operational Research (2015), 245, 109-120.
S.C. Kutzner, G.P. Kiesmüller. Optimal control of an inventory-production system with state-dependent random yield. European Journal of Operational Research (2013), 227, 444-452.
Coordination of processes in Supply Chains
Contact: Prof. Dr. Gudrun Kiesmüller, Chair of Operations Management
Modern supply networks are complex and often consist of many manufacturing facilities and inventory locations spread over the continents. Sometimes managers have many possibilities to replenish their inventories and have to decide about the number of suppliers as well as the corresponding order quantities. Since many products have to be planned and they sometimes have different lead times, it is not an easy task to coordinate all the replenishment processes. In this research project the coordination of multiple products is studied as well as the coordination between replenishment processes and transportation processes.
Selected publications:
F. Kleintje-Ell, G.P. Kiesmüller. Cost minimising order schedules for a capacitated inventory system. Annals of Operations Research (2015), 229, 501-520.
J. Arts, G.P. Kiesmüller. Analysis of a two echelon inventory system with two supply modes. European Journal of Operational Research (2013), 225, 263-272.
A.G. Karaarslan, G.P. Kiesmüller, A.G. de Kok. Analysis of an Assemble-to-Order System with Different Review Periods. International Journal of Production Economics (2013), 143, 335-341.