• A hybrid condition-based maintenance policy for continuously monitored components with two degradation thresholds

      Poppe, Joeri; Boute, Robert; Lambrecht, Marc (European Journal of Operational Research, 2018)
      Condition-based maintenance (CBM) makes use of the actual condition of the component to decide when to maintain and/or replace the component, thereby maximising the lifetime of the machine, while minimising the number of service interventions. In this paper we combine CBM on one (monitored) component, with periodic preventive maintenance (PM) and corrective maintenance (CM) on the other components of the same machine/system. We implement two thresholds on the degradation level to decide when to service the monitored component: when the degradation level of the monitored component surpasses a first ‘opportunistic’ threshold, the monitored component will be serviced together with other components, for instance with a (planned) PM intervention, or upon breakdown of another component, requiring CM. In case none of these opportunities have taken place, and the degradation level surpasses a second ‘intervention’ threshold, an additional maintenance intervention is planned for the monitored component in order to prevent a failure. Both thresholds are optimised to minimise the total expected maintenance costs of the monitored component, or to minimise the downtime of the machine due to maintenance on the monitored component. We perform an extensive numerical experiment to demonstrate the potential gains of this hybrid policy with two thresholds compared to using a traditional PM policy, and we identify its key drivers of performance. We also benchmark our results when only one threshold is implemented. Our model is validated and applied at an OEM in the compressed air and generator industry.
    • A win-win solution for the bullwhip problem

      Boute, Robert; Disney, Stephen M.; Lambrecht, Marc; Van Houdt, Benny (2006)
    • A win-win solution for the bullwhip problem

      Boute, Robert; Disney, Stephen M.; Lambrecht, Marc; Van Houdt, Benny (Production Planning & Control, 2008)
    • Altruistic behavior in supply chain management

      Boute, Robert; Lambrecht, Marc (Tijdschrift voor Economie en Management, 2007)
    • An integrated production and inventory model to dampen upstream demand variability in the supply chain

      Boute, Robert; Disney, Stephen M.; Lambrecht, Marc; Van Houdt, Benny (European Journal of Operational Research, 2007)
    • Analysis of a production/inventory system with multiple retailers

      Noblesse, Ann; Boute, Robert; Lambrecht, Marc; Van Houdt, Benny (2014)
    • Bullwhip reduction and win-win strategies

      Boute, Robert; Disney, Stephen M.; Lambrecht, Marc; Van de Velde, W.; Van Houdt, Benny (2005)
    • Characterizing order processes of continuous review (s,S) and (r,nQ) policies

      Noblesse, Ann; Boute, Robert; Lambrecht, Marc; Van Houdt, Benny (European Journal of Operational Research, 2014)
      We provide a novel approach to characterize the order process of continuous review and inventory policies, and study the impact of the batching parameter (the value of Q or ) on the variability in the order process. First, we characterize the distribution of the time between orders, as well as the distribution of order sizes. We find that the coefficient of variation (cv) of the time between orders is smaller than the cv of the time between demands. The size of the orders can exhibit either variance amplification or dampening, compared to the demand sizes, depending on the demand size distribution and the value of the batching parameter. This may motivate a supplier to adjust his imposed fixed order cost to influence the batching size. Second, we look at the compound order process, defined by the number of units ordered during an arbitrary interval. The compound order process always exhibits variance amplification compared to the compound demand, which increases linearly in the batching parameter for large values of Q or ; for small values, the variance amplification is fluctuating. We point out that the time interval, during which the number of units ordered/demanded is observed, also impacts the level of variance amplification, and we show to what extent larger time intervals (resulting in more aggregation of the data) lead to lower values of variance amplification. Both perspectives (looking at time between orders and order quantities, or observing the compound order process) provide useful information for the upstream supplier.
    • Coordinating lead times and safety stocks under autocorrelated demand

      Boute, Robert; Disney, Stephen M.; Lambrecht, Marc; Van Houdt, Benny (European Journal of Operational Research, 2014)
      We consider a supply chain in which orders and lead times are linked endogenously, as opposed to assuming lead times are exogenous. This assumption is relevant when a retailer’s orders are produced by a supplier with finite capacity and replenished when the order is completed. The retailer faces demands that are correlated over time – either positively or negatively – which may, for example, be induced by a pricing or promotion policy. The auto-correlation in demand affects the order stream placed by the retailer onto the supplier, and this in turn influences the resulting lead times seen by the retailer. Since these lead times also determine the retailer’s orders and its safety stocks (which the retailer must set to cover lead time demand), there is a mutual dependency between orders and lead times. The inclusion of endogenous lead times and autocorrelated demand represents a better fit with real-life situations. However, it poses some additional methodological issues, compared to assuming exogenous lead times or stationary demand processes that are independent over time. By means of a Markov chain analysis and matrix analytic methods, we develop a procedure to determine the distribution of lead times and inventories, that takes into account the correlation between orders and lead times. Our analysis shows that negative autocorrelation in demand, although more erratic, improves both lead time and inventory performance relative to IID demand. Positive correlation makes matters worse than IID demand. Due to the endogeneity of lead times, these effects are much more pronounced and substantial error may be incurred if this endogeneity is ignored.
    • Designing replenishment rules in a two-echelon supply chain with a flexible or an inflexible capacity strategy

      Boute, Robert; Disney, Stephen M.; Lambrecht, Marc; Van Houdt, Benny (International Journal of Production Economics, 2009)
    • Did just-in-time management effectively decrease inventory ratios in Belgium?

      Boute, Robert; Lambrecht, Marc; Lambrechts, O. (Tijdschrift voor Economie en Management, 2004)
    • (Dis)functionele voorraden - Het strategische belang van voorraden

      Boute, Robert; Lambrecht, Marc; Lambrechts, O. (2005)
    • Exploring the bullwhip effect by means of spreadsheet simulation

      Boute, Robert; Lambrecht, Marc (INFORMS Transactions on Education, 2009)
    • Extending the Production Dice Game

      Lambrecht, Marc; Creemers, Stefan; Boute, Robert; Leus, Roel (International Journal of Operations and Production Management, 2012)
    • Handboek productie- en logistiek management

      Lambrecht, Marc; Boute, Robert; Vandaele, Nico (2016)
    • Impact of service maintenance planning on inventory management

      Poppe, Joeri; Boute, Robert; Lambrecht, Marc (2014)