Application of AHP to Multi-Item Inventory Management Using Part Period Algorithm

This empirical study deals with integration of Analytical Hierarchy Process (AHP) with multi-item inventory management using Part-Period Algorithm. Among many variables which affects inventory systems, this study considers the variables of lot-sizing rules, sequencing, demand pattern, coefficient of variations, and change over cost. AHP is used to pick a sequencing rule and performance criteria. This study describes the application of AHP methodology in the form of multiple tables that will assist production managers in a Group Technology environment, to minimize employee and machine idleness. It will help managers make decisions on production order quantity, the sequence in which jobs should enter work centers, and in the determination of uniform production cycle times.

Design and Pricing of Discretionary Service Lines

For discretionary services, longer service duration implies higher service quality. We study the optimal design and pricing of discretionary service lines, a range of services that are vertically differentiated through their duration (quality), offered to a market with customers who are heterogeneous in terms of their sensitivity to service duration. In a resource-constrained environment with stochastic arrival of demand, longer service duration also implies longer wait, which all customers dislike. Hence, service line design takes into consideration both customer heterogeneity in quality sensitivity and customer disutility in waiting. We first study the case when the firm serves customers in the order they arrive (first in first out (FIFO)). Then we investigate a processing-time-based sequencing rule with two priority classes (two classes shortest processing time (2-SPT)) as a practical operational improvement of FIFO. We identify service variety reduction as an instrument to mitigate congestion, in addition to service time reduction and throughput control used for discretionary service design. Although FIFO results in a range of closely related service durations and an increasing price schedule, we show that 2-SPT gives rise to a clustered service line with a gap between the ranges of service durations offered for different priority classes, along with a decrease of demand volume and a possible price drop from the lower-quality to the higher-quality cluster. Finally, even without customer heterogeneity, it is still optimal for the firm to offer a variety of services under 2-SPT, driven by operational efficiency improvement, whereas under FIFO the service line collapses to a single service. This paper was accepted by Terry Taylor, operations management.

Potentialanalyse einer energiepreis- orientierten Reihenfolgebildung*/Potential analysis of an energy price-oriented sequencing - Integration of volatile energy prices in the manufacturing control to reduce energy costs

Durch die Zunahme der Einspeisungen erneuerbarer Energien nimmt die Volatilität des Strompreises stetig zu. Unter Berücksichtigung dieses Sachverhaltes können produzierende Unternehmen durch die Anwendung einer energiepreisorientierten Reihenfolgeregel Energiekosten sparen. Da die Anwendung dieser Reihenfolgeregel nicht nur Auswirkungen auf die Energiekosten hat, wird in diesem Fachbeitrag eine Potentialanalyse vorgestellt, welche neben den Energiekosten zusätzlich die Termineinhaltungskosten von Fertigungsaufträgen berücksichtigt.   As a result of the increasing feed-in of renewable energies, the volatility of the electricity price rises. Considering this, manufacturers can save energy costs by applying an energy price-oriented sequencing rule. Since the application of this sequencing rule does not only have an impact on the energy costs, a potential analysis is presented in this article which, in addition to the energy costs, also considers the schedule compliance cost of production orders.

Effect of routing flexibility and sequencing rules on performance of stochastic flexible job shop manufacturing system with setup times: Simulation approach

Routing flexibility is a major contributor towards flexibility of a flexible job shop manufacturing system. This article focuses on a simulation-based experimental study on the effect of routing flexibility and sequencing rules on the performance of a stochastic flexible job shop manufacturing system with sequence-dependent setup times while considering dynamic arrival of job types. Six route flexibility levels and six sequencing rules are considered for detailed study. The performance of manufacturing system is evaluated in terms of flow time related and due date–related measures. Results reveal that routing flexibility and sequencing rules have significant impact on system performance, and the performance of a system can be increased by incorporating routing flexibility. Furthermore, the system performance starts deteriorating as the level of route flexibility is increased beyond a particular limit for a specified sequencing rule. The statistical analysis of the results indicates that when flexibility exists, earliest due date rule emerges as a best sequencing rule for maximum flow time, mean tardiness and maximum tardiness performance measures. Furthermore, smallest setup time rule is better than other sequencing rules for mean flow time and number of tardy jobs performance measures. Route flexibility level two provides best performance for all considered measures.

Disordered and Multiple Destinations Path Planning Methods for Mobile Robot in Dynamic Environment

In the smart home environment, aiming at the disordered and multiple destinations path planning, the sequencing rule is proposed to determine the order of destinations. Within each branching process, the initial feasible path set is generated according to the law of attractive destination. A sinusoidal adaptive genetic algorithm is adopted. It can calculate the crossover probability and mutation probability adaptively changing with environment at any time. According to the cultural-genetic algorithm, it introduces the concept of reducing turns by parallelogram and reducing length by triangle in the belief space, which can improve the quality of population. And the fallback strategy can help to jump out of the “U” trap effectively. The algorithm analyses the virtual collision in dynamic environment with obstacles. According to the different collision types, different strategies are executed to avoid obstacles. The experimental results show that cultural-genetic algorithm can overcome the problems of premature and convergence of original algorithm effectively. It can avoid getting into the local optimum. And it is more effective for mobile robot path planning. Even in complex environment with static and dynamic obstacles, it can avoid collision safely and plan an optimal path rapidly at the same time.

Simulation-Based Sequencing Algorithm for MRO Operations of Train Couplings

Sequencing rules are often used in production control to improve key performance indicators, such as cycle time, mean tardiness and on-time delivery. However, for Maintenance, Repair and Overhaul (MRO) processes, there is a development need for sequencing rules, which effectively improve these indicators since specific requirements have to be considered and recent studies have mainly been using standard rules and do not allow a clear conclusion. This paper describes the modeling and validation of a real-case scenario, the MRO of train couplings by means of an event-driven simulation. The simulation model is used in order to derive and test a new sequencing rule, the Fix-and-continue algorithm (FACA), as well as to compare its results with standard sequencing rules concerning average cycle time, mean tardiness and on-time delivery. Thereby, the potential of the algorithm is revealed.