Design and Implementation of a Service-based Scheduling Component for Complex Manufacturing Systems Lars Mönch Department of Mathematics and Computer Science, University of Hagen, Universitätsstraße 1, 58097, Hagen, Germany Keywords: Service-oriented Computing, Scheduling, MES, Complex Manufacturing Systems. Abstract: Scheduling is highly desirable in complex manufacturing systems. However, there is still a mismatch between academic scheduling research, the scheduling solutions offered by software vendors, and the requirements of real-world scheduling applications. In this paper, we describe the design and the develop- ment of a scheduling component prototype that is based on web services. It exploits the idea of a hierarchical decomposition of the overall scheduling problem allowing the integration of different problem- specific scheduling algorithms for sub-problems. We discuss how appropriate services can be identified and implemented and how the resulting scheduling component can be used to extend the functionality offered by manufacturing execution systems (MESs). 1 INTRODUCTION scheduling solutions in the semiconductor manufacturing industry). In this paper, we research This research is motivated by scheduling problems the problem of designing a scheduling component that are found in complex manufacturing systems, as that can be used by an MES. In a certain sense, this for example, semiconductor wafer fabrication paper extends previous work carried out for the ERP facilities (wafer fabs). Complex manufacturing sys- domain (cf. Mönch and Zimmermann, 2009). The tems are characterized by a diverse product mix, design of the component is derived taking an many machines, a large number of jobs, sequence- appropriate hierarchical decomposition of the overall dependent setup times, and batching. Here, batching scheduling problem into account. After identifying means that several jobs can be processed at the same appropriate services, we implement a prototype time on the same machine. Scheduling is chal- based on web services. Such questions are rarely lenging in such an environment. However, it is discussed in the literature so far (cf. Framinan and highly desirable because of the increasing automa- Ruiz, 2010 for a recent survey of the architecture of tion pressure. In contrast to previous papers (cf. scheduling systems). Mönch and Driessel, 2005), we are not interested in The paper is organized as follows. In the next proposing a new scheduling technique. Instead of section, we describe the problem and discuss related this, we deal with the question of how to design literature. We present the hierarchical decomposition scheduling components from a functional and also of the overall scheduling problem in Section 3. from a software technical point of view. It turns out Furthermore, we describe how appropriate services that the data available in Enterprise Resource can be indentified. The implementation of the proto- Planning (ERP) systems and Advanced Planning type is described in Section 4. We discuss also some Systems (APS) are not fine-grained enough to allow limitations of the proposed approach and future for making detailed scheduling decisions. research needs. Furthermore, their actuality with respect to time is not appropriate. MESs are a natural carrier of scheduling functionality (McClellan, 1997; Meyer et 2 PROBLEM DESCRIPTION al., 2009). However, the scheduling capabilities of packaged MESs are often not appropriate because 2.1 Problem they are too generic (cf. Pfund et al., 2006 for the results of a survey of the acceptance of packaged In current MESs for complex manufacturing systems, 284 Mönch L.. Design and Implementation of a Service-based Scheduling Component for Complex Manufacturing Systems. DOI: 10.5220/0004002702840290 In Proceedings of the 14th International Conference on Enterprise Information Systems (ICEIS-2012), pages 284-290 ISBN: 978-989-8565-10-5 Copyright c 2012 SCITEPRESS (Science and Technology Publications, Lda.) DesignandImplementationofaService-basedSchedulingComponentforComplexManufacturingSystems dispatching functionality often is offered instead of hierarchical decomposition of the overall scheduling the more sophisticated scheduling functionality. problem. The resultant design is validated by a Optimization kernels are typically based on genetic prototypical implementation of such a component. algorithms or on generic commercial constraint programming and mixed integer programming 2.2 Related Work libraries (cf. Fordyce et al., 2008). Scheduling systems are mainly developed only for parts of the A web service-based specification and implemen- manufacturing system, for example for the leading tation of ERP components is described, for example, bottleneck machine group. There is only little by Brehm and Marx Gomez (2007) and Tarantilis et interaction of software vendors and academic al. (2008). However, a direct application of these research (cf. Kellogg and Walczak, 2008). There are ideas to scheduling is not possible because of the several reasons for this situation. different level of detail. A conceptual proposal for 1. Scheduling of production jobs is often an MES based on web services that can be used in combined with transportation scheduling, small- and medium-size enterprises in Mexico is process planning, staff scheduling, and finally discussed by Gaxiola et al. (2003). But again, no advanced process control decision-making. specific details of possible scheduling functionality 2. Global scheduling systems fail because humans are included in this paper. This is also true for the on the shop floor are not involved in the resul- recent survey paper by Framinan and Ruiz (2010), tant scheduling decisions. It seems that often the where the usage of web services is only mentioned, notion of reasonable automation is not taken but not further elaborated. into account. A service-oriented integration framework for 3. Scheduling algorithms depend to a large extent complex manufacturing systems is presented by Qiu on the objectives and constraints taken into et al. (2007). A certain portion of a traditional MES, account. That means that slight changes in the especially with respect to feedback from the shop objectives and the constraints might lead to floor, is implemented within the framework, but totally different algorithms. Dispatching rules again, scheduling functionality is not covered. strongly support this behavior by its inherent There is some work done for the identification of myopic view. Generic scheduling solutions have services (cf. Winkler and Buhl, 2007 for the finan- some limitations with respect to dealing with cial domain and Mönch and Zimmermann, 2009 for this situation. They are often not well accepted ERP-related services). However, to the best of our by people on the shop floor. knowledge, there is no work available that addresses 4. The data for scheduling decisions is located in this question for scheduling services in complex different operative application systems. MES- manufacturing systems. A distributed scheduling and Material Control System (MCS)-related system for complex job shops based on software data are very important in this context. agents is presented in Mönch et al. (2006). But in 5. Supplying appropriate data to the scheduling contrast to web services, software agents and multi- algorithms is important. However, scheduling agent-systems are still not widely accepted in algorithms that take many details into account applications on the shop floor. In this paper, we will require at the same time data that is fine-grained. show that some of the scheduling functionality Analyzing these insights results in the conclusion described by Mönch et al. (2006) can be provided that striving for a more detailed modeling is in- using principles of service-oriented computing. applicable because a more detailed consideration of constraints leads to sophisticated algorithms and also to a more difficult data supply. Therefore, it seems 3 IDENTIFICATION OF important to focus on the quintessence of APPROPRIATE SERVICES scheduling, i.e., considering the finite capacity of the manufacturing system is more important. However, 3.1 Distributed Hierarchical it is possible to deal with the finite capacity on a Decomposition more aggregated level. In this paper, we address the question of how a As discussed in Subsection 2.1, we are interested in scheduling component has to be organized to take making manufacturing system-wide scheduling this vision into account. Therefore, the design of a decisions without increasing the level of detail for service-based scheduling component is discussed modeling. This goal is mainly reached by an appro- that is based on an appropriate distributed priate hierarchical approach. 285 ICEIS2012-14thInternationalConferenceonEnterpriseInformationSystems We start by describing the assumed physical an aggregated model is used taking the capacity only decomposition of the base system of the on the work center level into account. Consecutive manufacturing system. The routing of the jobs, the operations that are related to one work area are dynamic entities in the system, takes place between combined into macro operations. This results in different groups of parallel machines. Parallel aggregated routes that consist of these macro machines offer the same functionality in a operations. The resulting start and completion dates manufacturing system. A single group of parallel can be used to set production goals for each machines is called a work center.