Journal of Materials Processing Technology 139 (2003) 302–309 Petri Net-based workflow management systems for in-process control in a plastic processing plant Richard Y.K. Fung a,∗ , Alan Y.M. Au a , A.W.H. Ip b a Department of Manufacturing Engineering and Engineering Management, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong, PR China b Department of Manufacturing Engineering, Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong, PR China Abstract To manage a complex system, an operation model is proposed for evaluating the effectiveness and efficiency of each possible plan. During the planning process, an easy-to-use modeling system for operation modeling could be very useful for assisting the shop floor manager to understand and predict the performance of operation plans. In this paper, the Petri Net is used as a tool to realize the proposed modeling concept. Derived from the basic Colored Petri Net (CPN) language, a Modular Colored Petri Net (MCPN), composed of a number of CPN Modules (CPNMs), is proposed for this adaptive modeling approach. The CPN in each CPNM represents the discrete event logic of the corresponding operation. Despatching rules of the material and activities are modeled by the components and functions of the CPNs in these CPNMs, and the dynamics of the system can be modeled by the transition firing and connections amongst them. In this way, the time and cost for the development and maintenance of the shop floor operation model can be reduced. The application of the system in in-process control in a plastic processing plant is illustrated in the paper. © 2003 Elsevier Science B.V. All rights reserved. Keywords: Workflow modeling; Colored Petri Net 1. Introduction 1.1. Workflow management A workflow management system (WMS) is defined as a system that completely defines, manages, and executes workflow through a software application where the order of execution is driven by a computer representation of the workflow logic [1]. The basic functions of a WMS, including the definition of tasks and procedures, are discussed in [2]. Management of workflow covers the manipulation of infor- mation involved in controlling, monitoring, optimizing and supporting a business process. Since workflow management develops a systematic foundation to specify and manipulate information, it can be adopted to solve many communica- tion problems in production management. With an effective WMS in the system, business policies and practices can be automatically deployed, implemented, monitored, measured and, if necessary, improved. Moreover, with an in-depth un- derstanding and a well-defined formal definition of the busi- ∗ Corresponding author. E-mail address: richard.fung@cityu.edu.hk (R.Y.K. Fung). ness processes in an organization in the development and operation of a WMS, the flow of business processes can be continuously improved through systematic analyses. Adop- tion of an effective WMS can also foster better tracking of business processes and enhance the reliability of the opera- tion system. A typical plastic processing routing involves a large num- ber of steps in complex sequences in various stages of the operation, such as planning, preparation, forming, finishing, decoration and recycling. Examples of some common steps are given in Table 1. These complex sequences of tasks involve various types of resources such as machines, operators and their skills, etc. It is found that since each step requires only its spe- cific resource, other resources are usually in an idle state. In order to optimize the productivity of the resources, the allocation of work to them must be carefully planned and managed. A workflow system for a material processing en- vironment to speed up its work by eliminating non-value work both within and between operations and to balances the overall work load to improving the overall efficiency is required. It is used as a tool to assist different levels of executives, engineers and clerical staff to improve their productivity. 0924-0136/03/$ – see front matter © 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0924-0136(03)00240-1