Construction of a Virtual Production Line Including a Buffer for Simulation of Electric Power Consumption

The digital eco-factory has been proposed by the authors for simultaneous simulation of green performance, productivity and manufacturability. The digital eco-factory is constructed on a virtual production line modelling an actual production line. The virtual production line has been constructed by sequentially connecting machine agents which have been generated from their behaviour model. For example, a virtual PCA (Printed Circuit Assembly) line was constructed by connecting sequentially a solder paste printing machine, two or three electronic part mounters, reflow furnace and testing machine. In this virtual PCA line, the connection between machines is not considered exactly. Usually the processing time for a job for each machine is different. It means usually there is a residence time before proceeding to the next process. For smooth production processing, it is important to control the production flow. In this paper, behaviour of a buffer is modelled and a buffer agent is generated. Buffer agents are put in the intervals between machine agents. A buffer agent controls flow of material/product on the virtual line by communicating with other machine agents. A machine buffer has activities such as storing, loading and unloading. The buffer adjusts the start timing of the job for material/product. When the next machine which processes the next step of the job is occupied, the buffer agent stops to feed material/product. When the buffer storage is full, the buffer agent lets the previous position machine agent know. Buffer function is important to simulate production condition with high accuracy. Through the construction of a virtual PCA line including buffers, the importance of a buffer agent is shown.