Integrating discrete material flow simulation in product lifecycle management.

Cotet, Costel Emil ; Popa, Cicerone Laurentiu ; Anghel, Florina 等

1. INTRODUCTION

We agree here that PLM is not about defining a piece, product or technology, but it is a business approach which sustain the management of an entire products, processes and services portfolio (Cotet & al., 2007).

PLM is the name introduced in 1999 by IBM which defines the strategic approach used for creating and managing the digital information related to a product, from initial concept, through design, launch, production and use to final disposal, and which integrated men, processes, systems and information.

Also, PLM can be seen as a business solution which aims to streamline the flow of information about the product and related processes throughout the product's lifecycle such that the right information in the right context at the right time can be made available (Ameri & Dutta, 2005).

The difficulty to implement PLM consists mainly in the fact that PLM is more a concept than a system, which involves all the functional and organizational aspects of an enterprise, supposing also knowledge management cooperation between actors inside and outside enterprise (Carutasu & al., 2008).

2. A GENERAL VIEW

The request to implement PLM modules come to our UPB-PREMINV research centre from virtual enterprise (VE) architectures consisting of an industrial partner's network who are performing different specific modules integrated in a project. The first request from this target group was for a package of CAD/CAM/CAE services and training modules based on a VE oriented curricula meant to define the manufacturing architecture for a new product. Then the industrial network requested for a solution to optimize the preliminary manufacturing architecture. We proposed them an integrated solution (figure 1).

Our methodology starts with the marketing studies which integrate the customer requests in the product design. Then after the research design department propose a sketch of the new product the CAD modelling department must provide the 3D design of the new product. The 3D virtual prototype of the product must be analyzed using CAE techniques based on FEM analysis in order to simulate his behaviour in working conditions. If the simulation validates the product parameters in working conditions the next step is to realize the CAM film chart. Based on the CAM film chart we can generate the operation plan, the necessary tools and machines type. Based on those data we can produce a model of the manufacturing system. In order to optimize this preliminary manufacturing architecture we perform a discrete material flow simulation. In our case the material flow contains parts and tools. The purpose of the material flow simulation is to identify the flow concentrators where the production chain is slowed down or blocked. In order to eliminate those bottlenecks we can use technological or functional remodelling. The technological remodelling is the less expensive using new manufacturing solutions based on the same architecture. If we use functional remodelling we modify the manufacturing architecture and the costs are higher. In both cases an economical impact analysis must certify if the optimizing costs are covered by the benefits of the increased productivity.

[FIGURE 1 OMITTED]

3. METHODOLOGY DETAILS

We define discrete material flow based on distinct and countable entities circulating according with fixed trajectories. A lot of applications are in manufacturing where we can model and simulate the parts and tools flow during the production process. In those discrete material flow simulations we can create a model (that will contain: machines, parts, tools, etc.) for the whole manufacturing system based on data transmitted by the system modelling department. The purpose is to achieve an optimum configuration for the system, regarding machines placement in the working place, the parts manufacturing order, etc. Having all the structural manufacturing elements (work points, transfer and transport systems, buffers, etc.) modelled, we can easily see all the operations and production phases, if it's necessary for the operator to intervene, the appearance of eventual problems, etc. We define diffused manufacturing systems as architectures with more than two work points connected by transport & transfer systems and using deposits at local or system level. We define then concentrate manufacturing systems as architectures based on a single work point surrounded & assisted by transport, transfer & deposit facilities (Cotet & Dragoi, 2003). Diffused as well as concentrated manufacturing systems could be mass production, batch production and job shops (Dhouib & al., 2009). In figure 2 one can see a diffuse manufacturing system containing 4 work points, 4 conveyors and a buffer during simulation. After the material flow simulation analyzing the reports of all the structural manufacturing elements activity we can identify eventual bottlenecks (flow concentrators) where the material flow is slowed or blocked. As we shown before in order to eliminate the flow concentrators and increase the productivity we need to choose between: a functional remodelling (changing some of the machines placement, the order of some operations, the speed of some conveyors or manufacturing times) or a technological remodelling (reconsidering all the system data: the type of the machines, tools, materials used etc.). With or without a manufacturing architecture modification as a solution for eliminating flow concentrators we need to perform a second simulation in order to validate the optimized manufacturing architecture design by obtaining an increased productivity. Last but not least a financial analysis must confirm the profitability of the manufacturing optimized architecture. That means that the productivity gain covers the expenses implied by the functional or technological remodelling. We can define four levels of integration of the discrete material flow in PLM:

At the first level main parameters for the work points modelling in material flow simulation are provided form CAM simulations describing the manufacturing process. This way the material flow simulator is integrating the process simulation results at the level of the work point in order to provide a complete model of the manufacturing system. Also the part parameters as resulted from the 3D virtual prototype are introduced separately in the material flow simulator in order to calculate the necessary buffers capacity and avoid possible collisions during the transfer and transport phases. Designing the flow simulator solution and establishing the material flow planning according to the general productivity strategy is the main focus of this level.

At the second level the simulation algorithm is applied for each manufacturing system of the virtual enterprise network. At this level the main focus is on developing the manufacturing architecture optimization strategy by identifying which processes and flows will modify, in which department. At the third level the virtual enterprise material flow is simulated. In this model the work points are the terminating simulation models describing the virtual enterprise partners manufacturing systems material flows. The fourth level focus on measuring and quantifying the benefits of discrete material flow simulation in optimizing the VE manufacturing architecture.

[FIGURE 2 OMITTED]

4. CONCLUSION

The necessity of implementing an integrated discrete material flow simulation--PLM system as presented partially in figure 1 was dictated by three main reasons: reducing the time-to-market for new products, reducing the costs by centralizing the procedures/operations and optimizing the manufacturing architecture and processes. The entries in the system are represented by the parameters of machine tools, tools and parts and the exit is the optimised architecture of the system. The main limitations of the system are: execution plans, available execution phases and the CAD--CAM--CAE system ability to analyse the working behaviour of machine-tools, tools and parts. The implementation of such an integrated system for a VE architecture brings the advantage of controlling data from many systems across an organization, providing the user with a robust manufacturing architecture optimizing engine and with the necessary information in a user-friendly web environment.

Our future research will focus on extending our solution by implementing a multipolar project planner integrated system able to simulate the costs evolution during the entire project for different optimizing material flow solutions based on material flow concentrators' elimination.

5. REFERENCES

Ameri, F., Dutta, D. (2005). Product Lifecycle Management: Closing the Knowledge Loops, Computer-Aided Design & Applications, Vol. 2, No. 5, 2005, ISSN 1686-4360, pp. 577-590, USA

Carutasu, G; Botezatu, C; Botezatu, CP (2008). Knowledge management system for implemententing integrated management in romanian industry, Annals of DAAAM for 2008 & proceedings of the 19th international DAAAM symposium OCT 22-25, 2008 Trnava SLOVAKIA, pp. 205-206, Publisher DAAAM International Vienna

Cotet, C.E., Dragoi, G.S. (2003). Material Flow Management in Validating Concentrate and Diffused FMS Architectures, In: International Journal of Simulation Modelling IJSIMM, no. 4, December 2003, pp.109-120, ISSN 1726-4529

Cotet C. E., Popescu D., Guran M., Dragoi G., Carutasu G., Carutasu N.L., (2007), Using PLM training & consulting in university-enterprises partnership, in DAAAM International Scientific Book 2007, Vol. 6, ISSN 1726-9687, ISBN 3-901509-60-7, pp. 139-153, Editor: B. Katalinic, hard cover, Publisher DAAAM International Vienna, Vienna

Dhouib, K., Gharbi, A. & Ayed, S. (2009). Simulation based throughput assessment of non-homogeneous transfer lines, In: International Journal of Simulation Modelling IJSIMM, Volume 8, no. 1, March 2009, pp.5-15, ISSN 1726-4529