Proceedings of European Business Research Conference Sheraton Roma, Rome, Italy, 5 - 6 September 2013, ISBN: 978-1-922069-29-0 A Study on the Influence of Review Period Interval in Closed Loop Supply Chains (CLSC) Using System Dynamics Hassan Fainaze* and Lewlyn L.R. Rodrigues** Periodic review of capacity plays an important role in CLSC especially in capacity planning. Managers have to takes decisions regarding the time interval for the review of capacity expansions and how much they have to add to their capacity considering the investment cost. In the periodic review system of capacity, the capacity is reviewed periodically and decision regarding expansion will be taken accordingly. The focus of this paper is on the study of the review period interval on the CLSC system using system dynamics and establishing the relationships between different variables in a CLSC system and to simulate the influence of the review period interval on demand, production capacity, production backlog, serviceable inventory, recycling rate, and the total profit. The results has indicated that even though our total Investment cost will be more for a shorter review period interval, the total profit in the system can be very successfully increased when we are following a shorter review period interval. Field of Research: Management, Closed Loop Supply Chain and System Dynamics. 1. Introduction In today‟s competitive market, customers‟ satisfaction has been one of the important focused areas in every organization. And also because of the restrictions from the government in bearing responsibility regarding proper disposal, forced the manufacturers to concentrate on CLSC system and reducing the cost. The systematic review system and optimum period of reviewing will help in achieving the customer satisfaction in an effective way. Over the last decade or so, closed loop supply chain management has emerged as a key area of research among the practitioners of operations research. A lot of research is being carried out to make the CLSC more efficient and economic. The smooth and efficient functioning of a business involves the smooth and efficient functioning of the principal areas of the supply chain, one of these areas is capacity control (Poles and Cheong, 2011). In this paper the focus is on the study of the review period interval for the capacity expansions in the CLSC system. In this paper, a system dynamics model is developed to cope with the dynamics of closed-loop supply chains in capacity planning. Forrester introduced SD in the early 60‟s as a modeling and simulation methodology for long-term decision-making in dynamic industrial management problems. 2. Literature Review The concern about environmental protection and also the economic benefits of using “used products” has spurred an interest in designing and implementing closed loop supply chain. In recent decades, many companies focused on reverse logistics activities have achieved significant successes in achieving their targets. In CLSC system, it is important to consider the capacity expansion related decisions regarding recollection, recycling and remanufacturing facilities (Blumberg, 2005). *Mr. Hassan Fainaze, Department of Mechanical & Manufacturing Engineering, Manipal University,India Email: hassanfainaze@gmail.com **Dr. Lewlyn L.R. Rodrigues, Department of Humanities & Management, Manipal University, India Email: rodrigusr@gmail.com Proceedings of European Business Research Conference Sheraton Roma, Rome, Italy, 5 - 6 September 2013, ISBN: 978-1-922069-29-0 Long term capacity planning in closed loop supply chains involves a huge investment cost. Managers have to make many decisions regarding the quantity and the time for capacity expansions related with collection, recycling and remanufacturing capacities. Managers can adopt either of the following two strategies, strategy of early large-scale investments or a flexible strategy of low volume but more frequent capacity expansions. The flexible strategy is the better strategy compared with the large scale capacity expansion strategy as it involve fewer investment risks. Flexible policies also help to avoid overcapacity in collection, recycling and remanufacturing capacity (Georgiadis and Athanasiou, 2013). System dynamics (SD) is a simulation technology that helps to study complex dynamic systems based on the feedback control theory and the computer imitation technology. SD method is an effective tool for better understanding complex problems. System dynamics is proposed to predict the future trends which are difficult to estimate in related with a complex system (Sterman, 2000). 3. Problem Definition The focus of this research is on a global steel production which includes the following distinct operations: supply, production, distribution, use, collection (and inspection), remanufacturing, recycling and disposal. The forward supply chain includes producer, distributor and customer. Managers face difficulties in choosing the strategy to be followed, either a plan of early large-scale investments, or a low-scale plan combined with more frequent capacity expansions, which is more responsive in capacity adjustments but less cost effective. In many CLSC systems, overcapacity in the production system has reported as a reason for decrease in profit margins or losses (Georgiadis and Vlachos, 2004). In particular the aim of this paper is to develop a model of production and inventory system for remanufacturing and recycling using a System Dynamics simulation modeling approach and to study the influence of capacity review period and to evaluate system improvement strategies. 4. Methodology & Model Construction The approach in this case is to develop a system dynamics model as a methodology in order to analyze the different factors related with production, distribution, remanufacturing and recycling in a closed loop supply chain system. The steps involved are adapted from (Sterman, 2000) modelling process: i) ii) iii) iv) v) vi) vii) Define the dynamic problem to be solved and its scope; Identify the dependent and independent variables involved and their relationship; Select suitable software to model the system; Construct the stock and flow diagram; Simulate the model; Verify the model; and Validate the model. The global steel production has taken under consideration for this research. The initial production capacity of steel is 2.964 MMT per day (OECD, 2011). Initially the crude steel will be produced based on the production backlog and the product will be taken to the Proceedings of European Business Research Conference Sheraton Roma, Rome, Italy, 5 - 6 September 2013, ISBN: 978-1-922069-29-0 serviceable inventory to meet the orders from the distributors. The serviceable inventory is a sum of the remanufactured products and the newly manufactured products. From the distributor inventory, the products are sold to customers as per the demand. After a period of time, these become used product and the available used product will be collected depending upon the collection capacity, and most of them will become uncontrollable disposed products. The collected products will be inspected and the failure percentage will be recorded and the reusable products will be taken to the reusable product inventory for remanufacturing and recycling to take place and the unusable products will be disposed. From the inventory of reusable product, products which can be remanufactured will be taken for remanufacturing and low quality products will be taken for recycling. The low quality products will be recycled based on the recycling rate which will be influenced by the recycling capacity. The Causal diagram and the Stock & Flow diagram of the model are presented in the Figures 1 (adapted from Wang and Murata, 2011). 5. Simulation and Analysis The model was simulated for studying the influence of the review period interval on various endogenous factors in a CLSC as discussed below. Capacity has to be reviewed periodically and then a decision has to be made whether or not to invest on capacity and to what extent. The length of the review period generally depends on the construction cost of facilities as well as the total profit, but it is a decision variable in our model. As it is an exogenous factor, it is important to study its influence on the entire process. In the industry under consideration, on an average, the review period interval has varied from 365, 1095, 1825, and 2555 days; results were plotted for 7920 days i.e. for 22 years (year 2001 to 2022). The basis for this time interval of simulation was the past 12 years‟ production data (Steel Statistical Yearbook archive, BOF route steelmaking costs & EAF steelmaking cost, 2013) that was available and it was intended to forecast for another 10 years. 5.1. Demand It can be observed from the figure 2 that, till 552nd day demand has no change with change in the review period interval as remanufacturing and recycling processes requires an initial set up period. Later on from 553rd day, review period interval will have an influence on demand as the market share can be increased by focusing on the green image impact through recycling and remanufacturing processes. After 916th day, if we are following a review period interval of 365 days, the demand for the product will increase further due to increase in the remanufacturing and recycling rate mainly because of the increase in their capacities compared to other review period interval simulations. By the end of 7920th day, it can be seen that the demands for the product will be 7.42 MMT per day, 7.37 MMT per day, 7.03 MMT per day, & 6.84 MMT per day for the review period intervals of 365, 1095, 1825 & 2555 respectively. Proceedings of European Business Research Conference Sheraton Roma, Rome, Italy, 5 - 6 September 2013, ISBN: 978-1-922069-29-0 Figure 1: Stock & Flow Diagram of CLSC under Consideration RMI Cover time Expected orders to SI SI <Expected remanufacturing rate> Desired RMI Expected distributors orders SI Desired SI Discrepancy Production Production backlog backlogs Production orders reduction rate RMI Discrepancy DI SI cover time Orders backlog Orders backlog reduction rate Production SI adj time <Production efficiency capacity> Expected retailer's orders RI Expected demand D Unit timeDemand slope Desired RI RI cover time Total Demand Desired DI Market RI DI Demand <Time > DI Cover time Discrepancy Discrepancy Demand Retailer's Distributors orders order Retailer's Demand backlog backlog Retailer order backlog backlog reduction orders reduction rate rate DI adj time RI adj time Demand market share Retailer's Servicable Distributor's Customer's in <Reuse Inventory Shipment to production Inventory Shipment to Inventory Sales ratio> hand products rate distributor retailer Transportation RR Delivery time Shipment time Remanufacturing Production Obsolecence time Expected Shipment time to efficiency Recycling time rate remanufacturing rate Expected retailer Efficiency Expected used Avg product <Remanufacturing recycling rate Remanufacturing products Capacity> life Recycling rate rate Remanufacturing RCyR Used Uncontrollable Recycling time Uncontrollable product disposal Products time Reuse ratio disposal rate <Recycling Remanufacturable UP capacity> products Recollection Probability of getting <Expected Customer's high quality product Products accepted for recycling rate> Collection controllable disposal remanufacturing Sorting time time Product Re-Usable Collected Recyclable Available Products taken for Products products Products keeping time used Collection rate Products accepted recycling products for re-use <Collection Controllable Inspection Failure Capacity> Collection RM Order Efficiency disposals Reusable stock percentage time RM reduction backlogs Rawmaterial keeping time rate Disposed Orders Products <Expected Products rejected RM adj time orders to SI> for re-use Raw Input rate Materials % Electricity Rem Cap Con Rem Cap <Time> Electricity % Electricity recycling Recyc Cap Con % Electricity Slope Con Cost BF % Labour BF Recyc Electricity Cost RemLabour Other <Electricity> EAF Cap <Labour> Electricity Cap Con Recyc Rem Cap Costs Con Labour <Electricity> Reheat cost Other Recycling Con Electricity costs Cap Con Recyc Capital Electricity Labour Cost % Labour Electricity Cost % Labour Capital Cap Con Cost Cost BF Electricity Cost EAF recycling BF Cost % Electricity Cost Labour <Electricity> remanufacturing <Labour> EAF Residual Recycling BOF Cost Capital Con. Rem Cap Labour Cost removal cost <RC Labour Cost Production Cost % Labour Expansion Recy Cap Construction cost Cost BOF EAF Remanufacturing rate> Construction remanufacturing Cost per unit <% Iron Ore EAF PRoduction Electricity cost <RCyC <% Iron Ore Labour Con. Cost <PC Expansion <Recycling recycling based steel based steel Cost BOF Remanufacturing Cost Expansion production> rate> rate> production> rate> Labour Cost Col Cap Electricity Cost per unit Cost per unit tonne Construction cost Prod. Con. Con.Cost BOF <Labour> remanufacturing Recycling for production <% Scrap Cost BF Electricity Cost Investment cost Other costs Other Const Con. Cost steel based <CC steel Prodn Cap Remanufacturing Production <production rate remanufacturing Cost BOF production> expansion EAF cost rate> Construction rate> cost Labour Cost <Remanufacturing Prod. Con. Total Cost Total Total Con. EAF rate> Investment Variable Cost Cost EAF Cost Total Variable Cost Cost Capital Con. <Input <% Scrap <Remanufacturable changing rate steel based rate> products> Cost EAF Total Total steel Raw material Profit Revenue production> Other Const <Servicable Revenue Less Total Inventory Inventory> cost Iron Ore based steel Cost EAF rate Others carrying cost Collection Cost for production cost Revenue <Raw Materials> raw generating Excise Duty cost <Collected rate <Shipment material per Unit carrying Products> to tonne steel <BF & BOF Employee R&D distributor> production steel <Re-Usable <Recyclable cost Benefits making> Products> products> <Collection Cost per unit Selling price to Depreciation rate> tonne for Scrap based steel % Iron Ore based distributor collection production cost steel production Interest & Raw material Taxes <EAF Storage gathering cost Ocean Steel % Scrap steel based SP Slope <Time> frieght Administration Interest charges Making> steel production Insurance Handling Cost % Electrodes % Ferro EAF Electrodes % Refractories % Oxygen Alloys Ferro Alloys <Refractories> % Flux EAF EAF Coal Slope Oxygen Electrode Cost Refractories <Time> <Time> <Fluxes> EAF Coking Coal Scrap Slope Cost EAF% Oxygen Oxygen Cost <Lime transport Coking Coal Flux Cost EAF Steel Scrap BF stone> Ferro Alloys Oxygen Cost EAF % steel scrap Limestone Cost % Coking Cost BF % By- Product Steel Scrap % Limestone EAF EAF <Oxygen> Coking Coal Coal Cost BF credits EAF <Steel Other Cost EAF Steel Cost BF Other costs By-Product Scrap> By Products <Ferro EAF credits Other Cost BF Making Steel Scrap Cost BF BF & BOF steel Alloys> % Other costs <Time> Ferro Alloys Cost EAF Iron Ore Iron Ore Cost making Fluxes Cost Fluxes Iron Ore EAF % steel Scrap Coking CoalThermal Energy % FerroAlloys Slope BF BF Iron ore EAF Refractories % Fluxes EAF EAF Cost EAF transport Cost BF % Refractories Lime stone <Coking % Coking Coal % iron ore Cost BF Thermal Coal> EAF % Thermal <Thermal Refractories Energy Cost Energy> Lime stone Energy EAF % lime stone Thermal % Thermal Energy Energy Proceedings of European Business Research Conference Sheraton Roma, Rome, Italy, 5 - 6 September 2013, ISBN: 978-1-922069-29-0 Figure 2: Influence of the Review Period Interval on the Demand Demand 8M Tonnes/Day 1 4M 2M 2 1 2 6M 1 2 3 4 3 4 1 2 1 2 3 4 1 2 3 4 1 2 4 3 1 2 3 4 1 2 3 4 1 2 1 2 3 4 3 3 4 3 4 0 0 792 1584 2376 Demand : Review Period 1 year Demand : Review Period 3 year Demand : Review Period 5 year Demand : Review Period 7 year 3168 3960 4752 Time (Day ) 1 2 1 2 3 1 2 3 1 2 3 4 5544 6336 7128 4 1 2 3 4 1 2 3 4 7920 1 2 3 4 2 3 4 4 5.2. Serviceable Inventory It can be clearly seen from the figure 3 that the serviceable Inventory for the review period interval of 365 days will be increasing steadily as our production capacity expansions will be done at exact pace whenever required. It can also be seen that for the review period interval of 1095 days, the serviceable inventory will be at a steady level for an average of about 23MMT between 1800 and 2220th day as we will be in shortage for the production capacity. Once we start expanding our production capacity the serviceable inventory will increase suddenly as we have to meet the pending distributor‟s orders. Similar sort of pattern with little shift can be observed for the review period intervals of 1825 and 2555 days. Figure 3: Influence of the Review Period Interval on Serviceable Inventory Servicable Inventory 60 M Tonnes 45 M 30 M 15 M 1 2 3 2 3 4 4 1 1 2 3 1 2 3 4 1 2 3 4 1 2 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 1 4 2 3 3 4 0 0 792 1584 2376 3168 3960 4752 5544 6336 7128 7920 Time (Day ) Servicable Inventory Servicable Inventory Servicable Inventory Servicable Inventory : Review Period 1 y ear 1 : Review Period 3 y ear : Review Period 5 y ear : Review Period 7 y ear 1 2 1 2 3 3 4 1 2 3 4 1 2 3 4 1 2 2 3 4 4 Proceedings of European Business Research Conference Sheraton Roma, Rome, Italy, 5 - 6 September 2013, ISBN: 978-1-922069-29-0 5.3. Production Backlog The production backlog has a great impact by the review period interval which we are choosing (Figure 4). For the capacity review period interval of 365 days, the production backlog will be very low compared to the 2555 day review period interval. In case of 2555 day review period plan, the production backlog will start piling up from the 1707th day and it will reach a peak point of 1288 MMT by 2684th day and after that the production backlog will start declining once we start expanding the production capacity. Similarly the production backlog will reach 503.1 MMT on 2324th day for the review period interval of 1095 days and 1019 MMT on 3775th day for a review period interval of 1825 days. Figure 4: Influence of the Review Period Interval on Production Backlog Production backlogs 2B Tonnes 1.500 B 999.9 M 3 499.85 M 4 -200,000 4 1 2 3 4 1 2 3 4 1 2 3 0 1188 Product ion backlogs : Review Product ion backlogs : Review Product ion backlogs : Review Product ion backlogs : Review 1 2 3 2376 4 1 2 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 3564 4752 Time (Day ) Period 1 year Period 3 year Period 5 year Period 7 year 1 5940 1 2 1 2 3 4 1 2 3 1 2 3 4 7128 3 4 1 2 2 3 4 4 5.4. Recycling Rate It can be observed that till 552nd day recycling rate will be zero since it requires some time for the recycling to start and later on the recycling rate increases depending upon the availability of reusable products during the review period (Figure 5). Proceedings of European Business Research Conference Sheraton Roma, Rome, Italy, 5 - 6 September 2013, ISBN: 978-1-922069-29-0 Figure 5: Influence of the Review Period Interval on the Recycling Rate Recycling rate 2M Tonnes/Day 1 1 1.5 M 2 2 1 1 3 1M 1 1 4 4 4 3 1 2 1 0 2 3 2 500,000 2 3 1 1 2 3 4 1 2 3 4 0 Recycling rate Recycling rate Recycling rate Recycling rate 792 : : : : 2 1584 Review Review Review Review 2 3 4 3 3 4 4 4 4 2376 Period Period Period Period 3 1 3 5 7 3168 3960 4752 T ime (Day ) year1 year year year 1 2 1 2 3 1 2 3 4 7920 1 2 3 4 7128 1 2 3 4 6336 1 2 3 4 5544 2 3 4 4 It can also be seen that the recycling rate for the 365day review period interval will be increasing in a steady rate and will be able to recycle 1.71 MMT per day by the end of 7920th day. By the end of 7920th day, if we are following 365 day review period we will be able to recycle (1.71 MMT per day) almost double the products which we may be able to recycle if we are following 2555 days review period interval (0.9 MMT per day). 5.5. Production Capacity In our consideration, production will be reviewed initially on the 30th day and reviewed regularly depending on the review period interval that we are deciding. During the initial stage of production we were having a production capacity of 2.964 MMT per day which later on will be expanded to 3.6 MMT per day after few days. Production capacity of 3.6 MMT per day will be maintained till 1125th day and later on the production capacity will be expanded depending on the capacity expansions required. It is clear from the figure that for the review period interval of 2555 days, the production capacity will be maintained at 3.6 MMT per day till 2585th day and which will later on expanded to 7.17 MMT per day for the next 2555 days and by the end of the 7920th day we will be able to produce at the rate of 8.5 MMT per day (Figure 6). Proceedings of European Business Research Conference Sheraton Roma, Rome, Italy, 5 - 6 September 2013, ISBN: 978-1-922069-29-0 Figure 6: Influence of the Review Period Interval on Production Capacity Production capacity Tonnes/Day 10 M 3 7.5 M 4 4 2 5M 2.5 M 1 1 2 3 4 1 3 4 1 1 2 2 4 1 2 1 2 3 1 3 4 2 4 2 1 3 3 1 2 3 4 2 3 4 1 2 3 4 0 0 792 Product ion capacity Product ion capacity Product ion capacity Product ion capacity 1584 2376 : Review : Review : Review : Review 3168 3960 4752 Time (Day ) Period 1 year Period 3 year Period 5 year Period 7 year 1 5544 1 2 1 2 3 1 2 3 4 7920 1 2 3 4 7128 1 2 3 4 6336 2 3 4 4 5.6. Total Profit It can be observed from the figure 7 that the total profit will be same till 730th day. In 731st day the total profit for the review period interval of 365 days will be less as we have to invest extra amount on increasing the capacity for recycling and remanufacturing. Similarly we have to make an extra investment on 1856th day and 2584th day for the review period intervals of 1825 days and 2555 days respectively. Till 2538th day the total profit for the review period interval of 2555 days will be more due to fewer inventories and later on the total profit in the case of the review period interval of 2555 days start reducing because of the low contribution margin and it can be clearly seen from the figure that the industry will have to face a loss if they are following a review period interval of 2555 days. By the end of 7920th day, the industry can achieve a profit of about $624343 Cr if they are following 365 day review period plan, almost 3 times the profit we can achieve through 1095 days review period plan. Proceedings of European Business Research Conference Sheraton Roma, Rome, Italy, 5 - 6 September 2013, ISBN: 978-1-922069-29-0 Figure 7: Influence of the Review Period Interval on Total Profit Total Profit 8e+012 5.85e+012 $ 1 3.7e+012 1 -600 B 2 1 1 2 3 4 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 0 Total Profit Total Profit Total Profit Total Profit 2 1 1.55e+012 1188 : Review : Review : Review : Review Period Period Period Period 2376 1 3 5 7 y ear y ear y ear y ear 2 2 3 4 2 3 4 3564 4752 Time (Day ) 1 1 2 3 4 1 2 3 4 4 1 2 3 4 4 7128 1 2 3 3 3 4 5940 1 2 3 4 1 3 4 1 2 2 3 4 4 6. Model Validation The most commonly used and reliable method for validating a system dynamics model is to check the simulated values against the actual values. In this model, we have taken the market demand for comparison and it is observed that the model follows the trend to a given degree of accuracy. The gaps which are identified between the two may be because of the external factors which are affecting the demand in the market. Figure 8: Actual vs. Simulated market demands 7. Conclusion In this paper, a System Dynamics simulation model of a closed loop supply chain system for was developed. The main objective of this research was to study the influence of time interval for capacity expansions on the entire system. Through simulation analysis, we Proceedings of European Business Research Conference Sheraton Roma, Rome, Italy, 5 - 6 September 2013, ISBN: 978-1-922069-29-0 concluded that the total system cost increases more rapidly if higher capacity is allocated for production, recycling, and remanufacturing processes, i.e., the total cost will be more if we are following a shorter review period interval. 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