1. An overview to push & pull systems By: Tiruvannamalai R. S. Date: 11/16/2001

3. Objective Definitions Comparison of push & pull systems AHP for push & pull system POLCA - A case study Hybrid push/pull systems Conclusion References Agenda

4. Objective To provide an overview to Push production systems Pull production systems POLCA Hybrid push/pull systems

5. Definitions 3 Pull: Production is triggered only in response to actual consumption of inventory. Push: Production is triggered based on due dates of customer orders or desired restocking to inventory levels. FORECAST DEMAND

6. Comparison between pull and push systems WIP Cell 1Cell 4Cell 3Cell 2 Material Flow Withdrawals trigger production Pull System: 2 Information Flow Custome r demand WIP Cell 1Cell 4Cell 3Cell 2 Information Flow Material Flow Push System: MRP schedule triggers production Forecast ?

7. Characteristics of push and pull systems ParametersPushPull Historical dataCustomer demand Same as material flowOpposite to material flow Make to stockMake to order Forecasting errorsFluctuation in customer demand Planning information Flow of information Manufacturing technique Inventory level affected by 2, 3, & 4

8. Comparison between push and pull systems ParametersPushPull Lead Time Manufacturing cost Inventory, WIP level Customer service Throughput Changing product mix and variety Machine utilization Product introduction Demand fluctuation Manufacturing environment Suitable Not suitable FasterSlower RepetitiveCustomized 1, 3, 4, 5, & 6

9. Methodology for selection of push & pull systems

10. Methodology for selection Analytic Hierarchy Process(AHP) approach: A simple decision-making tool To deal with complex, unstructured and multi-attribute problems To classify push, pull and hybrid push-pull systems in production planning To analyze push-pull systems using quantitative and qualitative criteria To devise a 3D state-space model To simulate multiple environments 8

11. Three-dimensional state-space model (AHP model) High Low Unreliable suppliers & lead time Serviceability, Commitment, & Costs Demand Fluctuation 1 5 3 78 4 2 6 1 & 5 - Uses pull systems 2, 4, 6, 7 & 8 - Uses push systems 3 - Employs push/pull systems 8

12. POLCA

13. P aired-cell O verlapping L oops of C ards with A uthorization “Novel material control strategy used in QRM, which combines the best of push and pull methods to limit congestion while at the same time providing a high degree of flexibility.” 9

14. POLCA (contd.) Where does POLCA work? High level material requirement planning system (HL/MRP) Cellular organization Flat BOM’s 9

15. POLCA (contd.) Key features Key features: To release authorizations by HL/MRP To control card based on material control methods To produce control cards (POLCA cards) To use POLCA cards for each pair of cells 9

16. Case study- CFP corporation Products- Customized faceplates & nameplates Features- Printing, holes, notches, bends Strength- Small batches for specialized markets Uses cell concept to satisfy highly varied markets 9

17. Applying POLCA-CFP Corporation (contd.) Printing cells Fabrication cells Assembly cells Shipping cell P1 P2 F3 A1 F2 F1 A2 A3 S1 P1/F2 Loop A3/S1 Loop F2/A3 Loop 9

18. Applying POLCA-CFP Corporation (contd.) P1 F2P1/F2 P1/F2 P1/F2 Loop F2/A3P1/F2A3 F2/A3 F2/A3 F2/A3 F2/A4 Loop P1/F2 P1/F2 9

19. 9 Advantages of POLCA over push-pull systems Assures that each cell only works on jobs that are destined for downstream cells Uses of HL/MRP authorization to prevent buildup of unnecessary inventory Flows in longer flexible loops Overlapping loops gives greater degree of flexibility

20. Hybrid push/pull Issues – 1. When to push ? 2. When to pull? Hybrid push-pull: Pushes through certain manufacturing stages and pulls else where based on the characteristics and value addition in stages Draws a demarcation for determining stages in production that needs to work in push and those in pull

21. Hybrid push/pull Delayed differentiation strategy: A method to combine push and pull systems within a production line Push strategy Pull strategy Push-pull boundary Customer demand Forecast 7

22. Hybrid push/pull (contd.) Advantages: Allows to realize advantages of both push & pull approaches Helps to improve economies of scale Helps to reduce FGI Caters to a wide range of customer demands Provides better shop floor control 7

23. Hybrid push/pull (contd.) Area of research: Locating the push-pull boundary Looking for more than one possible differentiation point Work done so far: Literature review Determined the various stages in a multi stage production line

24. Hybrid push/pull (contd.) Work planned ahead: Model a multi stage production line with hybrid push/pull system Determining the push pull boundary line

25. Summary Comparisons between push & pull systems Methodology for selecting push & pull systems POLCA Hybrid push pull Area of research Future work

26. References 1)APICS International Conference & Exposition-Oct 28-31, 2001. 2)Black, JT. (1991). The design of the factory with a future. New York: McGraw Hill,Inc. 3)Bonney, M. C., Zhang, Z., Head, M. A., Tien, C. C., & Barson, R. J. (1999). Are push and pull systems really so different? International Journal of Production Economics, 59, 53-64. 4)Grosfeld-Nir, A., Magazine, M., & Vanberkel, A. (2000). Push and pull strategies for controlling multistage production systems. International Journal of Production Research, 38, 11, 2361-2375. 5)Huang, C. C., & Kusiak, A. (1998). Manufacturing control with a push-pull approach. International Journal of Production Research, 36, 1, 251-275. 6)Krishnamurthy, A., & Suri, R. Push can perform better than pull for flexible manufacturing systems with multiple products. Center for Quick Response Manufacturing. 7)Levi, D. S., Kaminsky, P., & Levi, E. S. (2000). Designing and managing the supply chain. New York: McGraw Hill,Inc. 8)Razmi, J., Rahnejat, H., & Khan, M.K. (1998). Use of analytic hierarchy process approach in classification of push, pull and hybrid push-pull systems for production planning. International Journal of Operations & Production Management, 11, 1134-1151. 9)Suri, R. (1998). Quick response manufacturing. Portland, Oregon: Productivity press.