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This review explores the fundamental concepts of push and pull production systems in supply chain management. Push systems produce based on forecasts, while pull systems initiate production only when there is demand. Key differences, advantages, and implications on inventory management are discussed. Additionally, the complexities and challenges of supply chains, their flows, and the bullwhip effect are analyzed. Strategies to mitigate the bullwhip effect and improve supply chain efficiency are highlighted, emphasizing the importance of continual improvement and responsiveness.
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Push and Pull Production Control “Push” system: Determines when and how much to produce based on forecasts of future demands “Pull” system: Initiates production of an item only when the item is requested
Pull vs Push Systems • By pulling material in small lots, inventory cushions are removed, exposing problems and emphasizing continual improvement • Manufacturing cycle time is reduced • Push systems dump orders on the downstream stations regardless of the need
Supply Chain What is a Supply Chain? Network of entities: • Suppliers (and their suppliers) • Manufacturers of semi-finished and finished products • Distributors • Customers
Supply Chain Flows Downstream flows: Upstream flows:
Challenges in Supply Chains • Complex networks • Complex products • Uncertainties: • Pressure points:
Improving a Supply Chain Initially can focus on individual nodes: • Points to review: • Stocking levels • Service levels • Improve existing operations
Control Knobs • Service level target • Supplier lead times: average and variability • Review periods • Process cycle times • Process variability • Forecast error • Capacity
Bullwhip Effect Bullwhip: Increasing variability of orders up the supply chain
The Bullwhip Effect • Consequences of the Bullwhip:
Bullwhip Picture borrowed from Hau Lee
45,000 350,000 40,000 300,000 35,000 250,000 30,000 25,000 200,000 20,000 150,000 15,000 100,000 10,000 50,000 5,000 0 0 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 Bullwhip in Electronics Industry Peripheral Product Consumables 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 1 4 7 week week Unit orders from a major retailer to manufacturer Total unit sales at outlets of retailer Slide borrowed from Hau Lee
What Causes this Effect? Lee et al. 1997: Reactions to demand signals Order batching Price fluctuations Shortage gaming
What Causes this Effect? Reactions to demand signals Order batching Price fluctuations Shortage gaming