Within the Lean, safety stock represents a buffer stock held to deal with unexpected fluctuations in demand or delivery. It is a strategic stock held to prevent production downtime or customer dissatisfaction.

In the Lean, holding inventory is considered a form of waste (Muda), as it takes up capital and space. However, safety stock may be necessary to ensure process continuity and maintain customer satisfaction. Therefore, the goal within Lean is to minimize safety stock by eliminating the root causes of variability.

Safety stock is affected by factors such as:

• Demand variability: The more unpredictable customer demand is, the greater the safety stock required.
• Variability in delivery time: Uncertainties in supplier delivery time require increased safety stock.
• The desired service level: A higher desired service level (a lower chance of selling "no") requires a higher safety stock.

Within Lean , methods such as Kanban and Just-in-Time (JIT) are preferred to reduce inventory levels while increasing process stability and predictability.

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