Safety capacity in lean environments is where take time is greater than cycle time. Take time is the average time between the start of production of one unit and the start of production of the next unit1. Cycle time is the average time it takes to complete one unit of a product or service2. Safety capacity is the amount of capacity that is reserved to deal with unexpected events or fluctuations in demand or supply3.
In lean environments, the goal is to minimize waste and maximize value by producing only what the customer wants, when the customer wants it, and in the exact amount4. This means that the production system should be synchronized with the customer demand, and the take time should match the cycle time. However, in reality, there may be variations or uncertainties in the demand or supply, such as changes in customer preferences, seasonal patterns, quality issues, equipment breakdowns, or supplier delays. These variations or uncertainties can cause disruptions or imbalances in the production system, leading to stockouts, overproduction, waiting, defects, or rework5.
To cope with these variations or uncertainties, lean environments may use safety capacity as a buffer or contingency plan. Safety capacity is where take time is greater than cycle time, meaning that the production system has some extra capacity to produce more than what the customer currently demands. This extra capacity can be used to absorb the variations or uncertainties and maintain a smooth and stable production flow6. However, safety capacity should not be confused with excess capacity, which is where take time is much greater than cycle time, meaning that the production system has a lot of idle or underutilized resources. Excess capacity is a waste that should be eliminated or reduced in lean environments7.
Therefore, safety capacity in lean environments is where take time is greater than cycle time.
References: 1: Take Time Definition 1 2: Cycle Time Definition 2 3: Safety Capacity Definition 3 4: Lean Manufacturing Definition 4 5: The Seven Wastes of Lean 5 6: Capacity Planning Tools 6 7: Excess Capacity
