Calculating Line Changeover Costs in Shared Sub Assembly Infrastructure
Subassembly changeover costs must sum direct technician labor, idle station depreciation, downstream line starvation risks, and post-swap calibration scrap.
WIP Buffer Depletion
Meaning
Reduction of partially completed inventory held between sequential workstations. WIP buffer depletion occurs when the upstream machine stops producing parts while the downstream machine continues to operate. This process reduces the total amount of inventory sitting on the factory floor.
It defines the amount of time a production line can continue to run after a failure occurs at an earlier stage.
Flow Stability
Buffers are designed to absorb small variations in production speed and minor machine glitches. When these piles of parts start to shrink, it indicates that the balance of the line has been lost. WIP buffer depletion is a warning sign that the downstream station will soon run out of material.
Monitoring these levels prevents a single failure from stopping the entire factory.
Supply Disruption
Major mechanical breakdowns lead to the total exhaustion of the available stock. As the buffer reaches zero, the downstream workers are forced to stop because they have no parts to process. WIP buffer depletion measures the severity of a supply chain break within the factory walls.
Measuring how fast the buffer disappears helps managers estimate the time available for repairs.
Starvation Risk
Running a line with very low inventory levels increases the chance that a station will go idle. This state of starvation is the direct result of uncontrolled WIP buffer depletion and leads to lost productivity. Efficient factories try to keep buffers small to save space but large enough to survive a standard machine reset.