Simulation for Electronics & Automotive
High Volume, Tight Coupling, No Room to Absorb a Stop

Automotive components and electronics assembly are the high-volume discrete case. Cycles are fast, many stations run in series, and takt times leave almost nothing spare. When a line runs to a takt and inventory between stations is kept low on purpose, a stoppage anywhere spreads right away in both directions, in a way averages can't describe.

Lean removed the inventory, not the variability

Pulling inventory out of a line is good practice, but it doesn't make the line more reliable. The variability is still there, and now it spreads down the line instead of being absorbed.

Every lean program makes this trade, usually without putting a number on it. The question isn't whether to hold buffer but which form to hold it in (inventory, spare capacity or time). How big should a buffer be? works through why the buffer never really disappears.

What tends to be binding

Series length punishes good machines

85% OEE is a single-machine benchmark. Five machines at 85% in series with no buffering give a line near 44%, and an assembly line is far longer than five stations. The arithmetic is here.

Micro-stops, not breakdowns

On a tightly coupled line a stoppage measured in seconds never lets the small buffers refill, so its cost is carried all the time rather than now and then. It looks negligible on a loss report and is often the largest recoverable item on the line.

Mix and sequence

Model mix changes station-level work content, so the constraint moves with the build sequence. A line balanced for one mix is unbalanced for another. The balance is only true on average, and the line is never actually running at the average.

Supplier and inbound variability

On a machine report, a station starved by a late delivery looks the same as a station that broke. The cause is outside the plant, and only a model that represents both can assign it correctly.

The same mechanisms, documented