Takt time vs cycle time vs lead time: calculate the right clock
A worked shift example separates customer pace, observed process speed and end-to-end delivery time, with practical checks before changing the line.
Contribution per unit
Selling price less the avoidable variable costs attributed to one additional good unit.
Use a consistent accounting boundary agreed with finance. Potentially lost units multiplied by contribution estimate economic exposure only when output and demand make that contribution recoverable. Fixed costs do not automatically become incremental incident costs. See the downtime calculator and business-case guide.
See also: Bottleneck · Simple payback
Use the concept: Cp, Cpk, Pp & Ppk calculator · Automation ROI & payback calculator · Downtime cost calculator
In depth
SMED changeover study: measure last good to first good
Use a time observation sheet to separate internal and external work, preserve safe setup steps, and verify a repeatable changeover improvement.
Automation ROI and payback: a business case operations can verify
Separate installed cost, cash savings, released capacity and recurring expenses, then test a conservative scenario before approving automation.