Episode 02 / 08 · Rework also uses electricity · About 3 minutes

Doing it twice does not make two products.

The machine counter says 1,200, but the warehouse has only 900 good units. Nobody has to be wrong: they are counting different things.

And… action!

A-Qin

The counter says 1,200. Good day's output, right?

Two hundred of those passes were the same pieces coming back for rework.

Tan

Run the same piece again and the counter goes up. My favourite trick.

Manager Fang

Let's separate processing passes, units that pass first time and units that finally pass.

Rework adds electricity; it doesn't erase what was already used

Of 1,000 units entering production, 800 pass the first time. The other 200 are reworked: 100 then pass and 100 are scrapped. That leaves 900 final good units, although the machine has performed 1,200 processing passes.

Make the unsuccessful part visible too

Allocate all 500 kWh to the batch and divide by 900 good units: about 0.556 kWh per good unit. Electricity used in rework and scrap cannot simply disappear from the calculation. Reducing rework may improve time, quality and energy performance together, but the results still need checking.

Pause here. What would you choose?

How many final good units does this batch deliver?

Try it: power curves and electricity per good unit →

Sources: story manuscript pp. 8–11. This adapted story uses teaching scenarios, not customer measurements or equipment operating instructions.

Rework adds electricity; it doesn't erase what was already used

Make the unsuccessful part visible too

How many final good units does this batch deliver?

See you in the next scene.